There are lots of thread on IIS describing how most battery packs are designed to be short duration high amps jump start devices. They're not designed for multiple discharge/recharge cycles. You can be lucky, but its not unusual for people to spend $100 on a jumppack, later buy a cheapish charger for $60, then later another replacement jumpack. You've spent $200 in no time when you originally didnt want to outlay more than say $60.
On the other hand, for about $200 you would have a quality rig with something like
CTek 5 stage charger, and a decent
deep cycle battery.
Quality battery is a bit more, but worth it, particularly once you accumulate more gear for dew heaters, laptops etc down the line as usually happens. If you still buy a powerpack, probably worth still buying the decent CTek charger to get best possible life and performance from your battery anyway.
Option for backyard 240V/12V, something like
this
(can't find the 3A Dick Smith one I bought years ago for $60)
Trouble with astronomy is there's always a better quality option for 50-5000% more than you really wanted to pay, that you eventually wishing you'd bought
