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How can I charge a 12V Car Battery?

Discussion in 'Electronic Basics' started by [email protected], Jun 25, 2005.

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  1. Guest

    This may sound a bit of a silly question, but currently I use one of
    the small 12V 7Ah sealed lead acid batteries to charge my lipos with
    (via a lipo charger) - but I only get about 3 charges before the 12V
    has dropped too far.

    ....so the obvious solution is to buy a 12v car battery (about 70Ah).

    The question is; will I be able to charge the 12V car battery with the
    same charger that I use to charge the 12V sealed lead acid?

    As I understand it a car battery is just a lead acid battery? So same
    technology and same voltage just higher Ah. Will I blow myself up if I
    use the small 12v lead acid charger on the big 12v car batt?


    Thanks

    David Bevan
    http://www.davidbevan.co.uk
     
  2. Tom Biasi

    Tom Biasi Guest

    Hi David,
    The charger you have will charge the larger battery but will take longer.
    Car batteries are pretty heavy to be lugging around.
    Regards,
    Tom
     
  3. Ban

    Ban Guest

    The voltage should be OK if it is the same kind of battery. There are
    Gel-cells around, that require less voltage. So make sure the charger is for
    liquid acid lead batteries. It might get more hot when charging and it will
    take forever with that car battery, but it should be suitable.
     
  4. Steve Banks

    Steve Banks Guest

    Alternative sugestions:

    1. Walk back to your car to charge the lipos (or the lead battery)
    2. Since car batteries are huge, maybe another 7ah battery will give you
    enough charges.
    3. How about some sort of foot pump like generator that you can pump the
    small lead battery back up, or possibly a lipo directly to save a few
    strokes, perhaps even while you are flying.
    4. Buy more lipos and pre-charge them?

    If you can shlep a battery to the pit area, then your car probably isn't
    that far away and is an excellent source for 12 volts (at least here in the
    states).
     
  5. Funfly3

    Funfly3 Guest

    buy a cheap car charger from a car shop and buy a car battery from Macro for
    £17/£19 and its got 3 a year guarantee that's what I use
     
  6. John Miller

    John Miller Guest

    Beware of cheap (unregulated) chargers used routinely. They will boil
    your electrolyte, and generate excess hydrogen while they're at it.
     
  7. I OK I'll 'fess up - I don't know - WHAT'S a LIPOS ??????

    AWEM
     
  8. Funfly3

    Funfly3 Guest

    Lithium Polymer or LiPo for short at the moment these are the way forward
    for a lot of electric flying my 11.1v 2600mah LiPo weighs 140 grams, my 9.6v
    2400mah NiCd pack weighs 500 grams, LiPo have a much greater charge density
    than normal packs or in other words are lighter and smaller for the same
    capacity
     
  9. Funfly3

    Funfly3 Guest

    What's the price of a regulated charger that will charge a car battery
    routinely??? a 10AH charger is around £45 so a 50AH is going to be a lot
    more and the battery has a 3 year warranty all for £17 cook it then take it
    back
     
  10. Poxy

    Poxy Guest

    And they have an unfortunate propensity to spontaneously burn up SUVs.

    Exhibit A:
    http://www.rcgroups.com/forums/showthread.php?t=140641
     
  11. Doug McLaren

    Doug McLaren Guest

    | > Lithium Polymer or LiPo for short at the moment these are the way
    | > forward for a lot of electric flying my 11.1v 2600mah LiPo weighs 140
    | > grams, my 9.6v 2400mah NiCd pack weighs 500 grams, LiPo have a much
    | > greater charge density than normal packs or in other words are
    | > lighter and smaller for the same capacity
    |
    | And they have an unfortunate propensity to spontaneously burn up SUVs.

    And if you'll read the description of the story you linked to, they
    didn't `spontaneously' burn up that SUV. The pack was damaged --
    that's hardly spontaneous, even if it was slightly delayed.

    And to be fair, NiCd batteries can cause fires too when damaged.

    Yes, LiPos do require that some care be taken with them, and if you
    fail to take proper care of them they can catch fire. But 1) under
    the right (wrong) conditions, other batteries can cause fires/catch
    fire too, and 2) they're not the sticks of unstable dynamite that
    people seem to make them out to be.

    | Exhibit A:
    | http://www.rcgroups.com/forums/showthread.php?t=140641
     
  12. Guest

    I think its one of these...

    http://www.jperkinsdistribution.co....ies/Chargers&subcatname=Lead acid - gel cells

    ....the output from my charger is 12V/450mA so I guess it would take
    Is it safe to charge a car battery unattended? I usually just leave my
    current 12V on charge permenantly in the garage and just take it off
    charge to go flying. I always supervise LiPos when I charge them, but
    they only take 1h, I dont really fancy baby sitting a 12V car battery
    for 100h!

    Thanks

    David Bevan
    http://www.davidbevan.co.uk
     
  13. Tim Auton

    Tim Auton Guest

    You're getting Amps and Amp-hours confused. A 10A charger can charge a
    100Ah battery.


    Tim
     
  14. Tim Auton

    Tim Auton Guest

    Is this for charging in the field or at home?

    If it's for use at home, get a 13.8V (or 12V) power supply. I've got
    the Pro Peak 20A one. £35 and it's got more than enough oomph for
    everything I need. I've not seen another PSU with similar capacity
    anywhere near the price, except in a PC of course :)

    http://www.sussex-model-centre.co.uk/Pro+Peak+Power+supply-5167.htm

    If it's for the field I wouldn't get a car battery. Decide how many
    charges you want, then buy cyclic or deep-discharge rated SLA of
    appropriate capacity. Do you really need 30 charges out of a field
    battery? Lugging a car battery around is no fun, if you drop it acid
    pours out and they aren't rated for deep-discharge cyclic use so you'd
    be lucky if it lasts a year.

    A cyclic-rated SLA will give you over 500 genuine cycles, which is
    several years of flying for most of us.


    Tim
     
  15. Guest

    1. Walk back to your car to charge the lipos (or the lead battery)

    Charging from my car is an option I had thought about since it has got
    a 12V output in the back. The thing that put me off was that the LiPos
    are best charged outside of the car (since in certain circumstances
    they can catch fire) and I didnt really want to leave 2 or three LiPos
    (at £50 each) laying around on the floor where someone might walk off
    with them.
    Not too sure if thats a serious suggestion? :)
    At £50 each I have bought 3 batts and 2 chargers as this allows for
    almost continuous flying.

    Thanks

    David Bevan
    http://www.davidbevan.co.uk
     
  16. Buy a small tractor battery. They're about $18 at your local auto parts
    store. Buy a cheap auto battery charger for it. You should be able to get
    one in the $20-30 range. I have two tractor batteries. (They're not very
    heavy) I keep 'em both charged.

    Of course the simplest solution is to use your CAR BATTERY to charge your
    lipos! That's what I do when I'm at the field.

    A final solution is to buy a 12V power source to use your li-po charger in
    the house!

    The little gel cells just don't have enough amp hours to last long.
     
  17. You'll quickly ruin the car battery if you charge it constantly. You need to
    charge it and then put it on a trickle charger if that's what you want to
    do.
     
  18. Guest

    Decide how many charges you want, then buy cyclic or deep-discharge rated SLA of appropriate capacity.

    Is SLA short for sealed lead acid? As thats what I have got now and I
    cant seem to find them over 7Ah? I am charging 1600mAh LiPo packs, and
    get 2 or 3 charges before the charger refuses to charge (as input
    voltage has dropped)

    I guess if im realistic then I will go to the patch with 3 charged
    LiPos and probably wont want more than 10 flights which will mean
    7x1600mA = 11Ah - so I guess I would need a minimum of 15Ah in the 12V.
    Please let me know if you can find such a battery.

    Thanks

    David Bevan
    http://www.davidbevan.co.uk
     
  19. colin

    colin Guest

    lead acid batteries can go with a hell of a bang too if they generate enough
    hydrogen gas wich then gets ignited.
    (like if u acidently short one out after over charging it !)

    Colin =^.^=
     
  20. Tim Auton

    Tim Auton Guest

    Search for "sealed lead acid" on your favourite search engine and
    you'll find loads of suppliers. One at random:

    http://eurobatteries.com/sitepages/sla.asp


    Tim
     
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