I have a hitronex 5000mah 4s lipo 40c but one cell won't charge over 3.87v. Is there anyway to fix this to get it back up to 4.2v again. You may have guessed I know very little about lipos. Any help would be appreciated
Charging using a balance charger should do the trick.
This type of charger connects to the main battery leads and the connector that comes out of it at the same time and balances by holding fully charged cells at 4.2V while bringing up the low cells at the same time.