This circuit, Figure 1 , uses Linear Technology's LT6700-1 dual comparator to control a constant-current discharge circuit. Figure 1: NiCd battery discharge and conditioning circuit, in this example, ...

1C would be 3 amps in your case. our resident battery geek (Syonyk) can fill in the gaps about maximum charging rate. in the R/C world we beat the piss out of NiMH batteries which I don't recommend.

Instructables user [msuzuki777] had amassed quite a collection of batteries over the years, but was finding that some of his rechargeable AA and AAA cells seemed to be at the end of their useful li… ...