12v battery in car phone charger

Discussion in 'General Electronics Chat' started by contender1, Nov 19, 2013.

  1. contender1

    Thread Starter New Member

    Nov 19, 2013
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    0
    im trying to run an in car mobile phone charger from a 12v golf caddy battery.
    Its basically a small car battery but i just cant seem to get it to work when i attach it to the phone i get the little charging signal for a while then it stops and rather than charging it seems to drain the phones battery. i have had one charger fail attempting to get this to work and a second one has started to overheat.
    Is there any reason this shouldnt work thanks in advance for any help.
     
  2. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
    1,190
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    Something is really wrong.... Did you check the voltage of the battery ????
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,151
    3,058
    I agree - if the battery is holding voltage there should be no problem. It's very easy to check the voltage under load.
     
  4. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,397
    497
    You could try adding Blocking Diode.
     
  5. contender1

    Thread Starter New Member

    Nov 19, 2013
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    0
    well thats a second charger died :-(
    I thought in theory there was nothing wrong with what i was doing.
    I measured the battery and it was 12.5v and around 11.95 when the charger was connected. the light was flickering on the charger and quickly overheated and died.
    Think i best get rid of that battery.
     
  6. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
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    Is the battery stand alone or connected to other batteries ????
    Are you running the charger when you are charging the battery??
    What are you using the car charger to charge???
    Could it be bad charger ???
    The reason I ask these questions is because I built offroad trucks and most time the cigarette light is directly hooked to the battery with a fuse ..
     
  7. contender1

    Thread Starter New Member

    Nov 19, 2013
    3
    0
    no its just a standalone sealed lead acid battery.
    i measured it before charging and it was on 9.5v the charger in the beginning was outputtjng 14.5 volts and dropped down to 12.5v as the voltage in the battery increased.
    All im trying to do is charge tbis 20Ah battery so i can take it night fishing to keep my smartphone running to browse internet play music etc via a standard in car charger which i thought would be simple
     
  8. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
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    There's always the matter of polarity to consider, then connectors and cabling. I wouldn't expect the power LED on the charger to light up at all if there were a problem but it's possible your polarity is reversed. Can you post a picture of the setup?
     
  9. wayneh

    Expert

    Sep 9, 2010
    12,151
    3,058
    The OP needs to answer this one.

    Something is fishy, assuming the chargers that are burning out aren't simply crap to begin with. I think we need more detail - photos would be nice - to sort this out. What are the chances you have the leads reversed?

    [Haha, KJ6EAD beat me to it !]
     
  10. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,041
    1,670
    Am I understanding this correctly that you are trying to charge the 12V 20ah LA battery with chargers designed to charge cell phones and you are wondering why they keep burning up? ? :confused:
     
  11. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
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    The way I read it ( and I could be wrong) is he's trying to run the automotive type phone charger from the 12 volt battery.We don't know if he's using the phone while charging.
     
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