You can't see the sand inside a ammo box.
Bag of sand, lipo battery bag of sand. All inside the ammo box.
A big metal tackle box or tool box is another good one. Some guys even line them with drywall.
I doubt they would get hot enough through the metal walls. If you go with the sand bag thing, that will help contain it regardless.
In reality as long as you follow the directions on your charger and storage charge the batteries like they are supposed to be, you want have any
issues. Cautionary...
I don't have a garage or any place outside to store them but I keep them close to the front door and can get rid of them outside if need be. If we leave for a couple days then I put my ammo boxes with the lipos in my BBQ.
Another good one is just a simple metal filing cabinet and even lined with...
I've seen guys using a BBQ to store their Lipo's, a few build a brick box for them, @tntpoof built a really cool Lipo box.
I've also seen sand bags using baggies and surround the battery. If there is a fire it melts the plastic and the sand helps contain the fire.
I use Lipo bags and ammo boxes. Any good metal box would work. As far as the Lipo bags, I have one for each battery. If have a Lipo fire in the box, the bags will help contain it and not catch other batteries on fire. To me, it's just smart thing to do. Others may think different but that's...