2C or 8C?

https://www.aliexpress.com/item/25p...ec-4973-8725-5b97bfe6e90b&transAbTest=ae803_5

The internal resistance is 15.5 which is close to the 13 Samsung 25R (8C) has, so how come the discharge rate is just a bit over double the capacity which is about 2C?

Not sure, but I think somebody ran some discharge tests on those. Heating is the limiting factor on discharge rate.

fechter said:

Not sure, but I think somebody ran some discharge tests on those. Heating is the limiting factor on discharge rate.

Click to expand...

Doesn't it go together the IR an the heating factor?
How can one cell be 15mohm and the other 15mohm and have different discharging capabilities? (considering they have the same capacity and state oh health...)

Seems like that would be it, but possibly there is some other limiting factor like built-in protection. Could also be they just never tested them at higher rates.

There are other QC factors that affect suitability for high discharge.

If the sellers says lower rates only, believe them.

john61ct said:

There are other QC factors that affect suitability for high discharge.

If the sellers says lower rates only, believe them.

Click to expand...

Like what? I thought that the IR is the bottom line...

Overall quality of the manufacturing process, purity of the chemicals.

IR changes over time, different rates for different cells. Given a certain cycling / usage regime, if one make starts overheating bad after 50 cycles, the other goes 2-300, the latter is better made.

Just consistency from one batch to the next can vary a lot.

And even if IR were the only issue, it is not a static thing we can directly measure very accurately, how / when IR is measured will also give huge variations.

john61ct said:

Overall quality of the manufacturing process, purity of the chemicals.

IR changes over time, different rates for different cells. Given a certain cycling / usage regime, if one make starts overheating bad after 50 cycles, the other goes 2-300, the latter is better made.

Just consistency from one batch to the next can vary a lot.

And even if IR were the only issue, it is not a static thing we can directly measure very accurately, how / when IR is measured will also give huge variations.

Click to expand...

Interesting...
I have to say that I measured cells fully charged and the same cell at about 40% charge and the IR was the same

That makes sense to me, my experience has been that the real increased sag on cells starts when its more like 90 or 95% discharged. It should have decent resistance still, right in the middle of the discharge. The assumption is that the sag is caused by an increase in resistance when they get that low.


I have not done tests, I just saw that just before going over the cliff, sag under load increases. But not till right on the edge of the cliff. After that, I know to stop just a bit before that, so the cells stay balanced better. Or slow down, to try not to make em hot in the last mile.

As for the 2c, that's continuous. I would bet 4c spike would be ok.

It does look like the cells perform good at 2c.

Check this out:
https://endless-sphere.com/forums/viewtopic.php?t=90938

One test is worth 1000 opinions.

fechter said:

Check this out:
https://endless-sphere.com/forums/viewtopic.php?t=90938

One test is worth 1000 opinions.

Click to expand...

Thanks, very interesting!