[Dragsinger]

Tar,

for sure there is no harm in charging battery between runs. By doing so, the battery never becomes depleted and the alternator only has a small load when moving down track.

One key, keep good records. I do not expect the performance would be much different between charging and not charging but at least in theory there could be a small difference.

The goal of course, is consistent performance. If you run the fan with engine off it seems reasonable to replenish that battery reserve so the alternator does not have to do that during a run.