Dual battery system.

Information for people about to or have installed a dual battery in their 4WD.
Highlighting problems I have incounted along the way and how to significantly extend the lifespan of your battery.
I'm a electronics technician with over 25 years in the telecommunication industry working with 50v power.
Enjoy exploring the great outdoors, 2 months touring East, North and Central Australia, 3 months touring Western Australia, club trip to Simpson Desert and planning Canning Stock Route.

Im not receiving any financial gain from any particular product reviewed within this web site.
Just my personal experence on the good and the bad points so that you can make an informed choice of differant products and setups so you can tailor them to your own needs and budget.
The use of the information within this website is at the users own risk and should supplement it with your own research.

Looked around at finding it hard to decide, buying guide and fridge comparo 12v fridge/freezers that can have both fridge/freezer at the same time in the one unit with low power consumption and can fit in space allocated for it and requires no insulating cover and is Australian made (suits our climate).
Well after buying a 47L Evakool fridge/freezer, 55L a close second - has more capacity, thicker insulation and lower power consumption, but no second tie down handle, only a narrow groove in plastic handle.
Freezer/fridge statistics at ambient temperature of 20C
SettingMin freezer tempMax freezer tempMin fridge tempMax fridge tempRun time MinutesIdle time MinutesEstimated AH's used per day
Temperature measurements in celsius taken half way up inside of compartments on normal setting.

Evakool (47L) uses about 30AH per day, 1.25AH per hour on setting 3.5, -8 freezer and +2 fridge at around 30C. On normal setting uses 3.6A and economy 2.4A (runs for twice as long as normal setting).
With two thick cable ties at bottom of freezer/fridge divider to leave gap of a few mm's to allow cold air to pass under divider into fridge area, holes in divider are not enough to allow cold air through. Also placed a high density sleeping mat folded in half for fridge to sit on. Evakool power connector is hard wired to fuse panel via 2.5mm2 cable. Use original 12 volt lead supplied for AC adaptor.

Dual battery and voltage sensitive relay (VSR) installation.
It was time to install a dual battery system in the 4WD (3.4L petrol 1999 Toyota Prado RV6 - 90 series).

Installed a Fullriver DC105-12 105AH AGM deep cycle battery in a battery box (can hold up to a 130AH battery) in the rear cargo area (warranty void if mounted in engine bay due to heat).
In the long run it would have been better installing a 120 - 130AH battery to increase the longevity of the battery by not discharging it as deeply.

Flooded (wet) deep cycle batteries are dangerous and illegal inside a vehicle, only use AGM and Gel (spillproof and leakproof).
Battery box is held down by a 300KG lashing capacity polyester webbing strap passed through two slots cut in a piece of aluminium checker plate bolted to the floor using existing holes under the carpet (so it can not fly around in the event of an accident, a 30kg missile).

Met a couple in the Kimberleys - Gibb River Road, they were just running their fridge off one/main battery and needed to be jump started on on few occasions, they ended up running thier car engine a few times a day to keep main battery charged.
Was originally going to replace the main battery with a larger hybrid battery (both starting and deep cycle) but decided to install a dual battery system instead. Glad i did.

Battery box, fridge/freezer power cable and cigarette lighter socket behind back seat.

This was isolated from the main battery by a 100A continuous duty solenoid controlled by a modified voltage sensitive controller (on 13.4v and off 12.9v with 13 sec delay, old settings on 12.9v and off 12.6v) with 4 leds, linked, charged (>12.44v), inter (>12v<12.44v) and low (<12v) and switch to manually link batteries in case main battery is flat. Current drain 11.6mA from main battery and 13.9/13.9/12mA from auxiliary battery, depending on which LED is lit on auxiliary battery status.
Also solenoid operates, connecting main battery, when auxiliary battery reaches 13.6v (old setting 12.9v), when charging auxiliary battery from solar.
This was installed previously on another 4WD with a BP L100 powerbloc flooded deep cycle battery (90AH) that died prematurely from sulfation. Looking through the vent caps on top, the normally gray lead plates were all white.
Also fitted a voltage spike arrestor (surge protector) across battery to protect vital engine management computer (ECU) and other sensitive electronic equipment from damage/failure.

100A continuous duty solenoid, voltage sensitive controller (dual sensing) and auxiliary battery status.

This was all connected using 0.42m (to solenoid), 5m (to back of vehicle) and 1.27m (earth lead) of double insulated 16mm sq automotive or marine cable terminated on 16mm/8mm hole lugs covered in red/black heatshrink tubing and loom tube (split, ribbed conduit) with 70A circuit breakers at each end, 5 core cable to controller, 8 B&S - 85A (7.91mm sq) cable to 6 way blade fuse panel and 2.5mm square cable to accessories.

This system worked fine for 3 months touring Western Australia powering:
A cigarette lighter plug to cigarette lighter 3 way socket via 5m of 1.84mm2 extension lead (old 1m lead removed) up to a rooftop tent.
TV was connected to a caravan VHF/UHF antenna via 6m of coax cable.

Many 4WD's have anti vibration mounts of rubber between major body connections and the earth path is not always clear. If in doubt run an earth back to battery or known good solid earth.
This happened to me, measured 0.5v drop at 5A across earth on rear external cigarette lighter socket, moved it to a different spot on chassis, now reads 5mv drop.

Power consumption per day
AccessoryPower use per hour (amps)HoursTotal AH
Fridge/freezer1.25 (averaged)2430
11w fluorescent light0.783.52.73
LCD TV - digital tv0.710.7
LCD TV - av in0.1620.32
WD TV live + HDD0.6521.3

For most of the trip, leds showed charged but towards the end of trip was showing inter charge in the morning, every now and then there would be a strange smell of hot rotten eggs (hydrogen sulphide gas being released from battery - this generally happens when the electrolyte is nearly dried out and the battery is receiving a charge current due to localized hot spots or arcing within a defective cell).

After I got home a week later battery was showing inter charge, so charged over night, a few days later battery was showing low charge, after placing on charger after a few minutes current dropped to zero amps and would only run fridge/freezer for a few minutes before stopping.
So took battery back to supplier and they put battery on charge, then later tested it and found that all 6 cells were stuffed.
So I received a replacement battery at no cost, supplier said they only get a 2% fail rate on fullriver batteries.

When camping for a few days in the one spot, would use a 100w folding solar panel via 15m of twin 4.59mm (6mm - 31A) sq cable and 6A PWM (pulse width modulation) solar regulator (old model MP-3128), new model MP-3720.
The JUTA CMP12 12A regulator (simple on-off regulator, 30% less efficient than PWM, 70% less efficient than MPPT) which come with solar panel, interfered with solenoid system, causing solenoid to chatter, once auxiliary battery was charged, it tried to operate solenoid (700mA) to charge main battery.

Hot spots (electrical heating) or 'snail tracks' (micro cracks) on Rich Solar RS-M50 solar cells, still puts out maximum voltage/current (Voc and Isc), but for how long?

Sizing deep cycle battery.
For 3 days camping with no solar charging, 3 x 35AH (power consumption per day) = 105AH (current brand new battery at 100% depth of discharge (DOD). Cycle life 250.
Ideally it should be 50% or less DOD for long life, 2 x 105AH = 210AH, which I do not have the space for. Cycle life 700.
At 80% DOD, 105AH / 0.8 = 131.25AH. Cycle life 350.
The sweet spot is 30% DOD, cycle life is 1250. 105AH / 0.3 = 350AH.

Maximum power point tracking (MPPT).
The solar regulator adjusts the duty cycle of the switching frequency (pulse width modulation), to find the point where the solar panel is producing the most power.
solar voltage x solar current = solar power.
Where as a normal PWM solar regulator uses pulse width modulation to regulate the output voltage.
Once the output voltage on a MPPT regulator reaches say 14.4v it then transitions to a normal PWM regulator, current mode to voltage mode.

100w solar panel.
Voc = 21.96v
Isc = 6.28A
Vmp = 17.82v
Imp = 5.62A

17.82v x 5.62A = 100w in full sunlight at a particular temperature (standard test conditions)
Example charging at 10.5v, 12v and 14.4v

Normal PWM regulator and simple on-off regulators:
10.5v x 5.62A = 59 watts
12v x 5.62A = 67.44 watts
14.4v x 5.62A = 80.928 watts

Voltage loss in cable:
15m x 2 x 0.0041 (4.59mm2) x 5.62A = 0.691v (current cable - park car in shade)
15m x 2 x 0.00252 (8mm2) x 5.62A = 0.425v
12m x 2 x 0.0074 (2.5mm2) x 5.62A = 0.998v (old cable)

MPPT regulator:
15m x 2 x 0.0041 (4.59mm2) x 5.62A x 5.62A = 2.59w loss in cable.

At 10.5v (100w - 2.59w) x 0.95 (efficiency) /10.5v = 8.81A (92.5w)
At 12v (100w - 2.59w) x 0.95 (efficiency) /12v = 7.71A (92.5w)
At 14.4v (100w - 2.59w) x 0.95 (efficiency) /14.4v = 6.43A (92.5w)

As you can see from above, the PWM regulator is wasting 19 - 41 watts that could be sending 0.81 - 3.19A extra into your battery with a MPPT regulator depending on regulator efficiency (95-98%) and wiring (length and size).
With any MPPT controller, losses in wiring should be minimised by using heavy wiring, and the wiring should be kept as short as possible.
This is less important with a basic PWM regulator since excess voltage will be discarded anyway.
Also the solar regulator should be mounted as close to the battery as possible.

The excess 3.42 - 7.32 volts at maximum power point is converted into extra current by the buck converter in the MPPT regulator, average energy gain being 10%-25%, depending on operating environment, illumination (angle of solar panel/cloudy/sunny), temperature (cold/hot) and age of solar panel.
If temperature of the solar panel is high, you will not get 17.82 volts, you might get under 16 volts and gets worse as the temperature goes up.
You will get a better power gain in winter than in summer. Under very cold conditions a 100 watt panel is actually capable of putting over 108+ watts.
Solar panels have to have enough leeway built in them to perform under the worst of conditions.
Solar panel will convert about 16% of the incoming solar energy (light) to electricity.

A few manufactures are getting on the solar MPPT band wagon and putting out inferior products that don't perform as claimed. So buyer beware and do your homework/research.
Some MPPT manufactures only use solar voltage and not solar voltage x solar current = solar power to find maximum power point or contain no toroid core (doughnut looking transformer).

With 2 x 12v solar panels in series, it will suffer from shade quite badly.
If you cover half of one solar panel with shade it will drop the charge output quite dramatically, where as if they were 2 x 12v solar panels in parallel and you shaded one solar panel completely you would still have the other solar panel at full output.
You have to use the exact same model as the original solar panel, or else youll create an electrical mismatch with multiple sweet spots and regulator can only responds to the average.

12v dc to 230/240v ac inverters.
Handy for using items that can not be charged/used directly off 12v e.g. digital camera/video, shaver, mobile phone, satellite systems, etc.
There are two general types of inverters, true/pure sine wave or modified sine wave (modified square wave).

True/pure sine wave inverters produce power that is identical or better (free from interference/distortions/electrical noise) than the electricity from your power point at home.
Modified sine wave produces power that is not exactly the same as electricity from your domestic power point, it is sufficient for basic small power tools and most non sensitive electronic devices, but can damage some products or behave irrationally or overheating problems and additional electrical noise may be produced (buzzing sound) or a snowy picture on your TV screen.
Clocks that use the mains 50/60Hz and not a internal crystal for their timing and variable speed controllers or some chargers (use SCR's or Triac's) do not work on modified sine wave inverters.
To be on the safe side, only use a true/pure sine wave inverter.
Choosing the right inverter size depends on total wattage drawn by items connected to inverter, then add 50% more to account for peaks or spikes in the power draw. Some items, such as a drill, requires additional start-up (surge) wattage (typically 2-3 times the continuous wattage required) so will require an inverter with at least double the wattage or surge rating to allow item to reliably start up.

If drawing a load of 100w from a 380 Watt 12VDC to 230VAC pure sine wave inverter how much current is being drawn from 12v battery.

100 / 10 = 10 Amps (simple worst case guide).

To allow for inverter efficiency, in this case 83%.
at 12V (100 / 12) / 0.83 = 10.04 Amps.
at 14V (100 / 14) / 0.83 = 8.61 Amps.

As you can see, the amp hour rating of a battery is the most important measure when choosing a battery for power inverter use, to get the required run time you require.

If using a laptop or notebook then a 90W automatic car laptop power supply 3.75A or 150W car laptop power supply 6A or 50W in-car mini notebook power supply 3A would use less current than using a mains laptop/notebook power supply plugged into a 12v dc to 230v ac inverter (12v to 230v then 230v to 15 - 24v).

Regulated 12 volt supply.
Some devices will only run on a regulated 12 volt supply and will self-destruct if connected to the typical 13.8 - 14.4 volts of a car's electrical system.
A 11 - 28V to 12v 6A DC-DC Converter is required.

Multiple batteries in parallel connection to form one larger bank.
Each batteries voltage must be equal e.g. 12v and of the same age, model, capacity (AH) and chemistry (flooded/sealed, gel or AGM). Connect system to the positive of the first battery and negative to the last battery so that batteries will be charged/discharged equally.

Charge equaliser.
When 12v is taken from the lower battery (one connected to negative earth/ground) in a series two battery 24v setup to power 12v equipment, all the charge is taken from the lower battery and not the upper battery. A charge equaliser will ensure an equal charge (voltage) across the two batteries. Without flattening the lower battery or overcharging the upper battery.
Alternatively, you can charge a 12 volt auxiliary battery from the 24 volt system via a battery to battery charger or battery isolator.

State of Charge (SOC).
The easiest way to determine how much charge you have left in your battery is with a digital multimeter or voltmeter.
The following chart, column two compensates for 12v batteries that are in use (under load).
The third column is the open circuit voltage (OCV) of a fullriver 12v battery.
These voltages assume 100% healthy cells, and may vary a bit lower for older batteries.
Occasional dips into the yellow zone are not harmful, but continual discharges to the yellow/red zone will shorten battery life considerably.
For the longest life, batteries should stay in the green zone.

State of Charge Under load V Fullriver OCV Notes
100% 12.7+ 12.83+ Fully charged battery
90% 12.5 12.72  
80% 12.42 12.60 Long battery life above this point
70% 12.32 12.47  
60% 12.20 12.34  
50% 12.06 12.20 Try not to discharge below this point
40% 11.9 12.06  
30% 11.75 11.91 Shorter battery life below this point
20% 11.58 11.76  
10% 11.31 11.61  
0 10.5 10.5 Flat battery

Measurement with hydrometer on flooded batteries with removable caps.

Approximate state of charge at 25C
ChargedSpecific Gravity (SG)

Battery temperature correction - 0.004 points should be added or subtracted for each 5C +/- variation from 25C.

Why batteries fail. Tips for the longest battery life.
Measuring initial charging current.
After measuring charge current at 64A peak then settling on 58A at 13.5v within a few seconds, with battery initially at 11.04v. Current gradually tapers off over time to less than 1A as battery voltage rises to near 14.3v.
With 25AH discharge from fully charged (to simulate overnight stop of 16 hrs), measured current at 42A and decreasing and voltage at 13.68v.
Only did short tests, less than a minute, so as not to damage new battery.

So old battery was definitely dying a slow death from overcharging from too much current and voltage (no float mode).
The general rule with deep cycle batteries is if you discharge it slow, you charge it slow, plus normal charge rate is 10 - 20% of batteries amp hour (AH).
Some of the cost of a battery to battery charger will be saved in the extended life of your first set of batteries.
The recent trend to dc-dc alternator charging was inevitable, Collyn Rivers talks DC-DC charging in the Automotive & Electrical News April May 2012 edition, read full article and technically speaking Aug-Sept 2012.
Multi stage battery charging profile extends the life of your batteries by ensuring a full charge and conditioning, as well as entering a float mode and the ability to mix different battery types (GEL, AGM, flooded, VRLA or calcium) compared to main starting battery.
Lights, accessories and engine power consumption leaves about 80 - 22 = 58A spare.

Reducing charge current.
A efficient way is to use a DC to DC charger with a output current to suit the auxiliary battery.
A less efficient way is to charge the auxiliary battery through a 12v to 240v inverter and 240v battery charger.

Charge rates.
The fullriver DC series can only handle maximum allowable bulk charging current 0.35 x 105 (C20 rate) = 36.75A with constant voltage/current 3 stage charger.
Cycling application initial bulk charging current 0.25 x 105 (C20 rate) = 26.25A.
Recommended initial bulk charging current 0.20 x 105 (C20 rate) = 21A (on side of battery).
Century batteries maximum charge current limit 0.3 x 105 (C20 rate) = 31.5A.

DC to DC converter bulk charge current at 20%, 25% and 30% of the AH capacity @ 20Hr rate
Charge current (A)Minimum battery size (AH) capacity x 0.2Minimum battery size (AH) capacity x 0.25Minimum battery size (AH) capacity x 0.3

Depending on cable size and length, DC to DC converter input current can be up to 1.4 times its output current, if input voltage is significantly lower than output voltage.

Gelled batteries, must be charged at a slower rate (C/20) and lower voltage, to prevent excess gas from damaging the cells.
Charging batteries at more than they can handle can damage batteries.

Be carefull not to over tax your alternator (e.g. 80A x 0.6 (60%) = 48A continuously) or it will lead to your alternator's early demise.
If the "ALT" warning light (charging) comes on or dim or flickers or voltage across battery drops when you turn on the headlights or windshield wipers or fan at max, then your alternator is running at or near maximum capacity (100%).

Battery to battery charger installation.
Not wanting to destroy another battery within 6 months, bought a CTEK D250S dual (program/firmware/software version B33) battery to battery charger with 20A output.
Removed continuous duty solenoid, but retained its controller to monitor auxiliary battery charge status.

CTEK D250S dual beside back seat.

CTEK D250S dual feedback.
On first big test of CTEK D250S dual unit on a trip to Cape Otway over Christmas 2011, with a stop over in Geelong for 3 days, using solar panel for 10 hours on each day in bright sun light. Battery was showing 11.98 volts in the morning after 3 days, after arriving at Cape Otway after 2.5 hours, battery wasn't fully charged, it hadn't reached the float stage.
After staying for 3 nights using a 100w solar panel for half a day (sunny) and a few hours on the other two days (cloudy) and running car engine to try and keep some charge in battery.

The Voc of the solar panel MUST NOT exceed 22 volts (mines 21.96v), or you will destroy the CTEK D250S dual.

Power lamp is on solid when operating (no load current 6.9mA) and a fast flicker (3.5mA) when in power save mode (when idle for 6 minutes). Draws 0.4mA from auxiliary battery.
Cut in voltage 13.1v after 5 sec, cut out voltage 12.8v after 10 sec. The output power of the charger is dependent on the input voltage. With lower input voltage the output power is lower. Due to this it may take some time until the charger stops. It will however not drain the supply battery.
The charger will not charge the battery if the temperature is above 65C.

Met a couple down there, their century auxiliary battery died prematurely, mounted under bonnet using solenoid system, so they replaced it with a Optima battery, it runs their engel fridge for two days.

After getting home, disappointed in CTEK, decided to check how much current the CTEK D250S dual is putting into auxiliary battery on solar.

CTEK D250S dual readings are a average due to fluctuating levels in bright sun light with clear blue skies.
Solar panel (watts)Solar VmpSolar Imp Solar Watts inSolar (volts) Solar (amps)Auxiliary battery (volts)Auxiliary battery (amps)Amps expectingMain battery input (volts)Main battery input (amps)Engine
10017.825.622817.751.5812.712.035.6 - 7.5  Off

There is something seriously wrong with the MPPT algorithm on the charger. A PWM solar controller easily out performs it.
Apparently the CTEK D250s dual program/firmware/software is up to version B50 (Feb 2013) with more MPPT enhancements.

Modifying old setup.
Removed solenoid controller and 1.24m, 16mm2 battery negative earth lead (1.6mV @ 1A) and replaced with 1.395m of 25mm2 cable to use as a current shunt (50A/50mV) and voltage/current/AH digital power meter via 5m of cable to show auxiliary battery status and 3 pole double throw switch to show charge/discharge current by reversing 2 connections to shunt and 2 connections to ground/earth (one to each side of shunt).

Power meter.

Installing Redarc.
The CTEK D250s dual was replaced later by a Redarc BCDC1225-LV 25A (Australian made) to suit current and future vehicles (ECU controlled alternator) and due to CTEK's poor performance on solar, low charge current and strange behaviour.

Redarc BCDC1225-LV.

Preliminary testing of Redarc, readings are a average due to fluctuating levels in bright sun light with clear blue skies.
Solar panel (watts)Solar VmpSolar Imp Solar Watts inSolar (volts) Solar (amps)Auxiliary battery (volts)Auxiliary battery (amps)Amps expectingMain battery input (volts)Main battery input (amps)Engine
10017.825.6282.314.975.512.786.25.6 - 7.5  Off

Now for the big test over the Christmas holiday period (Dec 2013 - Jan 2014).

Redarc BCDC1225-LV feedback.
Nice little unit, first MPPT regulator i've owned that does what its supposted to do, seen up to 7 amps going into the auxiliary battery from a 100w solar panel (5.62A). Now getting an extra 1.38A into battery.

Only downside is its low float voltage of 13.3v (suits lifeline batteries or temperature is greater than 38C), its normally around 13.6 to 13.8v @ 25C as recommended by battery manufactures and has no remote temperature sensor.

In the bulk charging stage (constant current) the auxiliary battery still receives 21.4 amps while fridge/freezer is cycling.
At 14.5v (70 - 80% charged), AGM setting, it transitions to the absorption stage (constant voltage).
At around 2 - 3 amps (95 - 100% charged), it transitions to the final float stage (13.3v).
When fridge/freezer is cycling, it doesn't seem to effect the float stage (doesn't go back to bulk/absorption stages).

Noticed battery terminal voltage dropped faster on discharge when charged with the Redarc BCDC1225-LV than with the CTEK D250s dual (has a battery temperature sensor).
Especially now in the colder months with average temperatures around 13C.

Buying a DC to DC charger is a waste of time and money if it does not include temperature monitoring at the battery to maintain optimum charge/float voltages. Without it manufacturers would have to make compromises that would not suit all batteries or climates. By not compensating for temperature change, it will shorten battery life by undercharging (if cold) or overcharging (if hot).

Battery temperature compensation.
Approximately -3.9 mV/C/cell 6 cells = -23.4 mV/C for a 12V battery.
Temperature compensation prolongs battery life by up to 15 percent.

Temperature compensation for AGM battery
Temperature (C)Charge (V)Float (V)
4514.13 - 14.3313.13 - 13.33
4014.25 - 14.4513.25 - 13.45
3514.37 - 14.5713.37 - 13.57
3014.48 - 14.6813.48 - 13.68
2514.6 - 14.813.6 - 13.8
2014.72 - 14.9213.72 - 13.92
1514.83 - 15.0313.83 - 14.03
1014.95 - 15.1513.95 - 14.15
515.07 - 15.2714.07 - 14.27
015.19 - 15.3814.19 - 14.38

Re-installing CTEK D250s dual.
Did not want to spend any more money on a new DC to DC charger or MPPT solar charger, as there's no guarantee that its going to perform as expected.
Un-install Redarc BCDC1225-LV and re-installing CTEK D250s dual, as it did a superior job of charging battery due to remote battery temperature sensor, spends longer in absorption stage and higher float voltage, except for the solar side of it, will use a separate PWM solar regulator.

Day to day driving (less than 1 hour) when battery is not being used, it spends too long in absorption stage and never gets to the float stage, so battery is continually being over charged. Have now disconnected battery till its needed on camping trips, only applying a top up charge every 2 - 3 months.

Now takes longer to charge battery due to its 20A output instead of Redarc's 25A, may add relay to change over fridge/freezer to run on main battery when engine is running, to gain an extra 3.6A charge current.

Found over Jan - Feb 2017 Christmas holidays in Tasmania that CTEK D250s dual derates output current when unit gets hot, due to internal heat sink and plastic case, even when its mounted in cabin. Seen it as low as 10 Amps, driving on average of less then 200km a day, auxiliary battery never reached full charge (float stage).
Whereas the Redarc BCDC1225-LV stayed cool due to external heat sink and metal case.

Installed unit using 7.91mm (8 B&S - 85A) sq cable. Negative terminal to chassis, auxiliary battery terminal to 2 x 15A blade fuses wired in parallel on 6 way blade fuse panel to auxiliary battery and separate 5AG fuse holder and 30A 5AG fuse for main battery terminal via 16mm sq cable to main battery. Solar terminal was left disconnected.

The ideal dc to dc battery charger.
Lithium batteries (LiFePO4) chargers.
Enerdrive DC2DC+ ePOWER battery charger looks promising as a possible replacement. A very versatile unit and can charge lithium batteries (LiFePO4) as well as a program feature to set bulk/absorption/float voltage, charge current (5/10/15/20/25/30/35/40/45/50A), absorption to float terminate current, ignition or voltage sense, LCD display, separate input for solar regulator (MPPT) and remote temperature sensor.
The fact thats its programmable is infinitely better (future proof) than one with preset charge algorithms only.
Its only down side is its only a 3 stage + equalisation stage charger, no calcium mode (only adjustable to 14.8v) and its "when in use" current of 50mA (1.2AH per day compared to Redarc's 0.192AH - would need to disconnect battery when in storage for long periods). Its for in cabin use ONLY to protect from dust and moisture to internal electronics and internal cooling fan, NOT under bonnet.

A battery management system (BMS) is highly recommended to prevent catastophic failure in LiFePO4 batteries by monitoring individual cells and terminal voltage then disconnect battery if any issues.
AGM to lithium conversion and self sufficient touring and lithium batteries and Outback Travel Australia and reality check.

Projecta IDC25.
The quiet achiever getting it just right while everyone else quickly released theirs to market. It will be a serious contender for the Redarc BCDC1225 (low float voltage, no separate solar input and no remote temperature sensor) and CTEK D250s dual (poor performance issues on solar and no select battery chemistry).
If I had the choice today between the three, I would pick the Projecta IDC25 as it has it all and price.

Product comparison
FunctionRedarc BCDC1225-LVCTEK D250S DualEnerdrive DC2DC+ ePOWERProjecta IDC25
12v or 24v input12v only12v only12v & 24v12v & 24v
Maximun input voltage32v (28v on solar)22v16/32v (23/45v on solar)32v (23v on solar)
Charge stage statusYesNoYesYes
Output current25A20A5/10/15/20/25/30/35/40/45/50A20A at 9 - 11v and 25A at 11 - 32v
Ambient temperature range-20C to +80C-20C to +50C -10C to +80C
De-rate output current>55C at 85C no charge currentYesDe-rate >50C shutdown >58/60CYes
Standby CurrentMain battery 0mA / Aux battery <8mAMain battery 3.5mA / Aux battery 0.4mAAux battery 50mA when in useMain battery 20mA / Aux battery 9.5 - 10.5mA
Power use per day0.192AH0.084AH / 0.0096AH1.2AH0.48AH / 0.228AH - 0.252AH
Select auxiliary battery type (chemistry)Calcium/Standard lead acid/AGM/GelNot adjustable by userGel/AGM/Flooded/Lithium/adjustableCalcium/Wet/AGM/Gel
Bulk/absorption voltage15.3v/14.9v/14.5v/14.5v14.4v14.4v/14.6v/14.4v/13.9v - 14.6v or adj 13.8v - 14.8v (0.1v step)15.4v/14.7v/14.4v/14.1v
Float voltage13.3v13.6v13.7v/13.6v/13.3v/13.5v - 14.2v or adj 13.0v - 13.8v (0.1v step)13.7v
Settings programmableNoNoYesNo
Solar MPPTYesYesYesYes
Solar inputExternal changeover relay requiredYesYesYes
Performance on solarExcellentTerrible  
Use solar and alternator inputs simultaneouslyNoYesNoYes
Efficiency96%92%DC 95% Solar 97%>94%
Suit ECU controlled alternatorYesExternal changeover relay requiredYesYes
Unit On/OffIgnitionIgnition with relay or 13.1v/12.8vIgnition or 13.2v/12.8v or 26.4v/25.6vIgnition or 13.4v/12.8v or 26.8v/25.6v
Charging stages352/3 + equalisation (flooded mode only)3 + equalisation (calcium mode only)
Maintain 100% charge in cool climatesPoorGood  
Temperature compensationNoYesYesYes
Desulfate modeNoYesNoNo
Remote control/displayOptional LED onlyNoOptional - 20mAOptional LED only
Ingress protection ratingFully sealed - Silicone elastomerIP65 (Dust tight, water jets for 3 minutes)In cabin use ONLY, NOT under bonnetIP67 (Dust tight, immersion up to 1m for 30 minutes)
Dimensions (L x W x H)150 x 120 x 37mm197 x 93 x 49mm74 x 172 x 242mm149 x 122 x 42mm
Cost$389 - $474.95$297.99 - $355$469 - $539.60$305 - $354

Plug and socket types.
Merit plug, metal merit socket, plastic merit socket, 6/9/14mm2 50A anderson plug/socket and weatherproof cigarette lighter socket.

Testing battery.
Did a battery capacity test on fullriver battery at average 4.9A using an old headlight as a load.
Now 4 years and 7 months old (Apr 2015) with infrequent use (christmas holidays and easter break) per year, capacity is gradually declining, now using setting 4 instead of 5 on fridge/freezer and getting two days instead of 3 days out of battery. So christmas holidays 2015 - 2016, will be a new battery.

When fullriver battery dies or holds 70 - 80% (73.5 - 84AH) or less of the rated capacity, it has reached the end of its service life and will replace it with a 120 - 130AH one. Lose about 6.82AH per year, 15 - 25AH more capacity, life expectancy of 6 - 8 years due to extra capacity compared to about 5 years with 105AH battery.

Kulkyne Kampers battery performance test of different battery types.

Past and present deep cycle batteries
BatteryCharging systemLasted in serviceStatusReason
BP L100 Powerbloc 90AH FloodedVoltage sensitive (sensing) relay (VSR)3 Years 11 months (Dec 1997)RetiredSulphated
Fullriver 105AH AGMVoltage sensitive (sensing) relay (VSR)6 months (Sept 2010)RetiredNot holding charge
Fullriver 105AH AGMCTEK D250s dual & Redarc BCDC1225-LV4 years 7 months (Apr 2015)RetiredLow AH's (73.72AH)
SSB 130AH AGMRedarc BCDC1225-LV9 months (Sept 2016)RetiredLow AH's (78.22AH)
Fullriver 120AH AGMCTEK D250s dual Nov 2016New battery

BP L100 Powerbloc 90AH flooded deep cycle battery feedback.
Used to spill acid every where, which is the main reason for choosing valve regulated lead acid (VRLA) batteries as future replacements.
Battery was mounted under bonnet in starter battery position and starter battery was relocated elsewhere in the engine bay.
Sold vehicle after using battery for 3 Years and 11 months and battery was stored in garage for years before being thrown out.

Fullriver 105AH AGM deep cycle battery feedback.
First one died in 6 months from overcharging with too much voltage and current. Electrolyte most likely dried out due to excessive gassing.
Battery was mounted in the rear cargo area (warranty void if mounted in engine bay due to heat) and due to space limitations under bonnet.
Solid preformer when charged correctly. The main reason for getting a DC to DC charger to reduce charge current and float voltage.
Requires a few discharge/charge cycles to reach peak capacity if battery has been left idle for some time.

New Fullriver 120AH battery.

SSB HVT-86D 130AH AGM deep cycle battery feedback.
The standard SAE terminals on battery (developed here in Australia) can be unscrewed and replaced with the provided 8mm bolts and washers.

Tested it over the christmas holidays January 2016 on a trip to Fraser Island. It turned out to be a disappointing performer compared to 105AH Fullriver battery.
After getting home after 26 days, decided to leave the fridge running to see how long the battery lasts. After using only 105.39AH (25C) at a battery terminal voltage of 10.5v after 67 hours (2.79 days), when it claims to be a 130AH @ 20Hr rate deep cycle battery. Manufactured date was November 2015.
After recharging with a 240v charger, battery used 113.5AH to reach 100% state of charge.

Retested battery 9 months later now only 72.74AH (15C) or 78.22AH (25C), average discharge current of 4.7A, lasting 14.9 hours and recharge used 84.56AH.
Turned out to be more of a starting battery than a deep cycle battery (as labeled), its capacity is deteriorating rapidly with each charge/discharge cycle when used in a deep cycle application.
So far, number of charge/discharge cycles, 30% DOD 25, 50% DOD 0, 80% DOD 2 and 100% DOD 2.

Battery capacity temperature dependence.
Battery capacity (how many amp-hours it can hold) varies with temperature.

Battery capacity vs temperature
Temperature (C)Capacity (%)

Peak capacity of a battery (AH's).
The amount of usable energy is defined by the amount of active material (lead dioxide and spongy lead) in lead alloy plates (size and number), quantity and concentration of sulfuric acid, temperature and age of battery.
The capacity increases with each charge/discharge cycle as the amount of active materials increase and become more porous till it reaches a peak were capacity begins to decline, as shedding of active material gradually falls to bottom of battery.

Batteries plate thickness.
The heavier the battery is for a given group size then the thicker the plates will be.
So the more charge/discharge cycles and abuse they can take and therefore longer life, due to more active material remaining as the plates gets gradually eaten away with use.
So weight and number of cycles are two good guides when comparing and buying deep cycle batteries.

LiFePO4 or AGM deep cycle battery.
Move to LiFePO4 deep cycle battery (July 2015):
New Enerdrive DC to DC charger $469 to $539.60.
100AH LiFePO4 battery $875.50 to $1390 - life expectancy of 10+ years.
Battery management system (BMS) $130 to $231 (not required if BMS is built into battery).
Total $1474.50 to $1929.60.
Current system with new 120 - 130AH AGM deep cycle battery: (number of cycles at 100% 80% 50% 30% DOD)
Fullriver 120AH $359 - $419, same number of cycles (250 350 700 1250) as old battery, higher initial charging current 30A and weight 36.5Kg vs old battery 30.2Kg.
Bosch BAC12-120RFR 120AH $365 - $395, about 600 - 700 cycles, up to 36A charge current and weight 36.2Kg.
Lifeline 125AH $675 - $779, number of cycles (380 550 1000 1800), up to 312.5A charge current, under bonnet use, float 13.1 to 13.4 volts and weight 34Kg.
Neuton Power 120AH $387, unknown number of cycles, up to 24A charging current and weight 33.5Kg.
Zap 130AH $279 - $299, number of cycles (250 - 600 1200), up to 24A charge current and weight 33.4Kg.
Century 120AH $389 - $419, number of cycles (350 500 800 1350), up to 36A initial charging current and weight 32Kg.
Ritar 120AH $329 - $349, number of cycles (350 500 850 1350), up to 36A initial charging current and weight 32Kg.

Batteries less than 32Kg for 120AH, 32.7Kg for 125AH and 33.4Kg for 130AH.
OSTAR 130AH - $250, number of cycles (350 - - -), up to 36A charge current and weight 32Kg.
Pro Power 130AH $329, number of cycles (300 - 650 1600), up to 30A initial charging current and weight 31.5Kg.
Power Sonic PDC-121200 120AH $290, number of cycles (300 - 650 1600), up to 30A initial charging current and weight 31.4Kg.
Fusion 124AH $308, number of cycles (300 - 650 1600), under bonnet use, up to 30A initial charging current and weight 31.4Kg.
SSB 130AH $320 - $416, unknown number of cycles, under bonnet use, max charge current 36.4A and weight 31.4Kg.
Kickass 120AH $349, number of cycles (300 450 900 1500), up to 25A initial charging current and weight 31Kg.
Exide LCG31-120 Stowaway leisure cycle gold 120AH $399 - $489, unknown number of cycles, up to 42A charge current and weight 30.7Kg.
Sentry 124.8AH $???, number of cycles (225 - 450 1100), up to 36A initial charging current and weight 30.5Kg.
Giant Power 125AH $360, number of cycles (300 - 700 1650), up to 30A initial charging current and weight 30Kg.

Decided to stick with AGM deep cycle batteries, the cost of moving to LiFePO4 batteries is high and immature technology compared to lead acid batteries at present. With the expected 10 - 15 year lifespan of the lithium battery would mean two to three AGM replacements in that time ($640 - $960) and the fact that when they fail, they do so suddenly, whereas lead acid batteries deteriorate gradually.
LiFePO4 batteries are having premature battery aging problems, capacity losses due to operating temperature (a 10C rise above 23C results in cycles/life being cut in half), charge and float voltages set to high.
The cost will have come down and issues fixed hopefully and more options and sizes available when due for a new battery in about 5 years.

Past and present starting batteries
BatteryDateLasted in service
Century Yuasa 55D23LNov 19995 years 6 months
Bosch B68May 20054 years 9 months
Supercharge Gold Plus MF75D23L CalciumFeb 20102 years 6 months
Century 75D23LAug 20124 years 9 months
Century NS70LX MF29 Apr 2017 

May try a Century 4x4 (Australian made) or Exide Extreme as starting battery next time when due for replacement.
Currently only driving once per week with a parasitic drain of 20mA (3.36AH) from radio, clock, engine ECU and alarm, so a battery with some deep cycle ability would be ideal.
Vibration and impact from corrugations and 4WDing is a real battery killer so getting one designed for off-road conditions that has a higher vibration resistance.

Power dissipation
As power flows through a wire that resistance causes heat, too much and the insulation breaks down over time, and at some point it will melt leaving the wire exposed to shorts to chassis.
With higher ambient temperatures, it takes less current to reach operating limits of cable e.g. in engine bay.
The heat can even be enough to start a electrical fire in the surrounding material e.g. under carpet in vehicle, cannot dissipate heat as easily as open air.
So using the right size wires is important for you and your vehicles safety, if unsure ask someone who knows what their doing (qualified auto electrician), better to be safe than sorry.
Also as your wiring runs get longer you need to use a larger wire size to compensate for increased voltage drop e.g. vehicle to caravan.

The following equation is useful in choosing the required wire:
R = E / (I x L)

R = Resistance of wire in Ohm/m (should be equal to or less than, from table below and wire can carry required current).
E = Maximum allowable voltage drop in the wiring in volts (0.25v).
I = Current drawn by appliance in amps (= Wattage/Voltage).
L = Length of wire of the complete circuit in metres (count twice - both in and out).

The following equations is useful in finding power dissipated in wire:
P = I x I x R
P = (V x V)/ R
P = I x V

P = power (watts) = heat.
I = current (amps).
R = resistance (ohms).
V = voltage (volts).

Power dissipation over 6.69m length of cable @ 58A.
Resistance per metre from table below. Chassis resistance is negligible.
I x I x (L x R) = P
for 16mm2 cable: 58 x 58 x (6.69 x 0.00115) = 25.9w or per 100mm section 0.387w.
for 13.5mm2 cable: 58 x 58 x (6.69 x 0.0014) = 31.51w or per 100mm section 0.471w.
for 10mm2 cable: 58 x 58 x (6.69 x 0.00183) = 41.18w or per 100mm section 0.616w.

Any cable less than 10mm2 will trip corresponding size circuit breaker (see table below), using the same length of cable.

Tested with 0.1 ohm 5 watt resistor.
0.5w (warm).
1.0w (warmer).
1.5w (hot).
2.0w (hotter).
2.5w (too hot to touch).

Fuses and circuit breakers
There are two types of fuses instantaneous (fast blow), blows immediately when its rated current is exceeded and time delay (slow blow), sustains current in excess of their current rating for a short period before blowing e.g. 70A circuit breaker will trip within 1 minute at 90A load and within a few milliseconds under short circuit conditions.
Fuse current rating should be selected to be 135% of the steady-state current of device.
Cable needs to be sized to suit fuse current rating and able to carry the extra fault current, or else cable will melt/burn before fuse blows.

Cable specifications and maximum fuse rating

Cable specifications (will vary with cable manufacturer and temperature rating of cable)
Nominal area (mm2)Auto cable (mm)Amp rating at 30CMax fuse ratingNearest SAE (B&S) (AWG)Resistance at 20C (ohms/m)
0.22 1.41240.088
0.5 7520.50.03893
0.56275 0.0331
0.75 85 0.02523
1 107.5170.018
1.5 1510 0.012
2.5 2015130.0074
4 3625110.0046
6 4835 0.003
10 846070.00183
13.56 1037060.0014
16 11070 0.00115
20.28 1359040.0009
25 168110 0.00078
25.72 16811030.0007
32 188120 0.00062
32.15 18812020.0006
35 210135 0.000554
39.55 21013510.0005
49.20 24615000.0004
50 246150 0.000386
64.15 2922002/00.0003
70 305200 0.000272

Running alternator at full output for an excessive period of time (more than 15-30 minutes) will lead to burned windings - after 20 hours in the stator and cause premature alternator failure.
The fan at the front or internal of the alternator sucks air through the alternator from the back to the front, ensuring cooler air to cool the internal parts.
The average original equipment manufacturer (OEM) alternator is rated for about a 60 percent duty cycle, e.g. 80A x 0.6 = 48A continuously.
An alternator typically takes about 1 HP (745.7 watts) for every 25 amps of power generated.
How to spot problems with alternators and find solutions and alternator secrets.
Top 5 signs of alternator problems.

In the latest model vehicles, some alternators are ECU controlled and can drop the charge voltage to as low as 12.7 volts. On Toyota Prado turbo diesel 120 series (2/2003 - 11/2009) down to 13.1 - 13.2 volts.

Also vehicles with regenerative braking, have the same problem and can drop the charge voltage to as low as 12.5 volts.
Most battery to battery chargers and electronic voltage sensing isolators/relays (VSR's) connect at 13.2 - 13.4 volts and disconnect at 12.7 - 12.9 volts.
This means the auxiliary battery simply cannot get fully charged or may not charge at all when engine is warm.
Some manufacturers have solved this problem with battery to battery chargers that have both auto sensing and ignition input.

Expect brushes on an alternator to last for in excess of 160,000 km's before they need replacing. So inspect the brushes during the timing belt service.

Christmas holidays 2014, at 144170km main battery voltage was showing 13.2v at idle and 13.9v at fast idle. Managed to get home OK.
Prado 1999 V6 3.4L manual engine power loss, over Christmas holidays 2015.

Brush holder installed over slip rings on Denso alternator, brushes at centre of picture.

Checked brushes (minimum exposed length 1.5mm, standard 10.5mm) on alternator, still 6.5mm left, so good for another 140,000km's. Cleaned out all the dirt/dust and carbon powder, polished copper slip rings with very fine emery paper (cloth damped with methylated spirits probaby would have been better), reassembled alternator, all OK now.
Main battery voltage was fixed at 14.3v from about 100,000km, now main battery voltage varies between 14.3v and 13.6v over time as engine warms up, also depends on ambient temperature.
Pulling the connector out, there was a fine white dust (dirt/dust or dried up dielectric grease?) on terminals could have been the problem or excess carbon powder shorting things out or dirty/oxidised slip rings.

Denso alternator with end cover removed.
Top - diode pack, middle - brush holder, bottom - connector and regulator.

Starter motor.
Petrol engine starter motors (2.5kW - series field DC motor) can draw on average of 200 - 300 amps, diesel engines have a very high compression ratio and can draw on average of 300 - 500 amps.
Amps can be much higher on initial turn over as it has to overcome the inertia of the stationary flywheel/engine.

2500w / 12v = 208.33 Amps
If cranking for 3 seconds: 208.33A x (3 / (60 x 60)) = 0.174 AH

Capacity: 55AH (new battery) at 25C
Peukert exponent: 1.2
Peukert Capacity = 20(55/20)1.2 = 67.33 at 1 amp discharge
Available cranking time = (67.33/208.331.2) x 60 = 6 mins 40 secs (actual time will be less than this, due to initial higher current, age of battery and decreasing temperature).

As you can see it takes very little amp hours (AH) from battery so alternator can quicky recharge battery in a few minutes. Battery just needs to suppy heaps of amps for that short period.

Battery charging efficiency factor.
Battery charging efficiency factor for flooded = 1.25 (80%) or 1.2 (83.3%), GEL = 1.1 (90.9%) and AGM = 1.15 (87%). Restoring the last 10 - 15% of a full charge requires typically 2 - 3 hours.

Peukert exponent.
Discharging at higher currents reduces the total capacity available in battery e.g. 20Hr rate at 5.25A - 105AH, 10Hr rate at 9.5A - 95AH and 5 HR rate at 17.2A - 86AH.

Peukert exponent for Fullriver DC105-12.
Reserve Minutes = 170 min @ 25 Amps.
t1 = 170/60 = 2.833 hrs.
20 Hour rating = 105 Ahr.
I2 = 105/20 = 5.25 Amps.
n = (log 20 - log 2.833)/(log 25 - log 5.25) = 1.252.

Note that Peukert's exponent increases as the battery ages.
The available capacity will decrease with increasing Peukert's exponent value.

Peukert exponent range for different types of batteries:
Flooded batteries, between 1.2 and 1.6
AGM batteries, between 1.05 and 1.15
Gel batteries, between 1.1 and 1.25

T=C(C/R)n-1/In or T=R(C/R)n/In or T = C/(I/(C/R))n X (R/C).
T = time in hours.
C = the specified capacity of the battery (at the specified hour rating).
I = the discharge current.
n = Peukert's exponent.
R = the hour rating ie 20 hours.
C = R(C/R)n = the Peukert Capacity of the battery when discharged at 1 amp.
T = C/In.

Cycle life.
Cycle life (number of cycles) of the battery is dependent on the depth of discharge in each cycle. The deeper the discharge is, the shorter the cycle life (smaller number of cycles), providing the same discharge current.
A battery cycle is one complete discharge and recharge cycle, discharging from 100% to 20%, and then charged back to 100%.
Typical charge/discharge cycle life for deep cycle battery at 100% depth of discharge (DOD) 600 cycles, 50% 1200 cycles and 30% 1900 cycles. Cycle times depends on ambient temperature, charger characteristics, type, model and make of battery.
Cycle end-of-life of a battery is when available battery capacity is 80% or less of the original capacity and replacement is recommended.
Battery capacity (how many amp-hours it can hold) is reduced as temperature goes down (battery life increases), and increased as temperature goes up (battery life is shortened). At freezing, capacity is reduced by 20%.
Discharging to 75% = 0.25 full cycle, 50% = 0.5 full cycle and 25% = 0.75 full cycle.
Battery Bank Ah Rating Required = (Total Ah consumed in between charge cycles) multiplied by 3.57 (28% DOD), to obtain long life out of battery. Normally multiplied by 2 (50% DOD) for the best storage vs cost factor.
A battery that is continually cycled to 5% or less will usually not last as long as one cycled down to 10%.
Full capacity of a new battery is not available until a few charge/discharge cycles have accurred.

Battery Capacity (AH's).
To estimate C20 capacity if unknown:
Reserve capacity (RC) is measured in minutes of a fully charged battery discharged at 25A until the battery drops below 10.5 volts.
If RC is 200 minutes or less, RC minutes x 0.58 = C20 capacity.
If RC is more than 200 minutes, RC minutes x 0.50 = C20 capacity.

Starting Batteries - Flooded and sealed (maintenance free).
Have thin lead plates suspended in sulphuric acid.
Not designed for deep cycling and will result in capacity loss and premature failure due to internal lead plates disintegrating.

Deep Cycle Batteries - Flooded.
Have heavier, thicker lead plates suspended in sulphuric acid.
Designed to be cycled many times.
Capacity has a flatter decline to start with, before losing it quickly towards the end of its useful life.

Deep Cycle Batteries - Dual purpose/Marine (Hybrid).
Have lighter, thicker lead plates suspended in sulphuric acid.
Compromise between starter and deep cycle batteries, so able to be cycled more than starting batteries, but less than true deep cycle batteries.

Deep Cycle Batteries - AGM (Absorbed Glass Mat).
Higher performance than the regular flooded type.
Mechanically strong and electrical reliability, so can stand vibration better.
Electrolyte (concentrated sulphuric acid) is absorbed in a mat of fine glass fibers, this makes the battery completely sealed and spill proof and leak proof. Often known as VRLA (valve regulated lead acid).
Much higher charge rate (up to 5 times higher) compared with a standard deep cycle battery and are sensitive to overcharging, float voltage should be reduced to 13.5 - 13.8V and they do not like heat.
Fewer number of charge / discharge cycles compared to standard deep cycle batteries.
Capacity declines gradually, as the battery wears.

Deep Cycle Batteries - GEL.
Electrolyte (sulphuric acid) is mixed with a silica gelling agent, making them a fully sealed battery and spill proof and leak proof.
Do not like being overcharged > C/20, voids (bubbles) can develop in the silica gel from excess gas which will never heal, causing a loss in battery capacity.
Long service life for deep cycle and resiliency to deep discharge damage.

Lithium batteries (LiFePO4 or LFP ).
Made from non-toxic materials, lithium ferrous (iron) phosphate, aluminum foil, copper foil and graphite (carbon).
They have less weight (70%), smaller physical size, no sulphation problems, negligible peukerts effect (<1.1), 80% discharge NOT 50% rule and longer cycle life (up to 4 - 7 times) than lead acid batteries.
Do not require temperature compensation when being charged and have around 95% charge efficiency.
Lithium batteries do not tolerate over-charge (>15.2v) or over-discharge (<10v), it may lead to reduced life or be permanently damaged, in extreme circumstances cells can vent/swell/burst/explode/heat up/catch fire.
A battery management system (BMS) is highly recommended to prevent catastophic failure due to risk of unbalance caused by small differences in internal resistance or capacity between cells (4) causing one or more cells to become over charged or discharged. This controls a normal relay or solid state relay or latching relay that disconnects loads and/or chargers on out of range conditions.
Some 12v batteries have internal cell balancing on all 4 cells as well as built-in BMS and automatic protection from over charge, over discharge and over temperature conditions.
Have a very flat discharge curve of 12.8 - 12.7v to about 20% capacity left, then around 10%, voltage starts to rapidly fall until fully discharged at 10V.
Require a charger with constant current / constant voltage (CC/CV) charging. Using a pulse charging method (desulfate stage), can have damaging effects.
Still in the early stages of development, but in a few years time when prices have come down, they will be in reach of most people.

AGM deep cycle batteries (20 hour rate C/20 or as specified).
Century C12-105DA (105AH - up to 30A charge current) can not be mounted under bonnet. Every Battery.
Century C12-120DA (123AH - up to 36A charge current) can not be mounted under bonnet. Every Battery.
Century C12-140DA 140AH - up to 40.2A charge current.
Fullriver DC105-12 (105AH - initial charging current 21A) can not be mounted under bonnet. R & J Batteries.
Fullriver DC120-12B (120AH - initial charging current 24A) can not be mounted under bonnet. R & J Batteries.
Fullriver DC150-12 (150AH - initial charging current 50A) can not be mounted under bonnet. R & J Batteries.
Optima blue/yellow top with long life (8 - 15 years) but low AH for size, no current limit as long as battery temperature remains below 51.7C, can be mounted under bonnet. Every Battery.
Lifeline GPL-31T 105AH - up to 262.5A charge current, long life 5 - 8 years, float charge 13.1 to 13.4 volts, can be mounted under bonnet. Every Battery, 5 year warranty (marine and RV use).
Lifeline GPL-31XT 125AH - up to 312.5A charge current, long life 5 - 8 years, float charge 13.1 to 13.4 volts, can be mounted under bonnet. Every Battery, 1 year warranty.
Lifeline GPL-30HT 150AH - up to 375A charge current, long life 5 - 8 years, float charge 13.1 to 13.4 volts, can be mounted under bonnet. Every Battery, 5 year warranty (marine and RV use) and review.
Exide stowaway leisure - gold LCG27-110 & LCG31-120 110 AH & 120AH, can be used in extreme temperatures - Marshall Batteries and review1 and review2.
Ritar DC12-100S (RA12-100SD) 100AH @ 10Hr rate and up to 30A charge current and Alco Battery Sales.
Ritar DC12-120S (RA12-120SD) 115/120AH @ 10Hr rate and up to 34.5/36A charge current and Every Battery.
Ultimate UL100-VO 100AH, can be fitted under the bonnet of vehicles without affecting the warranty and up to 25A charge current.
Ultimate UL110 107AH, should NOT be fitted under the bonnet of vehicles and up to 27A charge current.
Remco RM12-100DC 100AH, not suitable for under bonnet applications and up to 30A charge current.
Hoppecke trak bloc 12TB90 & 12TB115 100AH & 130AH.
Giant Power 105AH & 125AH - up to 27A & 30A charge current.
Absorbed Power GT12-105C 105AH - up to 22.5A charge current.
Vision 6FM100D-X 100AH - up to 30A charge current.
PowerSonic PDC-121100 or PDC-121200 107.2AH &120AH - up to 32.1A & 36A charge current.
Fusion CBC12V105AH & CBC12V120AHS 104AH & 124AH - up to 30A charge current, under bonnet use, hb+ Battery Specialists - Carrum Downs VIC.
Zap NPC105-12 & NPC130-12 105AH & 130AH - up to 21A & 24A charge current.
Bosch BAC12-120RFR 120AH - up to 36A charge current, not suitable for under the bonnet use.
OSTAR OP121050 & OP121300 105AH & 130AH - up to 27A & 36A charge current.
Pro Power 105AH & 130AH up to 27A & 30A initial charging current.
Sentry SA12V105 & SA12V125 105AH & 124.8AH, up to 31.5A & 36A initial charging current.
Kickass 120AH up to 25A initial charging current.
OZ Charge OCB-100-12 98.4AH.
OZ Charge OCB-110-12 98.4AH.
OZ Charge OCB-120-12 107AH.

Narrow sleek profile (slim design - for compact spaces) deep cycle batteries - front mounted terminals.
Remco RM12-100FT 100AH @ 10Hr rate and up to 30A charge current.
Remco RM12-110FT 110AH @ 10Hr rate and up to 33A charge current.
Remco RM12-150FT 150AH @ 10Hr rate and up to 45A charge current.
Ritar FT12-105D 105AH @ 10Hr rate and up to 31.5A charge current.
Ritar FT12-110D 110AH @ 10Hr rate and up to 33A charge current.
Ritar FT12-125D 125AH @ 10Hr rate and up to 37.5A charge current.

Flooded deep cycle batteries.
Century N70T 100AH.
Century 89T 115AH.
Exide industrial DC12V105 and DC12V115 105AH and 115AH, vibration resistant, for extra heavy cycling duty.
Exide endurance ED6 and ED7 98AH and 125AH, built strong to withstand the pounding and vibration of 4WD, tech anti/anti.

Gel deep cycle batteries.
Fullriver DCG102-12 102AH.
Gel Tech 8G31DT 98AH.
Gel Tech 8G5SHP 125AH.

Hybrid batteries (dual purpose/marine - both starting and deep cycle).
Deka Intimidator/Seamate 8A31DTM 105AH AGM - unlimited current recharging at regulated voltages and durability in harsh environments and temperature extremes. Every Battery.
Exide marine stowaway MSDC27 and MSDC31 110AH and 120AH AGM - Marshall Batteries.
Exide MegaCycle AGM 200 MC-31 and XMC-31, both dual terminal design and 100AH - spec's.
SSB HVT-70ZZD & HVT-86D AGM 105AH and 130AH, max charge current 29.4A and 36.4A and are suitable for under bonnet use and review1 and review2, hb+ Battery Specialists and Independant Battery Distributors.
E-NEX DC31MF 100AH AGM, very poor cycle life (about 250 at 30% DOD) compared to XDC series (about 750) and other major brands (1250+).
Century Marine Pro 730 (Supersedes Marine Pro 720) 100AH - flooded.
Century Marine Pro HD 110AH - maintenance free.

Fuel cells.
EFOY fuel cell - runs on methanol, very expensive.

Lithium deep cycle LiFePO4 batteries.
SP-LFP-100/200/300AHA 100AH, 200AH & 300AH and up to 33A, 66A & 99A charge current.
AA Solar 40 - 300AH and up to 0.5 x rated capacity standard charge current, 10 years warranty and life expectancy of 15 - 20 years.
ev power - 100AH.
ev Works - Winston (ThunderSky) batteries.
The Outback Buddy - 100AH.
Fusion V-LFP-12-100 100AH and up to 50A charge current and All Purpose Batteries.
Revolution Power Australia 100, 150 & 200AH and up to 50, 70, & 80A charge current.
Pro Power 100, 150 & 200AH and up to 50, 75, & 100A charge current.
Sentry SL12V100 & SL12V120, 100 & 120AH and up to 50A charge current.
REC - Battery management system (BMS).

LiFePO4 battery to battery chargers.
Enerdrive DC2DC+ ePOWER charger 50A (adjustable 5/10/15/20/25/30/35/40/45/50A), with MPPT solar and short review.
Redarc 25A & 40A, with MPPT solar.
GSL NGBC1222 & MCB-1225L 22A and 25A, no solar.

Battery to battery chargers with solar input.
Enerdrive DC2DC+ ePOWER charger 50A (adjustable), LCD display (optional remote display), remote temperature sensor, program (custom settings), operating current 50/70mA, ignition or voltage sense, two totally independent DC inputs for alternator and solar MPPT - 12 Volt Technology or Australian Direct or Arnolds Boat Shop or Batteries Direct or Keoghs Marine.
Redarc BCDC1240 40A with solar MPPT (requires up to 55A input @ 10.5V) or BCDC1225 25A with solar MPPT (requires external 60A SPDT relay to connect solar - relay kit or Jaycar SY-4074, no load current < 100mA, standby current < 8mA (ign off), other models, good report and install.
Redarc BMS1215S2 15A, AC, DC and solar MPPT battery management system or BMS1230 30A, maximum charge current set by user, AC, DC and solar MPPT inputs.
ABR Sidewinder 30A dc to dc charger MK2, adjustable bulk/absorption and float voltages, ignition activation option, solar compatible.
ABR Sidewinder 30A dc to dc charger MK3, adjustable bulk/absorption and float voltages, ignition activation option, dual inputs for solar and alternator.
Amperor Power Integrator 25A, MPPT solar 100w+100w, operating current 90mA, standby current 20mA, product review.
Matson MA20DCS with solar (120w min) 20A, quiescent current <10mA, ON at 13v and OFF at 12.2v.
MP3742 Powertech 4 Stage 30A DC to DC buck/boost charger, programmable cut-in/cut-out and charge voltages with MPPT solar controller. Not released as yet.
interVOLT DCC Pro 25A, standby current <10mA + 10mA (remote display), remote LCD display and separate MPPT solar input.
Projecta IDC25 25A, standby current main 20mA/aux 9.5 - 10.5mA, remote temperature sensor and separate MPPT solar input (operates simultaneously with alternator input).
CTEK D250S Dual 20A - poor performance issues on solar.

Battery to battery chargers with no solar input.
Sterling battey to battery chargers BB1250, 50A model, sleep current draw 5mA, RV Powerstream Pty Ltd.
Sterling battey to battery chargers BBW1260 and BBW12120, 60A and 120A, sleep mode current 5mA.
Sterling Pro Charge B BBW1212, 20A, sleep current <1mA, USA on line store.
Redarc BCDC1206 & BCDC1220, 3.5 - 6.5A and 20A, standby current <150uA and <5mA.
GSL Electronics 12v to 12v battery charger 25A.
RanOx DC to DC multi stage battery charger/booster, adjustable output current 5 - 25A, adjustable bulk/absorption and float voltages, quiescent current < 10mA (not available anymore).
Projecta DC20 3 Stage Automatic 12V to 12V 20A battery Charger.
Motormate 4-Stage DC-DC Chargers, SDC series, 20, 30 and 40A.
Matson MA20DC (120w min) 20A, quiescent current <10mA, ON at 13v and OFF at 12.2v.
Powertech 4 Stage 40A DC to DC Boost Charger, 8-16VDC input voltage.
Votronic VCC 1212-25 IUoU & 1212-45 IUoU 25A & 45A.
Arrid Twin Charge BCTC20 and Twin Charge Gen 5 BCTC255.
Power Train DC to DC battery charger 20A.
Victron Energy 50A buck-boost DC-DC converter, charging a 12/24V service battery, quiescent current 7mA.

Solar regulators.
Roc Solid solar regulator with MPPT PS-2024-D 20A with LCD display, use 12v or 24v solar panels, sleep current 9mA, good report on them or PS-2012-BC 20A, smaller, cheaper and no LCD display, can only use 12v solar panels, temperature compensation sensor for both models is extra.
Morningstar Sunsaver MPPT 15A, self-consumption 35mA.
MPP Solar PCM 2012 20A or PCM 3012 25A MPPT controller, standby power <1W (~80mA), review and youtube.
Avoid Wellsee MPPT solar controller - no toroid core (doughnut looking transformer), just an open air inductor, beware and aren't MPPT.
SolarMate (also rebadged as other names) charger controller MPPT1224-40 - only a PWM regulator, under 1.5 in manual "if insufficient PV power is available" (tested with 200w solar panel), self consumption over 160mA, they claim < 10mA, beware and isn't true MPPT.
Powertech 12v/24v 30A MPPT solar charge controller MP-3735, new model now includes external temperature sensor, <50ma idle current, beware.
12V/24V 120W/240W 10A true MPPT solar regulator with modified software, also known as tracer 1210 with original software, other tracers, self consumption <10mA(24v).
Juta solar charge controller MPPT-20 and inside unit and review
GSL Electronics solar regulators, quiescent current 40mA and review.
List of charge controller manufacturers.

Folding solar panels.
120w folding solar panel with waterproof MPPT solar regulator.
Flexible roll out 68/136/200w solar panel kits with 20/25A PCM-2012/PCM-3012 MPPT charge controller, rolasolar on youtube and review.

Battery monitors.
Nasa BM1 compact LCD display battery monitor and BM-1 battery monitor and BM-2 battery monitor, consumes 1.5mA.
Digital DC power meter (similar to Turnigy, Watt's Up and Doc Wattson meter's) MS-6170 20A or MS-6172 0 - 200A requires 50 mV external DC current shunt, consumes 8.5mA/12mA peak, only measures current in one direction, USB data adaptor.
Enerdrive battery monitors - eLite and ePro, consumes 9mA.
Xantrex LinkLITE and LinkPRO, consumes 9mA.
BMS-001 Diverse battery monitor, consumes <3mA.

Battery chargers 240v.
Projecta Pro-charge - manual rejuvenation mode, normal (14.4v) and calcium (14.7v) battery type, float (13.7v), select charge rate and 6 stage.
Projecta intelli-charge - auto rejuvenate cycle, select chemistry type, power supply mode and 7 stage.

Electronic voltage sensing isolators.
Piranha DBE140S and DBE180S.
Redarc smart start SBI.
Projecta 100 and 150A, standby current 30mA.
Enerdrive, 13.3v engages, 12.8v disengages and dual sense.

Portable power.
Ark portable power.
Ecoboxx portable solar generator.
Solarpod 240, Buddy and Pro 1000.

12v dc to 230/240v ac true/pure sine wave inverters.
Sinergex 300w, 72 - 91% efficiency and 0.23A no load current draw.
Powertech 200w, >86% efficiency, <0.75A no load current draw.
Powertech 400w, >86% efficiency, <1A no load current draw.
Projecta 300w, 85 - 90% efficiency and 0.5A no load current draw and review.
Victron 350w, 89% efficiency and 0.26A no load current draw.
Latronics 500w, 90% efficiency and 0.42A no load current draw.
8zed 150w with USB port, 'cup style', 90% efficiency and USB output of 5VDC at 2A.
8zed 300w, 90% efficiency and <0.7A no load current draw.
Exeltech 250W, 85 - 87% efficiency and 1.1A no load current draw and spec sheet.
Xantrex Prowatt SW - International 700W, 90% efficiency, <1.0A no load current draw.
Xantrex Prosine - International 1000W, 90% efficiency, <1.83 idle mode / <0.125A search mode no load current draw.
Morningstar 300W, 84 - 92% efficiency, 0.45A no load current draw, 55mA standby current draw and inverter off 25mA.

12v dc regulated car power adaptors.
12VDC 3, 4.5, 6, 7.5, 9 or 12VDC 1.5A Car Power Adaptor.
12VDC 3, 4.5, 5, 6, 7.5, 9.5, 12VDC 3A Car Power Adaptor with USB Outlet 5v 1A.
Digital Car Power Adaptor 1.5/3/4.5/5/6/7.5/9v 3A and USB 5v 500mA.
60W Regulated Car Power Adaptor 5, 6, 9 & 12V 5A.
5v 1A USB Car Adaptor.
Cup Holder Power Extender with Dual USB Sockets 5v 1A and 0.5A.
11 - 28V to 12v 6A.

Charge Equalisers.
Redarc charge equaliser on two battery 24V negative earth, 3 - 60A.
GSL REC-1240 and REC-1260, 40A and 60A.