van Moof S1 battery revision

djonko22

1 µW
Joined
May 10, 2024
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Location
Delft
Hi,

DISCLAIMER: I am a beginner with batteries but have some experience with electronics repair.

Last year, I acquired a VanMoof Electrified S. The bike had some issues, the main one being a suspected dead battery. After 15 minutes of biking, the eBike lost power and displayed some errors.

I removed the battery from the bike, checked the voltage, and identified that one of the 10 packs of 18650 LG cells had a significantly lower voltage. Due to other projects, I put the bike in storage.

Now, I'd like to try to fix the eBike again. I remeasured the voltage of the cells. It has 40 cells in total, arranged in 10 packs in series of 4 parallel cells. The battery is a Darfon 36.2V 11Ah/392.2Wh, model number: e4c08. The cells are LG GBMG11865 P237H244A1.

Using a voltmeter, I read the following voltages for the 4-packs:

  • 3.3V
  • 3.3V
  • 2.5V
  • 3.4V
  • 3.4V
  • 3.2V
  • 3.4V
  • 3.4V
  • 3.4V
  • 3.3V
Total: 32.7V

My questions are:

  1. It seems that just one of the cells is problematic. Is it viable to replace this one LG cell with a similar one?
  2. If it is viable, how should I proceed?
Kind regards,
Sander
 
You have a 10s4p battery. The parallel group of 4 cells having only a voltage of 2.5v needs to be replaced. Each of the 4 cells in each parallel group is rated at 2750mAh when new (4 x 2.75Ah =11Ah battery capacity of your 10s4p when new).

Assuming the average capacity of these used cells is now closer to 2500mAh you could use 4 Samsung 25r cells or 4 off-brand 2600 -2700mAh 5.0amp MCD (4 x 5amp = 20amp max discharge rate) when repairing that parallel group.
 
Assuming the average capacity of these used cells is now closer to 2500mAh you could use 4 Samsung 25r cells or 4 off-brand 2600 -2700mAh 5.0amp MCD (4 x 5amp = 20amp max discharge rate) when repairing that parallel group.
Would capacity be the main concern? My thought is that the won cells may have a higher IR, while the 25R has a pretty low IR. Will that affect the charge/discharge rates and require mor balancing?
 
Will the lower resistance of a new 4p group of 25r cells (fully charged) be discharged to 50% SOC before any of the other nine 4p groups reach 50% SOC? That's assuming the other nine 4p groups also have the same capacity of 2500mAh when fully charged, but a higher IR than the 25r 4p group.
 
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