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Old 08-04-2012, 12:24 AM   #49 (permalink)
bwilson4web
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Quote:
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:

Quote:
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.

Quote:
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?

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