around 13<>13.5v is not uncommon on a battery that had recent charge cycle & like luke pointed out is surface charge.
standing battery would read between 12.4<>12.7v
battery after charge will read around 13.2v for some time, normally takes 12hrs before true standing voltage can be read.
Only way battery gets excessive voltage is if alternator voltage regulator faulty so that needs testing to be sure of charge status from alternator.
If battery over charging it possible cells are dry, sealed battery would be scrap in that circumstance.
My hunch is starter unit issue or wiring. Hard to be conclusive with details so far.
standing battery would read between 12.4<>12.7v
battery after charge will read around 13.2v for some time, normally takes 12hrs before true standing voltage can be read.
Only way battery gets excessive voltage is if alternator voltage regulator faulty so that needs testing to be sure of charge status from alternator.
If battery over charging it possible cells are dry, sealed battery would be scrap in that circumstance.
My hunch is starter unit issue or wiring. Hard to be conclusive with details so far.