Question [SOLA] 1 Year Old Set[Not Switching On][Help]

OK guys . . . probably an easily solvable problem. But i need advice.

here goes . .

Recently i got an Xperia Sola. Its my sister and she was using it for almost an year. Now bought new one so i get to use the old SOLA..
So the problem now is that its not Switching ON. I put the phone on wall charger for almost 2 days continuously. I think the battery is messed up.
On wall charger/ PC i'm getting this bright red LED but it only lights up for some time, say some minutes. then it goes off and nothing happens , no lights nothing. i don't think its in bricked state because my sister doesn't know anything about Root, cwm, custom ROM etc so its still in factory settings. i tried to switch it on Still nothing.

i'm thinking of buying a new Battery.

Any advice . . ?? what should i do ?

Sony Xperia ION(LT28h)
Android Version - JB 4.1.2
Kernel - Stock Kernel + CWM
Tweaks - init.d + build.prop
Bootloader Status - Un-Locked
Firmware - Sirius/Z2 Full Port V2 Build - 6.2.B.0.211

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