Welcome, to the forums.
Another new member reported “battery” message with the Tether Tools battery eliminator. Apparently, the Tether Tools device is not a true DC adapter. It contains a battery, which is continuously charged. The problem seemed to be that the camera can drain the battery faster than it can recharge. I do not recall exactly which camera the other member was using.
I think the Tether Tools may be a poor design because of the inclusion of the battery. I do not understand what purpose it is to serve. A DC adapter is supposed to replace the need for a battery, but that is not the case here.
Plug the Tether Tools adapter into a wall socket, but do not install the battery. Give it a couple, or a few hours, to charge up the internal battery. Let it go overnight to be sure it is charged, if need be.
Once it should be fully charged, try installing the battery adapter in the camera again. I would expect the low battery message not to appear. At least not for an extended session of constant use.
If you can get a refund, I recommend that you do so. Even the Chinese knockoffs of the Canon AC/DC adapter kits work better than that Tether Tools setup, IMHO.
BTW, the cheap knockoffs imported from China do not work very well, either. Bite the bullet and order the Canon setup, even if it is on back order for a few weeks or months.
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