Monday, August 27, 2012

Testing update

I've tested about one third of my cells, and all of them so far are in excess of 60Ah capacity. The cells come from CALB at about 50% charge, the PowerLab 6 takes about 6 hours to charge from half to full, discharge and recharge.

Below are some graphs that the PowerLab spits out, the raw data is also available, so I plan to look at the stats when I'm done testing the entire set.

Here you can see that the PowerLab puts in a little over 30Ahs, rests for 15 minutes, removes a little over 62Ahs, waits for 15 minutes, then puts back in a little over 63Ahs.

Here you can see the steep "knee" as the cell gets full, the plateau as the charger changes from constant current to constant voltage mode at 3.60v, the drop as the surface charge dissipates during the 15 minute cool down. Then we see the sharp drop as a 30A load is applied and the slow drop until the steep knee as the cell approaches empty, and a quick recovery as the load is removed at 2.80v for another 15 minute cool down period. In the final phase, we see a steep curve as charging starts at 30A constant current, then a long fairly flat charging curve and another steep knee as the cell gets full again, followed by the constant voltage plateau to finish.

The CALB paperwork lists this cells internal resistance as 0.44 mOhm. The PowerLab measured it at 0.5 mOhm. The other cells have been similarly off, and similarly flat on the graph. I'm not sure what that means, if anything.

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