Battery maintenance ?

sunnysidesunnyside Registered Users Posts: 11
I bought 2 new 6v Decca golf cart batteries for my van conversion about 8 months ago, the conversion is going a little slow so the batteries have just been sitting on the bench, they have been losing a small amount of voltage, what is the best method of maintenance until I put them in service. I have also changed my plans and would like to buy 2 more to increase my ah, this will not be a problem will it, 8 month old unused with new? NB here so please forgive.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,347 admin
    Re: Battery maintenance ?

    Flooded cell batteries generally need to be recharged at least once per month (24 hours on a smallish charger)--Or you are starting to settle into sulfation range (soft lead sulfate change into a hard lead sulfate crystal)--Which takes acid and lead out of any further electro-chemical reactions.

    So--First, measure the specific gravity for each cell, and the resting voltage of each battery (and log). Next, get them on a charger and start charging them... For two of them in series, you want to see at something like 14.2 to near 15.0 volts held on the batteries (and something like 5 amps) for at least 4-6 hours (monitoring battery voltage, current, temperature) and see if you can get to reasonable specific gravity (1.260 to 1.270--depending on model/vendor initial fill, etc.).

    You have have to discharge/recharge a few times to see if you can ever improve poor specific gravity--But is not out of the question that these batteries may be toast now from setting uncharged for 8 months. A typical flooded cell lead acid battery will discharge ~25% per month (very roughly). If they were kept very cold (sub freezing weather would be your friend here), they might still be OK. If they were stored "warm" (70F and above), there is less chance they are good.

    Sorry--Lots of questions (resting voltage, specific gravity) and fuzzy answers--But until you measure, charge, and test--You will not really know.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • sunnysidesunnyside Registered Users Posts: 11
    Re: Battery maintenance ?

    Thanks Bill, Will a 12V battery tender work on my 6V batteries if they are wire in series or do I need to buy a 6V one and keep them separate
  • BB.BB. Super Moderators, Administrators Posts: 29,347 admin
    Re: Battery maintenance ?

    If the batteries are used as a 12 volt pair (in series) and have about the same voltages--You can use a 12 volt battery charger.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • sunnysidesunnyside Registered Users Posts: 11
    Re: Battery maintenance ?

    Thanks Bill, the voltage in the batteries is 6.01/6.02V I have put them on a 12V 6A charger, wired in series. Should I find a 20A charger for the initial charge time or will my 6A work.
  • BB.BB. Super Moderators, Administrators Posts: 29,347 admin
    Re: Battery maintenance ?

    I would just start with the 6 amp charger--Ideally, if you were going to equalize those batteries, you may need a 10-12 amp charger.

    Longer term, what are you plans for AC charging (backup genset, plugging into camp/home AC outlet)? If using AC charger--I would then get a battery charger that fits your needs for on the road use now--If not for this set of batteries, for your next set (:cry:). Just keep the present set for now and use them to get your RV system setup and debugged--Then buy a new set for going on the road (lead acid flooded cell batteries just do not store will without charging--yours are ~50% discharged right now).

    It is actually a bit on the difficult side to get AC battery chargers that are designed to properly charge/equalize a deep cycle battery bank like yours. Iota makes very good chargers, but they are not really configurable. You don't need the IQ4 module if charging with genset... If you will park the van seasonally on AC power, then an IQ4 module would be nice (get the external one and you can install when needed).

    Or get a Battery Minder for floating you batteries (not cheap)--I use this one on my in-laws rarely driven car and it keeps the battery charged without boiling it dry (GPS, OnStar, Lojack, car computer, etc. loads will kill a battery in 2-4 weeks of non-driving). I have to reconfigure the unit every time is it powered down (does not save settings)--But it is just 2-3 button presses and defaults to GEL/AGM settings.

    You can get AC Inverter+Chargers (Magnum, Xantrex/Schneider, and others) that are highly programmable--But they are usually for larger systems.

    Xantrex in times pass made a very nice TC2 family of chargers--But they have been hard to source. A TC2 20 or 40 amp charger would be fine for your needs. If you are using a small genset like a the Honda eu1000i, then the 20 amp would probably be the largest you would want to use.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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