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balmar alternator upgrade-gctid732905

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    #16
    So in the instance where both the starboard and port engines are charging the house battery, doesn't that confuse either the starboard alternator or port ACR or both? Seems like one or both would sense power coming from the other side and be fooled into thinking the house battery was fully charged.

    Paul
    US Army (Retired), Federal Way, WA

    1990 Bayliner 3288 - the "Janna Lea"
    MMSI: 338181912

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      #17
      On my 4788, I installed a Blue Sea Automatic Charging Relay (120 amp continuous, 210 amp for 5 min) to connect each engine start battery to the house battery. The stock 110 amp alternator is then directly wired to the engine start battery (without the isolator). During engine start, the connection is released to protect the ACR from excessive current. In operation, the ACR attaches the house bank when the engine battery is sufficiently charged for a sufficient length of time. Prior to installing the ACRs in place of the isolators, a single engine with a standard 110 amp alternator was unable to keep up with house current draw when cruising at 1600 rpm. With the ACRs and both alternators contributing to the house battery bank, we can charge during a slow cruise.

      One potential ACR life issue may exist, however - when the house bank is significantly discharged and the alternator has charged the engine battery sufficiently (e.g., above 13v for 90 seconds or above 13.6 for 30 seconds), the ACR connects that engine battery to the house battery, the alternator and engine battery voltage drops and if below 12.35 for 10 seconds or 12.75 for 30 seconds, the ACR will release the connection and wait for the engine battery to come back up to the required voltage, and then tries again to attach to the house battery. This switching is a result of the alternator being unable to supply sufficient current at that rpm to keep the voltage high enough. However, after a few cycles, the house battery voltage does stay high enough and the ACR's stay connected. If in this situation, I just run the generator to help charging the house batteries for a little while.
      1997 4788 with Cummins 5.9 (315 hp)
      12 ft Rendova with 40 hp Merc 4 cycle
      Pacific NW

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