Agm or sealed batteries still have vents and are still prone to leaking. How far from the parked car are you going because you can always change off it too, or have a special spot in the trunk. Keeping the battery upright. As long as the trail is well worn down could use a wagon.
I do want you to realize a car battery is 40lb + your gear you could be carrying around up to 60+ with out even know it and it wouldn't be hard to get to 100 before you know it.
But back to you original question is it possible yes, can you do it yes will it work yes.
If you want to give it a try you can always pick up a 40lb dumbbell and see if you really want to do it. Return it after your quick experiment. Good luck have fun