Running Batteries in Parallel
 

I decided to upgrade my house battery for my stereo and decided on a XS Power XP950 due to having a modest stereo. After receiving, I realized I can turn 2 XP950's sideways and secure in the factory location. I would also like the benefit of longer playtime while anchored. Just wanted to make sure there were no long-term issues with running two small AGM batteries in such a configuration.

Speakers:
Six Polk 6 1/2's
Two Rev 10's
One 12" Alpine Type-X

Amps:
Polk 5000.5
PPI 950
PPI 1000.1

Any help is greatly appreciated...Thanks!!!

The biggest question is "Can your alternator keep up with the draw?" If not, dual batteries won't help. You can wire the batteries straight parallel but the more common method for marine setups is to wire stereo and maybe accessories separate from the starting system and use a manual switch, isolator, or relay to prevent the starting battery from getting run down from the stereo running. In my setup I ran the stereo and a fuse panel block for things like ballast pumps on a second battery and it's wired parallel via a continuous duty solenoid to the starting battery. That way even if my stereo drains the battery, I can still start the engine but at the same time when the engine is running both batteries are being charged. As far as long term goes, straight parallel wiring is slightly better for the batteries since they'll both discharge and recharge at the same rate. I don't know if it's a big enough issue to worry about though. There are diagrams online for a wide variety of dual battery setups depending on budget and what you want out of them.

I replaced my alt with a 250 amp HO marine alt

Boat is a 2012 Super Air Nautique 210 so it already has dual batteries on a perko switch. Instead of having a single house battery, was going to use two XS XP950's which together are the same size as a standard group 24.

I bet that PCM has a 90A alt. Dont see those amps being an issue for that. However, with these being only 35 Ah each, combined they are about same as a typical group 24. I dont see the alternator knowing the difference and no more play time either. Seems like a $260 investment for a net zero.

Yes, you can wire 2 batteries in parallel on one side of your dual bank switch.