Too hot or too little voltage?


New Member
I was riding up a hill at the end of a very hilly 23 mile ride with a 500 watt motor with a 10.5 battery. On this last hill the motor quit with one bar of voltage showing. I turned off the motor and kept pedaling up the hill with great difficulty. After a while I tried the motor with level 1 assist and it worked! I got home and charged the battery and the bike worked fine. Was it too hot or too low voltage?


Active Member
I couldn't say which was the problem, but I expect it was the low battery. Court has a video up someplace where he is talking to the BionX rep, and the rep pretty much said you can't overheat the system with normal use.

As always, your mileage may vary. I am not affiliated with BionX, just a random forum user, so take anything I say in that context ;)


Active Member
Some systems gave temp sensors, but it was likely your low voltage cutoff.

Two things make me think this. First, the voltage of a battery drops as it runs down. A 48V battery might measure 54V hot off the charger, but when drained, it might measure 42V. Second, while under heavy strain, such as going up a hill, voltage will temporarily sag. When you remove that strain, it'll go back up a bit.

My guess is that your battery was low, say 44V. Then, on the hill, it sagged to 42V and cut off to protect itself. While you pumped up the rest of the hill, the battery rested and unsagged back up to 44V, and you were able to limp home without inducing more sag.