Help with Ebike charger repair?

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Twistgripper   10 mW

10 mW
Posts: 23
Joined: Sep 20 2019 5:11am

Help with Ebike charger repair?

Post by Twistgripper » Apr 29 2020 2:30am

Hi, I have an ebike 48v LiIon charger (states 54.6v actually) not working. I received it like this with the bike and do not know the details of how it failed. it was only plugged into the bike/battery it was intended for - all new from factory but bought at auction...

I would order a new one because they are fairly cheap, but the shipping will take several weeks to a couple months because of Covid! So i'd like to attempt to repair. I'm ok with a meter and soldering iron, but i dont know enough about electronics to know how to test all the components.

When I turn it on, instead of getting a constant ~52vdc, I'm getting wildly and quickly fluctuation between 4-27v on my meter. It does this with or without load (plugged in to battery or not). There are no signs of scorching or overheating anywhere on the board (I looked with magnifying lamp thoroughly on both sides).

Re-soldered some crappy joints - no change.
- checked fuse - good.

If I put my ear right up to it, I can hear a noise I could only describe as sounding like a synth version of a uk Police siren. No signs of anything overheating on the board. Its loudest over the transformer. Suspect transformer bad?

when plugged in, the green led does light, but does not turn red when plugged in to battery to charge like it's supposed to.

Pics here:

Any help is like "test the mosfet, cap, resistor" etc - pls include HOW to test them..

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Drunkskunk   100 GW

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Joined: Apr 14 2007 11:37am
Location: Dallas, Texas. U.S.A.

Re: Help with Ebike charger repair?

Post by Drunkskunk » Apr 30 2020 1:36pm

How positive are you that the Ebike's battery is good? many Lithium chargers will not attempt to charge the battery if they detect a problem, such as the battery's voltage being too low.
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999zip999   100 GW

100 GW
Posts: 9467
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Help with Ebike charger repair?

Post by 999zip999 » Apr 30 2020 1:51pm

How's the battery in your meter sometimes a low battery in a meter will give terrible results

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