Controller/BMS Issue

[ToughRowToHoe]

Hi All, I just recently rebuilt my bike and while at it upgraded my wife's. Both bikes now use KT Controllers (or knock offs) based on the wiring: Amazon.com

With 52 volt Yose downtube batteries:Amazon.com

Worked great for about two months, but eventually developed a problem. The controller started kicking off like it had hit the low voltage limit. If I feathered the throttle in slowly it would be OK until I hit a hill. To keep it from kicking off while ascending the hill, I had to back off the throttle. However, this only occurred with one of the batteries. There was no problem at all with the other battery. It has now begun happening with both batteries. And the first battery progressively got worse. This also is happening with the second battery. I've tried a few searches on Endless Sphere but didn't find a similar issue. Any ideas what might be the cause?

 

[ZeroEm]

Sounds like the batteries are getting weak. I would watch the voltage sage as you ride and note the voltage when it's kicks off.

 

[E-HP]

Well if you pull 40A from a battery that’s rated for 10A and 30A peak, you probably can kill the packs in a ride or two. The pack is made with generic Chinese cells, so the 30A peak is a dream.
Based on the battery’s bad reviews, might be lucky you didn’t have a fire.

 

[amberwolf]

Hi All, I just recently rebuilt my bike and while at it upgraded my wife's. Both bikes now use KT Controllers (or knock offs) based on the wiring: Amazon.comhttps://www.amazon.com/Electric-Bicycle-Brushless-Controller-Intelligent/dp/B0DJ1616CK

Wiring doesn't have anything to do with what kind of controller it is. The label will tell you what kind / brand it is. If it says KT or KunTeng, then.... Otherwise, it is whatever it says it is.

With 52 volt Yose downtube batteries:Amazon.com

Worked great for about two months, but eventually developed a problem. The controller started kicking off like it had hit the low voltage limit. If I feathered the throttle in slowly it would be OK until I hit a hill. To keep it from kicking off while ascending the hill, I had to back off the throttle. However, this only occurred with one of the batteries. There was no problem at all with the other battery. It has now begun happening with both batteries. And the first battery progressively got worse. This also is happening with the second battery. I've tried a few searches on Endless Sphere but didn't find a similar issue. Any ideas what might be the cause?

Most commonly that is caused by bad cells (or fake ones or recycled garbage, etc), poor construction, etc. See the many many battery troubleshooting threads over the years for how to test them.

Also, if the batteries have been used at or beyond their ratings, then the usage itself has damaged them beyond whatever problems they started with.


Generally battery problems are the cells, and fixing that correctly requires replacing all of them with new, quality, matched cells, that are *actually* rated for the usage they'll see. If you replace cells you'll probably need all the tools to do it, which will probably cost as much as a cheap to middling battery, not counting the cells (which will probably cost up to as much as a new good battery, if you're really buying the right cells and they're actually good).

Replace just the "bad" cells and the rest of them will probalby follow soon enough, requiring further repairs again and again for more and more money..

 

[docw009]

I would agree, high current wore out a cell and killed its capacity, which put more load on the remaining cells. They wear out, and It cascades down the line,

 

[ToughRowToHoe]

Thanks all.