[EricH]

Bring:

• ALL batteries that are competition legal for matches. 2 isn't always enough.
• ANY Backup Batteries you have around.
• ONE or TWO old batteries (non-legal and marked as such) for practice in the pits (to allow comp. batteries to charge)

Change every match. There is nothing worse than having a battery die mid-match because it wasn't charged. Also, they'll charge "faster" if they've already got some voltage. (Same charge rate, less to fill, faster charge timewise.)