OCV curve principles

See :

Do we need to measure the curve at different temperatures? How significan are the differences?

Relaxing time

⇒ We will use 90min relaxing times to maximize accuracy of our curves

We will use an 8-ch cycling machine to measure OCV on cells

The programming software looks like this:

First, make sure the cell has been fully charged according to the instructions below:

Step	Mode	Set1	Set2	Cutoff	Comment
1	C-CV	1	4.2	0.1	Fully charge the cell before measurement
2	Wait	0	0	90

Then, after a relax time > 90min, follow:

Step	Mode	Set1	Set2	Cutoff	Comment
1	D-CC	1	2.5	360	Discharge for 6 min = 100 mAh @ 1A. Cut at 2.5V (depends on cell, see datasheet)
2	Wait	0	0	90	Relaxing time
3	Cycle	0	0	36	For a 3500mAh cell, 35 * 100mAh ⇒ At least 36 cycles to ensure complete discharge

Due to the hysteresis effect, the curve is slightly different when in charge vs in discharge

See

Make sure the cell has been completely discharged according to the instructions below:

Then, after a relax time > 90min, follow:

Step	Mode	Set1	Set2	Cutoff	Comment
1	C-CV	1	4.2	0.1	IMPOSSIBLE TO CHARGE FOR 100MAH ON THE ZKE TESTER?
2	Wait	0	0
3	Cycle	0	0

See procedure here:

On a relaxed cell, with a cut-off of 2.65V (such as Samsung 35E):

Step	Mode	Set1	Set2	Cutoff	Comment
1	C-CV	0.1	4.2	0.1	Charge to 100% at 0.1A
2	Wait	0	0	90	Relaxing time
3	D-CC	0.1	2.65	0	Discharge to 0% at 0.1A
4	Wait	0	0	90	Relaxing time
5	C-CV	0.1	4.2	0.1	Charge to 100% at 0.1A
6	Wait	0	0	90	Relaxing time
7	D-CC	0.1	2.65	90	Discharge to 0% at 0.1A (2nd time, should be more precise, compare with 1st)
8	C-CV	1	3.6	0.1	Charge to ~30% SOC for storage

Compare 2nd discharge with 1st discharge. Same curve? If so, delete 2nd discharge in the procedure

See tests here: