Sorry missed this one previous.
Well basically you need a new battery, as I said in the other thread there are ways to maximise battery life, and continually keeping it charged is not one of them, that said you have had a few years out of it so it could be worse.
But once your battery has reached the stage yours is at there is no return, it needs replacing, all I can do is suggest a method that i apply to all my battery's (with slight variations depending on the type), when you first get it plug it in a charge it, I personally let it charge overnight at the least, a good 16 hours or so even if the book says it only needs say 5 hours.
Then fully flatten the battery and fully recharge it again but from this time onward use the books guide as to charging time, now repeat this several times in the first say 6 times of doing it (thats what I use), after this you can charge it as you like, but if it's fully charged and your using the mains take it out, it wont hurt it, and there may be "some" benefit to this (but nothing I could swear to), but lets say you would flatten the battery every week, so that would mean you have to charge it say 4 times a month as an example, once a month, maybe every other month let it go fully flat and full recharge it again, then continue as you need just remembering every so often to keep it at it's best.
Some will say this is overkill, maybe it is, but I have got battery's some years past their dates where people would have gone through 2 or 3 sets of battery's in the same time, so there is definitely a madness in my method.
The newer battery's are far superior than the old Ni-Cd battery's we used to use, so they aren't as demanding in their regime, but even so I have personally found it to extend the battery's working lives by doing the above, the only way to know is to try it and see, but it will obviously take years before you truly appreciate just what it does for you, all I can say is I have my old Nokia 8210 in my draw, it's about 10 years old now, and it still has the same battery as the day I got it and it works fine holding a charge for a few days, OK it isn't the week it used to serve, but others have gone through about 6 battery's in this time so go figure.
There is 1 exception to this charging regime though, as I briefly said above the Ni-Cd battery's are different, they suffer from what is termed BMS (Battery Management System), basically they remember the level of charge they had when charged and if you hadn't fully flattened the battery before charging it next time it will remember how long it was done the last time each time, so next time it will only charge to that level, no easy way to say it but see if this helps, charge a battery for 1 hour, then each time you charge it after knock 5 minutes off the time, eventually you reach a point of zero where it is dead, that is in effect what happens so you shorten the battery's life by not discharging fully then fully recharging again, hope this helps.
Now in closing there may be slight exceptions\variations to this depending on what it is, a maker sometimes has a specific requirement perhaps so use common sense with this, it also assumes you are using the proper charger for the job, as far as I'm aware all modern chargers have a cut off sensor and will stop charging when it is no longer required, using a charger that does not have this and therefore just keeps charging could cause damage to it, and temperature is another factor, due to yours being in the laptop all the time it will be in a hotter environment than if it were in a radio say, this will also shorten it's life, so a cooler pad for your laptop may help prolong it's life, and it certainly wont hurt the laptop.
