If you find yourself surveying with a very old version of this Terrawave battery pack and it is suddenly not charging, or only works when it is connected to the wall charger, the fuse in it may have gone bad.
Remove the main unit cover, and you will see a plastic housing with a glass fuse in it. The glass fuse was broken, so I replaced it with a fuse I purchased from RadioShack (4/$2.00). After replacing the fuse, the battery took a charge, and worked properly after obtaining a full charge overnight.
The symptoms I had were that the battery did not take a charge from the wall wart, and the wall wart did not show that there was a load on it. The light stayed green - indicating the battery pack was not charging.
The battery pack would not power on an attached access point unless the battery pack was connected to wall power.