Depends on their quality...
I charge my old and abused Sanyo RC1700 at 6 amps, and 5 mV cut-off pr. cell. 4-5 amp might be better, if you are not sure of the quality or you want them to last longer.
Basically, you should have the cut off as ow as possible, without fale peaks. Can take some try's to find the right spot. Also ensure, that they not exceed 50 degrees celsius, when they peak. Around 45 degrees is good.
Schumacher Mi5 - Sanwa MT-4 / RX-462 / KO Propo PDS-2123 - Nosram 5600 X-treme Saddle Pack - LRP SPX Zero/X12 17,5 - Nosram Stealth Touch Evolution - MAAS SPS 9250