Does it need to be upside down?
I've never done it, but there are some stuff that you need to know like... does the bottle need to be upside down? Or not!!
Did you know: Pressure between tanks equalises? However, as the same as decanting from a large tank to a small one, pressure will work for you..as evident filling gas bottle from tanks.
But when you connect a gas bottle to the fill of the car... doesn't the gas flow one way? Into the car only not out of the car? Till it equalises pressure, if the bottle pressure is higher than the car tank pressure.
It need to be upside down I agree. Top up.... vapour. Top down...... liquid. BBQ bottles don't have the tube inside to deliver liquid like a fuel tank. So BBQ bottle needs to be upside down.
I'd be concerned about that hose clamp. Depends if the bottle is a liquid-out like forklift or vapour-out like BBQ bottle. Cars fill with liquid, so a bbq bottle to be inverted to expel liquid .
What happens when the pressure equalises?
Then you have enough gas to get you to the servo and let the pump do the rest the filling. This system is only for emergency runouts .
Bbq bottles need to be upside down to get liquid into your car. Forklift cylinders or auto cylinders need to be in the position they are designed to sit on a for or in a car to get liquid out. Liquid withdrawal 45kgs or 190-210kg liquid withdrawal tanks have a tube that runs to the bottom. They are designed to run liquid out of the liquid taps. Without a pump, it will only run until the tank you are filling has lower pressure than the bottle you are emptying unless you have a pump or can increase pressure in the bottle you are emptying or decrease the pressure in the tank you are filling. Cars need liquid in the tank to run properly.