that the battery is gone.
Assuming that 'tweaking' the connection lead from the old charger into the charging port has not damaged the port, then the next culprit would seem to be the battery.
The test of course is, does the laptop work direct from the charger/mains supply? If so, then the new charger is working.
Laptop batteries do fail in time. The general consensus here is that batteries last for 18 months to 2 years or so, or up to 300 cycles; that's 300 'fully charged to run down to fully charged' cycles.
So after 3 years your own battery has done well, but time to buy a new one I feel.
I would suggest you get the new one as recommended by the vendor/supplier o the machine, and not any cheaper ones available. Some of those have been known to cause problems. In the meantime, remove that dead battery now and just use the mains adapter/charger. Leaving a dead battery installed can also be dangerous.
I have a Fujitsu Siemens Esprimo V5535 that I have had for about 3 years from new. It was all working fine, until I started to have problems with the mains charger, which had got kinked over time. For months I had to jiggle the connector where it plugs into the laptop and angle the cable a certain way for the wires to straighten out enough to allow charge through.
Last time I used the laptop I let the battery run right down. That was several months ago.
I have only just replaced the charger, and plugged it in for several hours to charge the laptop up again.
The light on the charger is showing there is power getting to it from the mains but my laptop is still dead.
Could it be the battery that is now the problem ? Would the battery have died while the laptop was left alone ?
All help and advice gratefully recieved.