I have two 12 V, 200 Ah batteries (deep cycle lithium) that I use as auxiliary batteries for my van conversion (total 400 Ah). I connected the batteries in parallel, but made the mistake of connecting them incorrectly to my inverter/charger - the positive and negative leads that are going out to the inverter/charger are coming from the same battery, instead of the positive from battery1 and negative to battery2.
Can this cause damage? I've been running things like this for 6 days, and only realized my mistake because I ran out of power in half the expected time. Also, what exactly is going on with this false setup? Am I only using power from one of the batteries? I just charged the batteries via shore power (still with the same incorrect wiring), and the system read out went from 10.2 V (dead) to 13.2 V (..overcharged? problem?) in only 45 minutes... which seems way too fast even for one 200 Ah battery (though I do have a great charger that was pulling about 80 A). Clearly I'm a bit of a noobie, so any comments or words of caution are warmly welcomed!!