That depends on how quickly you want them charged, and how long you want the batteries to last. A safe fast charge on Nicads and Nimh cells is "C", which is the capacity of the pack in mA. So for a 270mah pack, "C" would be .27 amps, round it to .3 amps.

Charging a little faster gets the charge done faster, but wears out the batteries faster. Charging slower is better for the batteries and they will live longer.

Now, you are talking about Nicad or Nimh cells, right? Not a 2 cell Lipo pack? Lipos are totally different.