How old is the battery? What is the voltage across the terminals? With the engine off the voltage will be between 11.9V (fully discharged) to 12.6/12.7V (fully charged)? If the voltage is 11V or less the battery has a dead/shorted cell and needs to be replaced.
How is it driven? Short trips will run the battery down. If you drive mostly short distances consider using a trickle charger to top off/fully charge the battery. I use a Battery Tender www.batterytender.com to keep the batteries charged on cars I don’t drive every day. It’s a little expensive (~$60), but cheaper than any car battery.
Ed B.