I've got an 850 mah 4s LiPO that shows full charge on my battery tester and on my balance charger, all cells read full charge. I put it in my drone and fly for a minute and suddenly the voltage in my goggles drops from 16.7 to under 10 after just about a minute of flight. I suppose I should retire this battery. Thoughts?

Lipo is probably old and sagging a lot. If you confirm that you drone is correct, I would retire the lipo.

Yeah, another battery and seemed fine. I'll drop in in my saltwater bucket. Sigh.

Not all lipos are made the same. Some just do not last, especially the abuse lipos go through.

(02-Oct-2023, 08:21 PM)voodoo614 Wrote: Not all lipos are made the same. Some just do not last, especially the abuse lipos go through.

Yeah, that's fair. I thought it was a good brand, though it has been through a couple hard crashes. It's a Tattu, which got good reviews, but who knows what the inside looks like after being abused by my students.

If any of the cells were inadvertently or carelessly run below 3V at any point, those cells will have suffered permanent damage and the LiPo will never be the same again. Limon recently put out a video showing some really good battery testing, part of which he purposely ran batteries down below 3V per cell to see what effect that would have on their continued use after they were recharged again. All of them immediately lost performance following their next full charge cycle. Jump to time position 09:08 in the video linked to below to see the results of that part of the test. This shows how important it is to NEVER let your LiPos drop below 3V per cell.