Our team carries a minimum of 8. They are numbered in a rotation according to their tested charge and pretested load capabilities. The pit setup also runs 4 chargers all the time. We have a pit crew person assigned to keeping track of the batteries and always haviing a freshly charged battery for each round. When we get the round schedule for the day we assign a battery number to each round and that way you never have a dead battery in a competitng robot.
The magic number of 8 serves two purposes. First- by the time you get to the 8th battery, the 1st one is well charged if you need it. Second- in the elimination rounds 8 batteries usually gets you through the three rotations. We have a little rolling cart with numbered slots for our batteries so we can take them to the field for the close-set elim matches.
Like our drivers/players, our batteries must compete for a number in the rotation. They do this by performing well in practice at home and holding the highest charges of the pool (currently 17) Generally they show their gratitude for being chosen by performing well.
Batteries do die after a few years, especially if you crash around a lot. It is always good to have a fresh set for the season..
Also- please dont forget the little auxilliary batteries. Without them you might have some problems with all the sensors this season. They also seem to charge rather slowly.
WC
