Jeff Durham wrote:

In my boat, I have a dual onboard battery charger. One side is connected to
my engine battery. The other goes to my trolling motor battery. With
regards to my trolling motor, what happens if I hook up another battery in
parallel to my trolling motor battery? My trolling motor is 12V and by
hooking up in parallel, I still have 12V.

My question has to do with how the onboard charger from one side would
charge those two batteries hooked up in parallel. Is it possible that if
one battery is not as full as the other, that the charger would "cook" one
battery too long? Keep in mind that I am only talking about the two
batteries hooked up to the second output of my charger. The first output is
hooked up only to my outboard battery.

Thanks,
Jeff

An interesting question. I just talked to John at Charging Systems
International and he says that this hookup will not hurt the charger,
but the second battery will not be charged. To use a 2 bank charger to
charge 3 batteries will require a double pole double throw switch in one
set of electrical leads to allow you to mechanically switch the leads
from one battery to the other. I don't know what brand charger you have
but this company has a trade in policy for upgrading to a 3 bank unit.

I have no connection with this company, but I live close to the plant
and have been a satisfied customer for many years.