First I am no expert on the subject, however, I have been following this thread and have watched numerous videos on the subject, mostly posted by Australians, and best I can figure is a lithium service battery will provide significantly more runtime for accessories than the included second battery which it seems is primarily a backup to main starting battery. Therefore, I think a dual purpose lithium battery, which is also designed/capable of starting the vehicle, will be a better option than the included second battery or a lithium battery which is not able to start the vehicle. My plan is to have a professional install this type of battery and run all my accessories, including a refrigerator/freezer, and some of the power outlets on the roof off the service battery isolating the starting battery to simply start the vehicle.
Good answer
The main difference between a Lithium and a LeadAcid is that the Lithium can accept a larger current (so charges faster) and can delivers more current (discharges) for longer.
This ability to last longer is called the
DoD (Depth of Discharge).
LA batteries are happy with a C/10 delivery rate, so a 110Ah battery will discharge happily at 11A and will also be happy to charge at 10 to 11 Amps.
Any more and they can be damaged.
Lithium batteries are typically C/2 so you can suck 50% of its rated current out and charge at 50% too, some Lithoium batteries can accept a C/1 charge/discharge rate, but not for long.
LA batteries don't like the cold either
Back to
DoD. LA batteries are in the 25 to 40% range.
If you discharge to 25% and then recharge, it will last considerably longer than if you discharge to 50% before recharging (more than twice as long).
Lithium doesn't suffer from this effect and typically has a DoD of 80%, above this and the curve of death gets a bit steeper.
In short a typical lithium battery can have 5000+ cycles at up to 80% DoD. That’s 4x the cycles at over 3x the DoD. That’s a much longer lived battery.
However ... (there's always one of these).
To charge a lithium battery you have to be a lot more careful than with a LeadAcid.
Because they have a lower internal resistance the Lithium battery can 'demand' a lot of power which can damage the alternator and potentially let the smoke out of the wiring/charging circuit if the current exceeds its nominal rating.
To overcome this you need to have a current limiting DC/DC convertor between the alternator and the Lithium battery and a charging circuit that can cope with the expected current.
The recommendation is 50% of the alternators capacity, so a 100A alternator would need to be limited/shunted to 50A and the charging circuit wiring would need to be able to handle that current with a safety margin...
The other issue is that you need to control the input (float/charge) voltage to be below 14V, again a specificaly designed Lithium battery DC/DC charger is needed.
