You need to borrow a load tester. It is just a heavy duty heat sink which
draws current from the battery. If the voltage drops during the test, the
battery is dying.
I have to borrow one to test my setup come
Spring

--
Dennis Gibbons
dkgibbons at optonline dot net
"Rick & Linda Bernard" wrote in message
...
Anyone have a good way of testing 12V deep cycle batteries?

What I was figuring on doing was using a 50watt 12V lightbulb and
measuring
voltage with time. The only problem is that this may take a few hours.