Thursday, November 8, 2012

Slow Charge

I did another charge discharge but this time I did it at an 8 amp current. The charge/discharge algorithm is set for CC/CV and it set to terminate at C/5. Not sure if I should go that low for the amps. So with the fast charge I got like 11 amp hours in and another two if I finished the charge at 20 amps instead of 45 amps. End voltage for the slow charge/discharge is set for 3.5 volts on the high end and 2.5 on the low end. So with the slow charge I got 13 amp hours and the same with fast charging. The cell is puffed from my initial FAST CHARGE to 3.7 volts. Ouch. I do believe it damaged the cell by over volting the cell. I am going to try one more cell but will for sure stop before 3.7 volts. 3.5 or 3.55 will be about it even with fast charging.

One thing I noticed is that the voltage drops and reaches 3.1 volts it is quite obvious that the charge is over. There is really very little amp hours from that point on. It took a good hour plus to pump in 2 amp hours. So at that end 3 volts is really the end of charge. See the Graph. It is right there. Can't refute that. Not when it is repeated over and over. The more graphs that are done the more it becomes obvious. No need to use a BMS either to fiddle around with that last bit. Just need a good smart charger and controller. Set your voltages to 3.5 on the upper end and 3.0 on the bottom resting voltage. So on your controller you could set your voltages to 2.5 under load before cut back or off as once the current is lifted the voltages will rise.

I noticed that the peak voltages are pretty much the same on the Hi-Power as well as the end voltages. The voltages drop at around 3.0 volts and peak at 3.5. You could even do 3.45 if you wanted.

Here are my last Graphs.

No comments:

Post a Comment