3.9C cell with 28mΩ resistance?

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rg12
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3.9C cell with 28mΩ resistance?

Post by rg12 » Apr 16, 2018 4:58 am

Hey Guys,

I measured the awesome Samsung 25R (8C) and it has 8mΩ resistance.
Then tested the LG M26 (3.9C) and it has 28mΩ resistance.

Is that normal for a 3.9C cell to have such high resistance?
All cells are new and tested on a few different batches and they all show the exact same numbers.
Mongoose EC-D 2007 (19" motocross wheels), 21s 10Ah LiPo, Greentime 72V 80A Controller, 12kg Hub Motor

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MadRhino
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Re: 3.9C cell with 28mΩ resistance?

Post by MadRhino » Apr 16, 2018 6:09 am

The state of charge and temperature does affect impedance of a cell. Those parameters should be measured equal, to compare 2 cells.

Then, both impedance readings that you have measured are within the manufacturers spec
Your Samsung cell impedance should be 7 to 16 m/ohm, 28 m/ohm after trip
If my memory is good, I recall your LG cell should be 60 m/ohm after trip. So, probably twice the impedance of the Samsung cell when in exact same state of charge and temperature.
Make it fool-proof, and I will make a better fool.
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fechter
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Re: 3.9C cell with 28mΩ resistance?

Post by fechter » Apr 16, 2018 8:51 am

It might depend on how you are making the measurement too. AC measurements are pretty useless.
"One test is worth a thousand opinions"

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rg12
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Re: 3.9C cell with 28mΩ resistance?

Post by rg12 » Apr 17, 2018 3:55 am

It's a DC cell IR tester.
Both tested brand new, same temp, same state of charge.
Charged many from different batches (all new) and all have the same specs.
Can it be that a 4C cell has almost 4 times higher IR than 8C?
Mongoose EC-D 2007 (19" motocross wheels), 21s 10Ah LiPo, Greentime 72V 80A Controller, 12kg Hub Motor

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rg12
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Re: 3.9C cell with 28mΩ resistance?

Post by rg12 » Apr 21, 2018 8:39 am

rg12 wrote:
Apr 17, 2018 3:55 am
It's a DC cell IR tester.
Both tested brand new, same temp, same state of charge.
Charged many from different batches (all new) and all have the same specs.
Can it be that a 4C cell has almost 4 times higher IR than 8C?
Bump...
Mongoose EC-D 2007 (19" motocross wheels), 21s 10Ah LiPo, Greentime 72V 80A Controller, 12kg Hub Motor

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MadRhino
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Re: 3.9C cell with 28mΩ resistance?

Post by MadRhino » Apr 22, 2018 1:59 am

rg12 wrote:
Apr 21, 2018 8:39 am
rg12 wrote:
Apr 17, 2018 3:55 am
It's a DC cell IR tester.
Both tested brand new, same temp, same state of charge.
Charged many from different batches (all new) and all have the same specs.
Can it be that a 4C cell has almost 4 times higher IR than 8C?
Bump...
You will know when you pull 4C continuous off them. My guess is they will get hot.
Make it fool-proof, and I will make a better fool.
Current bikes
Street: https://s20.postimg.org/ewrvugywt/Session_04_2015.jpg
Dirt: https://s20.postimg.org/lbqwr55ml/IMG_0157.jpg

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