/diy/ - Do It Yourself

>>1508321
>school project

>>1248817
If you do buy used...
Look over the cylinder - specifically the crown. Look for the DOT number - "3AA2015" - Should have another set of numbers after it, the month and year of manufacture. If it's <5yrs old, you're good. If it's more than 5 years, it'll need a retest.
So look for another stamp on it - month, a four-character "RIN" number, year. There may be multiples of those every 5- or 10-years.
Wait, 10 years? Yes, 10 years. If a cylinder meets certain specs, it can get a star after the retest year, which indicates it can go 10 years between retests. A "+" indicates it can be overfilled 10%. There may be other characters after that, like "UE" for ultrasonic examination instead of a traditional hydro test. Don't worry about those. You're just checking that the cylinder's in-test.
Otherwise you'll have retest expenses before anyone will fill it.

Check over the rest of it, make sure there's no dents/dings/major scrapes in the sidewall. Be wary of cylinders with a lot of layers of paint, that can hide ugly shit underneath, and some retesters won't accept it unless it's cleaned/stripped.

Check that the valve is the same as what you have on the regulator. There's a "CGA" number you need to match up. Likely be a CGA580 valve.

Valve covers are required for transport. There's coarse- and fine-thread covers, shitty suppliers will thread a coarse cover onto a fine-thread cylinder or vice versa. Make sure you have the right one, and don't lose it.

I used to work in the cylinder retest industry.

>>1237727
>battery is 85mm by 65mm
Might be a custom cell.
If you know the capacity, that's really the critical part. Get something just a touch smaller physically with the same voltage and same or more mAh rating, it'll be fine.

No, you cannot recover a swollen cell. Don't charge it, don't poke it... unless you're okay with "may vent with flame".

>>1237960
>columbine ambulance
pic related