8C and 12C cells with same IR

rg12 · Jul 19, 2018

Hey guys,

I have brand new Samsung 25R cells (about 1 year old stock according to the codes) and also Sony VTC5 cells with the same MFG as the 25R.
Tested the internal resistance with a tester and both show 8.2ohm
Is there something I'm missing? because the 25R is rated for 8C and the VTC5 at 12C

eee291 · Jul 19, 2018

Did you cycle them at all?

I had some cells that had to be pulsed a few times at high currents, to get the IR close to new.

rg12 · Jul 19, 2018

eee291 said:
Did you cycle them at all?

I had some cells that had to be pulsed a few times at high currents, to get the IR close to new.

Internal resistance can be lowered after use? I thought its the opposite

eee291 · Jul 19, 2018

Well after they sit a year the IR will be higher than normal. I once built a pack of Sanyo 18650 GA's.

On the first charge the cells got quite warm(almost HOT!), but after letting them cool the IR of the pack went down quite a bit. It never got warm after that.

Of course, this is not the same as high IR after 1000 cycles or over/under discharge.

rg12 · Jul 19, 2018

eee291 said:
Well after they sit a year the IR will be higher than normal. I once built a pack of Sanyo 18650 GA's.

On the first charge the cells got quite warm(almost HOT!), but after letting them cool the IR of the pack went down quite a bit. It never got warm after that.

Of course, this is not the same as high IR after 1000 cycles or over/under discharge.

but both are about a year old...so it should maybe stay relative and still the 12C should have lower resistance...

rg12 · Jul 20, 2018

Just googled it an it seems that most rate it as a 20A cell (8C) so I guess there's my answer..

Hillhater · Jul 22, 2018

rg12 said:
Hey guys,

I have brand new Samsung 25R cells (about 1 year old stock according to the codes) and also Sony VTC5 cells with the same MFG as the 25R.
Tested the internal resistance with a tester and both show 8.2ohm
Is there something I'm missing? because the 25R is rated for 8C and the VTC5 at 12Cz

If 8.2 ohm was really the result for both cells,..then yes, you have a measuring problem !
Neither of those cells should measure more than 0.05 ohm ..!

veer · Nov 3, 2021

rg12 said:
Tested the internal resistance with a tester and both show 8.2ohm

What internal resistance tester do you use? I'm looking for one, but can't seem to find a good one that lasts.

rg12 · Nov 19, 2021

veer said:
rg12 said:

Tested the internal resistance with a tester and both show 8.2ohm

Click to expand...

What internal resistance tester do you use? I'm looking for one, but can't seem to find a good one that lasts.

3 years later...awakened from the dead!
https://www.aliexpress.com/item/400...81-8&pdp_ext_f={"sku_id":"10000006026681566"}

veer · Nov 21, 2021

Thanks for your reply! I'll try to find that from someone who will ship to my location. :thumb:

pwd · Nov 25, 2021

I have one of these testers (YR1035) and it uses an internal 18650 cell vs a 9V:
https://www.aliexpress.com/item/4001288864976.html?spm=a2g0o.productlist.0.0.457f312dsYEJMr&algo_pvid=2acd3f13-7045-49f4-afb4-60f992930792&algo_exp_id=2acd3f13-7045-49f4-afb4-60f992930792-2&pdp_ext_f=%7B%22sku_id%22%3A%2212000025616979301%22%7D

I think it is better all around than that yellow SM8124A unit

8C and 12C cells with same IR

rg12

100 kW

eee291

100 kW

rg12

100 kW

eee291

100 kW

rg12

100 kW

rg12

100 kW

Hillhater

100 TW

veer

1 mW

rg12

100 kW

veer

1 mW

pwd

10 kW

Similar threads