i have a lead acid battery 12 Volt 7AH.....i have bought since 2 months and i was use it very rarely. now i found it empty with volt of 11.8
so i'm chargig it using a normal computer power supply 12 volt , it's being charging now for about 2 hours but the volt doesn't exceed 11.9 .....what does it mean
You need a charger, NOT a power supply - in order for current to flow into the battery the charger feeding it has to be higher than the battery voltage. You can't charge a 12V battery (nominally 13.8V) off a 12V supply.
But I have found cheap 12VDC wallwarts that are 14-15 and used them for a trickle charge. It will take a while based on the current it can provide. But a though until you do build/buy one.