Danger danger potentially ill advised self filling co2 bottles

[stz]

Well long story short I couldn't really get it to work. 4.7kg bottle, tare weight 10kg, weighs 10.4kg. Put it in the freezer. Connected it up to a 75kg bottle with siphon tube. Bleed the pipework. Managed to put enough it the smaller bottle so total weight was 11.2kg. Vented the smaller bottle to get it ice cold, tried again, 12.2kg, vented it again, tried again 12.7kg. I'm giving up. Thought it might be ... potentially dangerous, but easy?

 

[stz]

Thinking about it what did I really expect? Unless the receiving bottle is REALLY cold and the donor bottle can be kept warm and stays so then any liquid transferred over is going to quickly evaporate, build pressure and the bottles will reach equilibrium. The internet made it look so easy.

 

[stz]

Ok so I left the smaller bottle in the fridge all day today and brought the larger one in the house for a few hours before trying again. This time it took it up to 13.9kg It is actually an SB sized bottle so will hold 6.4kg when full so I got 60% full. I think if I completely froze the receiving bottle overnight in the freezer and had left the larger bottle inside all day so it was even warmer it might actually work out fairly straightforward? Seeing as when installed in my kreezer the 6.4kg bottle used a little over 5kg of gas in ... 14 months? It'll keep me going.

 

[Richie_asg1]

When we used to fill the bottles for paintball it was just a matter of charging the bottle then venting it which chills it enough to take a full charge after that. Then weighing it.
It was important to leave a little headspace otherwise there is nowhere for the liquid to expand into when it warms up a bit..... such as in a car journey later.
We had one pop a burst disc in a car. Quite memorable.

I wouldn't worry at getting close to the full charge and just be happy with the fill at the pressures you have. - You can always go back for more.