Ebay seller Petrolscooter from UK claims that 36v speedcontroller cannot handle 40V?

#1
http://www.ebay.co.uk/itm/Electric-...ike-Bicycle-/173023535661?hash=item284901a22d This is the kit I bought and I tried it with G-max 40V lithium battery which has 18650 cells in it. Nothing happened when I tried to start the motor, only the light on throttle. Seller told me that I destroyed the speedcontroller with too much current? This is their answer to my first attempt to solve the problem (not the last :) Is this bs or not? New message from: petrolscooter (272,618RedShooting Star) Hello, I have spoken to my colleague. The problem is very likely to be the voltage he is using This kit is designed to work with 36v not 40v or above, you can get away with maybe 1-2 volts extra but not 5-6 volts or more It may show power as the power indicator would work with 24v - 48v but the speed controller and the motor would not like the extra voltage at all. I would recommend you purchasing another Speed Controller, we do sell them for £39.99. This would then solve the issue you are having. If I can assist with anything else please let me know. Kind Regards - Sales
 

harryS

Well-Known Member
#2
A little education on 18650 cells. The nominal voltage is 3.7 volts when half discharged. At full charge, a cell is 4.2 volts, and it is industry practice to shut them off when they reach 3.0 volts. Your typical 36V battery will have 10 groups of cells in series. At full charge, then you get 42 volts on the battery.

When a 36V ebike battery is showing 36 volts, it's about 60% depleted, and if it is a really cheap one, there might not be much useable power left.

I'm sure that your G-Max is like Ryobi, who also sell 36V batteries, but call them 40V batteries. It is possible you have a bad controller, but I doubt you damaged the controller with the GMAX. Such BS from your seller. They should know the controllers are good to 42 volts (and more).

I have run my ebikes on "40V" Ryobi batteries, by the way. They're weak, but work on small motors. Is the bike working now?