Once per match, the player can decide to use an energy booster which will allow him to recover up to 30 units of energy.
There are three levels of boosters: +10, +20, and +30 energy units.
It is possible to buy these boosters before or during matches. Once the booster is added to the arsenal, it can be used immediately by the player: the Ballman will thus benefit from a boost of energy improving his performance.
The timing of using the booster is crucial as it is allowed to use it only once per match! You will probably be more interested in using it at the end of the match when your Ballman is tired. Be careful, however, not to delay too much using it, otherwise the match will slip away without you being able to benefit from this energy boost!