vauxhall omega flat battery - gingerwinger
i have a omega v6 94. a strange thing has happend twice in 10 days. in the morning the car starts first time every time. drive to work 13 mile stop the car then 10 mins later go to start it but the battery has gone flat. jump start it and its fine. then today it did it again. when you put your hand on top of the battery its very warm and the battery terminals are very hot...... please help if you can
vauxhall omega flat battery - Dynamic Dave

Had similar happen to my old Vauxhall Cavalier Mk3.

Either the terminals connecting to the battery terminals are loose or dirty; or in the case of mine it was the cable connecting to the +ve battery lug that had semi detached themselves causing a high resistance joint. The heat transfered to the battery and put a hairline crack right down the side of it, subseqeuntly leaking acid all over the battery tray. I had to have a new battery lug fitted onto the end of the cable to solve it, and obviously a new battery.
vauxhall omega flat battery - Victorbox
The starting fine then not were the exact syptoms I had on my Cavalier's original AC Delco battery over a period of several months. Mostly it was fine and never left me stranded. One day it just died. Could be yours is giving you early warning that one of the internal plates is breaking down. Many years ago I watched a Lucas outlet test my battery (not AC Delco) in the days when you could unscrew the top-up caps. The faulty cell boiled like a kettle so this could be why the battery top is getting hot.