How should MH25 look when charging a battery.

Sorry for the flair none of the others would work.

Having lost the charger for my D7100 battery, I bought an MS25 from ebay. I put the battery in and the light flashes. After a long time the light goes out and no longer flashes. Shouldn't the light just stay lit instead of going out? Do I have a defective charger? The battery is new.