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Old 08-04-2012, 12:24 AM   #49 (permalink)
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Originally Posted by Daox View Post
I've pretty much finished up the first round of testing on the first cell. . . .
Well done! Love your charts which I can't find from the vendor.

Just a couple of questions. I've re-ordered them to look at charge and discharge:

Originally Posted by Daox View Post

Looking at these excellent discharge curves, I get the impression regardless of the starting voltage, the bulk of the energy starts at ~3.278-3.302V. Charging over this voltage does not appear to give any corresponding increase in total energy. So I'm wondering what is the smallest peak charge voltage that would give a starting discharge of 3.278-3.302V? Would a peak charge of 3.5V still put the cells in a state that they still start their discharge at 3.278-3.302V?

At the end, it looks like 3.017-3.055V is also where the available energy pretty well falls off. You went ahead and stopped it at 2.813V but I'm thinking of cell powered, battery management. I might stop it at 3.0V only to make sure the BMS logic continues to run without external power ... for a long time. My rough estimate from your charts is about 2Ahr, 10% of the rated capacity so I might go a little lower depending upon BMS load.

Originally Posted by Daox View Post

What first attracted me was the initial 3.431V on both charge cycles. Given the discharge went to 2.813V, we're looking at ~0.62V 'recovery' after the discharge ended. After the cells are discharged to 2.813V, have you measured the unloaded, recovery voltage, what they float to once the discharge ends?

The reason I ask is the open circuit voltage after discharge, what ever it float up to AFTER discharge to 2.813V, helps us understand the initial V*I, power needed to start the charge cycle. It also gives an idea of the dV needed to force charge into the cell.

In a similar fashion, what happens to the cell open voltage once the charge completes? Does it droop?

Bob Wilson
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Last edited by bwilson4web; 08-04-2012 at 12:39 AM..
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