Battery drained or shut down when fully charged

Hi all,

I have been using Torch 9800 OS v6.0.0.284, Platform 6.4.0.120 for 2 years. Around 3 weeks ago, the phone started acting weird. When the battery was still 80% full, it's either suddenly shut down completely without any notification or flashing the "Battery drained" pop up before turning off. When I put it on charger, it will reboot and show empty battery (when charged after shutting down without notification) or 80% full battery (when charged after the "battery drained" pop up). The application I used intensively are Whatsapp and Blackberry Messenger, ocassionaly browser and Facebook as well. On standby mode, battery can reach around 50-60% before finally turned off. No OS updates and no new installation recently.

Not sure whether this is due to the OS, the device itself, or the battery. Indeed I can always try to purchase new battery to test it, but I'm thinking on asking around whether it's really likely battery issue and not system issue so it won't be a wasteful purchase. There were several annoying problems with the system occurs recently such as sticky messages on the notification area, system hang when opening the browser, etc.

Does anyone experience this before, or any idea what is likely the issue? Thanks in advance,

I have seen this issue a few times at customers. A new battery fixed the issue.

/JP