4Sevens CR123A

[rookiedaddy]

anyone here using 4Sevens' CR123a batteries? do you check the Voltage of the 2-battery pack? I find it interesting that mine are mostly 0.03V apart, e.g. 3.22V/3.25V, 3.24V/3.27V fresh.
as these are shrink-wrap in 2 per pack, I really didn't expect to have such a different Voltage. My 12-Pack SureFire batteries all giving consistent Voltage reading, likewise for Sanyo and Panasonic... as these are put into 2-cell lights (Quarks), the one near the head will consistently get drawn more and if the lower Voltage cell is install near the head, that will potentially leave a larger Voltage gap.
can you share your experience and findings?

 

[Popsiclestix]

anyone here using 4Sevens' CR123a batteries? do you check the Voltage of the 2-battery pack? I find it interesting that mine are mostly 0.03V apart, e.g. 3.22V/3.25V, 3.24V/3.27V fresh.
as these are shrink-wrap in 2 per pack, I really didn't expect to have such a different Voltage.

I will assume you have a cheapie DMM. In that case, A difference of 30 mV is well within the +- 0.5% accuracy of your multimeter.

...as these are put into 2-cell lights (Quarks), the one near the head will consistently get drawn more and if the lower Voltage cell is install near the head, that will potentially leave a larger Voltage gap.
can you share your experience and findings?

This is not how electricity works. The same current will be drawn through both batteries. Now if one battery is at a slightly lower state of charge, it will have a higher internal resistance. This higher internal resistance will cause its voltage to sag more under the load.

Since the power supplied by the battery is its voltage times the current, the "good" battery would end up supplying more of the power. This has a somewhat power balancing effect up to a point.

The danger occurs when the first battery is not only completely depleted, but the "good" cell is attempting to "charge" the bad cell. In Lithium primaries, this causes a chemical reaction that causes the cell to vent.

Measuring a lithium batteries state of charge with open-circuit voltage really don't tell us much. More useful is the voltage/current sustained when different loads are applied.

 

[rookiedaddy]

I will assume you have a cheapie DMM. In that case, A difference of 30 mV is well within the +- 0.5% accuracy of your multimeter.

Haha... :laughing: It's not a Fluke for sure...
Hmmm... I'm not sure I understand the +- 0.5% on the multimeter, fyi, the difference is measured multiple times from the same pack of cell upon break package, and from samples of 12 sets of cells, most giving a difference of 0.03V from one cell to the next in the same shrink-warp package, just for clarifications; fwiw, I do however get consistent V reading from other brands of cell like SureFire, Sanyo, Panasonic from same box each.
So... you mean the multimeter can give a different of +-0.5% on measurement even if the cell is actually at the same Voltage? and the more reliable way is to measure them under load? How many ohm resistor should I apply for measurement?

This is not how electricity works. The same current will be drawn through both batteries. Now if one battery is at a slightly lower state of charge, it will have a higher internal resistance. This higher internal resistance will cause its voltage to sag more under the load.

Since the power supplied by the battery is its voltage times the current, the "good" battery would end up supplying more of the power. This has a somewhat power balancing effect up to a point.

The danger occurs when the first battery is not only completely depleted, but the "good" cell is attempting to "charge" the bad cell. In Lithium primaries, this causes a chemical reaction that causes the cell to vent.

Measuring a lithium batteries state of charge with open-circuit voltage really don't tell us much. More useful is the voltage/current sustained when different loads are applied.

Thanks for the heads-up and warning on this... greatly appreciate it. :twothumbs Will there be same risk (vent) when the cells are discharge at low current, like 1ma, in moon-mode?

 

[Popsiclestix]

Haha... :laughing: It's not a Fluke for sure...
Hmmm... I'm not sure I understand the +- 0.5% on the multimeter

From what I understand most multimeter have a range of 0-5V.

So the +-0.5% basically means that if you take any measurement in this range, the value maybe +- 25mV (0.5% of 5V = 25 mV).

Suppose you have 2 cells, A and B: Both A and B have a true voltage of 3.70V

If you were to take a multimeter and measure A and B.

A could be measured at 3.725V and B could be measured at 3.675V.

This is a difference of 0.05V. Larger than the differences you measured in your first post.

fyi, the difference is measured multiple times from the same pack of cell upon break package, and from samples of 12 sets of cells, most giving a difference of 0.03V from one cell to the next in the same shrink-warp package, just for clarifications; fwiw, I do however get consistent V reading from other brands of cell like SureFire, Sanyo, Panasonic from same box each.
So... you mean the multimeter can give a different of +-0.5% on measurement even if the cell is actually at the same Voltage? and the more reliable way is to measure them under load? How many ohm resistor should I apply for measurement?


Thanks for the heads-up and warning on this... greatly appreciate it. :twothumbs Will there be same risk (vent) when the cells are discharge at low current, like 1ma, in moon-mode?

I will assume your light is a 2-cell light with a buck-boost driver. (The buck driver will obviously not light your LED once you fall below the minimum Vf)

Most boost drivers I know have a 0.9-1V minimum working voltage. If the cells in question have a small imbalance, the light will stop working well before one is reverse-charged.

 

[rookiedaddy]

From what I understand most multimeter have a range of 0-5V.
So the +-0.5% basically means that if you take any measurement in this range, the value maybe +- 25mV (0.5% of 5V = 25 mV).
Suppose you have 2 cells, A and B: Both A and B have a true voltage of 3.70V
If you were to take a multimeter and measure A and B.
A could be measured at 3.725V and B could be measured at 3.675V.
This is a difference of 0.05V. Larger than the differences you measured in your first post.

thanks for the explanations. i just wonder what causes the these 4Sevens cells to "trick" the meter to give different reading from one cell to another while I keep getting consistent V reading across cells from same box (presumably same batch) from SureFire, Sanyo and Panasonic using the same meter. :thinking:

Request: do you or anyone else with 4Sevens' cells and a Fluke can post and share the V reading of yours? :bow:

I will assume your light is a 2-cell light with a buck-boost driver. (The buck driver will obviously not light your LED once you fall below the minimum Vf)
Most boost drivers I know have a 0.9-1V minimum working voltage. If the cells in question have a small imbalance, the light will stop working well before one is reverse-charged.

:sweat: pheewwww... that's good to know. thanks. fwiw, I only use these 4Sevens cells in 4Sevens' lights.

 

[MCFLYFYTER]

From what I understand most multimeter have a range of 0-5V.

So the +-0.5% basically means that if you take any measurement in this range, the value maybe +- 25mV (0.5% of 5V = 25 mV).

Suppose you have 2 cells, A and B: Both A and B have a true voltage of 3.70V

If you were to take a multimeter and measure A and B.

A could be measured at 3.725V and B could be measured at 3.675V.

This is a difference of 0.05V. Larger than the differences you measured in your first post.

It is my experience that the percentage of error is the difference between actual voltage and the dmm reading. If you are getting the same reading on a cell 10 times in a row, you are getting a good reading. It is safe to say that the difference is very close to the actual difference. Basically the error is from actual to measured, NOT measure to measured.

 

[cckw]

I keep watching this thread to see what the other guys who use these have to say.

 

[MCFLYFYTER]

I keep watching this thread to see what the other guys who use these have to say.

I think most guys are trying to make the wife happy right now. Well, I know the smart married men are. :laughing:

 

[rookiedaddy]

I keep watching this thread to see what the other guys who use these have to say.

:devil:

It is my experience that the percentage of error is the difference between actual voltage and the dmm reading. If you are getting the same reading on a cell 10 times in a row, you are getting a good reading. It is safe to say that the difference is very close to the actual difference. Basically the error is from actual to measured, NOT measure to measured.

that's what I thought, and I'm still confuse and puzzle by the inconsistent reading from one cell to the next in the same pack.

I think most guys are trying to make the wife happy right now. Well, I know the smart married men are. :laughing:

thanks for the reminder... now I have lots-a explains to do..

 

[Meterman]

Suppose you have 2 cells, A and B: Both A and B have a true voltage of 3.70V

If you were to take a multimeter and measure A and B.

A could be measured at 3.725V and B could be measured at 3.675V.

This is a difference of 0.05V. Larger than the differences you measured in your first post.

When pigs fly! And did you ever see an oyster walk upstairs?


MCFLYFYTER has explained it correctly in post #6 :

Basically the error is from actual to measured, NOT measure to measured.

Popsiclestix, it would be nice if you'd edit that in your post to not continue confusing any newbies.

Wulf

 

[rookiedaddy]

thanks Meterman.

I'm still hoping that someone with access to these 4Sevens CR123A cells and a multimeter (not necessarily a Fluke, since it looks like not a multimeter issue) to share their reading and experience. :bow:

Btw, anyone using Cytac 1500mAH CR123A battery? Can you share a photo or two of the positive and negative terminals end? These are claim to be PTC protected cells. oo:

 

[shark_za]

I opened a 4sevens 2-pack today.

Cell 1 DMM1 = 3.22v
Cell 1 DMM2 = 3.21v

Cell 2 DMM1 = 3.28v
Cell 2 DMM2 = 3.27v


2x Surefires I got sometime last year, still new in pack.
3.15v and 3.15v on DMM 1.

Measuring error can be between DMM's but the difference between measurements on the same DMM can only be out by the slightest fraction.

 

[rookiedaddy]

shark_za, thanks for posting your results.
i guess with that small a difference, it's no cause for concerns. but i just couldn't shake it off that these should have given the same reading from the same pack.

 

[jirik_cz]

I don't think that 0.03V difference is significant...

 

[McAllan]

I will assume you have a cheapie DMM. In that case, A difference of 30 mV is well within the +- 0.5% accuracy of your multimeter.

Probably true.

However - the same voltage should on batteries should give same readout. Just try with the same cell multiple times in a row. Unless it's on a border of the last digit it reads the same each time.

So for pairing cells (voltage vise) a cheap multimeter is very fine and if it tells 30 mv difference between two cells this means the difference is 30 mv +- <=0.5% and one on the last digit (or two?).