smugmonster
1 µW
Hi, I've just got back from my first ride on my first e-bike, which was curtailed because the BMS cut power from the battery after 2 or 3 miles. The battery is a 5P 10S I built using a Vruzend kit. Disconnecting and reconnecting power to the controller got me going again but the same thing happened several times. I'm hoping the expertise here will get me back in the saddle.
I measured the pack voltage as 39.4 and all the parallel cell groups, except one, at between 3.96 and 4.08. The exception was the last one, the negative terminal next to the BMS, which was just 3.34. So presumably that was why the BMS cut the power?
I disassembled the faulty parallel block to measure the cells individually and all 5 were 3.34. (I admit I was expecting the volts to vary, pointing to a bad cell or cells).
After putting everything back together I charged the battery, getting a pack voltage of 40, 4.03-4.18 for the other parallel cell groups and 3.41 for the faulty one once I noticed the green light was on the charger. After another hour the only difference is the two which were 4.18 are now 4.17.
So now I'm puzzled but hoping the answer is obvious to those with more knowledge.
Do I have one or more bad cells and the BMS isn't allowing the others in the group to go past that voltage. If so, is there a quick way of identifying the bad ones?
Or is it a bad BMS?
I measured the pack voltage as 39.4 and all the parallel cell groups, except one, at between 3.96 and 4.08. The exception was the last one, the negative terminal next to the BMS, which was just 3.34. So presumably that was why the BMS cut the power?
I disassembled the faulty parallel block to measure the cells individually and all 5 were 3.34. (I admit I was expecting the volts to vary, pointing to a bad cell or cells).
After putting everything back together I charged the battery, getting a pack voltage of 40, 4.03-4.18 for the other parallel cell groups and 3.41 for the faulty one once I noticed the green light was on the charger. After another hour the only difference is the two which were 4.18 are now 4.17.
So now I'm puzzled but hoping the answer is obvious to those with more knowledge.
Do I have one or more bad cells and the BMS isn't allowing the others in the group to go past that voltage. If so, is there a quick way of identifying the bad ones?
Or is it a bad BMS?