I have twin 502 motors and 2 batteries, one for each motor. I want to add a third battery to run my stereo off and hook it up so that I can recharge the battery when under power. How and what type of switch do you add to hook up the third battery?

The Perko website has a diagram and there have been multiple postings -- do a search for battery switch--

Buy an isolator. It will allow 2 alternators to charge 3 batterys without any switches or crossconnection problems. Let each battery start each engione as you have now and use the 3rd battery for house use. Email me if you want a diagram or more info.

Formula31 - I would like to have a copy of that wiring diagram. I want to install a third battery to supply a power inverter. Thanks

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Will do, snowing like a bandit right now and I have to get it out of the boat.

This is a good site for info. http://www.surepower.com/pdf/180119A.pdf#search='sure%20power%20battery%20isola tor'

http://www.surepower.com/pdf/180119A.pdf#search='sure%20power%20battery%20isola tor'

I like using a battery combiner rather than an isolator. Battery combiners are inexpensive and very reliable. Everything you need to know them can be found here:

http://www.yandina.com/combInfo.htm

Save yourself some money and use continuos duty relays. Cole Hersee makes a plasticized marine version for ABOUT $40.00. (part # 24117) They can be activated by key or oil pressure switch. Just connect then in between each engine battery and your third house battery. The house battery will be recharged from either engine while under way. This system has worked great for me and hundreds of my customers.

I do not like isolators in most applications. If one opens up, you will have three dead batteries, and possibly a ruined alternator because of it. If a Continuos duty relay dies, you will stil be getting a charge from the remaining relay, and it will not effect the engine battery in any way.


Steve Hixson