Im not sure this fits here but I found some interesting properties in my sg powered window motor today. I was charging the other day and the charge batt was hovering and ever so slowly increasing from 13.20 to 13.30 over two hours. I am able to trip it into self oscilliation at certain resistances for similar amp draw, but as you guess much faster switching times. When I set it to self oscillate, the charging batt jumped upwards in voltage instantly and climbed to over 14.60 volts within a couple of minutes.

I found it interesting that I could power the wheel and charge, but as soon as I kicked it into solidstate, the top end (13.5 - 15v) charged rapidly. It doesnt charge that fast when the battery is lower. It seems like a good way to top up the last 10% of the charge cycle. I have still to get a suitable pot to adust the frequencies but amp draw is very similar to its rotational state. The ssg circuit has a bridge to collect to cap and scr.