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The proper way to carge a rechargeable battery?

Discussion in 'Electronic Basics' started by Rui Maciel, Aug 31, 2010.

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  1. Rui Maciel

    Rui Maciel Guest

    After searching for information on how to recharge batteries I was left with contradicting
    suggestions regarding the proper way to do it and even what to expect from a recharged battery.

    So, in order to sort this out, can anyone tell me what's the proper/optimal way to charge a
    rechargeable battery?


    Thanks in advance,
    Rui Maciel
     
  2. Rich Webb

    Rich Webb Guest

    Which one?

    Hint: there is no one method that is correct for every battery
    configuration / chemistry / capacity.
     
  3. Sjouke Burry

    Sjouke Burry Guest

    A "safe" rule: 10% of capacity as charge current.
    Which results in a charge time of about 10-12 hours.
     
  4. Rich Webb

    Rich Webb Guest

    I wouldn't recommend that as the charging profile for a submarine's main
    storage battery. Granted, submarines probably aren't in the OP's problem
    domain and *usually* C/10 is okay for individual consumer-grade cells.
    Probably not optimal for a home-brew lithium ion battery pack.
     
  5. Grant

    Grant Guest

    Just adding to what Tim says:

    I'm reading that the floated cells are subject to corrosion too :( Volts
    too high they corrode, too low they sulphate, seems you need temperature
    compensated float voltage for max life. The old telco style flooded
    cells were happy with 13.5V for 6 cells. I think 13.7 is better than the
    old 13.8V for floating SLAs these days, but watch for temperature extremes.
    I'd add too that the newer "valve regulated" lead acid batteries operate
    under pressure (up to 5 atmos.) and can stand or require a little more
    voltage, there's info on the quality manufacturers' sites.

    OTOH cheapie batteries made from your old recycled car batteries can vary
    quite a bit. Proper charging can be quite involved if they're used for
    traction batteries, expect an overnight charge.
    Yeah, those new Eneloop style (precharged NiMH about 2100mAH for AA) are
    good, but those high capacity (AA > 2500mAH) are useless unless you have
    them in high discharge rate toys or frequently used cameras. I still
    charge them at C/10
    Not met one yet ;)
    Proper charging info is hard to find. It's an area I have an interest in,
    some manufacturers are very specific on requirements, others less so.
    I'm mostly working with SLA (sealed lead acid) batteries.

    Grant.
     
  6. Herman

    Herman Guest

    See this http://batteryuniversity.com/partone.htm
     
  7. Guest

    Starting batteries usually have AH specified, too. You might have to dig some
    to find the information.
    Perhaps within an order of magnitude. There will be no meaningful
    translation.
     
  8. Grant

    Grant Guest

    ....
    They list a reserve or standby time instead, since AH rating deemed too
    hard for mere mortals to understand ;)

    Actual AH depends on rate of discharge, I think standby time gives a
    figure at some agreed discharge rate, but I can't remember the figure.

    The standby rate can be found, from there you can work out AH at that
    rate, then interpolate to what load you want to run. Or, you could
    measure it yourself, standard method is constant current load X for
    Y hours down to say 10.5V for 6cell LA. Recharge the battery and
    try again with different X. Rinse & repeat.


    For example I have here a 12V 52AH battery weighs heaps and replacement
    cost is AU$600, I think it's still at 95% rating (was given to me) --
    obviously this thing has far more lead in it than the same physical
    size car starter battery.

    If you are after deep cycle standby battery, be prepared for sticker
    shock.

    Grant.
     
  9. Guest

    It's "agreed" to by the manufacturer. There is no standard and indeed there
    couldn't be since the rate of discharge is application dependant.
    No, there is no way of "working" that out. Manufacturers will give different
    capacities for various discharge rates, however.
    Pretty much. ...add a safety margin and you're done. ;-)
    Yep. It's a specialty item. You don't get the mass market pricing of a
    starting battery.
     
  10. Rui Maciel

    Rui Maciel Guest

    Thanks for the help, Tim. That was quite an informative post. It covered almost all the doubts I
    had on this issue. Yet, there is one which still lingers on, which is the dreaded "memory
    effect". I've stumbled on multiple contradictory claims on this issue, with ones claiming that
    there was no such thing while others defending that it was very real, going on suggesting
    recharging procedures to minimize this phenomenon.

    So, is there such a thing as a memory effect?

    I've added the book to my wish list and I plan to purchase it in the near future, preferably if a
    cheap used version happens to pop out somewhere. It looks quite interesting.


    Once again thanks for the help, Tim. Kudos!
    Rui Maciel
     
  11. Grant

    Grant Guest

    Oh, I though maybe there was some agreement for car starting batteries?

    Long time since I looked as my interest is more in the standby and traction
    area.
    That's because they do vary depending on discharge rate, by quite a bit.
    Too true :)

    Grant.
     
  12. Guest

    AH isn't the primary concern for starting batteries. AFAIK, there are
    standards for CCA measurements.
    ....and more importantly the construction of the cells. Like all engineering,
    there are tradeoffs to be made and not all make the same choices. The two
    parameters cannot be related.
    You also get the "marine" adder. ;-)
     
  13. Eeyore

    Eeyore Guest

    Depends hugely on the battery chemistry and any special
    construction/design limits.

    Consult the manufacturer.

    Graham
     
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