^^ Agree, that's the easiest and most common first step.

After the new battery is installed, monitor the voltage :
@ 12.1 volts with engine off
@ 13.8 - 14.2 volts with engine running.
You can buy an inexpensive digital voltmeter that plugs in the cigarette lighter for $5 or so at most parts stores.

If you are seeing higher voltage, suspect the alternator/voltage regulator.