I ran some test on my MH and got virtually same video as OP. I used a 75W lamp as a load. The two GC2 batteries are more or less full with CC regulating at 14.4V and 0.2A. CC = Blue Sky 2512i
With 75W light on, Vbat = 13.95V, I = 6.41A
With light off, Vbat = 14.10V, I = 6.38A
The time between the 2 measurements is 0.25 s.
Battery resistance is: R = 0.15V/6A = 25 mohm
Max current (greater than 6A) keeps going into the battery until Vbat = 14.82V. Two seconds have elapsed since turning off light. Finally the CC starts to regulate and pull back current (time interval between each set of measurements is 0.25 s):
14.70V, 1.63A
14.55, 0.77A
14.45V, 0.75A
14.45V, 0.75A
14.38V, 0.76A
It may be difficult to differentiate between the voltage jump due to battery resistance and the continued 6.4A voltage ramp for 2 more seconds.
If I remove the load at a lower voltage than 13.9V, then the CC will not overshoot 14.40V.
This is a CC problem. It doesn't react fast enough to a over voltage condition. Usually it's a don't care situation.
Sal
