Electron Wheel BMS replacement

[myros]

Hi! first time posting here

I have an electron wheel that for some reason has stopped charging or turning the wheel on.

I have a little experience with the system, the wheel had been given to me as it sat in a garage for 3 years and was no longer working. After replacing the battery cells the wheel worked great for a summer. After sitting in the shed for three months the wheel no longer charges or turns on.

I started troubleshooting the battery packs and they all read 4.1v which makes me thing there could be something wrong with the BMS. When I read the voltage at the pins for the individual packs 2 out 3 read 4.1v but one does not give me a reading.

I have not been able to find any information about the BMS used by the wheel and I was wondering if I could replace it with a generic one? or if anyone can help me understand where could i buy a replacement from?

I have posted a few pictures of the BMS and wheel components:

https://imgur.com/a/t2kXjJp

Thanks!

 

[amberwolf]

I started troubleshooting the battery packs and they all read 4.1v which makes me thing there could be something wrong with the BMS. When I read the voltage at the pins for the individual packs 2 out 3 read 4.1v but one does not give me a reading.

If you get no reading at a pin on the BMS, but at the cell end of the same wire you get a voltage, it means the wire is disconnected somewhere between. It can be broken at either end, or inside the insulation. Fixing that wire would then fix the problem.

 

[myros]

See the following two pictures:

https://imgur.com/a/NI9oFuk

In the second picture when I test the dots in pairs I get no reading for one of the battery packs in the BMS. When I disconnect the wires from the first picture and i test the cable ends I do get voltage there that i why I'm thinking there could be something wrong with the BMS.

 

[amberwolf]

See the following two pictures:

https://imgur.com/a/NI9oFuk

Unfortunately those imgur site pics don't show up for me, on any browser, most of the time (randomly, sometimes some do; I have no idea why). If you attach the pic directly to your post using the Attachments tab, and Upload button, then anyone that can see the post can see the pic.

In the second picture when I test the dots in pairs I get no reading for one of the battery packs in the BMS. When I disconnect the wires from the first picture and i test the cable ends I do get voltage there that i why I'm thinking there could be something wrong with the BMS.

That usually indicates a poor connection at the battery end of the wire, so that it has very high resistance. When there is absolutely no load on it, not connected to the BMS, it would then show a voltage. But when plugged in, the tiny resistance in the BMS drops taht down to nothing.

If there *was* something in the BMS pulling the voltage down that far, the cells attached there would have been drained dead, and their voltage would not rebound to a full-level voltage when disconnected from the BMS. They might go up a little, but not that much.


So, if the voltage on the cell went up to match the other cells, it's probably still a connection issue.

If the voltage only went up a little bit, it's probably a channel in teh BMS that's got a balancer stuck on, and it's killed that cell group.

 

[myros]

Thanks so much, will check all the connection points to the battery packs.

Here are the pictures that I posted to imgur:

 

[amberwolf]

Thanks for the pics--those "JST" connectors sometimes have spread pins on the contacts in the wire-end of the shell. If that happens, then probing from the wire-side of the shell, while plugged in, will show whatever is on the wire itself, even if probing the solder pad on the board shows nothing. (or vice-versa).

When you see that happen, it means the connection is bad, and you might be able to get the contact out of the shell without damaging anything, and very very gently squeeze it a bit to make a better connection (best to compare it to one that already works, on another wire, and make the bad one match the good one).