Tested my Panasonic cells (Opus), unsure of results

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I tested my first set of batteries on my Opus (3100 v2.2 I think) charger. The cells are Japanese made Panasonic NCR18650PF cells with a 2,950 mAh and 10 A discharge rating. The results I got we're between 2,800 and 2,850 mAh and internal resistance from 69-74. That was done in an unheated room probably around 40° f last night with my charge rate set to 1,000 mA and I think discharge was set at 700 mA. I'm not sure if the cold temp would have screwed up the results, if the internal resistance measurements are good for a Panasonic cell or if the results on my Opus charger are accurate.

I keep seeing people measure cells at higher than spec, I was really hoping to see 3,000 mAh but now I'm slightly worried that I have degraded or counterfeit cells.

Does the internal resistance seem ok? If cold has an effect on measurements, how much could that be off? How accurate do Opus charger test results seem to be?

I figured with a 10 A rating I should test at the highest charge and discharge rates possible (with 4 cells in the charger). I didn't babysit it so I'm not sure how long it took or if the cells got hot at all. If anyone knows how long I should expect, let me know.
 
The cells need to be warm to get the best out of them. I am pretty sure that internal resistance will be a lot higher in cold temp. I found that my samsung 30Q cells give much less capacity when cold.

Also if the cells are new, i would cycle rhem a few rimes before testing
 
The cells are new old stock I thought the heat from a charge-discharge cycle would be enough but I guess I was wrong.

Maybe I could put the charger in a coffee can or something to capture the heat around the charger rather than let it escape in to the room. I just need to figure out how to do it without making the cooling fan ineffective during an over temp event.
 
2800-2850mAh for PF is perfect result when tested with 700mA discharge rate under lower temp than 23°C. If you look in the datasheet, PF has minimum guaanteed capacity for the new cell of 2750mAh measured at 23°C and 580mA discharge rate.
 
Laboratories test their cells at room temperature and at like 0.2c to test capacity. Make sure you have this set of conditions if you want to get an accurate result.
 
brumbrum said:
The cells need to be warm to get the best out of them. I am pretty sure that internal resistance will be a lot higher in cold temp. I found that my samsung 30Q cells give much less capacity when cold.

Also if the cells are new, i would cycle rhem a few rimes before testing

Yup. This especially applies to low C rate cells, like 3C and under.

OP also tested for capacity at a fairly high discharge rate, so energy losses will be a factor in the capacity presented. Any cell will gtadually give up to 15-20 percent less amp hours, the closer you get to the cell's maximum discharge.
 
Pajda said:
2800-2850mAh for PF is perfect result when tested with 700mA discharge rate under lower temp than 23°C. If you look in the datasheet, PF has minimum guaanteed capacity for the new cell of 2750mAh measured at 23°C and 580mA discharge rate.

This sounds good, I guess I need to do a better read of the spec sheet instead of looking at 2,950 mAh and expecting to get it.

I thought the 1,000 mA charge rate and 700 mA discharge were conservative because 700 mA discharge on the bike is only about a 500 watt draw, I'm expecting my cruise to be around that or higher, with 5 A draw possible.

If anything my charging rate was aggressive, the 200 watt charger I'll use is only going to be a 280 mA charging current but that seems like almost nothing for an 18650 so I set it at 1,000 mA.
 
Capacity is spot on i would say.
IR for the pf should be about 29 to 30, thats personal results on my gear using 4 wire test.
If the IR of the cells are close thats what counts regardless of the testing method.
I would balance them them to 3.7 ish V before testing Ir and warm them up to room temp.
1 amp charge is fine.
No need to cycle them. If they are unused.
I usually test at 2.6A and get results around 2700. Less time consuming .
I have tested and used a few hundred new old stock PF cells. Good choice for the $
 
I've succumbed to peer pressure and have decided to buy enough cells to build a 18s12p pack rather than the 15s12p I intended.

I bought from the same eBay seller (divemaster85) and he says he has about 8 cases left and he's selling at $500/case plus shipping. I'm not sure if he will do international.

I think that's a pretty good deal for a pretty decent Japanese made cell. Just passing it along.
 
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