Rain kills controller?

[bancars]

I have a simple 36V DIY ebike. It rained a couple weeks ago (ebike was outside, battery was inside) and I rode the ebike the next day (road was still wet). Everything was fine for a couple miles, and then the motor quit. A few hours later (no rain that day), the motor worked for half a block, and then it quit permanently.


Clues:

*When I plug the controller into the battery, there's normally a small spark. After the motor quit, no more spark.

*I took the controller apart and found drops of water inside the case, and the film covering the largest capacitor was split. The capacitor metal body appears undamaged.

*One of the controller-side power wires was broken at the XT60 connector. I resoldered it, and after that the spark returned when I plug the controller into the battery. However, when the throttle wires are shorted (this has been my "throttle" for a few months), the controller makes a clicking sound, but the motor doesn't turn. (I don't have an explanation for why the power wire would have broken at the same time as the controller apparently failed.)

*Mutitester shows 36V across the battery's charging wires, but 0V across the battery's discharge wires. There *is* a spark when I plug the controller into the battery's discharge wires; I don't understand how that's possible when the multitester shows 0V-- maybe the BMS doesn't allow power to flow immediately? I measured several times, and always got 0V. I don't remember measuring across the discharge wires when the system was working, so I don't know if 0V is a normal reading. (Battery+BMS never got wet.)


Questions:

*What component needs to be replaced-- controller or BMS?

*What should I do about rain? Don't plug in when roads are wet? Buy a water-resistant controller? Buy another $12 M95-SH 350W controller and coat all the case openings with silicone caulk? Also, I haven't done anything to protect the battery internals from water.

*Should I add a 20A car fuse to the battery? I don't know if the BMS (Daly 12S 36V 20A LIFEPO4 separate port) functions as a fuse. It's scary to even think what might have happened if the loose battery power wire had shorted against the other power wire or against my thumb, if the BMS allows unlimited amps to flow through.

*Can anyone recommend a cheap on/off throttle? (not a twist throttle-- I had one and it only lasted a few months; an on/off switch should be fine, since my controller doesn't have enough power to burn rubber)

 

[amberwolf]

*When I plug the controller into the battery, there's normally a small spark. After the motor quit, no more spark.

This usually indicates the BMS of the battery has shut it's output off. That can be from overload, such as a short in the controller.

Or else it indicates a failed connection between battery internals and controller internals, such as broken connector wires.

*I took the controller apart and found drops of water inside the case, and the film covering the largest capacitor was split. The capacitor metal body appears undamaged.

It is difficult to tell for sure, but there is a glare on the metal where the black wire is right up against the bare metal of the damaged cap that could indicate insulation on the wire has failed and wire conductor is touching the can. That shouldn't directly be a problme because the can may be electrically isolated, and even if it isn't, it's probably negative side of cap, same potential as teh black wire would be. However, it, and the damaged cap shrinkwrap, indicate a problem with overheating, most likely of that capacitor, which usually happens when it has failed, or is insufficient for the controller's design.

*One of the controller-side power wires was broken at the XT60 connector. I resoldered it, and after that the spark returned when I plug the controller into the battery. However, when the throttle wires are shorted (this has been my "throttle" for a few months), the controller makes a clicking sound, but the motor doesn't turn. (I don't have an explanation for why the power wire would have broken at the same time as the controller apparently failed.)

If there was arcing at that broken wire, the RF from the arc could have damaged the controller. (usually the FETs, or the main low-voltage power supply LVPS).

FWIW, at least some controllers have a safety feature such that if the throttle input goes above some limit (around 4v to 4.5v) it shuts off teh controller, to prevent uncontrolled full power when the ground wire to the throttle breaks, or the 5v to the throttle shorts to the throttle signal wire.

So...even though it worked for you before, to presumably short the 5v to the signal wire, if it worked before because the 5v was a little low, if it now for wahtever reason is "norma'L full 5v, then it could trigger the safety shutoff, and fail to operate without a proper throttle signal.

*Mutitester shows 36V across the battery's charging wires, but 0V across the battery's discharge wires.

Is this with the battery disconnected from everything? If so, then that's why the system doesn't operate, because you don't have power to the controller. You might still get a spark because the FETs in the BMS don't *fully* isolate the battery, so a current could still flow for an instant between battery and controller capacitors. I haven't seen this, but it should still be possible.


Or only when it is connected to controller? If so, then it means the load of the controller is causing the BMS to protect teh battery by shutting off, which usually means a short in the controller.

*What component needs to be replaced-- controller or BMS?

Probably controller, but we need more info (see above).

*What should I do about rain? Don't plug in when roads are wet? Buy a water-resistant controller? Buy another $12 M95-SH 350W controller and coat all the case openings with silicone caulk? Also, I haven't done anything to protect the battery internals from water.

There are a number of threads about waterproofing, riding in the rain, winterizing, etc., that have good tips about this stuff. I'd look around for those, then select the things from them that are practical for you.

*Should I add a 20A car fuse to the battery? I don't know if the BMS (Daly 12S 36V 20A LIFEPO4 separate port) functions as a fuse. It's scary to even think what might have happened if the loose battery power wire had shorted against the other power wire or against my thumb, if the BMS allows unlimited amps to flow through.

A fuse won't hurt, just be sure to carry a spare. Use a good fuseholder, preferably bolt-on fuses, so it doesn't have a poor connnection at the fuse itself, which can cause problems up to an actual wiring fire. Put the fuse right at the output from the battery case, if possible, or even inside the battery case is better.

*Can anyone recommend a cheap on/off throttle? (not a twist throttle-- I had one and it only lasted a few months; an on/off switch should be fine, since my controller doesn't have enough power to burn rubber)

These are often used on little kids' foot scooters. But their controllers are designed for that, so to make it operate properly on yours you may have to add some resistors as a voltage divider for the input to it, so that it reduces the 5v down to whatever the max voltage on your controller is listed as (usually between 3.5 and 4v). That way you don't trigger any throttle-high-safety features and disable the controller.