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Dual Battery connection

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    Dual Battery connection

    Hello, I am new at all this and just learning. Hope I explain in clarity.

    1989 Bayliner 24 ft.

    I have a switch to isolate battery #1 and #2 and an off switch.

    When battery #1 position. The stereo is still working. But not enough crank power to start the engine.
    When battery #2 position. The engine starts.

    I figured battery one was low. Took it out to connect to a proper charger. But when tested it says the battery is at 100%

    Also, when I removed battery #1, battery #2 does not work anymore. I believe I reconnected the ground?

    I am assuming I have not wired both batteries properly?

    Should I make battery #1 house battery and everything come off that? Battery number #2 the start battery and only have the motor power come to that?

    Looking for any guidance for a newbie to boats and electrical.


    Welcome Fred and I'll start by saying I am not an electrician but a newbie similar to yourself but on my boat each engine has a battery to start it and are isolated from the rest. The house has 2 batteries that run everything else. The main battery control panel has a on/off switch for the engines, the genset, accessory (House)and there is one for crossover which I believe puts all batteries to the engines to start them in case the engine start battery fails. At least that is how I have interpreted it.!AoWYMzoV5zKHuQ7RleUESCbcpRkB


      thanks, yes starting to figure that part out. I am starting to think that one of my batteries just might not be holding a charge that well. Just not enough cranking power when used for anything else.


        Fred, Generally, one battery is for starting and the other for the house. They should be separate from each other unless the start battery is low, then you can gang both together for starting the engine. You said you tested the battery. How did you do that? If its just showing a full charge it may still not carry a load. If you don’t have a battery load tester you can pick one up on ebay or amazon they’re fairly inexpensive. Or, pull your batteries, charge them and take them to a battery store like Batteries plus or Interstate and they’ll load test them for you. New batteries are a lot cheaper than a tow. Chris


          My first question is about the switch. Is it a 1,2,off,all switch or just a 1,2,off switch. Second question, are there any other switches and how are they labeled.
          Seattle, WA
          Ocean Alexander 54