# Lithium 2450 button cell...how much current?



## Daravon (Aug 10, 2010)

I'm building a light meter and I don't have much room for a battery. I can fit a 2450 lithium button cell, I don't know if a 2450 primary lithium button cell will supply enough current. I will probably need to draw 20-40ma at 5V (~150mW) to run my lightmeter. I have a 5V boost driver so I can use voltages down to 1V. Can a 2450 primary cell drive this much current? The datasheet I found for the energizer 2450 lithium cell specs are all quoted at 0.39mA! I might need 2 orders of magnitude more than that.

I meant to post this in flashlight electronics-batteries included. A moderator is welcome to move it.


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## DM51 (Aug 11, 2010)

Moving it now...


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## Milan (Aug 11, 2010)

Sure, np. I got up to half an amp from CR2016 when shorting through MM the other time so this wont be a challege for 2450.

Even 2032 should power this for few hours if you need some budget solution.


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## Battery Guy (Aug 11, 2010)

Milan said:


> Sure, np. I got up to half an amp from CR2016 when shorting through MM the other time so this wont be a challege for 2450.
> 
> Even 2032 should power this for few hours if you need some budget solution.



No way a 2032 can sustain 150 mW for a few hours. The best performing 2032 for "high power" is a Sanyo, and it will last no more than 2 hours at 30 mW to a 2.2 V cut (trust me, I recently tested hundreds of 2032 cells from several manufacturers in this power range). Short circuit current will certainly be higher, but these cells simply cannot sustain that kind of current/power draw for any length of time.

To Daravon: You are unfortunately attempting to use a high energy, low power cell for a high power, low energy application. These cells are designed for very low current drains over long periods of time. My best guess is that you might get ~50 mW for an hour, but that would be pushing it.

I would be happy to test a couple for you and post the results. Give me a day or two to acquire some 2450s and I will discharge them at 150 mW to a 1 V cut. 

A single Energizer Lithium AAA cell would be ideal for this application if you can spare the room. That would easily give you 10 hours of runtime.

Cheers,
BG


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## Daravon (Aug 11, 2010)

I have a very similar device, already made, that runs on a 900mAh lipo and 5V boost IC. The trouble with this is that it is not rechargeable in the field, although at 900mAh/3.7V it lasts approximately forever. The device is used only intermittently at 150mW (seconds, minutes at the most) and then goes to sleep and draws a few uA permanently.

Unfortunately for this new design, the 900mAh lipo will not fit. A smaller lipo would, but would still have the charging problem, so would be unsatisfactory. So it looks like I need a swappable primary, which got me to the 2450.



> A single Energizer Lithium AAA cell would be ideal for this application if you can spare the room.



Good thinking! Now that I am using a boost IC anyway, I really only care about Wh. I was mentally leaving out AAAs because of only 1.5v, but the boost IC (this one) accepts between 1 and 4V. A AAA will fit in thickness, but I'm not sure about length. If it does, I will just use a AAA or two. If you want to test some 2450s, though, I already ordered a 2450 holder and some 2450 cells so I am still interested in how they hold up under 150mW loads. Sparkfun has a really neat rechargeable, 200mAh 2450 too.


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## Milan (Aug 12, 2010)

I said "few" not "a few". As long as I know english, it should make a difference.
And by saing that I assumed 2 hours max which you confimed (couple might fit better) and if Daravon is expecting intermittent use, I wouldn't see problem in it.

Anyway, we are mainly talking about 2450 so let's move on...

btw if you consider LiPo, these 400mAh helicopter types might interest you:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280491136868


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## Battery Guy (Aug 12, 2010)

Rather than debate the issue, I picked up a new 2450 (Energizer) cell from Best Buy this morning. It is made in Japan, so probably a rebranded Sanyo or a Panasonic. I discharged the cell at 150 mW to a cut-off of 1 V. I also did the same test on a Sanyo 2032 cell that was purchased about 1 month ago. 

Here are the discharge curves. The 2450 is blue and the 2032 is black. Note that the time axis is in *minutes*:







As I said, these are the wrong batteries for the application. If the duty cycle is is only few seconds followed by a long rest period, then you might get away with it. But Daravon indicated that the duty cycle could be "minutes at most". As you can see, a couple of minutes is all you will get from this battery at 150 mW.

Hope this helps.

Cheers,
BG


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## Daravon (Aug 12, 2010)

Wow! Worse than I expected. I believe that's only like 1/4C discharge current. Thank you for doing the test; I won't waste my time with them. I hope my math is not off; maybe I will measure my other device with a current meter to see how much it draws in practice.


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## Battery Guy (Aug 12, 2010)

Daravon said:


> Wow! Worse than I expected. I believe that's only like 1/4C discharge current. Thank you for doing the test; I won't waste my time with them. I hope my math is not off; maybe I will measure my other device with a current meter to see how much it draws in practice.



Most of these 3V button cells are designed for very slow continuous discharge currents (i.e. C/1000 to C/10000), or for very brief high current pulses of very short (less than 10 seconds) duration.

Have you figured out if the AAA lithium cell will fit? Too bad there are no AAAA lithium cells, as that would likely be perfect for you.

Cheers,
BG


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## Milan (Aug 12, 2010)

Wow, complete discharge curve using just permille of battery capactity.
I wonder how they do it in these flat LED keychains, shining for hours. But there are 2 cells in series so that might help.


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## twig (Oct 25, 2011)

Battery Guy said:


> Rather than debate the issue, I picked up a new 2450 (Energizer) cell from Best Buy this morning. It is made in Japan, so probably a rebranded Sanyo or a Panasonic. I discharged the cell at 150 mW to a cut-off of 1 V. I also did the same test on a Sanyo 2032 cell that was purchased about 1 month ago.
> 
> Here are the discharge curves. The 2450 is blue and the 2032 is black. Note that the time axis is in *minutes*:
> 
> ...



Wow... so what was a 620 mAh battery dropped down to about 2.871 mAh! Battery Guy, do you have any feel for what kind of mix of high current (say about 50 mA) to low current this battery can take before the advertised capacity starts falling off? For the design I am considering, it would be a device that would be in a sleep mode for a considerable amount of time, then be on for a short amount of time (perhaps as long as a second) with the 50 mA current draw (hopefully less... something in perhaps the 20 mA range), then going back to sleep mode (pulling about 50 uA). 

Do you have any idea what type of battery capacity numbers I would observe with such a setup? 

Thanks much!
-twig


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## Battery Guy (Oct 26, 2011)

twig said:


> Wow... so what was a 620 mAh battery dropped down to about 2.871 mAh! Battery Guy, do you have any feel for what kind of mix of high current (say about 50 mA) to low current this battery can take before the advertised capacity starts falling off? For the design I am considering, it would be a device that would be in a sleep mode for a considerable amount of time, then be on for a short amount of time (perhaps as long as a second) with the 50 mA current draw (hopefully less... something in perhaps the 20 mA range), then going back to sleep mode (pulling about 50 uA).
> 
> Do you have any idea what type of battery capacity numbers I would observe with such a setup?
> 
> ...



Twig

Are you also planning on using a CR2450?

BG


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## twig (Oct 26, 2011)

Battery Guy said:


> Twig
> 
> Are you also planning on using a CR2450?
> 
> BG



Currently it seems to be my leading candidate... but I'm looking at whatever I can. Requirements for this are small size, large capacity, and being able to handle perhaps a 40 mA draw for short bursts (hopefully for a duration of ~100 msec) every few minutes, with the background current draw being in the 55 uA range for the rest of the time.

The CR2450 seems to meet the size & capacity desire (on paper), but am unsure how well it is going to tolerate the current draw. If there are other solutions / technology out there that would be better, I'm all ears...

Thanks much!
-Twig


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## twig (Oct 26, 2011)

By the way, thanks in advance for any advice that you may have. 

-Twig


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## Battery Guy (Oct 26, 2011)

twig said:


> Currently it seems to be my leading candidate... but I'm looking at whatever I can. Requirements for this are small size, large capacity, and being able to handle perhaps a 40 mA draw for short bursts (hopefully for a duration of ~100 msec) every few minutes, with the background current draw being in the 55 uA range for the rest of the time.
> 
> The CR2450 seems to meet the size & capacity desire (on paper), but am unsure how well it is going to tolerate the current draw. If there are other solutions / technology out there that would be better, I'm all ears...
> 
> ...



Twig

This is a difficult question, and unfortunately the rated capacity is not really going to help you much with your application. In one respect, your application is exactly what Li-MnO2 cells are commonly used for: long idle times with infrequent high current pulses. However, when these cells are in "sleep mode for a considerable amount of time", the lithium metal anode can develop a relatively thick passive film on the surface that can result in a temporary increase in internal resistance. The result is that the cell cannot deliver maximum current until that passive film is stripped off. When such a cell is hit with a high current discharge pulse, the voltage collapses and the device shuts down. Subsequent testing of the cell may indicate that it is just fine because the initial current pulse stripped the passive film and subsequent pulses show no problems.

All I can tell you is stay below the manufacturer's recommended maximum pulse current, and be sure to use a cell from a well known manufacturer, preferably one made in Japan. If your application is critical and/or your are using pulse currents above the maximum specified by the manufacturer, and you have to be absolutely sure that the cell will deliver the 40 mA current for 100 msec after long idle time, then you may have to spend the time and $$$ to do accelerated aging tests.

I did a quick web search to look at spec sheets for CR2450 cells, and unfortunately could not find any that specify a maximum discharge pulse. Even Energizer, who normally has excellent spec sheets, did not provide this information. At the very least, you may need to call the manufacturer for recommendations. At the worst, you are in "no mans land" and will need to find someone who can do the appropriate testing for you to validate that this battery will work for your application. Hopefully you can find a reputable manufacturer that will give their "stamp of approval" for your specific application.

Sorry that I am not able to provide you with more concrete information.

Cheers,
BG


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## hellokitty[hk] (Oct 26, 2011)

You can get some pretty small 50 - 100 mAh lipos for a few dollars each.


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## Battery Guy (Oct 27, 2011)

hellokitty[hk] said:


> You can get some pretty small 50 - 100 mAh lipos for a few dollars each.



Twig says "it would be a device that would be in a sleep mode for a considerable amount of time". Small lipos might be an option if they don't self-discharge significantly during the "considerable amount of time" Twig's device will spend in sleep mode.


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## sunny_nites (Oct 29, 2011)

It has been my experience with small lipos, that they do not self discharge very much at all. But they don't have the round form factor that you may be looking for. 

I don't know the part number but I have run across small 3.6v rechargeable cells that are the size of a 2032. They are stamped with a 80mah rating and are usually found in small solar charged key chain flashlights from places like Deal Extreme, etc. I have used them in several devices and they seem to be happy putting out low current for extended times or high current for short times. They don't seem to have much self discharge but they do not have a protection circuit either.


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## murehan (Oct 2, 2019)

Battery Guy said:


> Most of these 3V button cells are designed for very slow continuous discharge currents (i.e. C/1000 to C/10000), or for very brief high current pulses of very short (less than 10 seconds) duration.
> 
> Have you figured out if the AAA lithium cell will fit? Too bad there are no AAAA lithium cells, as that would likely be perfect for you.
> 
> ...



Hi BG,
I hope you are fine. Do you have any suggestion for using 3V button cell for an application in which i need 500mA of current for 2 minutes. Can I charge it with capacitors and use high burst of 500mA?

Best Regards,
MR


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