Hey there.
I have the same mount and relatively new too. I went with:
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https://www.aussiebatteries.com.au/a...ery-and-ardent
(something like this. note that you may need a different charger for these batteries. The one I have is a 175 which is a beast)
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https://www.jaycar.com.au/12vdc-12-5...sort=relevance
(one of these to power the mount and my pimalucelab Eagle from the same unit when at home / testing alternate power option. I also purchased the double adapter from Jaycar and changed the fuse over...)
Both work really well. I didnt bother building my own battery setup. Noted that the battery bank / power bank isnt cheap!
All the best and good luck