TLS, Smaller gas bottles are more expensive and you end up not using all of them as you don't know just how much is left in them, making them very costly indeed.
But they are so good when used in a mug or jetboil they are almost essential for a weekend away

For example bottles like this
https://www.gooutdoors.co.uk/15894722/c ... e-15894722
wont fit in a jet boil, they are heavy and they take up a lot of space but they will see you through a weekend or more.

Whereas the smaller ones
https://www.gooutdoors.co.uk/15894772/c ... e-15894772
are perfect for you, but £ per weight and when dumped not quite empty they are more expensive too.

I'm sure most of us have a load sitting around almost empty in a box somewhere but won't throw them out "just in case"

Well here's the answer


They cost the around the same as a small bottle https://www.ebay.co.uk/itm/Butane-Propa ... 2749.l2649

How to use them.
1) Find a larger bottle with the same gas mix in it, I use a Butane/Propane mix


2) Weight the small empty(ish) bottle


3) Put this in the freezer for 20 minutes to make it colder than the larger fuller gas bottle

4) Shake the larger bottle very well, this mixes the Butane/Propane mix evenly

5) Connect the 2 together with the larger bottle up high with the adapter in between them and open the valve


Watch and listen here on this link https://flic.kr/p/2kMFVEC

6) Wait until the flowing gas stops, give the thing a few little shakes.

7) Lock the valve and unscrew them all quickly to avoid any loss of gas

8) Weigh the small gas bottle again



9) Stand back amazed and open a beer to celebrate your awesomeness

Nice one John. I've got one of the little adapters for filling from a tall cheap butane canister, but hadn't thought of this. Didn't realise how much cheaper the big gas canisters are since I've only ever bought the tiny ones (a big one will see you through a weekend? What are you cooking?! A 100g has lasted me a week before!).

thenorthwind wrote: ↑Sat Mar 20, 2021 11:07 pm Nice one John. I've got one of the little adapters for filling from a tall cheap butane canister, but hadn't thought of this. Didn't realise how much cheaper the big gas canisters are since I've only ever bought the tiny ones (a big one will see you through a weekend? What are you cooking?! A 100g has lasted me a week before!).

I did say a weekend or more

True... I guess "five minutes or more" would have been correct too

Any risks if you do this without scales.

If you overfill it when cold and it then warms up then there's a risk it could explode.

Nice instructions John - is the second weight above similar to a recently bought full one? Do you have/need a comparison target weight to be on the safe side?

I have this issue with some part filled ones that I'm a bit reluctant to take on a weekend away so will give this a go. Thanks.

Have I got this wrong? If you start with an empty cartridge and add 100g gas, that'll be the right amount.

empty wont quite be empty but basically yes - I would probably aim for 90- g personally just to have an error/safety margin

True.

Write empty weight and target weight on each cartridge in permanent marker to save the pre-weighing too.

Isnt it just equalising the pressure between the 2 bottles?

So the first time you do it, it works because the donor bottle is twice the size of the receiver bottle, but after that its going to have a lower effect the next time with the 2 bottles, and so on...

So at some point you'll end up with 2 half full bottles?

well yes but the half full will be less each time
ie
200 = 100 each

100 equas 50 each
50 = 25 each
etc

you will always get some gas out

Gravity. The gas is actually a liquid at this pressure, and denser than air. It flows into the bottom canister just like water would with two half full bottles if you put them together (OK, some slight differences to do with viscosity and the movement of air, and the different pressures). The temperature difference (resulting in a pressure difference) helps move things along too.

This is brilliant, thanks for sharing!

I write the gross and net weights on the bottom of the canister with a sharpie. And I also add a tally so I know how many times I've refilled it. I haven't refilled more than c. 5 times yet but when I get to around 10 or some other arbitrary number, I'll probably bin the canister

I have thought about this before but always worried I will blow myself up anyway I have just bought the little widget so if you see on the news a garage in the midlands exploding you will know its me

I have thought about this before but always worried I will blow myself up anyway I have just bought the little widget so if you see on the news a garage in the midlands exploding you will know its me

Chew wrote: ↑Mon Mar 22, 2021 2:02 pm Isnt it just equalising the pressure between the 2 bottles?

So the first time you do it, it works because the donor bottle is twice the size of the receiver bottle, but after that its going to have a lower effect the next time with the 2 bottles, and so on...

So at some point you'll end up with 2 half full bottles?

No, the top bottle is at room temperature and the bottom bottle has been in the freezer for 20 minutes, this is how the top canister empties into the bottle canister

99percentchimp wrote: ↑Mon Mar 22, 2021 12:07 pm is the second weight above similar to a recently bought full one? Do you have/need a comparison target weight to be on the safe side?

Yes it's similar to the new weigh, in fact it's heavier than the new jetboil canisters

Nothing has blown up in the garage since I filled them all up

trob6 wrote: ↑Mon Mar 22, 2021 9:46 pm I have thought about this before but always worried I will blow myself up anyway I have just bought the little widget so if you see on the news a garage in the midlands exploding you will know its me

If an idiot like me can do it and survive then most should be able to do it.

Double check how others have done it on youtube first (just in case)

JohnClimber wrote: ↑Mon Mar 22, 2021 10:18 pm

99percentchimp wrote: ↑Mon Mar 22, 2021 12:07 pm is the second weight above similar to a recently bought full one? Do you have/need a comparison target weight to be on the safe side?

Yes it's similar to the new weigh, in fact it's heavier than the new jetboil canisters

Nothing has blown up in the garage since I filled them all up

Thanks John... don't go testing to destruction on our behalf

Well I got the adaptor, cooled one warmed one and it works! I only went to 200 grams with the small canister though but I think that's plenty so thanks John and a few less canisters from now on to recycle.
Tim

Mine arrived yesterday too. Not that it matters, but it was bigger than I thought - I weighed it just to see if it was heavier than my Ti stove - it is Need to get a big canister and try using it.

On the safety front, all gas canisters will be designed and tested to take high pressures.
I think unless you are forcing gas in, not just using gravity and doing so while inside a freezer and then using the bottle in the open in the desert you will be fine.

I also have one for the cheap butane bottles but I will be looking to get this as I have several big ones that otherwise have no use.

Good work John. i buy the tall / thin and cheap Butane canisters and refill from those. You need a different type of adaptor but the principle's the same. Obviously Butane isn't as good in cold weather as a Butane / Propane mix.