Help! Bafang 250w Motor Keeps cutting out

[usamah]

Hello.

First time post

I recently brought a Bafang 250w with a 36v 20Ah rear battery (860c display)

However, it keeps cutting out.

Sometimes when going over bumps but usually there is no rhyme or reason to it and it just happens.

I am starting to think the BMS is faulty (no idea, reading online for any help).

I am in two minds about returning the whole unit and just building myself to take on a 20 mile there and 20 mile back commute because when it does cut out I am effectively carrying 10 kg extra dead weight with most of it on the back. Ideally I would like to get the unit to work.

When it does cut out, the screen goes off instantly, the physical battery check button on the battery goes blank/red and I have to put the key into the battery to turn it off and on again for the unit to restart (sometimes it doesn't) and the battery percentage always reads as 100% and after the reboot, also green on the physical battery check button on the unit.

I have no idea what else this could be, but have posted my settings just incase (I know they might be wrong, I just defaulted most of them).

Any help would be appreaciated.

Thank you very much !

 

[Nealh]

So this is BBS01 , if you have fitted a brake cut off/s then check carefully it's fitting as this will cause the issue you describe. In fact if fitted disconnect it/them and go for a ride to see if the issue goes away.

 

[saneagle]

It's not likely to be the BMS. If it were, it would probably stay off. It's more likely a connection issue or a short. It's not the brake switches because if it were them, the LCD would stay on.

 

[usamah]

Update:

IMG_3449.MOV

drive.google.com

Contacted the company, they are refusing to organise a collection saying I have to cover it (not true, fault was developed and notified in 30 days I am convered by the consumer rights act of 2015).

Now stuck with a broken battery.

 

[saneagle]

Update:

IMG_3449.MOV

drive.google.com

Contacted the company, they are refusing to organise a collection saying I have to cover it (not true, fault was developed and notified in 30 days I am convered by the consumer rights act of 2015).

Now stuck with a broken battery.

It's been a while since I've seen one of those key-switches. I thought they'd gone out of fassion. If the supplier won't help you, open up the battery and re-solder the wires on the back of the key-switch. Faults like you have used to be quite common due to badly soldered wires. The problem is that there's quite a lot of metal in the switch contacts, so you need a lot of heat to get a proper joint. When factory workers do it quickly, the solder sits there and looks like a good joint, but it isn't. When you re-solder, leave the iron on it for long enough for the heat to get into the contacts on the switch.

Also, it might be worth checking that the fuse is in nice and tight and that its holder isn't melted.

 

[usamah]

Thank you (both) for your responses btw !

If worse comes to worse, I will have to try that .

I have all the gear but no idea or confidence to do it.

It's kinda strange cause I've just tried to replicate the issue and it seems to happen instantly when light contact is made to the underside of the housing (EDIT: or it is turned on its side or upside down), does that line up with the wiring stuff ?

Currently in dispute with the company, hoping they do the right thing eventually.

 

[saneagle]

Thank you (both) for your responses btw !

If worse comes to worse, I will have to try that .

I have all the gear but no idea or confidence to do it.

It's kinda strange cause I've just tried to replicate the issue and it seems to happen instantly when light contact is made to the underside of the housing (EDIT: or it is turned on its side or upside down), does that line up with the wiring stuff ?

Currently in dispute with the company, hoping they do the right thing eventually.

When you open the battery, you can simply tug a few wires to see which one breaks the contact. It's clear that you have a connection issue. It can only be solved by opening the battery, except if it's the fuse, so worth checking that now if you have one that's accessible from the outside.

It's only a few screws to pull the end off the battery, when everything important (for your problem) should be revealed - nothing to be scared of. The end piece will remain attached by the two power wires, which probably have bullet connectors on. Maybe one of those is loose. There is nothing complicated in that end of the battery, just the switch and the wires, and maybe a fuse, and possibly a couple of thinner wires running back to the light.

 

[usamah]

On one hand I really wanna get the motor working cause my commute is 20 miles and cause I'm not the most experienced on hills it takes me about 2 hours. I'm really tempted just to buy a new battery and gamble on the fact the company gets forced to refund me (as is my legal right).

On the other hand, I don't really have the money to spend comfortably as it's another £300+, nor do I wanna close my options by voiding the warranty on the battery while it's early days. While the commute is long, it does feel a lot better than public transport because it takes 30 minutes longer but I get a lot of health benefits from it.

I've contacted 4 companies for quotes on repair as that is what Citizens Advise told me to do and all 4 of them refused to even quote me on a job outright.

If I don't get anywhere in 2-4 weeks, I'll buy a new battery and open up this one, hopefully fixing it and then I can use it as a spare.

 

[saneagle]

On one hand I really wanna get the motor working cause my commute is 20 miles and cause I'm not the most experienced on hills it takes me about 2 hours. I'm really tempted just to buy a new battery and gamble on the fact the company gets forced to refund me (as is my legal right).

On the other hand, I don't really have the money to spend comfortably as it's another £300+, nor do I wanna close my options by voiding the warranty on the battery while it's early days. While the commute is long, it does feel a lot better than public transport because it takes 30 minutes longer but I get a lot of health benefits from it.

I've contacted 4 companies for quotes on repair as that is what Citizens Advise told me to do and all 4 of them refused to even quote me on a job outright.

If I don't get anywhere in 2-4 weeks, I'll buy a new battery and open up this one, hopefully fixing it and then I can use it as a spare.

It's 4 screws to take the end off. You don't need any specialist skill or knowledge to see where the problem is.