I need a dual battery schematic

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Old 10-05-18, 08:26 AM
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I need a dual battery schematic

Hi all, I need some help. I need to wire 2 batteries in parallel so that 1 charger will charge both batteries, but the circuit on the second battery can never drain the first battery. I know I have to use diodes just not real sure where to put them. If anyone has any suggestions on another way to wire this up I would appreciate the input
 
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Old 10-05-18, 10:29 AM
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Welcome to the forums.

Once the batteries are connected in parallel..... there is no way to isolate them. Depending on the circuit and what you are doing..... you will need a mechanical way to isolate the batteries either using a switch or relay.

Tells us what you are doing.
 
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Old 10-05-18, 11:12 AM
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Not sure what the application is, but to do what you are asking, the diodes would be as such. Battery 1 (bat1) would only power circuit 1 (Ckt1) and battery 2 would only power circuit 2, yet you'd be able to charge both batteries simultaneously. Not sure if that's what you're trying to do or not. You said you wanted to put two batteries in parallel, which to me sounds like you're trying to get more ampacity and/or longer life, but then you said the second circuit can't drain the first battery, which would mean the second circuit is therefore not powered by the first battery (which means the batteries cannot be in parallel). Need some clarification.
 
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Old 10-05-18, 12:34 PM
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Clarification

I have a project truck and I am putting aftermarket lights, adjustable air bags, train horn, external speakers, amps, ext.! I want to put all of this on the second battery. But if j park it somewhere to play music and give a light show I donít want all of that to be able to drain my crank battery. Just like the auxiliary in a boat wonít drain the bettery you use to start engine.
 
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Old 10-05-18, 01:02 PM
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No reason to reinvent the wheel just Google automotive battery isolator.
 
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Old 10-05-18, 01:27 PM
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I have a project truck and I am putting aftermarket lights, adjustable air bags, train horn, external speakers, amps, ext.! I want to put all of this on the second battery. But if j park it somewhere to play music and give a light show I don’t want all of that to be able to drain my crank battery. Just like the auxiliary in a boat won’t drain the bettery you use to start engine.
Oh wow, yeah. Go with an automotive battery isolator as recommended. I wouldn't do this willy nilly.
 
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Old 10-05-18, 05:26 PM
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The isolators are....... ok but I never liked them or use them. They use diodes to isolate the batteries.
Don't use diodes. Get a 12vdc continuous duty solenoid..... like the Cole Hersee 24106. A very easy and effective circuit. The solenoid closes when the engine is running to charge both batteries. When the key is turned off.... the batteries are isolated. Be sure to fuse ALL accessories off the AUX battery. If the AUX battery is not near the main battery.... then it needs a large fuse where it connects to the main battery. A 100A fuse is usually good.

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Cole Hersee solenoid
 
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