Originally Posted by Blackhat6mike
Doesn't matter how many batteries you have as the converter is only going to produce just so much power to the batteries. More batteries only means the converter will run longer..
Well that may true in some cases but it is also false in others.
Wet cells have about a 20% of capacity limit ...regardless of the size of the charger.
If you have a single group 31 battery with a 100 a/h capacity...it can take about 20amps of charging current. Lets say you have a fairly standard 55 amp charger... it will only be working at 20 amps in bulk mode...adding another of the same battery...will allow it to work at 40 amps charging current ...still well below capacity. Charging 2 batts will not take any longer than charging 1.
Now if you had a charger that could not supply 20% of the a/h capacity of the new bank... then it would take longer to charge 2 batts than one.
As a practical matter...if you stay plugged in most of the time this is no big deal...but if you boondock and charge via generator...you want to size your bank/charger system @ 20%+ of capacity to avoid longer generator run times.