Gen battery doesn't charge on shore Generator, battery,?

Discussion in 'Announcements & FAQs' started by Rochester 1, May 23, 2020.

  1. Rochester 1

    Rochester 1 New Member

    Aug 18, 2017
    South Point Marina, Rochester NY
    1987 390 EC, 2015 Yamaha VXR
    Twin 7.4 litre 240hp Mercruiser Borg Warner velvet straight drive
    New to me 97 sundancer 500 with 240v,120v,24v and 12v systems
    7 battery's, 2 x12v =24v in series for Catapillar C12s, 2x12v in parallel for house, 1x12v for deisel westerbeke generator. 2 inverters, a 24v and a 12v. ....24v banks fine- batteries charge on shore and under way. 12v "house"charges on shore and with generator running. Here's my question... Not sure if
    Problem or normal...Stand alone 12v generator battery only charges when generator is running... It doesn't seam to charge on shore... The house batteries charge... Why not the generator.... The previous owner just said he put separate charger on gen battery if docked for long period....I probably would have it figured out by now but getting to battery banks is a bitch for a 270lb guy. Just looking for some insight. Can I hook up to 12v inverter and still keep it isolated from house 12v??? Or tie systems together but install s battery switch to isolate? Im not sure what takes gen battery down over time...since I believe its only for gen...
  2. Todd320

    Todd320 Well-Known Member

    Jul 21, 2016
    St. Petersburg, FL
    2007 Sea Ray 320DA
    Twin V-drive 5.7L 350 Horizon
    What make model of battery charger(s)/ac converter(s) do you have? Many are capable of charging 3 banks of batteries banks, so you might be able to simply run another set of wires from charger to gen battery. Or, you might discover, the cables are there but inline fuse blown. I have an IntelliPower PD2030, it has 3 outputs, but only two are used on my 320.
  3. Bt Doctur

    Bt Doctur Well-Known Member

    Aug 21, 2010
    New Jersey
    Ex SRV 240 Weekender twin
    in between
    Problem or normal...Stand alone 12v generator battery only charges when generator is running... It doesn't seam to charge on shore... The house batteries charge... Why not the generator.... The previous owner

    The generators charging system charges its battery , perfectly normal. Why do you feel the need to charge it on shore power when its not running.The boats house charger will charge it on shore power if its connected to the genny battery
  4. Henry Boyd

    Henry Boyd Well-Known Member GOLD Sponsor

    Apr 24, 2007
    Newburyport, on the peaceful and serene Merrimack
    ‘09 Sabre 38 Hardtop Express “Serenity”
    Volvo D6 w/IPS450 Pods
    First off, why is there an inverter on the 24v engine start batteries? Could you mean there is a 24 volt charger?

    Inverters create AC from DC, chargers convert AC to DC. There are devices that are dual purpose Inverter and Charger, but typically these are installed only on house banks largely because the inverter process can rapidly deplete batteries. Engine banks also should not be used as a power resource for an inverter because of the very nature of batteries. Starting batteries need rapid bursts of power, however batteries tailored for that also wear out quickly when subjected to deep discharge and re charge.

    On our boat we have a charger for all the engine batteries (mains & gen) and an inverter/charger for the house bank.

    With your setup, you really have three groups of batteries a 24v bank of starters, 12v deep discharge house bank, and 12v gen starting battery. Because the charging profiles are different, the two 12v batteries should not be on the same charging circuit. Additionally, if the 12v gen starter battery was on the inverter/charger, it would have to be isolated when the inverter process to protect it from being discharged to frequently.

    So that explains why the gen battery has no AC charger. Your choices are to leave it as it is, and run the gen enough to keep the gen battery charged (something you should be doing anyways to keep the gen healthy). Install a third charger. Or if you are worried about a flat gen battery buy and keep on the boat a small battery pack jump starter.
    Last edited: May 23, 2020
  5. carterchapman

    carterchapman Well-Known Member TECHNICAL Contributor SILVER Sponsor

    Mar 25, 2008
    Lake Chickamauga/Marietta, GA/Ft. Myers, FL
    2006 Sea Ray 58 DB
    MAN CRM V8-900s, Twin Disc Drives; Onan 21.5 Generator
    I have a 24v charger that charges my two banks of 2 each D8’s (one for each engine). I have a second 24v charger that does my thruster bank or two D8’s. Finally, I have a third charger (12v) that charges the genny battery. Each has a switch on the panel, and as Henry stated, I normally leave my genny charger OFF, but the other two stay ON.

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