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Old 18-06-2015, 01:21   #1
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Charging dual batteries - 6V in series and 12 Volt

Hello all,
I have just had two new Yanmar motors installed in the boat (Lagoon Catamaran) The issue I have is that the wiring was disconnected by the mechanic prior to an marine electrician being able to check the wiring. Now I do not have any charging to my house batteries where as before both battery banks would be charged by the running of the port motor.
Now the starter motor battery is being charged by the alternator but the house batteries are not being charged. The question I have is while the system was operating fine under what ever system was connected previously what is the best system to use now. My concern is that as the house batteries are two 6 volt AGMs in series will this effect the way I hook up a dual battery charging system or can I just use a standard VSR relay type system. Sorry if this sounds confusing but I am

Greg and Sue
SV Sunshine.
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Old 18-06-2015, 02:05   #2
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Re: Charging dual batteries - 6V in series and 12 Volt

Your 2-6 volt batteries in series are the same as a 12 volt battery for wiring purposes. If you are adding a "dual battery" system, you have a box with 3 posts that has diodes inside. Diodes allow current to travel in one direction only. They keep two battery banks separate while allowing them to be charged by one alternator. The center post (usually) goes to the alternator and the other two posts each go to the positive post of the different banks.
Some people just have a manual switch they turn on when the engine is running. A dual battery charging kit cost $100+. You can make you own by buying diodes for about $20.
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Old 18-06-2015, 04:30   #3
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Re: Charging dual batteries - 6V in series and 12 Volt

Are you sure you don't have a VSR in the system that was not hooked back up in the rewire?


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