RCR123a vs CR123a vs IMR - voltages, lifetime, and safety

BrightLignt said:

There are many threads on this, which I have browsed and not been able to get the information I'm seeking.

I have multiple devices that take CR123a, such as flashlights and endoscopes. I have a nitecore i4 charger, but I can get a new charger if need be. The standard CR123a is 3v while most people seem to recommend the 3.7v rcr123a over the 3.0v (3.2) options.

CR123As are labeled 3.0v, but are actually 3.2+v resting; however, they sag under load. These are similar to RCR123 LiFePO4 cells that are a nominal 3.2v, but come hot off the charger at ~3.6v. Li-cobalt/manganese chemistries for the 16340 (same size as CR123A/RCR123) cells are a nominal 3.6v-3.7v, but come hot off the charger at ~4.20v, so you can see where problems might arise, given the particular sensitivity of any given device--be it a flashlight, gastroscope, endoscope or remote control?

(1) Isn't it safer to get the 3v RCR123a because I know that my devices support this lower voltage and higher current?

Let's refer to the rechargeable 3.2v cells as RCR123s and the 3.6v-3.7v cells as 16340s, be they the Li-Co, or Li-Mn chemistry, to avoid confusion. You really need to know the voltage spec for each and every device that you'll be using rechargeable cells in.

If your endoscopes have a working voltage of 7v-11v and you plop in 3xCR123As, which is what it was designed around, you'd be fine. If you plop in three 3.2v RCR123s, which are freshly charged and roughly 3.6v, you'd be at ~10.8v, so you'd be fine there, but if you inserted three 4.20v 16340s hot off the charger, then guess what? Poof.

(2) Is my charger (nitecore i4) ok for the 3v and 3.7v RCR123a

No. Our NC i4 v.2 chargers only charge up NiMH/NiCad batteries, lithium-cobalt and lithium-manganese cells--the 3.6v-3.7v cells that we're talking about above. The i4 doesn't charge up the 3.2v LiFePO4 chemistry.

Xtar makes the SP1 an the VP2 chargers, which will charge up the LiFePO4 chemistry, but the SP1 has a 500mA rate for its low, whereas the VP2 has a 250mA rate, which might be softer on the smaller 3.2v cells, if you needed to go that route.

(3) What would you recommend between 3v and 3.7v RCR123a or IMR or standard lithium?

I don't buy stuff that can't be run on rechargeable batteries, but you're obviously a doctor and your choice of endoscopes might be limited. Buy what you need. I don't need to get LiFePO4 3.2v cells for anything that I own, but I was thinking about getting the SureFire marketed K2 cells just to charge up and fiddle with on my Xtar VP2 charger.

(4) Are IMR safer in that I know they will be able to deliver the current of the standard CR123a? I assume that they will have worse battery life because of the higher current.

Anything drawing over 2A, IMR chemistry is preferred. There's no way for us to measure lifespan, so I don't worry about it. A McShit Big Mac cost more than a quality 16340 cell. Like people, when they die, they die and the party train keeps on a moving. The IMR chemistry has a higher temperature to hit before thermal runaway occurs and things go south. This is why IMR cells generally aren't protected and cobalt chemistries are.

(5) Which will have better battery life between the different voltages in high-current situations? I would have assumed the higher voltage would get longer life, but I would have also assumed the lower voltage would be able to support higher sustained current and that doesn't seem to necessarily be the case.

LiFePO4 is a robust chemistry, but again, they're not that expensive, so if you want super duper output in your lights that can handle it, ICR and IMR chemistries are the way you should roll.

The particular batteries I'm comparing are: "Tenergy 30201 RCR123A 3.0V (3.2V) 900mAh" vs. "Nitecore NL166 RCR123A 3.7V 650mAh" vs. "AW RCR123a Protected 750 mAh"

I use AW brand ICR and IMR 16340s in my lights. ICRs in my lower drain lights and IMRs in my higher current lights and things are groovy. Price difference is negligible. I recently bought some Kinoko IMR 16340s for like $4.25 each and they're working out fine. I'm at 23 months of moderate use with my AW brand 16340s, FWIW.

I'm also concerned that the additional length on some of them will prevent me from using them, but I guess I will just have to try them to find out. Sorry for all the questions, I'm just trying to wrap my head around all this stuff.

Length is always an issue, but IMR cells don't have a protection circuit in them. ICRs and RCR123s will and might have circuits added that increase their length.

Just as an aside, there is more risk when running multiple cells and we generally like to step up to protected ICR cells when doing so. We'd want to run longer, but fewer cells if the device can handle the voltage differences ie:

You have a light that can take 3xCR123As, but has a voltage range of 9v-11v. 3xCR123As together are ~9.0v-9.6v, so you're good there. 3xRCR123s at 3.6v hot, yield ~10.8v, so you're good there. 3x16340 4.20v cells will give you 12.6v, so poof. However, what about running 2x16500 cells, instead of 3xRCR123s which are ~34mm in length and approximate a CR123A primary closely?

Well, two 16500s will give you 8.4v hot off the charger, but your range has a minimum threshold of 9v, so you're not going to be able to power it with that set of cells.

You have to think things through and know what the parameters are for each and every device, lest you blow them up.

My dad and brother are gastroenterologists and while my brother uses the sonogram machines now, my dad had nice Olympus gastroscopes with the light on them and I don't think that he'd be happy blowing that stuff up, since it was quite expensive, even back in the 70s.

Chris

:thinking:

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TEEJ said:

Just clarifying that while a cell might be fully charged at 4.2 v, in the light under load it's supplying ~ 3.7 v to start with, not 4.2 v.

That means 2 hot off the charger 4.2 v cells will supply more like 7.4 v to start with in the light....and 3 of them would start at ~ 11.1 v, and so forth.

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thedoc007 said:

But doesn't that depend greatly on what kind of load you are putting on it? If you are running a light on turbo, sure, that might give you a .5V drop immediately (per cell). But if you are running on low, you will not see any significant voltage drop, since the cell can deliver that current easily without voltage sag. In any case, good to be aware of the voltage range versus your cells. And ideally, the cells minimum and maximum (practical) voltages should both be within the spec of the driver.

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thedoc007 said:

But doesn't that depend greatly on what kind of load you are putting on it? If you are running a light on turbo, sure, that might give you a .5V drop immediately (per cell). But if you are running on low, you will not see any significant voltage drop, since the cell can deliver that current easily without voltage sag. In any case, good to be aware of the voltage range versus your cells. And ideally, the cells minimum and maximum (practical) voltages should both be within the spec of the driver.

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TEEJ said:

They are labeled as 3.7 v cells as that's what they deliver. ..not because they deliver 4.2 v until it drops to that.



So it's not the size of the load...it's that the rest change and delivery are different.

That means you charge it to ~ 4.2 v, put it into your light where when you operate it it gives you 3.7 v, for say a few minutes on turbo, take it out, and it might measure ~ 4.0 at rest....not the 3.7 v it was delivering in operation.

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TEEJ said:

Just clarifying that while a cell might be fully charged at 4.2 v, in the light under load it's supplying ~ 3.7 v to start with, not 4.2 v.

That means 2 hot off the charger 4.2 v cells will supply more like 7.4 v to start with in the light....and 3 of them would start at ~ 11.1 v, and so forth.

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To calculate the nominal voltage, we take a fully charged battery that measures 4.20V and then fully discharge it to 3.00V at a rate of 0.5C while plotting the average voltage. For Li-cobalt, the average voltage comes to 3.6V/cell. Performing the same discharge on a fully charged Li-manganese with a lower internal resistance will result in a higher average voltage. Pure spinel has one of the lowest internal resistances, and the plotted voltage on a load moves up to between 3.70 and 3.80V/cell. This higher midpoint voltage does not change the full-charge and end-of-discharge voltage threshold.

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