Why arent primary CR123 cells protected?

[kramer5150]

Something I was wondering. There seem to be just as many (if not more) fireball failures from primary cells than rechargeables.

 

[Lumencraft (Matt)]

This is only my guess, but I would say its because protection circuits would only add to the cost of each cell, and when you only use the cell one time and throw it away that could get expensive. Plus if i am not mistaken there are 3 reasons RCR cells are protected
1. Prevent over charging
2. Prevent cells from being discharged too rapidly
3. Prevent deep cell discharge.

In the case of primaries only 2 applies, so there is 2/3rds less need for them. Although cost I would say is most likely reason. Only MHO

 

[Sgt. LED]

They would have to take a loss in capacity wouldn't they?
Well if the cell remained the same overall size.

 

[mdocod]

Because there's no danger from heavily discharging (only reverse charging), and because they are never intended to be recharged (no need for over-charge protection). Over-current problems and short circuit is supposed to be stopped by the PTC found in them. Which will kick in if the cell is shorted for more than a few seconds, and can even kick in if used at moderately high drain rates for extended periods of time. (like the HOLA lamps in SF lights).

 

[ace0001a]

Here's a somewhat related question: If you use protected Li-Ion batteries in a flashlight that would happen to have a dangerously high current draw, would the protection circuit prevent it from "being discharged too rapidly"?

 

[Grox]

Here's a somewhat related question: If you use protected Li-Ion batteries in a flashlight that would happen to have a dangerously high current draw, would the protection circuit prevent it from "being discharged too rapidly"?

Yes, that's what over-current protection does - prevents the cell from being discharged too rapidly.

OP: Almost all primary CR123A cells do have a kind of 'protection', referred to as a PTC. Chinese cells tend not to as high quality PTCs as cells that are made in USA.

 

[mdocod]

Here's a somewhat related question: If you use protected Li-Ion batteries in a flashlight that would happen to have a dangerously high current draw, would the protection circuit prevent it from "being discharged too rapidly"?

Yes and NO... (depends on the cell)

the answer to this is complicated as so many things in life are....

Years ago, when loose li-ion cells were a relatively new concept for consumers into hobbies like this, pretty much all protection circuits were set with maximum current thresholds in the 1-2C discharge range for the cell it was being installed on. In many cases, the PCBs being used on little RCR123s, were set to a maximum discharge rate of ~1.2A, and as a result, they would not light up most tactical lamps, at the same time, many of those SAME PCBs used on the small little RCR123s, were also popping up on 17500 and larger size cells, so there were a huge number of protected cells out there that would not work for most tactical flashlights. The stage was set for some changes to this, and various manufactures stepped up to the plate and had offerings that broke a few rules to make things possible...

See... in order to get a bulb, that normally runs at say, 1.2A, to light up, you actually need a current threshold on the PCB set to around 2 amps, to give it enough overhead to get passed the initial current spike caused by a cold filament in the circuit (cold metal has lower resistance than hot metal). With that in mind, Pila, Wolf-Eyes, and AW all started providing a new style of protected li-ion cell. The current limits are set high to allow configurations to work, but often, they have to be set higher than ideal as far as absolute safety is concerned. For example, with a multiple tapping, an AW RCR123 will light up a P91, which is absolutely murder for that small of a cell. Different cell sizes have more extreme over-heads on the PCBs as it's often cheaper to stick with 1 or 2 PCB designs for an entire line up of cells than have a different PCB for each one.

The responsible use of protected cells is still dependent on the proper education of the user.

Eric

 

[ace0001a]

Yes and NO... (depends on the cell)

the answer to this is complicated as so many things in life are....

Years ago, when loose li-ion cells were a relatively new concept for consumers into hobbies like this, pretty much all protection circuits were set with maximum current thresholds in the 1-2C discharge range for the cell it was being installed on. In many cases, the PCBs being used on little RCR123s, were set to a maximum discharge rate of ~1.2A, and as a result, they would not light up most tactical lamps, at the same time, many of those SAME PCBs used on the small little RCR123s, were also popping up on 17500 and larger size cells, so there were a huge number of protected cells out there that would not work for most tactical flashlights. The stage was set for some changes to this, and various manufactures stepped up to the plate and had offerings that broke a few rules to make things possible...

See... in order to get a bulb, that normally runs at say, 1.2A, to light up, you actually need a current threshold on the PCB set to around 2 amps, to give it enough overhead to get passed the initial current spike caused by a cold filament in the circuit (cold metal has lower resistance than hot metal). With that in mind, Pila, Wolf-Eyes, and AW all started providing a new style of protected li-ion cell. The current limits are set high to allow configurations to work, but often, they have to be set higher than ideal as far as absolute safety is concerned. For example, with a multiple tapping, an AW RCR123 will light up a P91, which is absolutely murder for that small of a cell. Different cell sizes have more extreme over-heads on the PCBs as it's often cheaper to stick with 1 or 2 PCB designs for an entire line up of cells than have a different PCB for each one.

The responsible use of protected cells is still dependent on the proper education of the user.

Eric

Good info to know. So is there a way to find out the limits of the PCB that's in the 16340/RCR123s that we have?

 

[mdocod]

Good info to know. So is there a way to find out the limits of the PCB that's in the 16340/RCR123s that we have?

check with the manufacture/reseller (depending on the situation), if they can't tell you... test it with a variable load and current meter.