I have a 176T with a slider and I remember looking underneath the slide when extended and it has no access to the slide mechanism or motor (I think I remember putting some grease on a toothed slide bar which is accessible?). I believe the slider motor runs on 12 volts and I usually run it when plugged to 120 AC because the amp load thru the converter is fairly high. I have tried it on battery only for a short time just out of curiosity and its seems to work but for fear of draining the battery (unless in an emergency) I only ran it for a few seconds.
I would not run the slide when hooked only to the TV as the load on the TV might be too high - I have no data or technical info to back this up so you're on your own. You could make sure the battery is charged via the TV and then run it on battery w/o the TV hookup (my choice). If the motor or slide mechanism is bad you 'd need to fix them
Also, I imagine the access to the motor is from the inside with a panel removed ... But I really haven't looked specifically for the motor. In the spring ...