The specs on line say it has an (impressively large) 9.6v 45Ah internal battery, good for 10 hours operation eg
https://www.firstlightoptics.com/alt-azimuth-astronomy-mounts/sky-watcher-fusion-120i-synscan-mount-and-tripod.html
so if that is correct, a 17Ah external power pack is not going to increase the run time dramatically. How long do you want to run for?
Cheers
Robin