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Batteries/Electrical Systems for Dummies

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  • Batteries/Electrical Systems for Dummies

    The subject says it all.

    Looking for some basic information, so that I can properly reconfigure/rewire my 1998 Mako 191.

    Currently there is one Dual-Purpose battery, but I want to add a second battery and switch; simply for redundancy.

    If I'm understanding the previous owners set up, the single battery starts the outboard, but once running, the outboard's alternator powers the onboard electrical systems; navigation lights, pumps, radios,electronics, etc.

    Once the outboard is shut off, such as at a sandbar, the same Dual-Purpose battery provides power to the required accessories. Assuming that the battery isn't drained, once the outboard is restarted, the alternator takes over providing power to any accessories, as well as recharges the battery.

    Correct so far?

    If I am going to add a 2nd battery, mainly for some reassurance, would it be appropriate to get another Dual-Purpose battery? That way it has the capability to generate both cranking amps, and run electronics/accessories?

    With a Battery Selector switch, I'd use Battery 1 to get out, and for House Loads. Saving Battery 2 to assure I can get you motor started and back home safely.

    Given that principle, would the alternator only charge the battery that is selected? Meaning, if I drained Battery 1 at the sandbar, switch to Battery 2, start and go, will only Battery 2 be recharging? Would I need to physically switch back to Battery 1 to recharge once the outboard is running?

    I'm simply duplicating the existing system, but not sure if it's the best route.

    Am I better off purchasing a dedicated Starting/Cranking battery, and isolate the Dual-Purpose battery only for House Loads?

    This would bring me to my next question; What's the purpose of having a dedicated "Marine Battery Charger" if your outboards alternator does the charging? Is this more so for dockside/shore power?

    Sorry for the long post, but any feedback is much appreciated.

    And if it matters, electronics will include a VHF radio, single gps/fishfinder combo, as well as a marine receiver, amp and 4 speakers.

  • #2
    I have helped other CM guys on their rewire projects. There are two systems you can review for battery management. System one manufacturer uses Perko battery switch with ACR (Automatic charging relay) added feature. The battery switch is manually used to select between which battery is being used for motor starting while battery two is isolated to prevent draining it. By adding an ARC relay feature both batteries are charged by the motor alternator. Look at Perko manufacture with add on ACR feature. The second system is manufactured by Marinco, BEP management system. This system provides an integral battery management system with switches and VSR (Voltage sensing relay). Typically when adding a second battery battery one is the motor battery and battery two is the house battery. A few suggests are to move the batteries to under the console. To accomplish isolation it will require some rewiring. I have provided Excel spreadsheet for required components, wiring diagrams and subpanel layout. Let me know if you would like them. Estimated cost to add battery, install new motor cable extension cable, and rewire with new fuse panel runs about $1100-1500.
    Keyman[br]Paoli, PA


    • #3
      Blue Sea Systems has some good information on their support site.
      Steven Kwajalein Atoll, RMI


      • #4
        Here is another example of their support site
        Steven Kwajalein Atoll, RMI