I never knew a 12 V compressor would fill those tanks! Had I known that I would have been filling my son's paintball tanks years ago!
To be clear these compressors we are referring to are NOT Tyre (tire) inflation tools they are purposely designed for very high pressure filling of guns and pressure vessels, ( Tyre inflators run up to 100 PSI Air gun compressors up to 3500 PSI) Many of the imported one you can only run for five or ten minutes at a time. Sooooo if you are refilling a dive bottle its done five minutes at a time with ten minutes cooling between running.
The bigger and more expensive water cooled compressors can run longer and fill larger vessels.
YMMV depending on type of compressor and size of vessel / tank being charged. READ THE INSTRUCTIONS carefully because over this side of the pond more than a few folks have wrecked their hobby compressors by trying to refill big diving tanks in one go.
Compare the AVERAGE air guns air tube / bottle 180 to 300 mils in capacity then look at dive bottles 3 to 12 LITRES . You can see how much harder a budget compressor has to work filling a dive bottle.
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If you live far away from where scuba diving facilities, as someone else wisely points out check out who locally refills your fire fighters air bottles, some fire houses have their own, others are visited by a mobile service or a local company carries the contract.
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I have a 12v budget compressor set aside for if TSHTF, but I normally operate my guns from the three dive bottles and get them refiled as and when at the local airgun club who have a much larger professional compressor with three states moisture filtration and theirs can fill a 12 litre bottle in 15 minutes (they charge about $10 a fill but one fill lasts me a year on average)
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One or two other benefits of PCP airguns are when fitted with a moderator they are also silent, and they have NO recoil of note which makes them ideal for smaller and more nervous family members.