2005 Ford F150 loses voltage every time I change the battery

Is it basically the battery if your car starts to grind if you think its not the starter motor or the flywheel because my car keeps losing voltage evrytime I charge it and doesn’t stay the same?

If you are in the U.S. AutoZone will check your battery for free and if you buy it there they might even replace it for you. Not all states allow that service.