A fuse is always a good idea, of some sort.
A 2-3A PTC resettable fuse might be just the ticket for this app (unless it needs to be in very warm places):
For batteries, you’ll be looking at a 3S LiPo (“11.1V”), a 4S LiFePO4 (LFP) (“12.8V”) or a 4S LiPo (“14.8V”) battery. Note that the batteries are higher voltage when charged, and lower voltage when discharged, but the Jetson voltage regulators and carrier board circuitry should be able to deal with that.
Note that Lithium batteries do not like over-charging, and do not like over-discharging, so you need some kind of battery safety / charge control. Some batteries can be bought with “protection PCB” built in, which sometimes does this correctly for you. Othertimes, you need to design that circuitry yourself.
How heavy are you willing to go? How long does it need to run? A car battery and car battery charger may be all you need :-)
Main problem is making sure that you don’t over-discharge the batteries and kill them, because LiPos REALLY don’t like being discharged below 2.5V per cell – either they become worse batteries that get warmer under load and last shorter, or they just stop taking a charge after this happens.
I use custom circuitry to do this protection; you may get it from battery pack protection PCBs depending on what batteries you buy.
A 3000 mAh Lithium battery pack like this can run a Jetson for about 3 hours on heavy load, or longer on lighter load:
That battery is nice because it has built-in protection circuitry.
Perhaps this charger will work with it: