At three years old you may as well do yourself and replace it. We only rent batteries, we never really buy them. They break down inside and lose the ability to deliver full capacity.
In my business working of vehicles with two way radios I always knew the cold weather of Winter would bring out the complaints of radios running down batteries. Many customers would say their mechanics had tested the battery and it was the radio running it down. Simple measurements proved it was impossible so I would ask the customer to buy a new battery and keep the receipt and bring it to me if it did not fix the problem. I never bought a battery in 40 years except for buying one myself because a stubborn fleet mechanic refused to replace the fire chiefs battery in his new vehicle. Problem was solved and the chief was happy.
