Dumb Questions....Volume One.

oldmakooldmako Registered Users Posts: 14 ✭✭
I just added a 100W panel on the T-Top of my boat.  I used a Morningstar Charge Controller and two 10 AMP switchable CB's.  One between the solar panel the controller, the second between the controller and one of two identical deep cycle marine batteries.  The solar panel was added primarily to keep the batteries in a constant state and to carry them for long periods of lay-up.  I have wired the output from the CC to BATTERY, not LOAD.

The batteries are each wired to their own respective 1-2-BOTH-OFF switches.   I figure that with both switches left at ALL when the boat is not in use that the batteries will be in parallel and will both benefit from the solar panel.   

Q1.   Is this correct?

What happens when I run the boat?  I have two engines (Yamaha F225, Four-stroke gas) and each has a dedicated alternator / stator arrangement.   I believe that they are capable of putting at least 50AMPS.

Q2.   Do I need to de-select the solar panel prior to operating the engines?    I am concerned about overcharging the batteries.  And if so, should I just switch off the CB between the panel and the controller and leave the other CB in the closed position?

Q3.   Or, Is there any harm in just letting the controller handle all the work and leave it all connected when running the boat?  I occasionally use the boat offshore but when I do, I will select Port Engine to Port Batt and Stbd Engine to Stbd Batt.    This will keep the two systems isolated and provide redundancy to get home should one system fail.


  • EstragonEstragon Registered Users Posts: 3,127 ✭✭✭✭✭
    Assuming the boat is wired the way I think it is (each switch lets you choose to connect each engine to a chosen battery, both batteries, or none) :

    Q1 - yes, with both switches in the "all" position, both batteries should be in parallel.

    Q2. No, the charge controller should regulate battery voltage, and so should engine alternators. The higher regulated voltage will supply charging current to the batteries Neither source should supply enough voltage to overcharge.

    Q3. I don't see any reson to do anything differently than you already do, except to parallel the batteries for solar charging of both at dock/anchor. I'd periodically check resting voltage (or ideally specific gravity of electrolyte if flooded tpye) of each battery to see if one is needing remedial charging.
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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