Quote:
Originally Posted by Quoth
Solar powered calculators still exist Now about €2. Uses a coin cell too which last about 5 to 10 years.
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Many auto-darkening welding helmets have small solar panels that charge/back-up the coin cell batteries that power the auto-darkening filter. I assume the light of a welding arc is enough to provide sufficient power under normal conditions, as long as the batteries have any charge at all. Some popular cheap helmets don't have replaceable batteries, so even with the solar cell, they are claimed to only function for 6 years or so.