Results from the cap testing on first 4 cells-
3213mAh, 42mR
3336mAh, 51mR
3306mAh, 32mR
3277mAh, 53mR
Still early days with this charger for me, I find setting the discharge/refresh currents is not that clear, the first cell above had 1.5A charge rate, 1A discharge, the others seemed to do 1A in and 0.5A discharge…
With the 3 remaining suspect 30Q’s currently doing cap tests (where is the last cell from my original batch of 8?
), I’ve measured the temperature of the cells.
I used an adhesive strip of post-it note to hold down the thermocouple of my DMM, with a tiny blob of heat transfer compound on the surface of the 18605. I gently pressed the whole lot down with a folded piece of tissue, so my finger wasn’t acting as a heatsink. My DMM is not calibrated.
Results:
|
|
indicated T°C |
Measured T°C |
53 |
39 |
40 |
29 |
32 |
24 |
The discrepancy is not linear, the lowest temperature cell has a difference between S4+ indicated and measured of –7C; highest cell is –16C.
I don’t know if this is poor calibration, or whether the charger is showing (estimated) cell core temperatures, which would require Vapcell engineers to have worked out a rough correlation between the core temperature and surface temperature…?
Edit to add: Threw the numbers into Excel, calc’d equation is: Measured temp = (0.59*S4 Temp)+5.54
Also edit to add: Running a capacity test on a 30Q from reliable supplier 18650.uk, 1.5A charge, 1A discharge, cell currently reads 57C on the S4+, so I assume this temperature rise is normal at these currents.