5.9L gas engine. The battery always seems to be going dead. Do you think it is the battery or something else. It charges fine though.

Little more info please.....does it go dead overnight, or while you're driving?

In general, check the btty cables to make sure they're tight, and that they're not corroded; if your battery takes water, be sure it's filled up. If the problem continues, you may be looking at a new alternator. Need more info though....

I would take the battery down and have it tested to see if you have low cells if battery checks out ok then you have something running or shorting out running your battery down but sounds like low cells this is commen

The battery goes dead when it is turned off. When I am driving it is fine.

If the battery is old it will start to do this.

Yup, Bleed's right, sounds like battery time if it's old.