My dad bought a brand new auto darkening hood from TSC, and unless it's sunny out, it will not darken, artificial light will not charg it, not fun when you strike an arc and it dosn't go dark. I bought a used helmet, a known company, can't remember the company name, but it's probably 3-4 years old. it uses batteries and I have the sensitivity set so a flourescent light will make it go dark, after it goes dark, it will stay dark for a second or so, after you stop the arc.