Juggling Fuel Canisters

[nsherry61]

I just got back from a cross-country trip with my brother-in-law that left me with a box of mostly empty large (16 oz) fuel canisters that he could not take back with him on the plane. What to do? I have no use for the large canisters, but I like free fuel . . . so, I ordered a "fuel canister refill adapter" from Amazon for about $14, figuring it might be kinda funky, but I could probably manage, somehow to fill up my empty and partially empty small (4 oz, 110 g) fuel canisters from the partially full large ones.

WOW! It was way easier than I expected. So I thought I'd share what I did in case some others like the idea of reusing canisters, filling small canisters with the much less expensive fuel bought in quantity in the large canisters ($1.75/oz vs $0.75/oz), or people that don't wont to carry any more fuel than necessary, so they can transfer fuel to or from canisters to get the exact amount of fuel they want for a given trip.

The whole process was super easy.
1) Attach the adapter between the two canisters you are moving fuel from and to.
2) Place the canister you want to fill on the bottom in a pan of ice water (see attached picture)
3) Pour boiling water into the bottom of the upside down canister you want to transfer fuel from.
4) Let the canisters sit for a minute or two to cool in the ice water and warm from the hot water.
5) Open the refill adapter to fill (or partially fill) the lower canister.
6) Unscrew the canisters from each other and the adapter.
7) Go backpacking

fuel canister refilling.jpg

A few notes:
1) The 110 g canisters can easily be filled to about 130 g with no apparent issues. (Edit . . . NOTE: Overfilling canisters beyond the original gas weight is surely unwise and may be dangerous, therefore, if your canister is overfilled, reverse the process described above and transfer a little of the gas back out of the overfilled canister to retain a robust safety margin.)

2) The canisters being emptied only emptied down to about the last 10 g of fuel in most cases, since the fuel is transfering via a pressure gradient that requires pressure in the upper canister to be higher than the lower canister. With patience, you may be able to do a little better than I did, but you will never get every last gram of fuel out of the upper canister until you puncture is to let out the last remaining pressure before putting it in the recycling.

3) Having a kitchen diet scale (~$15) is super helpful in knowing how much fuel is in each canister and how much you have transfered. The same type scale is considered mandatory gear for most backpackers to be able to weigh all their other gear. I write the fuel weight on each canister with a sharpie so I know how much fuel I'm taking whenever I grab one to use, and I can grab one with the amount of fuel I want for a given trip. Just subtract the empty canister weight from the total weight to calculate available fuel.
- 110 g canisters weigh about 100 g empty
- 220 g canisters weigh about 150 g empty
- 550 g canisters weigh about 200 g empty