unprotected 14500 as single use?

[mfm]

Looks like that link refers to overcharging, and not over discharging. Or am I missing something again?

Ah, you are right, I read too fast. But it would still seem that overcharging can be dangerous:

When you over discharge, you loose cell capacity because one of the electrodes starts to dissolve. In the worst case, you for copper shunts that short the cell out during the next charge cycle. This can result in an explosion and fire.

from http://candlepowerforums.com/vb/showthread.php?p=1990837#post1990837

Also it can explode if short-circuited (and has no protection) and so on...

 

[Kaamos]

What about the 14500 3.6 V primaries, like Saft or Xeno? Anyone using those with flashlights? At least to me, they sound like rather interesting option, AA size, 3,6 V and up to 2750 mAh capacity. Well, somewhat expensive, but the capacity is almost 10 Wh in rather small package. Quite a lot more than CR123A, for example.

 

[45/70]

Yeah, the discussion had turned to whether a LiCo Li-Ion cell could "vent with flame" while discharging. I said that a healthy cell that has not been abused (which includes previously over discharging/over charging, discharged at a 10C rate, charged at a 10C rate, stapled with a staple gun, set on fire etc.) is not likely to "vent with flame" in normal use. Charging said cell, is a different story.....

Lithium primary cells (Lithium Manganese Dioxide) are quite capable of venting with flame when over discharged (although very rare, except with cheap cells), and especially when reverse charged, when used in series applications (not so rare).

balou as an answer to #1, as mfm quoted,

When you over discharge, you loose cell capacity because one of the electrodes starts to dissolve. In the worst case, you for copper shunts that short the cell out during the next charge cycle. This can result in an explosion and fire.

This is why you want to avoid over discharging LiCo Li-Ion cells.

As for #2, a Li-Ion cell with an open circuit voltage of less than 3.50 Volts, has very little capacity left. A voltage reading under load, of course, will be harder to interpret.

Dave

 

[45/70]

What about the 14500 3.6 V primaries, like Saft or Xeno?

Hi Kaamos.

The chemistry used in those cells, is by design, for very low discharge rates and long storage. They work well, for instance, in single 5mm LED AA lights, but they can't deliver much more than about 100mA current well.

As for safety, there is a recent thread here where someone blew one up trying to charge it in a Li-Ion charger. Other than doing that, I think they're pretty safe, or they wouldn't be used in such things as aircraft ELT's. :)

Dave

 

[Kaamos]

Hi Kaamos.

The chemistry used in those cells, is by design, for very low discharge rates and long storage.

Ah, that pretty much explains why they aren't used in "real" flashlights. Probably would make a nice moonlight-mode only emergency light, a "big" battery with a low-power white led but not much more. Thanks for the info!