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Please guide me to recharge a battery

  1. Feb 12, 2017 #1
    Hi Guys. I am trying to charge my scooter's battery which is : 12 volts 2.3ah
    The battery currently has around 3 volts.
    I am charging it with an adapter : 12 volts 2.0ah
    Can you help me how long would it take to charge and is it safe for me..
    Thanks.
     
    Last edited by a moderator: Feb 12, 2017
  2. jcsd
  3. Feb 12, 2017 #2

    berkeman

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    Welcome to the PF. :smile:

    That sounds like the battery is pretty badly discharged. What type is it? Lead-acid?

    Is your adapter made specifically for charging this type of battery? Are you certain it says "12 volts 2.0ah"? More likely it says 12V at 2A max output?
     
  4. Feb 12, 2017 #3

    berkeman

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    BTW, beyond any safety issues, recharging a 12V lead-acid battery with a 12V source will not give you a very full charge.
     
  5. Feb 12, 2017 #4
    If the battery is only showing 3 volts measured at the terminals then it's almost completely flat.
    How long it will take to charge will depend on the exact type of battery and what condition it is in.
    You should be safe with a 12v charger regulated to deliver 2 amps.
    Never ever consider charging with higher voltage or unregulated adapter in an attempt to get it charged faster.
     
  6. Feb 12, 2017 #5

    tech99

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    Actually I believe the recommended charge time for a flat battery is something like 12 hours, so that a current of 0.2 amps would be ideal. 2 A seems a bit fast. If using 2A then do not exceed the charge time of about 1 hour.
     
  7. Feb 12, 2017 #6
    Yes its a lead battery and the adapter is not specified for charging i m using it on my own and it say its 12v 2a...
     
  8. Feb 12, 2017 #7

    berkeman

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    tech99's warning is a good one. For such a flat battery, charging it at full speed does not seem wise...
     
  9. Feb 12, 2017 #8

    CWatters

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    Use the charger supplied with the scooter.
     
  10. Feb 12, 2017 #9
    My scooter is on petrol its battery generator is dead i believe so..
     
  11. Feb 12, 2017 #10

    tech99

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    I suggest putting a small bulb rated at about 12v 0.2 Amps in series and then charging for about 12 hours.
     
  12. Feb 12, 2017 #11
    A 12V lead-acid battery that has discharged to 3 volts is very likely failed. Even dropping below ~ 10.2 V for a short time does some damage to the plates. But attempt a charge and hopefully you will get some life out of it. The series light bulb is a good idea - it will limit current and protect your power supply and the battery.

    Why is it so low? Did it just sit unused for a while? Is the charger in the scooter OK?
     
  13. Feb 12, 2017 #12
    OP says the charger in the scooter is probably broken, so he needs to charge the battery just to get the motor started.
    If possible that charger in the scooter needs replacing, if lucky he can get something cheap but working from a vehicle scrap yard.
     
  14. Feb 13, 2017 #13

    sophiecentaur

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    How long since the scooter was last used? If the battery has been left in a discharged state for many months, it may well be dead. Lead Acid cells last much better if their charge is kept topped up.
    Do you have a meter to check the actual voltage on the battery on its own or when connected to your charging source?
    You could perhaps find if the scooter charger works when pushing the scooter along and measuring the volts. (No good if it has an automatic gearbox.)
     
  15. Feb 13, 2017 #14
    I left the battery charging for almos 2 hours on the same 12v 2.3a adapter ..
    The current voltage is 10.8v and when i try to charge it again it makes a noise like boiling..
     
  16. Feb 13, 2017 #15

    berkeman

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    Not a good thing. Why did you not use the trick with the series light bulb?
     
  17. Feb 13, 2017 #16
    - It would be good to know the exact type of the battery. 2.3Ah sounds like sealed lead-acid?
    - if so, then the maximal charge current for 2.3Ah battery should be something like 0.3-0.7A at most?
    - actually, reviving it from 3V sounds like some bad zombie movie. I too think that the battery is done.
     
  18. Feb 13, 2017 #17

    sophiecentaur

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    Did you ever read what it says on the side of the battery? They usually have instructions for charging conditions. BE sure to do that with the replacement you will need to buy.:wink:
     
  19. Feb 13, 2017 #18
    I think that it's good that it picked up some voltage (10.8V, in 2 hrs) but the boiling sound not a good sign! (You charged it full speed.) I would say it's either almost dying or , in case it can be revived, make sure you use it a bit (to lower the voltage) before you attempt further charging, to see also how it behaves, but make sure this time to use the series light bulb trick that tech99 and berkeman suggested:
    I think there is a [small?] chance you might be able to save it, but then find what the ideal charging and maintenance instructions are and try to follow them more consistantly, or do that with your next battery ...

    P.S. Also with that type of charging equipment and conditions that you followed I think you should have tried 45' min charging intervals (not even 1hr). That's why you should better use the series light bulb trick, if you have another chance ...
     
    Last edited: Feb 13, 2017
  20. Feb 15, 2017 #19

    CWatters

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    Are you sure its a 12V battery ?
     
  21. Feb 15, 2017 #20

    sophiecentaur

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    He must read what it says on the side but I would have hoped he would have done that already!!! It's dangerous to try to charge a battery with the wrong charging conditions.
     
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