I recently replaced the battery in my APC Back-UPS CS 650 and of course I didn't opt for an original APC battery, but just bought a similar one from the corner electronics shop.
Apart from the label both batteries looked exactly the same, but still the old one used to provide 20 minutes of backup time and the new one only 10 minutes. The label on the original battery only states 'original APC replacement' and things like 'wash your hands when spoiling the acid contained in it'. Nothing indicated exact specs, so I just bought one that looks exactly the same and has similar voltage (12V).
So what is different, does APC really manage to put 14Ah in their original battery and still only have a 12V/7Ah form factor? Did I buy a bad battery? Is it a difference between deep cycle vs. non-deep cycle battery? Are there different types of batteries that I should have been aware of before buying one?