Clicking sound, followed by loss of power

[shmimel]

I recently completed (semi successfully) my ebike project! I found a "broken" kit for cheap on FB marketplace, which only needed one wire soldered back up. Unfortunately it was close to the axle so I ended up replacing and resolding a new 9-pin connector up to the motor PCB.

After plugging everything in, I get some scattered success. Every so often, both under load and not under load, I'll hear a clicking sound and the battery cuts out. All I have to do to remedy is unplug the controller from the battery and replug back in. This leads me to think there is some faulty low voltage detection within the controller, not the battery, because I would have to "reset" the battery (by plugging it into the charger) if that was what was tripping.

Does anyone have any tips? The system is 48V 500W and the battery is 19.4Ah, and that's unfortunately pretty much all I know about it since it was a second hand gamble.

 

[amberwolf]

Which part is the sound coming from?

If it's from the controller, perhaps it has a relay that is turning off.

If it's from the motor, perhaps there is a piece of something inside it that is catching on something and jamming for an instant.

If it happens every time the cutout happens, and the cutout only happens when the sound happens, finding the source of the sound will help find the problem.


If it was LVC it wouldn't happen without a load, unless it also happened every time a load was placed on it. You can eliminate LVC issues by monitoring voltage during a number of these events. If you see the voltage drop just before the event, and it's always at the same voltage it cuts out at, then it probably is some LVC issue. If the votlages are significantly different each time, it's probably not an LVC issue.

If it's overcurrent (from damaged halls or FETs or other controller damage leading to wrong phase timing) it could be either controller or battery cutting out. You'd have to measure current during the events to tell if this was happening. If it always happens above some amount, it's probably an overcurrent.

If the battery has a contactor (relay) in it instead of the plain FET type control most BMS have, it'd click when it turns off. It also wouldn't have to be reset by the charger if it was just an overload from the controller--removing the overload by unplugging it from the system would allow it to reset itself in most cases.


Note that broken wires at the axle often indicate some kind of impact or other incident at that point, usually while in use, that can short wires in that cable together, or short them to the axle, which could be grounded to the battery negative thru the frame and whatever battery mounts there are, etc. If either of those happens, there's various things that can be damaged in battery or controller or motor or anything powered from the 5v in the controller, depending on the specific wires involved and the actual incident.

Some wire damage is not obvious, such as when an axle edge cuts into multiple wires and shorts them together--it can just *barely* cut thru the insulation, sometimes leaving one wire with a complete cut or break, but others appearing undamaged. Depends on the kind of insulation, impact, etc.

 

[Chalo]

I one had a similar intermittent failure with one of my bikes. It turned out to have a simple but scary cause. The motor to controller phase power leads were just ring terminals attached with short screws and nuts and then covered with heat shrink tubing. After a time vibrating against the bike frame and each other, holes had become worn in the heat shrink and the phase leads were able to make contact now and then. When they did under load, they clicked (sparked) and I lost power momentarily.

I replaced them with Anderson PP75 connectors so that problem would not reoccur.