I have used a brand of NiMH batteries for years with a charger from the same manufacturer. After reading up on batteries I found the following statement on battery university All about chargers
The Ah rating of a battery can be marginally different than specified. Charging a larger battery will take a bit longer than a smaller pack and vice versa. Do not charge if the Ah rating deviates too much (more than 25 percent).
After checking the rating of my charger I found it to indicate 1.2V 500mA. The batteries I have been recharging for years rate at 1.2V 900mAh. So is the charger I have used not suited for the batteries which are from the same manufacturer?