I tried this setup and got the input batt to climb as I have had the input battery climbing in the past with other variations.

I didn't get 2000v but I know one thing from my personal observations. It seems to damage the input battery. If it is just radiant spikes, it will kill the battery. There needs to be some current to put it in charging mode.

Also, the battery doesn't work well powering/charging/powering/charging, etc...

It needs to do one or the other. The lead ion movement needs to get going in one directly for charging over a long enough time. Getting it to do that while it is running screw up the battery. My observation.

I have tried other variations putting it to cap connected to input battery, etc... there may be other variations that work better than others.