Li Ion Pulse Charging - Proof of Concept Test Part 3

While the first pulse charger was running an extended test I built two more pulse chargers. I connected the long suffering cells I had over discharged previously mentioned and left everything alone for several days. Today I downloaded the data and calculated the mAh of the three batteries and voltage over time.

Battery E

The last result for this battery from the CC/CV charger was 171mAh. Prior to Run 1 above the cell had been discharged below 2V. The poor result for run 1 and subsequent deterioration appeared consistent with the folklore surrounding damage to batteries discharged below 2.5V. After 10 charge/discharge cycles on the original pulse charger the battery was put back on the CC/CV charger for around 5 days. It was then placed on a new pulse charger with different charge/discharge parameters. Run 11 reported a capacity of 160mAh, close to the reported capacity before the initial discharge below 2V.

Battery F

Battery F was also discharged by accident below 2V before Run 1. It completed 15 charge/discharge cycles on the original pulse charger. Unlike Battery E this battery was not put back onto the CC/CV charger after initial testing on pulse charger 1. It was simply left in a partially charged state while new pulse chargers were being built.

Just like Battery E discharging at a higher rate on the new pulse charger showed an increased capacity. Unlike Battery E only one peak was observed in the reported mAh capacity. Both batteries were on their pulse chargers for the same time period. Which appears to rule out daytime/nighttime temperature variations in the reported capacity since temperature would affect both batteries at the same time.

 

Battery Apple1

This battery was one of many recovered from an Apple Laptop Battery. It was left on the original pulse charger for over a week. The battery capacity was better than I expected which meant only 3 full runs were recorded. With just 3 runs the only observation I can draw is they were all nearly identical.

Conclusion

The hardware and software seems to be functioning correctly. The results suggest it would be worthwhile building a proper pulse charger for automated long term testing of LiPo batteries. In the meantime the batteries have been put back on the pulse chargers to see what happens.

The testing and results can be summarised as:

Battery E F Capacity at end of CC/CV testing 171 mAh 136 mAh Discharged below 2V before Pulse Charging Yes Yes Put on CC/CV charger prior to new Pulse Charger Yes No Jump in initial capaity after PCVer2 used 135% 48% PC Ver1 average capacity 69 mAh 53 mAh PCVer2 average capacity, excluding first 3 runs 90 mAh 67 mAh PC Ver2 increase over PC Ver1 31% 25% PC Ver2 average capacity compared to CC/CV capacity 52% 49%