[GeeTwo]

Edit: My post is intended not so much for OP, as to document our learned battery charging rules for benefit new teams. If we're doing something wrong/not quite right, I'd love to hear it.


We have used a wide variety of chargers over the years. The #1 key feature is to get something which explicitly supports gel/AGC batteries. The other "nice" feature is the "float charge", which keeps batteries topped off, more important if your team takes a serious break outside of build/competition season. [Edit 2: That is, if the batteries are not kept on float chargers, put each one on a charger every two weeks or so until it is "topped off".)

Based on my reading (and not contradicted by experience), at least as important as your charger is your usage/charging rules. During competition, change batteries between every match, and put the battery on a charger stat. During practice and demo, do NOT wait for your batteries to fail, but replace them on a schedule. If you're actively driving and shooting and such, it may be as often as every five or ten minutes. If you're just shooting balls using pneumatics, but doing little driving (as our robot is doing this year at many demos), you may be able to go to a half hour or more on a charge. If your batteries ever get below 12V with no load, you've let them work way too long. We currently try to get our battery changes for relatively low draws around 12.5V (or pereferably higher). Also, after use, put batteries back on a charger as quickly as possible. Lead-acid batteries sitting discharged are batteries heading for recycling.