Adding another battery

Ok i got 2 batteries currently, one for the motor and the other on an issolator for the stereo and acc. So how do I add a third for the stereo. Another issolator or some kinda switch. I have seen what I'm looking for but for the life of me i can't remember who makes it or what its called. Help a brotha out!!!

Just buy the exact same battery as the one you have for the stereo and hook it together in paralell. the 1 is for starting 2 has both batteries for stereo, will last 2x as long. then "all" will charge all three when running.

You may be looking for a "battery combiner", which is essentially an automatic battery switch.

Rod i think thats what it is any company you know of that makes a good marine one?

try www.hellroaring.com

West marine sells a combiner. There was a previous thread in March with a link to it on westmarine.com. The link even showed the wiring diagram. They are kind of pricey (about $80). I got one and also put in three separate on/off switches for just two batteries.

I just put in a setup that works great. I have one battery for starting the boat, and two other 6 volt golf cart batteries run in series for the house power (stereo and everything else). When you run two 6 Volt batteries in series it essentially acts like one big 12 Volt battery that can run a 25 amp load for 7.5 hours! These batteries are great because they are made to be run all the way down, then charged back up. For comparison, one typical group 24 deep cycle battery can only run a 25 amp load for about 2 hours.

The starter and house battery banks are isolated using a West Marine Battery Combiner. It ensures that one battery is used to start the boat, but that battery can not be drained by the stereo or other DC loads when the boat is off. When the boat is off, only the two golf cart batteries are drained. If you take this route it's also a good idea to have either one switch, or three on/off switches for better control. It's a great way to go.