You'd be much better off, powering you robot off a switching PSU or an ATX psu.
An ATW PSU will typically have over-current protection and can typically handle over 20 amps at 12 volts. However, don't expect to run CIMs (CIM, MiniCIM and BAG). The BAGs draw up to 40 amps at stall!
I believe the batteries fast-charge at 3A/hr. I think the bridge consumes 1 or 2 amps, by itself. Plus, you have a cRIO, DS, and other components, like a coprocessor. So, you'd probably see magic smoke from that $100 charger you saved up for!
---------AAAHHH!!! You're an FTC, not FRC. My bad. I'll leave that up because that would be useful for FRC teams---------
Again, just get an ATX PSU and hack it so it is always on. That only requires a paperclip. Battery chargers are not meant for powering things. They are meant for charging batteries! Don't ask up why you got magic smoke if you used a battery charger to power the robot.
This is what you aree probably looking for, and costs less than a good FRC charger. (I don't know what FTC uses)