Charger not charging to 42 volts...any ideas?

Hey guys,

So I tried out my second charger and it again is only charging to 40 volts when I plug it in…I bought one of the 42 volt balance board chargers off of Amazon and as you’ll see in the photo, it turns green and registers as fully charged…yet that is clearly not true…do these chargers have internal voltage cutoffs?? I’m lost…my BMS is wired properly and everything😐Any help would be great…

That BMS doesn’t look like one with balance charging. Do you have a link? It could be hitting over voltage on a cell group and cutting off charging. Take out the JST header and measure the voltage of each group using the leads from the header.

here it is:

I’ve bypassed it on discharge. It should be balancing though…all of the balance leads are covered by tape and I just measured each cell earlier and they are all the same voltage (3.6 at the time)

I mean measure the balance leads when your charger cuts off to see if one group is higher voltage than the others.

You have 3 cables going to battery negative right? Two on the BMS and one for discharge?

Yes I do. And every cell is 3.8 average…

I had this same problem two times because spot welding failed so bms charged one 4p group as 3p. Bms stopped charging both times at 40v. I think bms cut it there because of over voltage in broken group.

Weird eh?..

so then it’s only charging to 38v? For some reason the BMS cut off charging thinking something went wrong.

If you made sure each group has not hit 4.2v then I’d suggest using the battery to trigger the overvoltage release and try charging again.

This happens every time I try to charge…how would I do that?

So you’ve already discharged and charged the pack several times?

Yes. I’m thinking on of my parallel connections came loose…it is 10s3p pack…of that happened that could be the problem?

Yea, that’s why I asked you to check the voltage of every group. If a cell got loose and became a 2P or 1P group, it would get to 4.2v earlier than the rest of the groups causing and overvolt cutoff

Durp, stupid question I asked :smile: Update: so when I plugged the JST balance connector back in it start charging again…the light is back to red! The saga continues…

Also: with this new charger it only charged to 38 volts and my old 42 volt charger charged to 40 volts before it stopped. Not sure why they differed but I guess I’ll see what happens now as it started charging again!

Well one of the parallel connectors just may be broken…went back to check again and one cell reads 4.1 while the others are around 3.8…that may be it

Yep, that’s what it sounds like

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a few video about it

You still need to use a 12volt power supply out of old pc free or 48volt hp severe power supply even better

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You should not have to disconect bms and you can charge right up to 42 i set mine to 41 volt