Raleigh Velo display

[Puffindog]

I recently bought a used ebike for my wife, worked fine for a while. The battery condition display on the bike then went suddenly to a single bar from full. I thought the battery had failed. I'm an electronics engineer and I took a good look at the battery. The 10S pack (nominal 36 volt) gave a voltage of 40v (no load)., each cell pack at 4 volts or thereabouts( Fluke DMM). The push-button battery level on the battery showed full also. Charging is what you would expect, 3 miles (10mins) hilly trip at full assist takes about 1hr to restore with charger. Charger in at 42volts and full shows low on the handlebar display as well.

All the voltages on the BMS look correct. The BMS looks like it sends battery status to the control box as -ve pulses every few seconds (scope). The control box sends the same format digital info the display, presumably with additional speed data as -ve pulse. The only thing I would say is that the d.c. voltage on the data lines is about 3.2 volts, I would expect this to be 5 volts which is the norm for data comms. All connections checked, clean and good.

Any ideas (I have no circuit diagram or schematic for the system) how I proceed? Would you have to replace BMS, Control & Display all together to rectify the issue?

Bike still works fine, just annoying the "fuel gauge" is flakey. There seems to be not much technical info available for any ebike system

 

[Nealh]

Battery is knackered if it only charges to 40v, a good battery will be about 41.4/41.5v minimum, nothing wrong with the Velo's display. Even a knackered battery that charges to 42v isn't an indication of it's well being, the tell tale is put a load on it and if it collapses then it's had it.
What you see with the bars is known as voltage collapse as the knackered cells can no longer deliver the current asked of them, sometimes a bar display might drop one or two bars under load then rebound almost instantly.

Wire up a meter temporarily between controller and battery go for a ride or test load the static bike with wheel off the ground and use the brake to apply the load, tell us what happens to the voltage a couple of volts sag is acceptable but more of a collapse indicates an old worn battery.

 

[Lucylettuce]

Did you buy the bike from eBay from a seller in Grangemouth by any chance? I was interested until they said battery hadn't been charged for five years.

 

[Puffindog]

No, thanks for your response anyway.