multiple batteries???
 

ok my boat was formerly setup for 2 batteries. BUT i am thinking abtou putting some stereo gear in it. Along the lines of 4 subs and 6 mid/high range speaker. I would think this much stereo gear woudl kill one battery pretty quickly. Can i add mor ethan 2 batteries? I was thinking about 4 total. @ starting battery and 3 to power the stereo while the engine isn;t running.

Can the alternator charge 4 batteries? I don't have or use shorepower so the alternator would be the only way to charge them. I would be using 4 of the same batteries (west marine dual purpose).

As for hooking them up I figured i'd use the #1 switch for us the startign battery and then hook up the other 3 batts to the #2 part of the switch. Start on #1 and run on "all" to charge all the batteries and ewhen i'm chillin without the engine running go to just #2 for stareo power.

Will this work or will i just cook my alternator?

You can use bigger batteries instead of more, but yes you can increase the number too. Take a look at the "house" battery setups for cruisers or large fish boats for ideas.

-Greg

Your charger can only charge at a set maximim rate no matter how many batteries. Having a lot of discharged ones will just result in it charging a longer time and having to work harder. You might consider a higher output alternator, greater than 50 amps, but I'm not sure who makes a marine unit.
You could run an isolator. It's just a couple diodes on a heat sink that costs about $30. I've got my stereo power amps hooked to 2 batteries that are isolated from the starting battery on that side. No extra switches, everything takes care of itself, no problem starting.
Gary

do you by any chance have a wiring schematic for the isolator setup?

i think that is the way i'm goign to go. As for my alternator i'm pretty sure I bought an 80amp alternator when i replced the origonal one.

Sorry, no schematic, it's too simple. There are only 3 posts on it (input, output 1, and output 2) When you buy one, it will have a wiring diagram. It splices in the output wire from the alternator. One isolator output lead goes to the original battery, the other to the accessory battery(s). You then wire the stereo amp directly to the accessory battery. It will allow the alternator to charge both but not the accessory to drain your original starting battery.
Gary

Are you talking about a schematic for hookup or for the actual componants of the isolator, cause I'd thought of building my own before and as Gary said its too cheap to waste your time making one. my .02

hookup not biulding my own. What abotu if i want to put in a switch so in case i kill my starting battery i have the hosue batts as an emergency backup?

overall it seems pretty simple.

Yep.
3 batteries together as Bank "A"
1 separate battery as Bank "B"
Both banks hooked to a switch.
Switch output goes to all normal boat stuff that currently exists.

Bank "A" (the triple bank) has all stereo amplifiers wired directly to the batteries. Can also wire the "clock" wire to that bank on most head units, this will keep the station memory and internal equalizer settings intact ("Some" brands of head units will allow voltage leakthru on the clock circuit and should be avoided, else you can end up popping clock wire fuses). ** The head unit itself will remain wired to the boat's normal 12v circuit **

An isolator with outputs hardwired to the two battery banks.

Now you can run all the time on bank B (the single) for boat stuff. The jams will run off bank A (the triple). Your alternator will charge both banks ar needed, and you reserve the option of powering the boat off bank A if battery B goes tits-up.

You may or may not wish to wire courtesy lights and refrigerators to the stereo amp circuit. Depends on how you plan to use those items.

i was actually planning on runing only engine power and trim pumps off the starter battery.

Everything else will be run off the house bank. My dash has a switch specifically for "stereo" i was planing on putting a big for the stereo amps so they are only on if the switch on the dash is on. I've killed plenty of batteries and gotten manya juimp start with the old wiring setup i'm tryign to make this one more idiot proof. I'm tired of having to bring a 12v jumper pack with me all the time.

Okay, good plan. Promise me, though, that you will leave the nav lights connected to the common "out" on the batt switch. They need to have access to power regardless of which battery is still living.

I know too many people that have been on the raw end of a nighttime boating incident that involved one or more sets of navigation and/or anchor lights that were not functioning for one reason or another...