Two batteries, $275; New Charger $400, maybe it's the isolator

Discussion in 'Electrical Stuff' started by Tom Huntley, Sep 1, 2020.

  1. ttmott

    ttmott PhD in OCD GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    One is the same - the converter can both charge and operate the boat's systems up to 35 amps. If, for example the boat's systems demand 50 amps then both the battery and converter/charger contribute until the battery is depleted. If the boat's systems are demanding 25 amps and the battery is demanding another 30 amps in bulk charging then the converter charger will only provide bulk charging at 10 amps.
     
  2. Timvail

    Timvail New Member

    3
    Sep 3, 2020
    Georgian Bay Ontario
    1990 Sea Ray 350 Sundancer with 13 ft avon/40HP Honda
    7.4 Mercruisers
    So if I understand correctly, running the 8kw genny on the hook would provide me with infinite power then .
     
  3. CaptRonn

    CaptRonn Well-Known Member

    May 25, 2016
    on a large body of water
    1999 Sea Ray 400 Sedan Bridge
    Convert fuel into noise
    I just went through a similar problem on my 400SB.

    Replaced all batteries. Every time I took the boat out to anchorage, when I went to restart, starboard ignition was dead, had to do an emergency start and put something under the emergency switch to keep it engaged, or the engine would quit. Back at the dock I checked voltage at the STRBD ignition switch and had 12+volts, but when I engaged the switch volts dropped to zero.

    Next day in the dock, everything back to normal.

    I took everything in my system apart Sunday. First thing I noticed, when I removed the starboard batteries from the system, I still had voltage showing on the electrical panel, and my radio was still playing (cabin systems, starboard).

    I checked all cables, using multi meter I found no resistance so they were good. But strangely, when I checked continuity between port and starboard battery terminals I got a short.

    I literally disconnected every cable and checked each one individually up to the emergency solenoid. All cables good.

    I found the isolator was flaky. I also found some corrosion on the inside of the starboard battery terminal.

    So in conclusion, this is what was happening: the corrosion inside the strbd cable connector was reducing starting amps. The backfeed through the isolator to the strbd pos terminal was providing 12 volts, but few amps. Thus why the strbd ignition was dying.

    Solution? Cleaned ALL battery connections religiously. Removed battery isolator from system, so now my strbd and port systems are indeed separate, and can be joined by emergency start solenoid.
     
  4. ttmott

    ttmott PhD in OCD GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    12V? No - Generator fuel aside you have "infinite" up to around the maximum capability of the charger/converter; in excess of that the batteries supplement until they are depleted then you are back to what the charger / converter can provide.
     
  5. yobub

    yobub Well-Known Member PLATINUM Sponsor

    550
    Jul 29, 2016
    Chicago
    1998 400 Sundancer
    Cat 3116's
    I did this same upgrade on my 400 last summer. Did a direct replacement using the same wiring. I accidentally tripped one of those breakers @ttmott is describing. Had to track that down to get everything to work.
     
  6. marty51

    marty51 Member

    48
    Jul 30, 2008
    Lake Erie west end
    2002 410 Sundancer
    3126 Cats
     
  7. marty51

    marty51 Member

    48
    Jul 30, 2008
    Lake Erie west end
    2002 410 Sundancer
    3126 Cats
    If both battery banks are fully discharged does inverter/ charger provide 12v power to operate systems such as engine hatch?
     
  8. Boca_Vincent

    Boca_Vincent Member GOLD Sponsor

    41
    Nov 1, 2010
    SoFla
    370 Express Cruiser
    Cat 3116
    Well my problem turned out to be different. Went back to the boat after work yesterday to start tracing. Turns out these switches can go bad. The center one is my stbd bank. I have no continuity between the 2 lugs while in the on position. Everything is tight and the connections look good to me, so I went ahead and ordered a new one this morning. Guest 2304 extra-duty in case anyone is ever looking. Thanks, and good luck tracking down your drain issue. 20200915_175333.jpg
     
  9. CaptRonn

    CaptRonn Well-Known Member

    May 25, 2016
    on a large body of water
    1999 Sea Ray 400 Sedan Bridge
    Convert fuel into noise
    If you want, you can take that switch out, and disassemble it. They are really simple designs, and you can take a piece of sandpaper and clean up the contacts inside of the switch.

    The contacts will corrode over time and cause the problem.

    Also, there is quite a bit of corrosion on those terminal ends. Clean them as well.
     
    Last edited: Sep 16, 2020
    Boca_Vincent likes this.
  10. Shaps

    Shaps Active Member GOLD Sponsor

    373
    Nov 4, 2019
    Long Island,NY
    2010 Sundancer 500
    Twin Cummins QSC550 DTS w Zeus
    Whether or not you clean up the old or install new, i would add some dielectric grease to the contacts.
     
    Boca_Vincent and CaptRonn like this.

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