We have a battery powered heating/cooling unit in our truck which is powered by 2 x 25.6v 5kwh lithium batteries wired in parallel. The batteries are charged from the vehicles 160A alternator via a 30A charger.
This gives around 16-18 hours of run time but we would like to increase that as sometimes the truck is parked up for 2 or 3 days and we quickly run out of power.
Could we add an additional battery to the setup without causing any issues?
I was thinking of adding an 300AH deep cycle lithium battery as this would basically double our capacity but not sure if there would be any issues?
As a general rule it’s best to only parallel identical batteries, preferably from the same age or with the same amount of cycles.
When mixing batteries, depending on specs like internal resistance, the system will not draw or charge the same amount of power from the different batteries. This can lead to premature failure of the batteries.
I parallel all my 12V lithium. I have 50Ah up to 340AH for a total of 10kWh. Some are a year old, some are 4 or 5. I charge and discharge them via ESS every day they are in the shed. They are individually fused and connected to a busbar. Everything works totally fine. They may charge and discharge at different rates, and some may do more cycles, but I dont really care. I capacity test them once in a while, they are all Anderson connected, so easy to remove and use them when required. If you really are interested in what is going on, get one with a BMS that you can check SOC and cycle count or add a shunt to ea battery.