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  1. #1
    Join Date
    May 2001
    Location
    North Wales, sailing Aegean Sea or Menai Strait
    Posts
    21,694

    Default Overwintering batteries

    The eternal question. Last August we laid up Straitshooter, disconnecting all batteries from themselves and everything else. Just back at the boat, April 11, reconnected - 12.6 volts on the panel.

    In other years we have left them with solar panels charging, to find them destroyed when we returned.
    Answers to some technical queries at new website http://coxeng.co.uk

  2. #2
    Join Date
    Jan 2004
    Location
    Bricks & mortar: Italy. Boat: Aegean
    Posts
    10,431

    Default Re: Overwintering batteries

    We have a parallel dilemma Vyv. Our batteries are Trjoan T105, lead-antimony so a significant self-discharge rate. Fine for full-time liveaboard life, but since we've become part-time we've found they really don't like prolonged periods without charge. Equally, I'm reluctant to leave 340W of solar connected to them (or even one quarter of that) in our absence. (Which your past experience seems to support.) So last autumn I disconnected all four panels and rigged up a 20W panel through the same regulator. I'll know in a month or so how it's coped.

    If I were buying batteries for the boat's current usage, I'd definitely go for lead-calcium: much more tolerant of being unattended for long periods. I daresay Straightshooter's are also lead-calcium.
    All epigrams are false

  3. #3
    Join Date
    Nov 2007
    Location
    Cascais, Portugal
    Posts
    962

    Default Re: Overwintering batteries

    That's good news - we laid up Vivere last June and I disconnected the batteries (Trojan wet cell) before we moved to Portugal. We will get back to her next week to start the journey from the Netherlands to Portugal and I am now more hopeful that our batteries are also in good condition.

  4. #4
    Join Date
    May 2007
    Posts
    36,659

    Default Re: Overwintering batteries

    Quote Originally Posted by vyv_cox View Post
    The eternal question. Last August we laid up Straitshooter, disconnecting all batteries from themselves and everything else. Just back at the boat, April 11, reconnected - 12.6 volts on the panel.

    In other years we have left them with solar panels charging, to find them destroyed when we returned.
    When one person does well by disregarding the manufacturer's advice on one occasion, the rest of us should probably think twice before copying.
    If you gave the make and model of batteries, it might be a little more useful.

    Most solar regulators are designed for daily cyclic use, not long term storage/maintenance.

  5. #5
    Join Date
    Sep 2001
    Location
    Home - Sothampton, Boat - Gosport
    Posts
    9,884

    Default Re: Overwintering batteries

    Maybe it's because I've only got 40w of solar power, so not a lot goes in over winter, but my (sealed) batteries are now 5 years old and have been studiously ignored for the whole of that time. They're always fully charged when I come down to the boat, even in the middle of winter, as shown by the flashing LEDs on the solar controller - and the enthusiasm of the starter battery for dragging a VP2003 into reluctant life on a cold day.

    What was wrong with the batteries when the solar was left on? Dry would indicate overcharging, low voltage under, or a discharge rate exceeding the charge.
    Steve
    Never believe anything until it has been officially denied.

  6. #6
    Join Date
    Apr 2018
    Location
    Mooring, Faro
    Posts
    1,391

    Default Re: Overwintering batteries

    With a decent regulator (such as Victron) charging regime can be altered to allow just a maintenance charge when boat not being used for long periods.

  7. #7
    Join Date
    May 2016
    Location
    Suffolk
    Posts
    7,643

    Default Re: Overwintering batteries

    Quote Originally Posted by vyv_cox View Post
    The eternal question. Last August we laid up Straitshooter, disconnecting all batteries from themselves and everything else. Just back at the boat, April 11, reconnected - 12.6 volts on the panel.

    In other years we have left them with solar panels charging, to find them destroyed when we returned.
    We'd need to know the type of batteries that you have, the output of the solar panels, make and model of the solar controller and what "destroyed" actually means for that to be really helpful. Then it would only really apply to anyone with an almost identical arrangement.

    It might be acceptable to leave certain batteries just sitting there for 7 or 8 months, but i'd generally not recommend it. Certainly would be a poor plan with something like T105s.

    I have often said that cheap solar equipment can be a false economy and that absolutely applies to controllers. I seem to recall you saying in the past that you have a cheap PWM controller ? Can the charging parameters be customised ? Some can't and they could subject the batteries to a few hours of absorption voltages every day, which could be harmful, especially if the voltages are high. Very long periods on float can also be less than ideal when there are no loads and the float voltage is on the upper limits.

    With a good controller, that can be customised, all voltages can be set low, equalisation turned off (mine is always off) and even max current limited. It would be easy to set a regime that even T105's connected to a few hundred watts of solar would be happy with.
    Rainbow Marine.
    www.rainbowmarine.co.uk

  8. #8
    Join Date
    May 2001
    Location
    North Wales, sailing Aegean Sea or Menai Strait
    Posts
    21,694

    Default Re: Overwintering batteries

    PWM indeed but not a cheap one, it's a dual bank charger by SunWorks. Totally satisfactory over many years. Our experience with several battery banks left for six months or more has not been good in Greece, both wet cell and sealed types. Whereas on our motorsailer where we only have directly connected small solar panels on the starter and two domestics they seem to cope well in UK.
    Answers to some technical queries at new website http://coxeng.co.uk

  9. #9
    Join Date
    May 2007
    Posts
    36,659

    Default Re: Overwintering batteries

    Quote Originally Posted by vyv_cox View Post
    PWM indeed but not a cheap one, it's a dual bank charger by SunWorks. Totally satisfactory over many years. Our experience with several battery banks left for six months or more has not been good in Greece, both wet cell and sealed types. Whereas on our motorsailer where we only have directly connected small solar panels on the starter and two domestics they seem to cope well in UK.
    It's notable that the Sunworks website speaks of 'New: Winter Mode', so perhaps until recently they haven't been the right thing for wintering?
    https://sunworks.co.uk/product/dual-...oller-db2cblk/

  10. #10
    Join Date
    Jan 2008
    Location
    Moor & Dock- Leros
    Posts
    446

    Default Re: Overwintering batteries

    We have 180w solar thro a Morning Star MPPT controller, feeding 3 x 140ah open truck batteries. I always leave them connected over winter and after 5 seasons they’re still fine.

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