Batteries gets warm when charging?

Hi, I bought a fast charger (800 mah) and four SANYO 2700 mah batteries. After 4 hours of charging I touched the batteries and they were very hot! I never used rechageable batteries, so I don't know if this is normal. But, I don't think so.

The charger manual says that it cuts charging when batteries is near full capacity and then it enters in trickle mode, charging at 80 mah in order to not damage batteries. Ok!, but when this happens batteries are hot since 1 hour ago
Some advise please.

Thanks
Christian