On the back of your charger, it should say something like this:
Ouput voltage: 3.3VDC
Output current: 300mAh
etc.
But really, if it's the same type of material(NiMh for both) then it will work as long as it's made for that size of battery(AA, AAA, C, D, etc.)
Because all of the rechargeable batteries run on 1.2VDC and while the mAh rating differs on different qualities and materials of batteries, that doesn't effect whether the charger will work with them or not.
For example:
Charger outputs 330mAh
Battery is rated for 1800mAh
It will take the charger a while to charge the battery up to the 1800mAh needed for a full charge. While, if the charger was 1800mAh and the battery was also, then it wouldn't take very long to charge the battery fully.
Understand?
HTH,
David