If your battery has lasted 3 years, you have done well.
As you say it only lasts 5 mins. It's probably fully charged. at that point.
After about 600 charges or about 2-3 years,whichever is the sooner if would have reduced from it's original 1.5 hrs. (I'm guessing it's an li ion.)
To less than 10min.
It hasn't got time or strength to operate the warning.
All the best.