Fried by BBSHD controller doing the shunt mod

[K72nova]

I made a rookie mistake and blew zapped my BBSHD controller, what happened was I did the shunt mod and everything SEEMED fine. I made the mistake of testing the controller outside of the case just hooked to the bike, I only read .5Amp on my display but that could have been because there was no resistance. I decided to put the case over the controller to hook it up fully and try to see if it worked which was my second mistake. I should have pulled the controller off of the bike first but instead I tried to just put it on.

Here is where my question comes in, is there residual power on the controller in the form of a small battery or something like that? When I tried to put the case over the controller, I got a big zap from grounding onto the frame. BUT the battery was disconnected from the controller/motor, the motor was completely disconnected from the bike other than the controller being plugged into the motor. I have no idea other than some small power source on the motor/controller?

If there is a power source, how do I ensure that I kill all that power before I do this to another controller if I do ever decide to try again?

Also, does anyone know if the .5amp with no resistance is normal? I’m curious if my shunt mod actually worked or if I had screwed that up too?

I’m assuming that there is no chance of me figuring out what happened to the controller, but I did order a programming cable to plug in and see if I can do any troubleshooting, I didn’t see any obvious marking on the controller to see what could have blown.


Thanks!

 

[E-HP]

Capacitors discharging.

 

[spinningmagnets]

Yeah, capacitors. Turning on and off the current from the battery rapidly (during normal operations, to energize each of the three phases in their turn) will cause voltage ripple, and capacitors can be used to smooth out the voltage spikes. The side effect is that even after you turn off the controller and disconnect the battery, you can poke around a controller and then get a big spark if you touch the wrong thing (capacitors can store a certain amount of charge).

These types of capacitors in this application will also slowly drain down, so...after its been off for a while, when you go to connect the battery, the capacitors suck-up a bunch of charge from the battery pack, which is manifested as a big spark at the connector. The "anti-spark" connectors for batteries have an integrated resistor to allow the capacitors to fill up slightly slower, because if you allow there to be a large spark upon every time you connect the battery pack, it can cause corrosion on the metal contacts.

 

[K72nova]

Thanks for that info!

Is there a safe way to discharge the capacitor in this scenario? My initial though it to hit the throttle after disconnecting the battery, but will that be enough to discharge? Maybe hook up a light bulb to the leads from the battery?

 

[fechter]

Is there a safe way to discharge the capacitor in this scenario? My initial though it to hit the throttle after disconnecting the battery, but will that be enough to discharge? Maybe hook up a light bulb to the leads from the battery?

Either of those approaches should work. If you simply turn on the controller, it should drain the caps in about one second.

Depending on exactly what made contact, your controller might still be OK.

 

[K72nova]

Either of those approaches should work. If you simply turn on the controller, it should drain the caps in about one second.

Depending on exactly what made contact, your controller might still be OK.

Maybe plugging the controller into my PC will give me some insight but when I plugged the controller into the motor after the zap, I didn't see most of the info that I usually see on my display, only my battery info.

 

[Tommm]

Thanks for that info!

Is there a safe way to discharge the capacitor in this scenario? My initial though it to hit the throttle after disconnecting the battery, but will that be enough to discharge? Maybe hook up a light bulb to the leads from the battery?

Easy: unplug battery, turn on bafang display. It will work for a few seconds, then turn off as the caps are drained. Btw residual discharge is VERY small on the bafang. I had my battery disconnected for weeks and I could still power on the display for a few seconds.

 

[E-HP]

Thanks for that info!

Is there a safe way to discharge the capacitor in this scenario? My initial though it to hit the throttle after disconnecting the battery, but will that be enough to discharge? Maybe hook up a light bulb to the leads from the battery?

I just turn on my headlight, since it's powered through my controller.

Luckily controller capacitors are small. People used to get electrocuted working on old electronics before the caps discharged. A stun gun or defibrillator are basically capacitors, with a charging circuits built in.