Help troubleshooting an e-bike battery

[vankyan]

I've got an e-bike which doesn't turn on. The battery reads no voltage at the connection terminals and doesn't charge, but it turns on an reads as half-way charged. Internally the battery cells give 32V, but the circuit board doesn't pass that on to the terminal connectors. I found that a 40A fuse on the board is likely blown as it doesn't pass a continuity check. However, bypassing it reads a positive voltage at the terminals, but it keeps dropping, so something else must be wrong as well.





This is the board's top side. On the left is where the cells connect. The white big connector on the right is the charge check, the small white next to it is for the rear lights (no power there either). The charger comes in the black connector in the bottom right corner.



This is the back side of the board. The white 40A fuse next to the charger connector (bottom right) is likely blown


This is what the battery pack looks like

The pins of the battery connector read:
B1: 3.64V
B2: 7.29V
B3: 10.94V
B4: 14.59V
B5: 18.24V
B6: 21.7V
B7: 25.4V
B8: 29.1V
B9: 32.7V



When I plug in the charger, a small internal LED starts flashing on the board. When the battery cells are connected to the board it flashes slowly, when they are disconnected it flashes faster. When connected the charger pins read 42V/3.3µA

If I unplug the battery cells from the board, the charge check doesn't work and the internal LED is off. They turn on when I connect a charger despite the fuse being blown. They they stay functional even if I disconnect the charger.

Any help or advice is greatly appreciated!

 

[RunForTheHills]

It looks like this place has a direct replacement or repair service for that battery: Vogue Apollo 10INR19/66-5 TWS 36V E-Bike Battery Upgrade and Repair at KWS Seuren

 

[floydr]

Has the battery ever worked in the ebike?
Likely the BMS has shut down permanently disabling the battery. A 36V battery normally has 10 voltage sense connections. numbered B0, B1, B2, B3, B4, B5, B6. B7, B8, B9. There looks to be corrosion on the back side of the BMS. The battery is extremely unbalanced .7V many if not all BMS would shut down to protect the user from fire at much lower inbalance

B2-B1= 3.65V
B3-B2 = 3.65V
B4-B3 = 3.65V
B5-B4 = 3.65V
B6-B5 = 3.46V
B7-B6 = 3.7V
B8-B7 = 4V
B9-B8 = 3.3V

later floyd

 

[vankyan]

Has the battery ever worked in the ebike?
Likely the BMS has shut down permanently disabling the battery. A 36V battery normally has 10 voltage sense connections. numbered B0, B1, B2, B3, B4, B5, B6. B7, B8, B9. There looks to be corrosion on the back side of the BMS. The battery is extremely unbalanced .7V many if not all BMS would shut down to protect the user from fire at much lower inbalance

B2-B1= 3.65V
B3-B2 = 3.65V
B4-B3 = 3.65V
B5-B4 = 3.65V
B6-B5 = 3.46V
B7-B6 = 3.7V
B8-B7 = 4V
B9-B8 = 3.3V

later floyd

I made a small mistake:
B6 is 21.75V
B8 is 29.1V not 29.4V, so the differences are:

B2-B1= 3.65V
B3-B2 = 3.65V
B4-B3 = 3.65V
B5-B4 = 3.65V
B6-B5 = 3.5V
B7-B6 = 3.65V
B8-B7 = 3.7V
B9-B8 = 3.6V

which I think looks fine. Is there a place I could buy a replacement bms?

 

[E-HP]

which I think looks fine. Is there a place I could buy a replacement bms?

Just to be clear, you’re looking for a replacement BMS that also has a connector to power your rear lights?

 

[vankyan]

Just to be clear, you’re looking for a replacement BMS that also has a connector to power your rear lights?

Not necessarily I suppose it is easy to get the 5-6V it needs from somewhere. I just want to run the motor and the controller.

 

[floydr]

STOP Save up for a new battery the BMS shut down for a reason or have an ebike shop look at the battery. Safety First
if your charger is a 36V charger (42V max) and you charge a 9s battery with it your cell voltages would be 4.66V which is .46V over what lithium cells charge to. 4.2V max for NMC, LiCO cells. 10 sets of cells for a 36V battery. typical voltage range of a NMC cell is 4.2V- 2.8V a 36V charger charges to 42V
later floyd

 

[docw009]

You're missing a B10 for that 10th cell group, You need that cell group voltage to determine the health of the battery, Maybe you can pick it up measuring between the red output lead and B9, if you cannot recognize this group on the cells.

By the way, every BMS I've seen in my ebike packs doesn't care about the differential between cells groups. They will always charge if the group voltages are in the limits,

I see a STM program port on the BMS. There's a lot of stiff going on on that circuit board, Until you show there's no smart connection between the battery and the bike, other than positive/negative, I would think you need an exact replacement,

 

[amberwolf]

Three things:

1: A BMS behaves as described when it detects an out-of-limits condition, to prevent damage to the cells that can lead to a fire. You almost certainly do not have a BMS problem, but almost certainly a cell problem.



2: One of the 9 groups you do have numbers for shows it is far higher in voltage than the others, which usually means it has much lower capacity (and higher internal resistance), and so it's cells or interconnects within the group are failing.

Your initial measurements were probably before the BMS was able to drain down that high group, or before it self-discharged to match them (from internal cell damage). If you put the charger on the battery and measure right then, you'll probably see that group rise rapidly in voltage compared to the others.

A good BMS should detect a large (0.1v, etc) difference between groups and prevent charge or discharge of it, because it takes a significant difference in cell properties to cause this, and that means the pack has a problem that should be fixed before it gets worse. (requires replacing cells, which usually means all of them by the time a pack has aged this much, or if it is such poor quality that it is like this when new or not used much yet).



3: You should have 10 cell groups in series for a 36v battery that charges to 42v as your label says. There are 10 balancing resistors on there, for instance (the large black rectangles with 470 on them), one for each cell group.

If you get no voltage from the 10th group, whichever one it is in the series, then either those cells are dead, or the connection from the cells to the BMS has failed.

 

[vankyan]

I measured the big battery terminals at 36.35V. Circumventing the blown fuse still doesn't work regardless of whether the battery cells are connected ot not.