If your battery is fully charged, but you have no power, first check the connection to the battery. Is the wiring to the battery tightly fastened and in contact with the battery terminals?
Does the battery have a build-up, rust, dirt or corrosion on the battery terminals where the wiring harness connects to the battery? A layer can build up on the terminals of the battery, wiring harness ends or both over time, especially if the battery is outdoors or in moisture. This is particularly common on Sealed Lead Acid batteries where the terminals are not always stainless steel.
To remedy this, take a wire brush and clean both the battery terminals and wiring harness ends, reconnect tightly and give it another shot.
If the terminals are covered with a white crumbly sulfur type material, good chance this is the issue.
Another thing to check is whether a fuse has blown on the wiring harness or in the object it is operating?
If everything checks out, your battery has probably put on some age and ran its course (RIP).
i just charged batteries on my 2000 hino dutro 4617cc diesel and now have no electrical power at all. Batteries are good and connections clean and tight
Why my hurcules 20 volt shows full charge but acts Dead in my drill and all other batts work fine . ????