G works gas transfer valve.

[Mark B]

I’ve seen you tube videos where people use a dual lindel valve coupler to transfer gas from a 16 oz canister to a 4 oz canister . Saving money is the reason to do this. I understand that isopro is a mixture of iso-butane and propane . If I attempt to refill my small cans with a larger one will I get a mixed gas, ie. 20% propane / 80% iso- butane .  Or will I get all of one of the gases and then the other one after the supply of the first is exhausted. The point of this mixed gas is to have the propane present in each can to boost gas pressure as temperature declines. If I get all propane in one can and all iso butane in the other three can then I do not get the benefit of a blended gas product. Any one out there with experience doing this? Is it worth the time and trouble?

[Jerry Adams]

You get the same mix in the small canister, good idea

Make sure you don’t overfill or the canister will bulge or even burst

Weigh canister when empty, add 4 ounces or 110 g or whatever the stated capacity is to calculate max weight, weigh canister when you’ve filled it, make sure you don’t exceed max weight.

I am cheaper than you.  I buy these cans from the local Korean grocer.  $1.25 for 8 ounces.  Use something like https://www.amazon.com/Jeebel-Refill-Adapter-Filling-Canister/dp/B01MSEJQJB/ref=sr_1_1?s=sporting-goods&ie=UTF8&qid=1510842011&sr=1-1&keywords=Butane+Gas+Refill+Canister+Filling+Adapter to transfer.  But that’s only good down to freezing or so without some technique.

[David Thomas]

Because it is a liquid that is was flowing, it is a uniform mix of propane and butane.

If you tried to transfer vapor instead of liquids, the vapor headspace would be a little propane-rich / butane-poor but not by a lot.  And you’d need to keep heating the donor canister and cooling the receiving canister.

When you transfer from the donor canister, the donor canister is inverted above the receiving canister (and warmer than the receiving canister).  Open the valve.   Liquid propane/butane flows from donor to receiving.  Close the valve.  When you disconnect the valve from each canister, have the valve ABOVE the canister (so if you vent a short burst, it’s a burst of vapor, not the denser liquid.

As Jerry says, WEIGH YOUR CANISTERS WHEN NEW AND AFTER REFILLING.  Or look up fill weights that folks have provided on BPL.  Or add 100-grams to a completely empty 100-gram canister.  If you’ve over-filled, vent the excess, or attach a stove head and burn it off WITHOUT any thermal feedback (windscreen, Moulder Strip, reflective foil, etc).  For how long?  Burn it at full flame for 9 minutes if you want to burn off an ounce.  Burn it for 1 minute to burn off 3 grams.

After you’ve done it twice, it will seem easy.  And you’ll get a feel for how long it takes to transfer and hit your fill weight pretty close on the first try, reweigh, and get it really close with another few seconds of filling.  You also might start playing with partial fills (for a single overnight, say), to avoid carrying excess fuel.

You can also score partial canisters from hiker boxes, past trips, etc, and consolidate them into one full canister.

I keep all my old, small canisters (4- and 8-ounce ones) and then refill them all from one or two 16-ounce / 450-gram canisters all at once once or twice a year.

[Mole J]

I used one of these gworks last year

I refilled a few 100 carts with dregs of gas from part used 250 carts from Scout trips.

What I found was, with the refilled cans, that in cool conditions 28-35f , I was getting very poor performance and flaring if the stove was moved( liquid feed) . I was using a Primus ETA+ – similar to a Jetboil.   If I warmed the cart, performance improved. And, with a friend’s new Jetboil cart performance was also fine, so the stove was good.

I put this poor performance/flaring down to the refilled cans having a lower (even negligible) percentage of propane than the original mix, due to the previous usage of the donor cans having used up the propane faster than the butane , as is well documented. This poor cool temp performance was repeated over all the carts I’d refilled from dregs of others.

At room temperature performance was fine. Basically, the refilled carts performed close to like pure butane.

So, be aware.

 

[David Thomas]

Mole,

Yeah, using dregs from other canisters will be propane-poor and not be as good in cold weather.  Use a Moulder strip or mark them for summer use.

If you refill from a new 450-gram canister, the propane/butane ratio will remain the same for all refilled canisters.

[Jerry Adams]

Some canisters contain almost all isobutane (which has a 11 F boiling point temperature), and only a small amount of N-butane (32 F). Some canisters have more N-butane.

When you get to the last 5 or 10% of the fuel in the canister, you get a higher percentage of N-butane.

So, the dregs will have higher boiling point temp.  When you get to within 10 or 15 F of the boiling point, the stove will start slowing.  But you could use on trips when it’s a little warmer.

[Jerry Adams]

To use a canister at colder temps search for “Moulder strip”

Since you said you have inverted stove, it’s better because it has little evaporative cooling.  When you get to within a few degrees of boiling point temperature, then you have to pre-warm it.  You could take a Bic lighter and apply flame to side.

[Bob Moulder]

Mole J:

I’ve only seen photos and video of the stove I think you’re referring to, and I am pretty sure the burner head does not permit the use of the copper HX strip to warm the canister, and, because the metal shroud around the pot’s HX fins blocks radiant heat, I don’t think something like Jerry’s “Adams Reflector” would be of much help either.

A water bath will work in that instance, and probably a chemical handwarmer under the base of the canister, as well.

[Jerry Adams]

You could use a water bath.  Someone posted a cut off plastic container that weighed 0.3 ounces, that would work pretty good.

You have to have some liquid water to put in it and occasionally put a bit of heated water in to cancel out evaporative cooling inside the canister.

[Mole J]

Thanks.

Usually I use alcohol or Esbit. Both have been fine for those temperature and lower.

I’m not likely to use the Moulder strip method

The ETA stove is a heavy option really, I just use it for convenience on occasional overnighters/daywalks. I’ll just use ‘new’ “full fat” gas from now on. ;)

I also use a remote burner with preheat tube when it’s colder. Happy with that.

[Jesse Anderson]

Thread detour?

On the subject of propane quantities in backpacking fuels, what is the maximum percentage of propane that the backpacking style canisters can safely contain? I know some of my old canisters were a 70/30 mix, is that by weight or volume? Does anyone know where the safety limit is if you could add straight propane to a backpacking cartridge?

[Roger Caffin]

Propane levels have to be below about 30%, or the pressure in a canister can go dangerously high.
See https://backpackinglight.com/exploding_gas_canisters_the_hazard_of_overheating/
and
https://backpackinglight.com/effect_of_cold_on_gas_canisters/
for more details.

Cheers

[Bob Moulder]

 is that by weight or volume?

By weight…  there is no practical way to do it by volume. Besides, the manufacturer’s number printed on the can is weight of the compressed liquid.

Use a good scale with at least 1g resolution.

After you put in the propane, the rest is going to have to be in the form of the cheap, tabletop stove fuel which contains a melange of predominantly n-butane with a few other hydrocarbons, so it’s best to keep your initial propane transfer to about 20% of total weight to provide a little cushion for the “other hydrocarbons” in the mix. Of course, you’ll need another adapter for transferring fuel from the tabletop fuel containers.

It is FAR easier to simply forgo the propane altogether and use the cheap n-butane fuel and employ a canister warming method.

[James Marco]

Bob, I suggest you put the n-Butane in first. Otherwise, you end up in the situation where you have a canister with nearly 100% propane…

[Bob Moulder]

James, sorry but I’m not following.

If using a 110g canister and he puts in 22g of propane, does it matter which goes in first?

I can see the potential for dangerously overfilling with propane, but if one is determined to go down that road he’d best be damn careful and understand fully what he’s doing before going there.

Although I am sure I could do this safely, it is a totally unnecessary hassle given the other solutions to the problem.

 

 

[Jesse Anderson]

Thanks Roger and Bob.

Bob, I don’t really plan on filling used canisters with any amount of propane. Even though I trust myself fully to do so, there would either be expense of putting together a quality apparatus or buying one of the very sketchy looking kits on Ali. One doesn’t seem cost effective and the other seems like an accident waiting to happen. My question was more out of curiosity.

I do want to get one of the adapters to combine nearly empty canisters or refill small canisters from larger cheap ones, and I also plan on getting a butane adapter for a summer blend. Some day I’ll try the infamous moulder strip too!

[Bob Moulder]

Jesse,

Of course cost-effectiveness depends on how much you use it.

What got me interested in this in the first place is that I was doing a bunch of testing and using a heckuva lot of fuel, and was therefore looking for a cheaper alternative. The testing also naturally evolved to using mixes with less and less propane, until one day I discovered that I didn’t need propane at all, nor even isobutane.

At some point along the way I figured out the break-even cost at something like retail price for twenty 110g canisters (cost differential vs my refill cost), so mine “paid for itself” a long time ago.  Overall cost now is about 83¢ for a 110g canister or about $1.75 for the 230g size.

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