> Kerchner suggested that the real enemy is e-cigarette manufacturers, which have designed devices around 18650 cells.

> Korean company that makes LG-branded lithium-ion batteries, sent a letter to sellers and distributors of e-cigarette devices and equipment, telling them, “Individual consumer use and handling of 18650 cells is a dangerous misuse of the cells that can lead to severe burns and disfigurement.” It asked companies to stop selling LG 18650 cells, and to tell customers who had bought the cells in the past that they should dispose of them safely.

> Many Amazon sellers reported receiving emails last August saying Amazon had prohibited the sale of cylindrical-lithium-ion batteries, including the 18650.

I know 18650 cells normally come in battery packs with charging and protection circuit, and that even in the DIY electronics community, it's not recommended to build the battery management circuitry by yourself, unless you know what's you are doing.

But even if purchasing raw, unprotected 18650 cells is not recommended. Still, if a device is using these raw 18650 cells, it means the proper circuitry must have been already included in the device. If properly designed, a device with 18650 cells replaced should be as safe as the original one. So there should be no reason to disallow an individual customer to remove a dead 18650 from a device, purchase a new cell and replace it. I've personally seen raw 18650 cells found in flashlights and RC toys, replacing them is a routine procedure.

One of the three possibilities:

* 1. Most individual customers have no idea about the safety when handling these raw cells, and are handling and charging them in a reckless and dangerous manner, for example, using a low-quality, generic charger, or exposing them to mechanical shocks, high temperature, etc.

* 2. 18650 cells are inherently unsafe to be used with e-cigarette due to the nature of this application, or they are not safe to replace (easy to break something in this process), or many e-cigarette units do not perform battery management properly.

* 3. It's difficult to distinguish between good and counterfeit 18650 cells, due to the potential hazards, it's better for Amazon to ban them altogether?

As a result, Amazon and some battery manufacturers banned their selling to individual customers to avoid accidents and incidents due to the above unfortunate reasons. Otherwise, I think purchasing a new 18650 cell and replace the dead ones in your electronics should be perfectly acceptable.

Any comment?

Edit: So far, the conclusion seems to be a mix of all three issues:

1. The biggest problem is #3. It's difficult to find legitimate, authentic 18650 cells. As tristor pointed out (https://news.ycombinator.com/item?id=19839673), it's a notorious problem in the hobbyist community and e-cigarette community. If even people who know what they are doing are having trouble finding authentic cells, offering them to average customers is risky. zrobotics added (https://news.ycombinator.com/item?id=19839977) that the counterfeit problem is a supply-chain level issue!

> My normal port of call, Digikey, doesn't appear to carry any actual name-brand cells. I see adafruit & sparkfun, hopefully they source decent cells but who knows. There's also Jauch Quartz, who I've never heard of.

teilo also agrees (https://news.ycombinator.com/item?id=19839869) that the proliferation of poorly-made budget 18650s as well as counterfeit re-wraps of junk 18650s sold as quality brands such as LG.

2. Problem #2 is a secondary cause. teilo said a lot of poorly designed devices that lack correct protection, in the eCig world one can point to the mechanical mods which are basically a battery directly attached to a coil, with nothing but a switch in between. Dangerous and stupid. There are some very good eCig devices that have excellent current and reverse-bias protection, but they cost more.

3. The last cause is #1, the improper handling of these cells, such as shorting spare e-cigarette cells with metal objects in a pocket, or using bad chargers. Also, as Tepix and jhayward said, replacing a protected 18650 with a unprotected cell is very dangerous.