Bafang m625 mid drive kit with the new canbus is nothing but trouble. Please help pertaining to my newest issues with the battery

Audioguru139

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Jul 28, 2023
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2
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Florida
The seller disappeared off of Amazon shortly after I purchased the newest kit. M625 1000w mid drive with cam bus with the proprietary 50.4 19.6 ah 960wh data driven battery. Initially the data issues failed and after replacing three controllers I installed a different controller and bypassed all the junk. Still using the motor and the battery. Everything worked great until the week of July 4. Supposedly the hottest week on record earth wide and I live in Florida and use this bike to get to work. Essentially the battery just slowly stopped taking a charge. The charger is also truant on the receive data rx and transfer data circuit to toggle from green to red etc. anyway now the chsrger reads 58v with green light but once plugged into the battery it immediately starts blinking red and the voltage drops to 9v . Now the battery chsrge light indicator is stuck on with 3 out of 5 lights all the time and will take a charger. I’m still getting voltage at each cell pack. I am thinking that the bms just plainly got too hot. My problem is I can’t find parts becuase this is so new or I can’t find anyone or company that will help. I hate to throw away this battery over a bms. Please help? Thank you for the help in advance. It’s very appreciated.
 

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First, some thoughts and info on the most likely issue:

Still using the motor and the battery. Everything worked great until the week of July 4. Supposedly the hottest week on record earth wide and I live in Florida and use this bike to get to work. Essentially the battery just slowly stopped taking a charge.
Depending on exactly what you mean by this (which you would need to provide details on for us to know), this may simply mean that a cell or cells in the battery are not balanced with the others (not the same voltage) because the characteristics (capacity, internal resistance, etc) are different (normally they should all be identical).

A properly designed and working BMS will rebalance cells at the end of every charge cycle, if it is left on the charger long enough to do this, which can take hours for a slightly unbalanced pack, to days or even weeks for a really badly unbalanced pack.

If the BMS isn't working right, or not designed to balance (some are, some aren't), or requires some part of the system outside the battery to command it to do this and that part isn't working or present, then it won't rebalance.

If it isn't left on the charger long enough for the rebalancing to happen each charge / discharge cycle, it also wont' rebalance.

If a cell is failing in certain ways, it will keep draining the rest of those in parallel with it (same group), and it won't ever rebalance or if it does it won't stay that way even just sitting there.

If the balancer in the BMS on a channel / group fails stuck on, the same thing will happen.

If you can measure DC Volts at the + and - of every cell group, starting at the most negative one (wiht the fat wire running from it's - side to the BMS), and ending at the most positive group (with the fat wire running from it's + side to the BMS or case connector), and list those here in order, we can see if any of them are unbalanced, and how badly, which may point to other test to narrow down the source of the problem.

Note that a good BMS will detect a serious imbalance (usually set in the BMS as more than 0.1v difference between cell groups) and turn off the charge and discharge ports so it can't be used, to prevent possible cell damage that can lead to a fire.




The charger is also truant on the receive data rx and transfer data circuit to toggle from green to red etc. anyway now the chsrger reads 58v with green light but once plugged into the battery it immediately starts blinking red and the voltage drops to 9v .
What specific point drops to that 9v, as measured by what instrument (separate multimeter/voltmeter, or built in on the bike display, etc)?

Now the battery chsrge light indicator is stuck on with 3 out of 5 lights all the time and will take a charger. I’m still getting voltage at each cell pack.
What voltage are you getting at each point? (see previous test description) If they are not all identical, it's an unbalanced pack, and the issues above may apply.

If the BMS has failed, you can replace the BMS; it might not fit in the same place as the original, and sometimes wont' fit inside the case with the battery without case modification, or extending the wires from the cells to the BMS, etc.

Note that working inside a battery pack has risks, especially when doing repairs involving moving wires around or cutting / splicing things, etc. While not common, accidental shorts can result in a sudden uncontrollable intense fire, so it's best to work outside away from structures, trees, etc., unless you have a fireproof area to work in.


Next, some questions about the rest of the system that might help if it not a internal battery pack problem:
The seller disappeared off of Amazon shortly after I purchased the newest kit. M625 1000w mid drive with cam bus with the proprietary 50.4 19.6 ah 960wh data driven battery. Initially the data issues failed
What specifically does "the data issues failed" mean?

and after replacing three controllers I installed a different controller and bypassed all the junk.
What specifically does "bypassed all the junk" mean?

What "different controller" was installed?

(links to specific items may help us help you troubleshoot)
 
Thank thank thank you for the help. I could not help it and roped the battery all apart. All cells were exactly balanced and I found some issues on the bms near the little on off switch and near the 30 amp fuse close to the input side. In all honestly I did boost up to a 40 a conntoller but it was self learning and worked for months. I honestly just think between the smidge higher amperage combined with the hell heat I was out in all day that week it just simply melted. I ripped the batt apart and all cells are
Exact voltage but I haven’t load tested them yet. I’m so done this e-bike China made junk. This is probably the fourth kit I have been screwed on. I’m over it at this point. Thank you for spending your time to reach out though. Also California is as of 5 days ago passing a bill to stop kids under 16(not me) and anyone without a license(me) illegal anyway. Anyway, thanks for your help
 
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