The hydraulic pump motor is a high current device, something like 50 amps, maybe more for starting current. It is connected to the battery via a short #4 ga wire. I don't think the converter is capable of supplying that kind of amperage.
The pump does have a fitting on the end that you can connect a drill to and run the pump to operate the slides if the battery fails.
Curious if you have hydraulic slides, and if so have you actually tested yours with a dead battery to see if the slides will work. Probably will not if hydraulic. If you have cable slides, maybe.