So since my Bugs 4W folding drone has a battery charger with 4 lights to indicate charge level, I think I will try for 2 lights on solid with the third one blinking. Also I found out how to connect a multi meter or a battery tester to this drone battery. With really thin wire ends put on the test probes, it can fit into the row of battery contacts. And then touch only the first and the last ones with polarity correct by trial and error, and it shows charge level okay.