Danger in Draining CR123As?

[AFAustin]

A perennially popular CPF topic is lights that do a great job of draining CR123As---getting some performance while sucking the last bit of juice out of them. The Milkyspit Candle and Inova X5 are usually mentioned as standouts.

However, from time to time, I will see a mention of the dangers of over discharging CR123As. I have a couple of good "CR123A vampires" myself, an X5 and a Peak McKinley 1 LED. Is there some danger in letting them do their thing and suck partially discharged CR123As dry?

Thanks an advance.

 

[thezman]

From what I understand, not in single cell applications.

 

[AFAustin]

Yes, but what about all those loyal X5 owners, dutifully draining 2 cells at a time?

 

[AndyTiedye]

Yes, but what about all those loyal X5 owners, dutifully draining 2 cells at a time?

The stronger cell reverse-charges the weaker one and

 

[Oznog]

In single-cell applications it WILL damage a rechargeable cell to discharge it too far down, below 2.0v or so:
http://cat.inist.fr/?aModele=afficheN&cpsidt=18401298

"Protected" types can't be reversed or overdischarged, right?

 

[SilverFox]

Hello Andrew,

When we were exploring the reverse charging "rapid venting with flame" occurrences with CR123 cells, we came up with a recipe for failure. You start with mismatched cells (also, it seemed to follow cheaper cells), discharge them at around a 1C rate, add some heat, and do not disconnect the circuit when the lamp goes out.

When tests were done deviating from this recipe, rapid venting did not occur.

So, if your multi cell application involves using cheap cells that drains the cells in about an hour, in ambient conditions in the 80 - 90 F range, and after the lamp goes out you continue to draw current from the circuit, you run an increased risk of having "issues."

I don't believe the MilkyCandle and the X5 fit this profile.

I have noticed that when you feed the MilkyCandle a pair of mismatched cells, when you come back to check the cells (a week or so later... ) you will often find that one cells will show a slightly negative voltage. I am not aware of anyone having any "issues" with a MilkyCandle and I know they have been fed a wide variety of cells, including cheap ones.

Tom

 

[SilverFox]

Hello Oznog,

The protection circuit is designed to allow you to have a failure in your active circuit and not totally damage the cell.

A well designed charger will limit the charge to 4.2 volts. If the charger malfunctions, the protection circuit of the cell will keep it from exploding, but any over voltage is not healthy for the cell. The same goes for over discharge. A well designed application will shut down before over discharging the cell. If there is a malfunction, the protection circuit on the cell will minimize the damage to the cell. Some damage may still occur, but it will be minimized by the protection circuit cut off.

Unfortunatelly, not all chargers and applications are "well designed."

Tom

 

[AFAustin]

Tom,

Thanks so much for your post. As I have said, I never feel I have "the answer" to any type of cell question until you have posted your view.

I very much appreciate your expertise and kind assistance.

Andrew