Bafang bbs02b cuts off randomly

[xXSaneXx]

One day on way home from work I was riding my bike an almost home (a block away) I heard a ping sound an it shut off. I came to a stop an was confused. So I looked at my plugs an they were fine. I pressed the display an it powered on an i was on my way, then it shut off, so I had to pedal it home. There were no error codes or anything like that. I parked it a couple days because I couldnt do anything until my next day off work.
I have a canbus bafang bbs02b 750w with a 48v20ah battery with 30amp bms. I was told to go in my display an check my settings as after that happened it lost power to go over 10mph like the topspeed was rest to default. After i checked this, an reset the mph, it was fine unloaded, reached 35mph unloaded so i took it out for a test ride thinking i fixed it. I sat on it, I'm 195lbs, an i gave it throttle in pas1 an the display cut off. I waited a minute or 2 an turn it back on, did the same. I thought maybe the throttle was the issue so i tried the pedal route an it did the same thing.I was told to check my battery connection, they are fine. I took the cover off to look at my controller an phase wires an other wires are fine. Nothing melted or discolored. The gears are fine as well.
I tried to start it the other day, 2 days later an it wont power on at all. I bought a multimeter to test it but when the screen was able to power on it threw no error codes still. Anyone know what this could be as im confused. The bike i bought new an started installing the bafang on it the day I purchased it. So the bike, motor and battery have 128 miles on it total. I don't abuse it, as I used it to go back an fourth to work. I read theres a power button that resets the bms an am unsure where it it though.
Anyone on here ran across this issue? Is the display bad? Would it do that, but wouldn't it throw a code though?
Thanks for any help.

 

[E-HP]

One day on way home from work I was riding my bike an almost home (a block away) I heard a ping sound an it shut off. I came to a stop an was confused. So I looked at my plugs an they were fine. I pressed the display an it powered on an i was on my way, then it shut off, so I had to pedal it home. There were no error codes or anything like that. I parked it a couple days because I couldnt do anything until my next day off work.
I have a canbus bafang bbs02b 750w with a 48v20ah battery with 30amp bms. I was told to go in my display an check my settings as after that happened it lost power to go over 10mph like the topspeed was rest to default. After i checked this, an reset the mph, it was fine unloaded, reached 35mph unloaded so i took it out for a test ride thinking i fixed it. I sat on it, I'm 195lbs, an i gave it throttle in pas1 an the display cut off. I waited a minute or 2 an turn it back on, did the same. I thought maybe the throttle was the issue so i tried the pedal route an it did the same thing.I was told to check my battery connection, they are fine. I took the cover off to look at my controller an phase wires an other wires are fine. Nothing melted or discolored. The gears are fine as well.
I tried to start it the other day, 2 days later an it wont power on at all. I bought a multimeter to test it but when the screen was able to power on it threw no error codes still. Anyone know what this could be as im confused. The bike i bought new an started installing the bafang on it the day I purchased it. So the bike, motor and battery have 128 miles on it total. I don't abuse it, as I used it to go back an fourth to work. I read theres a power button that resets the bms an am unsure where it it though.
Anyone on here ran across this issue? Is the display bad? Would it do that, but wouldn't it throw a code though?
Thanks for any help.

How old is the battery, and what voltage is it when fully charged?

Displays are usually powered directly from the battery input to the controller {which is why their buttons can turn the controller on and off). If the display turns off, it means the controller isn’t getting battery input, like when the BMS trips.

 

[xXSaneXx]

I had it fully charged at 54.6v when it was doing 35mph unloaded an attempted to ride it. The battery is 5 months old but wasnt used until a month after I got it as I was building the bike, had to order adapters an other random things I needed to change on the bike haha

 

[xXSaneXx]

How old is the battery, and what voltage is it when fully charged?

Displays are usually powered directly from the battery input to the controller {which is why their buttons can turn the controller on and off). If the display turns off, it means the controller isn’t getting battery input, like when the BMS trips.

Is there a way to reset the bms? Like fully charged it an press a power button for a few seconds to reset it? I researched it on Google an there was claim you can do this but with Google using AI ... sone things are false ive noticed

 

[E-HP]

Cool. Good luck.

 

[xXSaneXx]

Cool. Good luck.

Is that a possible thing? Can it be reset?

 

[E-HP]

Is that a possible thing? Can it be reset?

This isn’t Google ai, it’s a forum. You can get more help troubleshooting if you take the time to answer the questions needed to troubleshoot, instead of ignoring them and responding with more questions.
Try ChatGPT. It’s a little better, and it won’t ask you for any info..

 

[gromike]

Maybe.
I have a Grin Satiator charger that can be set to "force charge", and doing that can sometimes wake up a bms.
Though, it won't fix a defective battery.

 

[xXSaneXx]

This isn’t Google ai, it’s a forum. You can get more help troubleshooting if you take the time to answer the questions needed to troubleshoot, instead of ignoring them and responding with more questions.
Try ChatGPT. It’s a little better, and it won’t ask you for any info..

I answered your question above, idk why you giving attitude. Looks like you need to take your own advice.. scroll up. I did answer.

 

[xXSaneXx]

Maybe.
I have a Grin Satiator charger that can be set to "force charge", and doing that can sometimes wake up a bms.
Though, it won't fix a defective battery.

Ok, but its weird if its defective with not many miles on it. I have a spare battery but unfortunately the hookups arent the same so I cant see if its the battery in that way. But also dont want to chance messing up that battery as well.

 

[E-HP]

I answered your question above, idk why you giving attitude. Looks like you need to take your own advice.. scroll up. I did answer.

Noted, my apologies, I missed that post.
If it’s fully charged and spinning the wheel, then the BMS has already reset. If it were a phantom voltage it wouldn’t be able to provide the 50W-100W it takes to spin the wheel at “no load”. You could have a faulty BMS, or there could still be bad cells in one of the groups that make that group sag more.
Can you try applying some load (maybe the brake) while monitoring the voltage to see how much it sags before tripping?

 

[xXSaneXx]

Noted, my apologies, I missed that post.
If it’s fully charged and spinning the wheel, then the BMS has already reset. If it were a phantom voltage it wouldn’t be able to provide the 50W-100W it takes to spin the wheel at “no load”. You could have a faulty BMS, or there could still be bad cells in one of the groups that make that group sag more.
Can you try applying some load (maybe the brake) while monitoring the voltage to see how much it sags before tripping?

Its all good man, I'll try that in morning. Im planning on charging it up. I talk to the company I ordered from but they really didnt give any help, just the trouble shooting i did above in my first post. Before I reset the display setting the first time, unloaded it was going only 10mph but pushing only 30-60w but was told thats normal unloaded but seemed odd to me. After I reset it an it was able to do 35mph unloaded it was reading 700+w like it should. Ill apply brake an hit the throttle an see what happens. Hopefully I can read it before the display cuts off. Would any of the wires not hooked up have anything to do with this? Gear sensors, brake sensors and lights. I dont use them as this is a mid drive bmx

 

[E-HP]

Its all good man, I'll try that in morning. Im planning on charging it up. I talk to the company I ordered from but they really didnt give any help, just the trouble shooting i did above in my first post. Before I reset the display setting the first time, unloaded it was going only 10mph but pushing only 30-60w but was told thats normal unloaded but seemed odd to me. After I reset it an it was able to do 35mph unloaded it was reading 700+w like it should. Ill apply brake an hit the throttle an see what happens. Hopefully I can read it before the display cuts off. Would any of the wires not hooked up have anything to do with this? Gear sensors, brake sensors and lights. I dont use them as this is a mid drive bmx

There’s something terribly wrong. 700w unloaded is crazy high, insane. 50w is normal. Your controller may need replacing, or maybe mechanical issues (bad bearings, etc.).. I would not run it too long that way, to avoid possible damage to the motor.

 

[docw009]

E-HP is right. With wheel off ground and spinning at top speed, wattage should be quite low, under 50 watts.

Your symptoms do sound like the battery BMS tripping. A tripped BMS will reset by turning the battery on/off switch if there is one, by disconnecting the controller, or by the controller shutting off and removing the load. Basically, they usually rest in a few seconds w/o the need to do anything, The only time they won't is if the load has a dead short.

If the 700 watts you saw was a false alarm. it might be worth the trouble to rig connectors on the other battery. You do want to know if it works.

 

[xXSaneXx]

There’s something terribly wrong. 700w unloaded is crazy high, insane. 50w is normal. Your controller may need replacing, or maybe mechanical issues (bad bearings, etc.).. I would not run it too long that way, to avoid possible damage to the motor.

Ok apologies... that was loaded.. was half asleep typing haha.
It went 100w,200w..an so on when I was able to ride it once. It did not shut off an went the normal speed. I mostly use pedal assist 3 to work as it does 20mph there. Pas4 an 5 its to fast for a bmx lol
But when I got home it turned off again. I hit a bump in my yard an it shut off... did I miss something?

 

[xXSaneXx]

E-HP is right. With wheel off ground and spinning at top speed, wattage should be quite low, under 50 watts.

Your symptoms do sound like the battery BMS tripping. A tripped BMS will reset by turning the battery on/off switch if there is one, by disconnecting the controller, or by the controller shutting off and removing the load. Basically, they usually rest in a few seconds w/o the need to do anything, The only time they won't is if the load has a dead short.

If the 700 watts you saw was a false alarm. it might be worth the trouble to rig connectors on the other battery. You do want to know if it works.

Was loaded..sorry..

 

[xXSaneXx]

But as of right now that battery is dead. I was told fully discharge it an then fully charge it. Not sure what that will do but the place i bought it from told me to try that.

 

[docw009]

What kind of battery is it? Who sold it? Is it in a case or a blue shrink wrap?

I own a UPP battery in a Hailong case that kept shutting off on me when I hit a bump. The external wires were solid, but when I looked inside, the BMS connector was half seated. That was July, 2021 when I bought the battery. Been good ever since.

 

[xXSaneXx]

What kind of battery is it? Who sold it? Is it in a case or a blue shrink wrap?

I own a UPP battery in a Hailong case that kept shutting off on me when I hit a bump. The external wires were solid, but when I looked inside, the BMS connector was half seated. That was July, 2021 when I bought the battery. Been good ever since.

Its a Effivolt battery Hailong battery in a 48v20ah case sold on ebay theough a Effivolt store. I forget i bought it near the end of 2025. Idk anything bought taking batteries apart, would prefer not to as I never have an seen alot of horror stories bout people taking batteries apart and causing fires. House fires suck as I been through one before, not ebike related.

 

[xXSaneXx]

I used a volt meter on my battery it reads 52.4. The charger turned green which means fully charged. It should be 54.6v. I plugged it in bike. Now its doing 35mph unloaded an it averages10-50w.
I took it for a ride, it was doing fine in the yard an as soon as I hit the pump to go into the street it shut off. No power.

 

[E-HP]

I used a volt meter on my battery it reads 52.4. The charger turned green which means fully charged. It should be 54.6v. I plugged it in bike. Now its doing 35mph unloaded an it averages10-50w.
I took it for a ride, it was doing fine in the yard an as soon as I hit the pump to go into the street it shut off. No power.

That’s a good clue. It indicates that the battery is far out of balance for one or more groups. The charging isn’t stopping at full charge, but when one or more groups is charged to 4.2V, while the others are below. A lot of times a weak cell group will appear to charge more quickly, if some cells are bad. The BMS is stopping the charge, instead of the charger.
If you can charge it outside, many times keeping the charger connected will allow balancing to occur, and the charger will periodically turn on and off as it balances. It could take a day or more to fully balance the pack
The caveat is that cheaper BMSs don’t have a balancing function, which would suck. Their instructions to you make me suspect that’s the case. If it does have a balancing function, then their instructions would be to leave it on the charger. Their instruction to fully deplete tha pack makes it sound like they want all the cells discharged, hoping that they would be all charged from fully discharged and hopefully are balanced after charging. Anyway, you could always ask the direct question of them, about whether their BMS supports balancing or not.

 

[xXSaneXx]

Unfortunately I dont have a spot outside to test without worries of it getting stolen haha! Its a mid drive bmx, so it gets ALOT of attention.
I put it on charger an light was red. In 15 minutes it turn green. A friend of mine told me to do what you said as well. Because he seen my issue as well. I dont flip the red switch on when charging, which I also didnt know that helped ballance the cells. Haha so I flipped switch on. Hopefully that helps. Meantime I did message the battery company an sent a pic of what they wanted