Battery balancing problem

[Carlosebermudez]

Hello Internet eBike Gurus, I need your help!

I recently bought a BBSHD 48v with the 850c display and a Chamrider 48v 30Ah battery with a 40amp BMS along with their 4amp charger.

I charged the bike once to 100% and when I start the bike the display shows only a 60% charge. I rode it hard on maximum PAS on some hills for around 5 miles. The second time, I charged it to 100% overnight and left it charging until 4 pm, the display showed 62%. This time I rode it slowly, at a maximum of PAS 6 on really steep hills and between 1 and 3 for the rest of the ride. Got around 5 miles this time and the route I followed was had an 800 feet hill climb but it was only a third of the ride, the rest was flat. I noticed it starting shutting off at around 50v. Today, I got a voltmeter and measured: 54.0 volts coming out of the battery few seconds after unplugged from the charger, and 54.5 from the charger (fans off).

I'm guessing the problem is either a faulty cell or I should let it balance. So I'm keeping it plugged for 24 hours to see if the voltage rises a little. I don't know if I can balance the pack without the charger, just letting the battery sit. Or should I turn the key to the ON position to power the BMS. don't know if that would make a difference.

 

[tomjasz]

I charged the bike once to 100% and when I start the bike the display shows only a 60% charge.

What was the voltage reading with a multimeter when the display showed 60%?

The second time, I charged it to 100% overnight and left it charging until 4 pm, the display showed 62%.

Same question.

So I'm keeping it plugged for 24 hours to see if the voltage rises a little. I don't know if I can balance the pack without the charger, just letting the battery sit.

NOTA GOOD IDEA! Especially if a problem is suspected. 2-3 MONITORED 8-hour charges, with a few hours rest between, would be better.

It's much easier to troubleshoot with multimeter readings confirming the percentage shown by the display.

 

[Carlosebermudez]

Thanks for the quick reply!

The first time I did not have a multimeter, so I can't say for sure.

I'm checking it right now and it still shows 54.0 volts. So no change since 2 pm. So I'm disconnecting it and following Thomas' recommendations. This would be the third time I charge the battery, first time 7 hours, second for 12 hours or so. This time 24 hours.

Connected it to the bike and the display shows 62%.

I'm checking out some YouTube videos on solar battery balancing and they live them overnight by themselves to self-balance. I'm wondering if I should do the same. But, should I turn the key? or should I just live it?

 

[tomjasz]

Connected it to the bike and the display shows 62%.

If the battery voltage is 54V it's over 95% charged. Check your display manual for setting up the voltage reading.

 

[tomjasz]

I'm checking out some YouTube videos on solar battery balancing and they live them overnight by themselves to self-balance.

Charging unattended is a poor practice. And how does solar work "overnight"?

Unless precautions are taken to protect from burning down the house! Are you solar charging?

 

[Carlosebermudez]

I have it on display Voltage.. and it reads 53.9-54.0 It's quitting on 50v.

 

[Carlosebermudez]

I meant when they balance the batteries when they are new. They hook them up and let them sit for a while without charging, just sitting there. I was wondering if the e-bike batteries were also connected similarly inside, or does the BMS need to be ON to balance the cells.

 

[Gionnirocket]

Curious... In the display settings you can select different voltages for different set ups.
What is your voltage set to in the display settings?

 

[Carlosebermudez]

Hi!

The display is set to 48v system. There're two other options. 52v (if I remember correctly). And a User Defined Value. But there's nowhere to edit that. Not even on the advanced setting.

 

[Gionnirocket]

It would be interesting to download the current controller programming and see what the cut off voltage is set to.
Do you happen to have the PC usb cable that connects to the display cable?

 

[Carlosebermudez]

I didn't buy it !!!! That's already on my amazon cart

 

[Gionnirocket]

Not sure that is your problem... But I found the cable very useful for tweaking the Programing to my style of riding, so it's a handy accessory to have anyway.

 

[Carlosebermudez]

Yes, I see that now. But my best guess is a damaged cell, cell group or BMS.

 

[Gionnirocket]

Very well could be... But I don't think that would explain the 60% charge reading on a full charge. Is the voltage reading on the display accurate now that it is set to voltage and not percentage?

 

[Carlosebermudez]

Sorry for the size of the pictures. It's the best I can do.

 

[Gionnirocket]

I wouldn't get hung up on the percentage reading, as long as the voltage number is correct.
The bigger issue is that it's cutting off at 50V.
I have a feeling a setting is off or something is corrupt in the controller/display
Have you contacted the seller of the kit? This may be a known issue.
Thomas has the most experience with Bafang.. maybe he has some insight.
If it's in the budget... I'd go for the Programing Cable

 

[Carlosebermudez]

I think so too. But the only issue I've found is that the battery does not charge to a full 54.6v. For what I read, when the Bbshd cuts power it does not shut the screen down. These feels more like the BMS protecting itself.

 

[Gionnirocket]

That makes sense. When you said it cuts out around 50v, I assumed that you were reading the display.
Easy test is to measure V at the battery connection after a shutdown. If you have 0v... it's the BMS
My battery only reaches 54 v as well on a full charge. Though I think that a function of the charger.

 

[Carlosebermudez]

My charger doesn't have any settings. It turns on the fan and charges it pretty quickly and then fan off and 54.5v on the output.

Yes, I was paying attention to the display and it flickered and went dead. I had to reset the battery, Key off and then on. After that it kept reading 50v but it wouldn't let me ride it more than an few yards on PAS1. I'm thinking about opening the pack and checking inside this wonderful piece of Chinese engineering, to see if any cell looks off or undervolted.

 

[Gionnirocket]

Why not return it... You only have 50km on the unit?