Is there a tester that allows you to check how much charge is still left on those big 6 volt batteries? Maybe like a load tester that would say 10 amps. Then check batterie 3 months later and it has 5 amps. It takes 4 amps to run feeder. Then I know the burn rate of my battery and can replace it before everything shuts down.

You should be able to pick up a tester at an automotive parts store.

try putting your tongue across the terminals. if the battery doesn't give you a painful shock, the amperage is too low.