Dangers of Li-ion Cells. Benefits of eneloop?

[LeifUK]

Oh, and as an after thought, do lights have protection mechanisms built in which stop using a cell when the voltage drops to a certain level?

 

[Robin24k]

Just wondering, is a 18650 any more powerful than a 14500? It isn't, right? It just has a longer runtime because the 18650 is larger mAh?
Now 2x CR123's should be twice as powerful because the voltage is doubled right?
thanks!

No, the battery size only indicates capacity. However, a higher capacity battery can sustain higher current better, so for high current drains, performance might be better. This is only noticeable with small batteries and large currents, so the 14500 would be OK.

I don't agree that the fact that millions of people, nay billions, are using lithium ion cells is proof that the ones used in lights are safe. As I explained earlier, the protection mechanisms on consumer devices such as iPods are better, and the cells more robust and less susceptible to damage. The charger is also matched to the cell.

I agree, bare/loose lithium-ion cannot be compared to proprietary batteries. As much as I dislike proprietary, there is a sound safety argument for it. The reason I am uncomfortable with using lithium-ion batteries in regular flashlights is the ability to leave the safety envelope. A device designed with battery safety in mind will have a low battery cut-off, but most flashlights turn off because of insufficient voltage to maintain regulation, not for safety reasons.

Another area of concern I have is with the batteries themselves. Even though companies like AW use quality cells and attach protection circuits to them, the batteries don't have any regulatory approvals, and the amount they sell is very small compared to the entire lithium-ion market.

These things probably are safe when treated properly, including watching them while charging. Personally I am too easily distracted and forgetful so I avoid them, but that is just my choice. I am slightly surprised that torch makers do not get together and design a standard which is safer, but then again that would require investment in new battery designs which would cost a fortune. And in case you are wondering what I mean, something like a battery design with a protection circuit built in, and more resistant to damage, rather than the stuck on ones we see now.

An alternative would be the 3.2V LiFePO4 chemistry, which are a lot safer and don't require protection circuits. I have a couple of these in AA format, and I mainly use them in my Streamlight PT 1AA or SureFire E2L AA (to reduce weight, it's quite heavy with NiMH). These batteries have less energy density than other lithium-ion, and generally you replace two AA's with one LiFePO4 14500 and a spacer, so runtime is shorter than NiMH (1AA lights will be brighter though).

Oh, and as an after thought, do lights have protection mechanisms built in which stop using a cell when the voltage drops to a certain level?

Generally, no, except for dedicated lithium-ion rechargeable systems (such as Pelican 7060, Inova T4, etc.). They're about as safe as you can get.