Well, for fun, I setup my old field test unit (ST-5888) on a patio table and let it gather light for a couple of days. Just got it connected to my hub and app, so it’s now online also. Battery voltage is only 2.37v so it’s in power save mode. Will have to see if it has any life left or not.
My main unit is now up to 2.53v. So seems to be working and charging slowly.