cmos battery should it be there

Yes, at least the one I tried reviving for a friend did. They got scammed on Amazon, but got their money back. So they gave it to me to tinker on, never did get it working (water damaged probably blew a few components internally [shrug] free electronics to play with).

IIRC, the battery is a lithium cell (2032?) in black shrink wrap, with twisted red and black wires about 2.5 inches long that should attach to the connector on the top left of the board (as you'd see it in the casing, the USB/HDMI ports facing away from you and the SD slot facing you (up) and on the right), with the cell sticky taped to the copper side of the heat spreader.

If it's not there order a new one, or find a compatible donor plug that fits, and pop a new 3v lithium 2032 cell in it. Make sure to insulate the cell of course, don't want a bare cell bumping around in there.

There should always be a power source for the CMOS. If there isn't a CMOS power source, then the device will not start up. However, some computers (like my MacBook Pro which I'm using right now) have a capacitor that is charged by the battery. You could search for something that looks like an ordinary alkaline watch battery (button battery). It will be the capacitor. If you don't find it, then then the CMOS could be powered by a solid-state chip battery.