Batteries hold less and less charge over a period of time. Consider yourself
lucky if your battery has lasted you 4 years.
Either replace your battery OR you can try having the old one reconditioned
but I doubt that a 4 year old battery is worth reconditioning.
Buy yourself a new battery, man. Don't be a miser!
Here a parable...
A man kept working out how much his donkey cost him in feed and decided to
try and reduce his costs by feeding the donkey less and less until at long
last he had the donkey surviving on almost nothing.
Then one day suddenly the donkey dropped down in the throes of death. And
the man said= "Oh, no, don't die on me now when I have thought you how to
survive on more or less nothing!"