Will this battery set-up work?

[scottiekarate17]

So i've just installed some tower speakers and light on my boat and want to put another battery. I've been reading a lot of the forums and really don't know much about electronics so i get very lost very easily in the forums. I was wondering if this would work to hook up my two batteries?

http://cgi.ebay.com/SPLIT-CHARGE-RELAY-KIT-12V-INTELLIGENT-SELF-SWITCHING_W0QQitemZ200299014169QQcmdZViewItemQQptZUK_Campervan_Caravan_Accessories?hash=item200299014169&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50

If that link doesn't work just ebay split charge relay kit and it will come right up.

Thanks

[Brit Rider]

Yes this will work fine.

The way it works is very simple and the ebay auction kind of bigs up and over complicates what is effectively a very straight forward circuit.

Basically there is a relay (automoatic switch) in between the batteries. When the boat is running, both batteries get charge from the alternator. when you turn off the ignition then relay opens (like tunring a switch to off) so that no current can pass between the batteries. one is totally isolated and all alone - you can't draw power from it. whilst the remaining battery will run all your electricals/stereo.

When you are ready to start the motor again, your stereo battery may well be dead, but its not a problem as when you turn the ignitio key, the relay snaps closed and lets power be shared between the batteries once more - thus the starter motor is able to get power.

This is a very cheap and effective way of having an auto split charge kit - but be aware: there are pitfalls to it. If you run the stereo battery allt hew ay down, or have a bank or stereo batteries - it will be hard work on your alternator to re-charge them all and could lead to shorted alternator life. The other issue is that once you turn the key, the power from your starting battery is shared with the dead batteries, thus will lower its output. This is not generally a big problem though so long as you don't run more than 3 batteries and so long as your starting battery is a decent quality - I'd recommend you run 2 optima yellow or blue tops.