VDC Reverve Power

Depends on the design of the charger. Some will burst into flames. Apparently you don't have one of those or you would not be asking the question. Best to ask the manufacture of the charger. It may be toast, it may be fine and you just need to clean part of a circuit board. There is no way to tell with out significantly more information.

Now that I think about it, did someone disconnect the charger and accidentally reconnect it backwards? If not you probably need a qualified repair person to visit. If someone did I would try just putting the connections back the way they are supposed to be. The fact that the alarm calls out this specific problem indicates it should recover once the error condition is removed.