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Battery issue

Discussion in 'Ask All Sailors' started by Gabor15908, Feb 13, 2018. Add this thread to a FAQ

  1. Gabor15908


    Joined Jan 22, 2008
    44 posts, 2 likes
    Hunter 376
    US Point Roberts
    In the summer, I forgot to check my 2-T105 house batteries. All the cells (6 on the two batteries) were exposed and dry. After refilling them with distilled water I tested them with a voltmeter and they seem to hold the charge. I re-changed them and immediately after the charge they were 13.3V. I took them off from the charger and left them on the boat at 40F temperature, with no load for two weeks. Testing them again with the voltmeter showed 12.66 V.
    The batteries were purchased in 2013, this is the first time I left them dry.
    Just trying to figure out if they would last another season or should I just dish out some $$ for new to new T105-s?

  2. Don S/V ILLusion

    Don S/V ILLusion

    Joined Sep 25, 2008
    5,027 posts, 265 likes
    Alden 50
    US Sarasota, Florida
    It's unlikely but possible they may retain some of their original capacity. The only way to find out is do a proper load test.

  3. Davidasailor26


    Joined May 17, 2004
    1,177 posts, 200 likes
    Beneteau Oceanis 37 LE
    US Havre de Grace
    Like Don said you'll need to test them with a known load to find out what know of capacity they still have left. The voltage when it first came off the charger is just a surface charge, and the 12.66 resting voltage isn't great, but also isn't enough to really tell anything.

  4. Benny17441


    Joined May 24, 2004
    5,397 posts, 311 likes
    CC 30
    US South Florida
    Load testing batteries can be a PITA but a ruined outing can be much worse. If I had any pending trips I would replace ($$$) them but if I just was going to hang around home base and do a few day sails I may put them through their paces to see if they are retaining charge and adequate capacity. I would make sure they are fully charged and promptly recharged after every use. 13.3V can be the voltage found right after charging while 12.66V is the normal voltage of a fully charged battery at rest. Now the question is how much capacity is stored behind that voltage; is it 90%, 75%,50% or 20%. At 90% the battery would have a very adequate capacity while at 20% the battery would discharge quickly; anywhere in between its adequacy would depend on the specific needs of the boater.

  5. Ken Cross

    Ken Cross

    Joined Oct 24, 2010
    1,628 posts, 201 likes
    Hunter 30
    US Everett, WA
    Yank one out and take it to a battery shop for load testing. If it's bad, change them both. As an alternative, you could purchase your own load tester. Most of us wouldn't use it frequently enough to justify having their own.


  6. nightowle


    Joined Aug 28, 2006
    221 posts, 30 likes
    Bavaria 35E
    US seattle
    you could also have a battery shop run it through a 24 or 48 hour conditioning cycle, if the load test merits it.

  7. Benny17441


    Joined May 24, 2004
    5,397 posts, 311 likes
    CC 30
    US South Florida
    What usually happens with a battery of diminished capacity is that we will discharge it deeper than the original threshold of 50% and we may not initially notice any fault. Well lets say we originally had a battery with a capacity of 110Ah but since it sulfated some now we have a battery with a capacity of 80Ah; can we safely take it down to 40Ah? You tell me. The reality is that we can, probably precipitating its demise without loss of functionality that is if our daily consumption is adequately met. How much longer will they last is anyone's guess.

  8. old vietnam vet

    old vietnam vet

    Joined Feb 7, 2018
    6 posts, 2 likes
    tayana 37 mk11
    windship us houston tx
    I let my starting battery go dry once, filled it then left on a 150 mile sail, when we went to start the genset which it also feeds, nothing dead as a door nail. Luckily the house batteries still had juice an we got started. load your battery up over suitable period and check voltage, also if you have battery charge indicator note amps out vs battery charge level.

  9. Gunni


    Joined Mar 16, 2010
    5,077 posts, 960 likes
    Beneteau 411 Oceanis
    US Annapolis
    Bang. You killed them Gabor.

    JCall likes this.
  10. Gabor15908


    Joined Jan 22, 2008
    44 posts, 2 likes
    Hunter 376
    US Point Roberts
    Thanks guys...I think I will dish out some $$$ for two new ones. They are 5 years old so in a year or two they have to be replaced anyway. Considering that my boat has vacuum flush toilet, 12V windlass, fridge and freezer, autopilot, macerator, etc ....just too much to risk to die on me on a long weekend on the hook.

    Gunni likes this.
  11. Chris Patterson

    Chris Patterson

    Joined Oct 17, 2011
    2,775 posts, 65 likes
    Ericson 29
    US Southport..
    Five years?
    Yepper, they're gone..

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