AW 20A 2200mAh Button-Top 18650 Bench Test Results...only a 15A battery

[Mooch]

I have a few theories on why we have different results Mooch sir. I see from your graphs you run the batteries down below 3.2v, in fact you go past 3.0v. I have my hobby charger set to cut off at 3.15v. I think this why we're seeing such a temperature difference. I don't like pushing any cell down below that when pulling 15+ amps from it, no matter what the manufacturer claim is for lowest safe discharge voltage. I learned the hard way with a venting sony VCT3 back in the day that failed at 20A when it hit 2.88v (rated to go to 2.5v).

Just completed the another test run using my biddy's IR thermometer, same two cells just one more charge on each-

Cell one (179)- Max Temp 59C/138F
Cell two (178)- Max Temp 60C/140F

Both cut off at 3.15V on load. I guarantee if I ran them past that would see temperatures much closer to yours sir.

Ahhhh...yes, that would explain it. I'm embarrassed that this possibility didn't occur to me as I've always pointed out that directly comparing test results from two different testers can be a problem if all the details aren't checked. Thank you.

I'll run a test on the 2200mAh AW cell, cutting off at 3.15V and see what the temp is.

It's always been tough to pick a cutoff voltage for testing. Is it better to go down to 2.5V to allow easy comparison to the manufacturer's data sheets? Or better to stop at the typical voltages that a regulated mod would cut off at, probably 3.2V or higher, or a mech user would notice a big drop in performance at. I ended up at 2.8V for my cutoff. For me, it gives a bit of a safety margin to handle the higher temperatures inside a mod, the lack of ventilation, and possible high ambient temperature. There isn't any "correct" number though. Thanks again for taking the time for this!

 

[Mooch]

I have a few theories on why we have different results Mooch sir. I see from your graphs you run the batteries down below 3.2v, in fact you go past 3.0v. I have my hobby charger set to cut off at 3.15v. I think this why we're seeing such a temperature difference. I don't like pushing any cell down below that when pulling 15+ amps from it, no matter what the manufacturer claim is for lowest safe discharge voltage. I learned the hard way with a venting sony VCT3 back in the day that failed at 20A when it hit 2.88v (rated to go to 2.5v).

Just completed the another test run using my biddy's IR thermometer, same two cells just one more charge on each-

Cell one (179)- Max Temp 59C/138F
Cell two (178)- Max Temp 60C/140F

Both cut off at 3.15V on load. I guarantee if I ran them past that would see temperatures much closer to yours sir.

Do you have any delivered-mAh data for the 2200mAh cell? My results, even down to 2.8V, were very bad.

 

[Morandir835]

I do sir, will find it on my computer later and post it for you.

 

[Mooch]

You solved it @Morandir835!

I got a max temp of 64°C with a cutoff of 3.15V at 20A. This is very close to your measurement considering the two different methods we use...good news.



The capacity was only 975mAh in my test though...terrible for a 20A-rated cell in my opinion. The 25R delivers about 1600mAh down to 3.15V at 20A.

The AW 2200mAh cell has a huge voltage drop and over half of its capacity, at 20A, is spent at under 3.15V. This is what made your temp measurement and mine so different. Most cells I test aren't this bad and there's just not too much of a difference between stopping at 2.80V or 3.15V.

A closer look at my data and the discharge graph at Dampfakkus.ge shows the two results being pretty close. He got slightly worse results than I did. This could be due to cell-to-cell variations or different voltage drops in our gear. I'm very much looking forward to your capacity measurements!