Also in regards to charging, I read that I need to be mindful about having the switch on battery 1+2 while charging because I may risk overcharging a battery. is that correct?
Correct, It isn't always best practice to charge battery's in parallel due to many factors, hence, many bass guys and the like that use 2,3,4 battery's created a need and POOF, eng's came up with the concept/inception of quad/triple/dual output on-board chargers.
Even if the battery's are identical, when paralleled, one/many battery/s can mask the needs of the other/s, not to mention they typically have to equalize/back charge(one discharges into the other if/when the alt/supply voltage sags/drops out at parallel time) when paralleled wasting power that might be needed.
Isolating each battery at charge time is a better method(see quad/triple/dual output on-board chargers)
and individually allows them to charge with their own needs/rates and can more accommodate individual variables that can dictate each batterys varying charge rate needs such as ambient temp of the batt, cell temps, dod, series resistance to name only a few.
So as far as charging while running, ACR's and the like always have to parallel battery's to charge the secondary/slave "house" battery and Perko battery switches parallel them as well in the "1+2" setting.
I personally prefer not to use either method above as some might and use a system that employs the same techniques that is essentially how the quad/triple/dual output on-board chargers are designed to and are working.......
I use what I deem a
smarter charger that breaks each batt out individually as needed, doesn't require paralleling (but does only when all batts are topped off), doesn't allow back charging and of course, isolates them automatically when ig is off!!.......Used this now for 4'ish yrs and it works well for me and my needs as I run 3 batts (2 house, 1 engine) with a 40 amp alt.
