Stereo battery question adding battery
 

Doing some additional stereo to new to me cafe
currently has [2] group 31 batteries
adding 2 pair extra speakers and a 800 watt amp [already has a 400 and 300 watt amp to run current speakers
wanting to add a extra battery
whats the best way to do this
1. Run 2 batteries together to run the stereo while parked [house side] and have 1 battery to crank engines [maybe using blue water isolater ?,to keep from running it down.]
dont want to have to move battery switches every time i park for a bit, also where when running engines would charge all three?and not pull from cranking battery while parked

Any ideas would be helpful

Run one isolated battery for stereo (or two if desired), put under rear seat. Let the two batteries in the engine compartment run everything else (engines, house acces., etc.). Stereo battery charges while engines are running or plugged into shore power.

I don't think you want to add just one battery to crank both engines. If that battery goes down, and you've already sucked all the juice from the stereo batteries, you are dead in the water. That's why you have a Port and Starboard battery in case you have to connect them to crank over the engine that has a weak battery. (Emergency start)

More than one way to scratch the cat, however having isolators before I would (and probably am) upgrading to a VSR. Voltage Switching Relay. Do a google search (search term: Marine VSR)and look at the two manufacturers being used mostly. ( DEP and Blue Sea Systems) to see reviews and which you may like better. Quick glance I did a month or so ago kind of pointed to the Blue Sea, but don't take that as fact. LOL.

Hook stereo to it's own battery - the VSR will charge it, and will keep it disconnected from the starting battery it is connected to when charging) . Leave everything else the way it is.

Starting and Deep cycles (if you go this route with batteries) can be mixed when charging from same alternator, but, they must be of same construction...meaning, Lead Plate with lead plate, AGM with AGM, and etc,etc.

ok say i add a extra battery just for stereo, do they last a good while if parked? one of those big group 31 agm's

I installed a whole new stereo system last year including a house battery for the amps. I installed a Blue Sea Systems - Automatic charging relay

https://www.bluesea.com/products/761...12_24V_DC_120A

to have the house battery charged by my starboard engine. I've had very good results with it. It basically combines both batteries in the same circuit to charge from the running engine and will isolate them automatically when either battery's charge falls below a certain voltage. This prevents one battery from taking down the other when it drains. When adding a house battery, I would also recommend adding a circuit breaker near the battery itself; this is an important safety measure in case something happens to the line from the house battery; not good to have stray voltage in gas filled spaces. This ACR will also isolate the batteries when it detects a draw on the starter solenoid, so you will only be starting from your main battery. Also has the ability to add a remote LED indicator so that you can see what state the ACR is in. It is pretty straightforward to install but you need the right fuses and size wiring for your application.

Awesome post HyFive

I may add this unit to my circuit.

Yep - just get a Blue Seas Add A Battery kit, a battery, battery box, and you're all set. It's the best way to go. I did this a year or two ago, and it works out quite well.

thanks for the help ordered the blue seas kit