Took the bull by the horns last night, and decided to top up the battery with de-ionized water.
The Optical Hydrometer had turn white about 2 weeks ago, even though the battery was running fine, no drop on any of the electrical devices.
In order to get to the cells, You need to remove the fuse unit off the positive pole on the battery.
After reading all threads on the possible outcomes of disconnecting the battery, I decided the fact I had the Clarion headunit, it wouldn't require codes.
When I opened the cells, all of them seemed fine with electrolyte covering all of the baffles, so I just poured in a small amount of de-ion in each.
Intially nothing happen to the hydrometer, started to replaced the fuse unit and the terminals, by that time the hydrometer had turned black - require recharging.
Put the key in the iginition, and turned to MAR, all the warning lights on the dash turn off like normal, just waiting for all the motors on the aircon to stop turning. Starting the car, everything running normal, including the radio, just needed retune the radio stations.
Took the car for a quick 15 min blast, returned and checked the hydrometer again, turn back to GREEN again. Job Done!