[DeMentor]

This year we had a lot of trouble with batteries from previous projects -- especially the 2009 ones. Three of the 4 batteries from 2009 were bad by the time we got to robot testing for this year's project, and additional batteries from previous years were also failing. We were not alone in this experience -- scanning the forums I find many other comments about poor experiences with some sets of batteries. This is getting to be a costly problem as I believe we need 4-6 batteries to be fully prepared for the championship rounds in the regionals, and veteran teams are now getting only 1 new battery in the Kit of Parts.
Therefore, we plan to spend more time on battery maintenance during the off-season, and you should do this too. This includes keeping all of our good batteries on float charge during the summer break. A float charger can be left on a battery forever with no risk of overcharging. A trickle charger (which is different than a float charger) can be used periodically, say 1 day a week -- but needs to be disconnected most of the time to avoid overcharging (which also shortens battery life). The "2A" setting on the chargers most of us use is sufficient for trickle charging -- but again, be careful not to leave batteries connected to a 2A charge all summer.
I've found float chargers listed online for as little as $10/each, and some float chargers claim they can be used for batteries connected in parallel as long as those batteries are of similar condition (I interpret that to mean the same battery manufacturer and model, and able to hold a charge).
There's a relatively new battery charging technology called "desulphation" that is claimed to be capable of recovering some of the lost battery storage capacity. I plan to test it against both good and bad batteries over the summer and will report results in a future posting.

Have a great summer break!
Mike