I have a Nitecore I4 charger (got it off eBay). The included documentation stated the following:
"When one or two batteries are charged, each slot will receive a maximum output current of 750 mA."
"When four batteries are charged at the same time, each charging slot will receive a maximum output current of 375 mA."
The I4 may not be the best charger available, but it's pretty good for a universal charger (it will charge Ni-Cd and Ni-MH).
Did you get the version 1 (White label) or the version 2 (yellow label)? The infor sheet on the one I ordered said 500mA charging 4 batts, and 1000mA charging 2.