Batteries not staying charged
Wednesday I was having issues starting my truck.
Took the alternator off and took both batteries to
be tested at Auto Zone. Batteries were fine
Alternator wasn't putting out the right volts maybe
8v. I bought a duralast gold they had in stock and
installed it. After install truck started right up no
issue. Drove it around for about 30 minutes and it
ran fine meter on the dash read over 16volt for the
batteries. Next day and today the truck hasn't had
any battery power and is barely starting. What
would be the cause of this?