16340 batteries are rechargeable batteries in the same form factor as CR123As. Last year I purchased 4 different 16340s to try out:
Two of these have integrated Micro USB ports for charging. That’s a nice feature, but the current iteration of my electronic support package contains a (now discontinued) Olight UC Universal Magnetic USB Charger (the Foursevens USB Flex Charger appears identical in every way but the logo), so I can just as easily charge the other two batteries when out and about.
Over the past few months I cycled through all of these 16340s in the Elzetta Alpha. The Alpha, carried on a Pocket Shield, is still my EDC light. Each battery performed in a manner than seemed identical to me, despite their slightly different specs. They worked great. Until they didn’t.
As a CR123A is consumed, the light output diminishes. This provides ample visual warning that it is time to change the battery. All of the 16340s caused the Elzetta to put out a steady amount of light right until the battery died. There is no visual warning that it is time to charge the battery. You just go to switch the light on and nothing happens. Or it switches on and you get great light for 10 seconds, and then it dies.
The life cycle of the 16340 only works if they are put on a fixed charging schedule that is built around maximum likely use. I don’t want to mess with that for my EDC light, so I’ve moved the Elzetta Alpha back to disposable CR123A batteries.
I’d be happy to save money by using the rechargeable 16340 batteries in an application that was less mission critical. But for all the devices I currently have that take a battery in that form factor, the CR123A is still superior. (Eneloops are still great, however.)