Issues with Bafang BBSHD + 14S9P battery pack from Em3Ev

I already emailed Em3Ev about the problem but because of their slow response time I decided to post it here too:

I installed the kit and battery two days ago. (Battery in the included bag for now)

It worked fine two days ago, and when I got home I charged it to 100%.

Yesterday I wanted to take it out again, but it didn't want to turn on. The on/off switch on the battery lit up when turned on, but when turning on the BBSHD using the displays button, the battery turns off, including the light on the on/off switch. I checked all the wiring but couldn't find any faults. It still wouldn't turn on.

I charged it for about a minute, and afterwards it turned on again. Then I rode it but noticed the speed not registering. After about 3 minutes of riding I got error 21 on the display and PAS and throttle stopped working. When I turned it off and back on it worked again for a short period of time.

I checked the sensor, and it's connected properly, but the light on it doesn't turn on no matter where I hold the magnet.

I let the bike sit for a while, and wanted to see if it suddenly started working again, but it was back to the first problem of not turning on again (and having to be 'jumped' to work again).


Today the BBSHD still wouldn't turn on, so I charged it for a minute again. After that it turned on again, but still no speed detection, so I tested someone else's sensor. That one also doesn't work on my bike, while it does on his.

I checked the BMS app, and everything seems fine there. Right now it's charged to 98% and 57.8v, and all cells are balanced to 6mah difference tops. At 100% it was at 58.7V.

I also noticed the motor will continue to be able to turn on after having charged it for a minute, but if I try to turn off the battery using the button, it doesn't appear to be doing anything. However when I turn on the motor again the battery turns off, leaving me stranded at the first problem with currently the only solution being charging the battery for a minute or so.

I just tried that again, and this time the off button worked once (with the display on this time). Afterwards I was able to turn on the battery and motor again. Then I tried it again, turning it off and on again, and this time the battery would, and the motor wouldn't turn on, so the same as it was before charging for a minute.

https://endless-sphere.com/forums/viewtopic.php?f=28&t=100011&p=1464181&hilit=bbshd+52v+cutoff#p1464181

Drain the battery down a couple of volts (below 54.4V) using a light bulb or other load, then see if it works. If it does, you may need the firmware updated, or just don't charge to 100% (that will also extend your battery's lifetime).

At any point have you measured battery output with your multimeter?

E-HP said:

https://endless-sphere.com/forums/viewtopic.php?f=28&t=100011&p=1464181&hilit=bbshd+52v+cutoff#p1464181

Drain the battery down a couple of volts (below 54.4V) using a light bulb or other load, then see if it works. If it does, you may need the firmware updated, or just don't charge to 100% (that will also extend your battery's lifetime).

Click to expand...

I will try this. Thanks.
I will charge to 80% most of the time, but will have to balance once in a while. I don't want to have to discharge it every time I do that.
With that issue, does it still work sometimes? Because as said I can get it started by charging the battery for a minute. Afterwards the motor will run, but not showing the speed and display error 21 after a while. When the error appears I need to restart the display for it to work again, but it will only work for 2-3 minutes before the error 21 shows again.

tomjasz said:

At any point have you measured battery output with your multimeter?

Click to expand...

I haven't, but I trust the BMS app to display it correctly. The Bafang display also displays about the same voltage.

Pizzabroodje said:

With that issue, does it still work sometimes? Because as said I can get it started by charging the battery for a minute. Afterwards the motor will run, but not showing the speed and display error 21 after a while. When the error appears I need to restart the display for it to work again, but it will only work for 2-3 minutes before the error 21 shows again.

Click to expand...

If you search the forum, there's some posts on that error (read about it when I was considering a mid drive), but the symptoms seem to be that the display shuts down, but the throttle and PAS still work, but you can't change the PAS level since the display shuts down. I don't recall the fix.

There's also this: https://flx.bike/blogs/news/fixing-error-21-aka-speed-sensor-error

E-HP said:

Pizzabroodje said:

With that issue, does it still work sometimes? Because as said I can get it started by charging the battery for a minute. Afterwards the motor will run, but not showing the speed and display error 21 after a while. When the error appears I need to restart the display for it to work again, but it will only work for 2-3 minutes before the error 21 shows again.

Click to expand...

If you search the forum, there's some posts on that error (read about it when I was considering a mid drive), but the symptoms seem to be that the display shuts down, but the throttle and PAS still work, but you can't change the PAS level since the display shuts down. I don't recall the fix.

There's also this: https://flx.bike/blogs/news/fixing-error-21-aka-speed-sensor-error

Click to expand...

Yeah I searched the forum for it, but can't find a solution. I can change the PAS level though (or do you mean if you don't change PAS you won't get error 21?).
I also saw that link, but I even tried another sensor and held a magnet in every possible way but to no avail so I think the controller or cable from the controller to the sensor is broken but would like to get this confirmed by someone who knows a little more about this.

In my experience (all with BBS02) how the error 21 (speed sensor problem) affects the system depends on the display that is installed. Some displays quit functioning, but still allow you to continue riding in whatever PAS level you were at, and also allow use of the throttle. Others shut the system down completely. And others discreetly display the error code, but continue working properly. I have not kept a record of which displays do what, but I expect your problem is with the sensor/sensor wiring. Your sensor substitution test was a good start and seems to eliminate the sensor.

In addition to my two trikes I have 4 other BBS02 systems installed on 4 other friends and relatives bikes, so I always keep a full system on the shelf for quick substitution of parts, and I have at least 3 different display units currently available. If you would like I will be glad to test these units and report what happens when error code 21 pops up, which is fairly easy to do on the delta trike since the sensor is on the front wheel and when testing the system with the rear wheel in the air it always results in an error code 21 because the front wheel isn't turning.

Edit: Which display do you have?

Rassy said:

In my experience (all with BBS02) how the error 21 (speed sensor problem) affects the system depends on the display that is installed. Some displays quit functioning, but still allow you to continue riding in whatever PAS level you were at, and also allow use of the throttle. Others shut the system down completely. And others discreetly display the error code, but continue working properly. I have not kept a record of which displays do what, but I expect your problem is with the sensor/sensor wiring. Your sensor substitution test was a good start and seems to eliminate the sensor.

In addition to my two trikes I have 4 other BBS02 systems installed on 4 other friends and relatives bikes, so I always keep a full system on the shelf for quick substitution of parts, and I have at least 3 different display units currently available. If you would like I will be glad to test these units and report what happens when error code 21 pops up, which is fairly easy to do on the delta trike since the sensor is on the front wheel and when testing the system with the rear wheel in the air it always results in an error code 21 because the front wheel isn't turning.

Edit: Which display do you have?

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That would be nice. I have the DPC-18.

I have never had a DPC18, so probably not much help, but here is a little summary on some other display units reaction to error code 21, and of course the speed and any speed limits do not work on any units when error code 21 occurs:

C961: BBS02 still runs, but is stuck in the current PAS level until you turn the display off and then on again, at which time you can select any PAS level, but then the error 21 comes back again and you are again stuck in that current PAS level, etc.

C963: Don't know. I had one but I think I gave it away.

C965: Displays the error code but still functions properly and allows you to change PAS levels.

850C: Displays the error code but still functions properly and allows you to change PAS levels.

I think I read somewhere in the forum about someone that had the Bafang stop working when error code 21 occurred. Don't remember what display they were using.

Did you get the voltage issue resolved?

Rassy said:

I have never had a DPC18, so probably not much help, but here is a little summary on some other display units reaction to error code 21, and of course the speed and any speed limits do not work on any units when error code 21 occurs:

C961: BBS02 still runs, but is stuck in the current PAS level until you turn the display off and then on again, at which time you can select any PAS level, but then the error 21 comes back again and you are again stuck in that current PAS level, etc.

C963: Don't know. I had one but I think I gave it away.

C965: Displays the error code but still functions properly and allows you to change PAS levels.

850C: Displays the error code but still functions properly and allows you to change PAS levels.

I think I read somewhere in the forum about someone that had the Bafang stop working when error code 21 occurred. Don't remember what display they were using.

Did you get the voltage issue resolved?

Click to expand...

Okay thanks, that's all different from what happens for me. Mine works untill I get error 21. Then it stops doing anything and just displays the error and if I remember correctly the PAS isn't even displayed anymore. I think it must be the either the sensor wire or the BBSHD controller, so I guess I'll have to get it repaired by Em3Ev.

I haven't been able to solve the other issue though.

Pizzabroodje said:

Rassy said:

I have never had a DPC18, so probably not much help, but here is a little summary on some other display units reaction to error code 21, and of course the speed and any speed limits do not work on any units when error code 21 occurs:

C961: BBS02 still runs, but is stuck in the current PAS level until you turn the display off and then on again, at which time you can select any PAS level, but then the error 21 comes back again and you are again stuck in that current PAS level, etc.

C963: Don't know. I had one but I think I gave it away.

C965: Displays the error code but still functions properly and allows you to change PAS levels.

850C: Displays the error code but still functions properly and allows you to change PAS levels.

I think I read somewhere in the forum about someone that had the Bafang stop working when error code 21 occurred. Don't remember what display they were using.

Did you get the voltage issue resolved?

Click to expand...

Okay thanks, that's all different from what happens for me. Mine works untill I get error 21. Then it stops doing anything and just displays the error and if I remember correctly the PAS isn't even displayed anymore. I think it must be the either the sensor wire or the BBSHD controller, so I guess I'll have to get it repaired by Em3Ev.

I haven't been able to solve the other issue though.

Click to expand...

I also just noticed the battery log says 'discharge short current'. However I don't know where it could have been shorted and why it doesn't short after charging the battery for a minute.
I have also noticed some corrosion and a burnt smell on the XT90S's between the battery and motor.

As a follow up:

Em3Ev said the surge of current from the BBSHD controller is causing the BMS to trip.
They say it can be solved by reprogramming the BMS.

The sensor is probably a seperate issue. Likely a broken wire (or controller).

They will take a look at the battery and kit when they're service technician is back from holiday.