My ebikes


New Member
My name is David and I live in Queensbury Yorkshire in the UK.
I have had ebikes for 15 years at the moment I have a 1500watt kit fixed on to a Claude Butler bike. At the moment I am having very bad trouble with my battery giving out 200 amps when my bms is only a 40amp bms.
Any advise on this would be great.


Well-Known Member
Welcome to the site.
I don't know of any meter under $1000 that will measure 200 amps. Mostly in that range people use a shunt that will put out 50 mv for a 500 amp current through it, then measure across the shunt with a millivoltmeter. What motor do you have that draws 200 A? My 17 AH 48 v luna battery hogs down to yellow led (under 48v with 53.6 full charge) if I draw even the 26 A my controller will supply up a steep hill. The bike slows to 4 mph with a 300 lb load on a 15% grade if my downhill momentum didn't carry me over the top. And that is a "1200 W" geared hub motor, which you are not supposed to be allowed to buy in the UK.
BMS definitely give you an upper current limit, if your parallel stacks of cells will even exceed that limit. The first two "batteries" I bought would only put out 5 to 7 amps into a 10 ohm 500 W load resistor. Piles of garbage, they were. Only one of the 14 stacks working in each. I took the top off and probed the BMS. Probably bad welds, but I'm not going to dig in deeper to find out.


Well-Known Member
I would think you're looking at some kind of false reading. 200A is short circuit territory, and most BMS are fairly good at restricting current to their rated numbers.

You might want to expand on how you're seeing 200A and what is going on when it happens.