There is a setting in the charger 'advanced' menu called 'keep going after done'. You can do this to keep your batteries closer to full voltage when you start a race, but I think this puts some extra strain on the battery, so I've also turned it off.

Select your lipo charge profile that you use for that battery, but hold down the button when selecting. This will let you edit the options for that charge profile. Enter the charge settings, then choose the 'advanced' menu and uncheck "keep charging after the done'.