Question about battery pack

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Alkahna

New member
Joined
Aug 10, 2021
Messages
2
Hello everyone,

I have a battery pack (from an electric lawnmover) that I want to rebuid.
One of the cells has gone bad (measuring 0V and it looks burn or something leaked below the red tape).

The pack consists of 10 LG LGDBHE21865 Cells and works out to 36V 2,5Ah.
Since only 1 cell is bad (the rest measure out fine) would it be ok to simply replace the bad cell?

If not I was looking at replacing all cells and using these ones (LINK) because they are not too expensive.
Would they work fine in terms of specs?
I was looking at charging and discharging voltages and they differ in some points:
  • LG: 2.50 V Cutoff vs. Samsung: 2,75 V
    • potential problem when using the came charging circuit/enclosure
  • LG: Discharge 20000mA Maximum
    • does that mean the same thing (except different value ofc) as "3.6 Max. continuous discharge 5.2A (@ RT)" in the Samsung specsheet?

regards
 

OffGridInTheCity

Active member
Joined
Dec 15, 2018
Messages
1,706
Hello everyone,

I have a battery pack (from an electric lawnmover) that I want to rebuid.
One of the cells has gone bad (measuring 0V and it looks burn or something leaked below the red tape).

The pack consists of 10 LG LGDBHE21865 Cells and works out to 36V 2,5Ah.
Since only 1 cell is bad (the rest measure out fine) would it be ok to simply replace the bad cell
Given 9 good cells then replacing 1 bad cell is an OK strategy. Just make sure the new cell is near the voltage of the other cells when you hook it in. You don't want to wire in a 4.1v (new) cell to set of 3.7v (old) cells. You can do this by charge/discharge to get the new cell close - say within 0.2v or so if you can.

If not I was looking at replacing all cells and using these ones (LINK) because they are not too expensive.
Would they work fine in terms of specs?
I was looking at charging and discharging voltages and they differ in some points:
  • LG: 2.50 V Cutoff vs. Samsung: 2,75 V
    • potential problem when using the came charging circuit/enclosure
18650 cells don't have significant power lower than 3.4v - so 3.0v vs 2.75v 'low' per spec is not a big deal.

  • LG: Discharge 20000mA Maximum
    • does that mean the same thing (except different value ofc) as "3.6 Max. continuous discharge 5.2A (@ RT)" in the Samsung specsheet?

regards
The LG LGDBHE21865 specs show 20a max discharge while the 'new one'(s) show 5.2a continuous discharge - a bit of apple to oranges comparison. Although - 5.2a continuous is on the right track and may work it depends on whether 20a max discharge is actually needed. If you have another pack - you could measure the max amps the motor is pulling and answer this for yourself.

Or you could look for cell(s) that can do at least 20a max discharge and at least 2500mah capacity.
* Brand-new - http://queenbattery.com.cn/43-ur18650nsx-2600mah-20a
* Second hand - https://www.batteryclearinghouse.co...h-high-drain-20a-cells-in-a-tool-battery-pack
 
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