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2000 Ford F450 needs a jump after sitting for a day

My battery is 100 percent charged, but if i let it sit for the day, it needs to be jumped to start

Disconnect a battery cable before you let it sit for the day. If the truck then starts, you have a parasitic draw that is too large. If the truck doesn’t start, you have either a bad battery of a charging system problem, perhaps a bad alternator. Some parts stores will check your battery and charging system for free. Understand, these guys are not mechanics but they get it right most of the time.

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And just how old is this battery?

The only way I know to tell if a battery is 100% charged is to draw fluid out of each cell into a battery tester that registers its state of charge (specific gravity). Not every battery has removable caps, so this test may or may not work on yours. This test is more meaningful than readings from a voltmeter.

If you like DIY, you should check this out. https://www.popularmechanics.com/cars/car-technology/a5859/how-to-stop-car-battery-drains/