Problem with SLA 36 volt battery charger

Discussion in 'General Electronics Chat' started by gsrnadeem, May 22, 2014.

  1. gsrnadeem

    Thread Starter New Member

    May 22, 2014
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    0
    Hello,

    I have SLA battery charger I'm using for my e-bike. All the sudden the charger stopped to charge and just get an output 8-10v instead of 36-44v.

    Can I get some help please on identifying the issue and fix it?

    I tried to troubleshoot the the charger with no luck to find the issue. I can't find the semantic for it, but this one is very similar to what I can see in the charger.

    http://www.seekic.com/circuit_diagr...tric_car_battery_charger_circuit_diagram.html

    I can provide more photos for the charger if needed. Now the led indicator is switching between red/green too fast and too dimmed as well.

    Thanks,
    Gaser
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Start looking for a replacement charger.
     
  3. gsrnadeem

    Thread Starter New Member

    May 22, 2014
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    0
    Replacement would cost $70-$100, and looking inside, I can't see any expensive parts, so I thought fixing it would be that easy and cheap if only I get help :confused:
     
    Last edited: May 23, 2014
  4. Brevor

    Active Member

    Apr 9, 2011
    279
    54
    Mr. Chips is correct, that is a switch mode charger. Start looking for a new charger.
     
  5. wayneh

    Expert

    Sep 9, 2010
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    Cheap maybe, but not easy. If your time has any value, you've heard the advice. A genuine schematic would help but as you know, these can be hard to find.
     
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,795
    951
    It sounds like a possible short on the output somewhere. Current limiting itself therefore.

    Ohm test between the two wires and perhaps visually inspect as well. If that is not the issue, pat yourself on the back for trying and pony up for a new charger.
     
  7. bwilliams60

    Active Member

    Nov 18, 2012
    725
    90
    Okay I'll bite. Somewhat of a newb but I don't see anything complicated on this board. Can someone explain why this should be tossed and replaced? What is meant by a switch mode charger?
    For the OP, the tall black capacitor in the corner, 400V 68uF, is the top of that thing bulged up. Just curious, noticed the solder joint on the opposite side looked disturbed.
     
  8. wayneh

    Expert

    Sep 9, 2010
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    Cost of labor, pure and simple. By the time you diagnose the thing, order the parts, install the parts, it's just not worth it. A schematic and access to tools such an oscilloscope would help speed up the diagnosis part. Probably still not worth it but at least it could be fun. Without those aids, frustration.

    The transformer is likely the only part with much cost to it, if you can find it at all.
     
  9. gsrnadeem

    Thread Starter New Member

    May 22, 2014
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    Which wires you are suggesting? for transformer or for the output in general.

    Do I need to disconnect the transformer to check it?

    Also, I checked the input to the transformer, and it reads 165dcv (and 365acv not sure about this one as it has the diodes in front of it, but could be my voltmeter)

    Also, checked the big capacitors, and diodes and they looks fine.


    For whom suggesting a replacement, as I mentioned this cost ~$100 and this one is not that old, used only for couple of times. I can't spend $100 every couple of months to replace this charger. I think my time worth spending in such ones.

    I can draw the schematic for it to whom is looking for, but the one I posted looks similar to what I can tell.

    I'm taking this project as this is my hobby and not only to fix it, but I'd love to play with electronics and I find myself there.

    Any help would be appreciated.

    Thanks,
    Gaser
     
  10. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    What is the mains voltage in your location?
     
  11. bwilliams60

    Active Member

    Nov 18, 2012
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    I get that part of it but he was asking for help to fix it, so there is no labor cost and I thought he wanted to be educated. Other than that, is there a reason why you shouldn't fix it? If we go with that way of thinking, we should throw out everything when it breaks because by the time you add in labor, nothing is worth fixing anymore especially if it is offshore. But I think we can take things and make them better :)
     
  12. inwo

    Well-Known Member

    Nov 7, 2013
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    Are you absolutely sure charger is bad?

    An over discharged battery can make a charger look bad!
     
    wayneh likes this.
  13. gsrnadeem

    Thread Starter New Member

    May 22, 2014
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    0
    I'm in US which means 110vac
     
  14. gsrnadeem

    Thread Starter New Member

    May 22, 2014
    6
    0
    Absolutely. The charger has a led (red when charging, green when float) this led is blinking weakly between red and green, and by checking the output voltage it is changing between 8vdc and 10vdc as if it charging and discharging.
     
  15. wayneh

    Expert

    Sep 9, 2010
    12,154
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    I was referring to the value of his own time. How many hours would you spend? One hour, yes. But what if it goes way past 10 hours with no end in sight? Knowing to stop before you get started is wisdom.
    People here with some experience (not me, but Mr. Chips and others) are trying to educate him on the proper path forward.
    Nope, go for it. If the prospect of spending a few hours to come to the same conclusion is not a deterrent, then jump in. People do get lucky, and it can be quite a thrill to win against the odds. Just be aware of what you're getting into.
    That's pretty much the way things are. Sad but true, especially with electronics. I fix what I can, but to quote Dirty Harry, "a man's got to know his limitations".
     
  16. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    In that case the max voltage you should see on the big fat cap is 154VDC. If your meter is reading 165V either the mains voltage is higher than nominal or your meter is flakey. At least the four main rectifier diodes seem healthy.
     
  17. bwilliams60

    Active Member

    Nov 18, 2012
    725
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    It was nothing personal and I hope you didn't misinterpret my reply, but to answer your question, I have spent way too much time figuring out things but I think after 35 years of experience in my field, I became a better technician because of those ones that made me pull my hair out. I don't like to be beat by something I know I can figure out with a little help. They were all hard lessons but ones I will never forget. I think if we are all honest, we have all done it at some time or another. Only when we get to this point can we look back and say, it's not worth the time. Everybody has to start somewhere and hard lessons are sometimes the best. If he has lots of time and some knowledge, have at er and see what you can figure out. No better teacher I know of than getting your feet wet. Well maybe that's not the best analogy when working with electricity!
     
  18. inwo

    Well-Known Member

    Nov 7, 2013
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    Sounds to low for 36v:confused:

    What does the battery read?
     
  19. MrChips

    Moderator

    Oct 2, 2009
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    I have a number of ebikes and non-functional ebike battery chargers.

    Here is an example of the result of faulty chargers:

    [​IMG]

    I have a number of battery sets (four 12V batteries per ebike) when the charger fails to detect full charge and fails to switch to trickle charge.

    The result could have been an explosion and serious fire.
     
  20. inwo

    Well-Known Member

    Nov 7, 2013
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    I have a ton of battery scooters and toys which are similar. Have not had a charger failure. However once batteries lose a cell, they never reach peak voltage and start heating.

    The chargers I have will not charge if battery gets below, say 30V on a 36V system.

    I have not found a suitable dummy load to test them.
    The only way I can test, is to charge the battery over the threshold, before connecting the auto charger.

    When reading voltage of a connected charger, you are reading battery voltage. (mostly)
     
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