What do you use 18650/14500/17500/18500/17670 batteries in?
I recently bought a flashlight that uses 18650 batteries instead of AA or AAA. The charger that I bought with the UltraFire batteries of that size claims that it can also charge batteries of the sizes I listed in my question. The thing is, I've never heard of these batteries before! What are they used for? What are they used in? And why did they decide to not just use one of the more standard AAA through D size batteries when they designed the device?