Hot batteries can become exploding batteries. If you don't completely understand your charging
system and electrical system
, it might be safest to SHUT the charger
completely and get a professional in to check things over. Shouldn't be hard to find one. Could just need water
. May be overkill but better than having a battery explosion and fire.
The manufacturing date of the batteries is always printed or stamped on the case. Sometimes right on top, other times on the side, near the top, and covered (intentionally) by one of the large labels.