Hi I'm translating this from google translate Sorry for the bad translation, fly more I have a combo spark. one of my batteries is on 50th charge but sometimes drops to 9v during flight. I tried to show it in the video, you can look at 0:43. I have a few questions, I would be glad if you answer.
1-) Is there any way to fix this?
2-) Is it dangerous to fly with this battery?
3-) How many volts does it give the critical voltage error?
I want to buy another battery, but very expensive in Turkey, where one battery of 500 pieces of money.
It is not possible to "repair" batteries. Your battery has high internal resistance, thats why cell voltages drop very quickly. It can happen because of mishandling. Lithium batteries should never be drained totally and then left laying around. They should be recharged to about 50% before storing. Spark batteries discharge themselves to about 50% when being lying around for 10 days. Also do not store lithium batteries at above room temperature.