Help: Dual Batteries for 2000 21i

[scottie4421]

I purchased a second battery and a West Marine Battery Combiner for my 2000 21i. I'd like to run the stereo off of the second battery, but I'm not sure how to wire it.

I noticed there are 2 positive wires going to the starting battery, 1 huge one, and 1 small one. At first glance, I thought this would be simple case of installing the second battery and combiner and wiring the huge cable to the starting battery and the smaller cable to the house battery. However, the stereo is somehow wired to the huge starting cable. I know this because I connected only the small wire to the battery and attempted to turn the stereo on....no luck. I then attached the huge wire and tried the stero.....wallah, there was power.

So, I need to figure out how the stereo is wired into the starting power, disconnect it, and wire it into the second battery.

Any help would be greatly appreciated! Pics would be great as well!

Thanks a ton!

- Scott

[Domsz06]

i'm guessing what the setup is that you should have a battery switch. The switch controls all of your boat's electroinics. I know on mine I have the big wires going to the switch. If you want to look at the back of your switch the power wire should be connected to the accessory terminal. I'd have to see pics for sure, but that's just my guess, it's how mine is wired in. The switch allows me to switch from one, two or both batteries. Run your ground to your battery, always best to run the ground back to the batt. If you need more help pm me and we can chat, or mail me at ellobo97@hotmail.com

Dom

[Tige M.D.]

your stereo head unit is most likely getting power from the dash area, ign. switch, acc power... if this is the case then you will have to rewire the head unit to take power dirctly from the house battery. if there are amplifiers in this system then the smaller of the two red cables is probably powering them.

hooking up the switch is easy. first decide which battery will do what. on the back of the switch there 3 posts. 1/a, 2/b and common. hook up your start battery cable to 1/a, your house battery to 2/b and the cable that goes to the starter to the common. take a black ground cable and connect it to both battery negative posts. there is probably a small red wire also hanging around back there. that is your auto bilge pump wire. hook this directly to your strongest battery. this way it will still work with the batteries turned off.

if you do this right with the switch off nothing will work but the auto bilge. position 1, 2, or all will start the boat. position 2, or all will power you stereo. DO NOT SWITCH positions while the engine is running. it wil kill your alternator.

if there is no amp then that smaller wire could be the auto bilge wire.

[Tip]

Greg,
Thanks for the warning not to turn the switch with the engine running. I've never done it, but I would never have thought it could damage the altenator.

[Tige M.D.]

what it does is cook the diode out of it. it will let the battery discharge through the alternator.

[scottie4421]

Thanks a lot for the suggestions fellas.....

[scottie4421]

I finally got the batteries installed and wired up. It works great!

I went with the Off/1/All/2 Perko switch and West Marine Battery Combiner setup. I wired the starting cable to the COM (common) terminal on the Perko switch and wired the positives from each battery to the 1 post and 2 post on the Perko switch. The 1 post is my starting battery and the 2 post is my accessories/backup battery. I wired the negatives from both batteries together using a negative battery cable, and tied the negative cable from the boat into this as well.

The Battery Combiner is hooked up according to it's instructions. It's simple, just hook each red wire to the positive on each battery and the negative to the negative on one of the batteries and you're all set.

I tested the whole thing out and everything works perfectly. Now I can switch between battery 1 and battery 2, and the battery combiner takes care of charging both batteries when the engine is running, regardless of which battery is being used as the starting battery.

If anyone else is interested in doing this, you'll need:

1 Perko switch (Off/1/All/2)
1 West Marine Battery Combiner
1 Battery
1 Battery Box
2 positive battery cables
1 negative battery cable
4 self-tapping screws for mounting the Perko switch
2 self-tapping screws for mounting the Combiner status LED

Be sure not to swith the Perko to OFF while the engine is running, this will toast your alternator.

Thanks a ton for the help!

[PColucci]

Clarification:

On the Perko switch, the 'Both' option sits between 1 and 2 (and there is connection the whole time switching from 1 to BOTH and from BOTH to 2). So you CAN switch them while engine is on, correct?? (the alternators current will always be flowing to one or both of the batteries).

the important thing is TO NOT MOVE THE SWITCH to the OFF position while running, correct???

Thanks,
Paul

[tigetek]

no, the switch contacts do open between positions. there are switches that can be wired to allow you switch while the engine is running. be sure to read the instructions carefully when doing this. it can and will cause you headaches.