EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: electr_peter on September 22, 2019, 07:22:02 pm
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Hi,
I have experienced multiple times failure of coin cell batteries to perform in low temperatures. Several times in a wrist watch (MSP430 based with radio), another time in garage door opener (868MHz type). I am wondering about coin cells limitations for such radio products (as burst of power are required for radio).
Coin cells in question are CR2032 lithium cells from reputable brands.
By low temperatures I mean +8 - +12 C or lower. Failing to perform at such temperatures with moderately used battery is strange IMHO.
I am looking for better data on button cells to add to current anecdotal experiences.
- How does temperature affect CR2032 lithium cells? How does internal resistance and current capacity change with temperature? Is there a sharp drop off at discussed range?
- Does cold accelerate aging of battery? Would keeping the battery (and device) warm help in the long run (w.r.t. battery life)?
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Hi,
I found some data.
http://data.energizer.com/pdfs/lithiumcoin_appman.pdf (http://data.energizer.com/pdfs/lithiumcoin_appman.pdf)
Andy
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ahbushnell, thanks for a link. Document states that at 0C chemical reactions slow down and voltage drops (as well as capacity). Cycling effect from low to high temps are not described - I suppose there are no significant long lasting effects.
In CR2032 cell datasheet http://data.energizer.com/pdfs/cr2032.pdf (http://data.energizer.com/pdfs/cr2032.pdf) operating temp range is -30 to 60C. I guess this means only that battery is somewhat operational and is not damaged in this range.
So I just need- a) change my batteries more often to new ones in the remote control
- b) keep remote control in warm place to keep it working
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Good luck!
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There was a discussion about coin cell capacity and how many just out of factory looking packaging are fake with limited life. Energizer was the example. An interesting suggestion was to buy no name cells. I use them to monitor a fridge at 2C with no problem.
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Seekonk, I think you are referencing discussion in https://www.eevblog.com/forum/dodgy-technology/crap-energizer-2032-batteries-from-amazon/ (https://www.eevblog.com/forum/dodgy-technology/crap-energizer-2032-batteries-from-amazon/)
I my case batteries just failed at low temp after few months of low usage (not immediately like in a link above).
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I've used Renata lithium primary coin cells before.
I provided Renata with the load profile of our system and they came back with a vs. temperature lifetime.
Most manufacturers probably can advise you (if it's not described by datasheet curves)
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Cold temperatures are better for primary cell storage ... but when you draw 1 mAh from a cold cell, it will be like drawing > 1 mAh from a room-temperature cell. Its internal resistance will be higher, so the voltage will be lower and more power will go into heating the cell.
If you have any control over device design, you can do at least two simple things:
- Spec a cell with a larger diameter. A CR3032 can deliver about 2.5 times the power of a CR2032. And CR16xx cells are rubbish.
- Install an appropriately sized ceramic capacitor in parallel with the cell. Peaky loads like radios with too small or no capacitor ruin cells. There's a white paper about this but I can't find it now.
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After longer experience with CR2032 performance in remote controls I present updated findings/recommendations:
- a) change my batteries more often to new ones in the remote control (before it stops working)
- b) buy new packs of CR2032 often as old batteries go bad after a while. Battery voltage maybe 3.2-3.3V on old unused cell, but due to internal resistance capacity is diminished to a point where it does not work in remote.
- c) keep remote control in warm place to keep it working. Cold temperatures may drastically decrease performance.
Coin cells go bad due to two main reasons - usage and age. If product usage is intermittent and low, batteries should be replaced anyway after some time. I traced few strange occurrences of "new" CR2032 not performing to the old batch, although it is tricky to do the quick test due to low currents/capacities.
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I found this document relatively interesting regarding that: https://data.energizer.com/pdfs/lithiumcoin_appman.pdf
You'll see, among other things, how a very low discharge current can increase the internal resistance to pretty high values.
It won't matter much for very low power devices such as watches, but for ones that require more "instant" current such as remote controls, that certainly can be a problem.
A typical CR2032 can see its IR increase to 100 ohms after a long time with a constant low discharge current like a few uA. For a watch that's typically not a problem because it will never draw a lot of current even during peaks. Say you have 5 uA on average and occasional peaks at 100 uA - at 100 ohm, that's 10 mV drop. Nothing to fret about. But say a remote draws also just a few uA when 'idle' and have peaks of a couple tens of mA when activated - now that can be several V of drop, meaning, dead beef.
Those batteries are actually a poor choice for remote controls in terms of lifetime. Sure they are good in terms of weight and volume...
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Lithium Coin Handbook and Application Manual, Energizer (https://data.energizer.com/pdfs/lithiumcoin_appman.pdf), page 6:
The IR increase during discharge is not constant for all drain rates. For example, very low uA drain rates can cause a significant rise in the battery IR early in the discharge.
Those batteries are actually a poor choice for remote controls in terms of lifetime. Sure they are good in terms of weight and volume...
Yeah, CR2032 is not great choice for high momentary power device like remote control. It only works if you do not use it, sort of catch 22 situation :-//
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I can't even remember the last time I replaced the coin cell in my car's key fob. Years ago for sure, and it is exposed to lots of extreme temperature variations in the winter where temperature will frequently dip below -30C. I keep the keys in an outside pocket on my jacket and do regularly spend a lot of time outside, so it definitely has ample opportunity to cool down.
Either it's one heck of a good quality cell, or the remote is a well designed for low power consumption and operation with reduced battery voltage, or both.
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just to add a point of view, I ave a little ague I carry about to measure blood sugar levels and I must say it doesn't like cold temperatures at all. Now is that the coin cell causing the problem or are they simply measuring temperature to keep the unit in spec. In other words has the coin cell failed to provide the required power (probably not as it is prompting with a temperature failure indicator) or has the meter itself refused to operate at the cold temperature. The meter does work after warming up.
So what I'm trying to say is that the engineering behind the device could be an issue. It could be that the battery is fine but the device was never really tested or designed for operation at low temperatures. Like many here I have key dongles and the like that continue to run fine in cold temperatures so it doesn't seem to be an inherent battery problem in many cases.
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Yeah, CR2032 is not great choice for high momentary power device like remote control. It only works if you do not use it, sort of catch 22 situation :-//
No, they are great for low power devices that never draw more than a couple mA on occasional peaks and a few uA otherwise. In that case, they have a pretty long lifetime compared to alkaline batteries.
A lot of such devices exist. Watches, simple calculators, low power sensors, ...
Another benefit is that they are well sealed. Alkaline batteries, even from the major brands, will end up leaking after only a few years. I don't think I've personally ever seen a lithium coin cell leak even after a couple decades. At worst you'll see some oxidation on the shell.
To each application the appropriate type of battery...
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Remote control in question is programmable with some fancy features which include blinking few LEDs and beeping when buttons are pressed. However, it definitely reflects negatively on battery performance compared to simpler remotes.
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I wouldn't always blame the battery, at low temperatures most RF remotes drift in TX (or RX) frequency giving low range or no response.
TI White Paper SWRA349 (https://www.ti.com/lit/wp/swra349/swra349.pdf) of lithium coin cells with added 100uF capacitor, and ESR goes from 10R to over 1k ohms when near empty.
There are "high drain" CR2032 e.g. Murata (https://www.murata.com/en-us/products/batteries/micro/overview/lineup/cr/high-drain) that take 50mA/3sec TX drain, or <3mA continuous, designed for RF chirps.
I can't buy lithium coin cells from distributors Mouser or Digikey in Canada due to air transport restrictions. Even though it's 0.07gm of lithium :palm:
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So I had the same problem on a 433 device, and soldered a small tantalum capacitor next to the battery.
And in fact, there was a solder pad already unpopulated for just that. So design already had it, but it was left out.
Any opinions if tantalum was the right choice? 106 capacity? Tantalum has no leakage right?
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Ceramic capacitors generally have lower leakage current for a given capacitance, but the difference is usually less than an order of magnitude. The bigger issue can be capacitance, because for any given dielectric, the leakage current scales roughly linearly with capacitance. A generic 100 uF tantalum might have an insulation resistance of 1 MOhm.
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So you think I overdid it? Quite possibly so. I will see how it goes.
So far, the doorbell always stopped on cold mornings. And then when I checked, the battery is still quite full. But of course, by then I heated it up with my fingers.
We will see how long it stays working with this potential overkill capacitor leaking.
Still think the vendor should not have removed the capacitor from the board though.
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A CR2032 cell will be OK in non freezing temperatures. If it is freezing, I recommend buying BR2032, which is similar, but wider temperature range.
And if it is used as a remote controller/RF etc application, with large current peaks, it is expected to buffer the battery with something like a 100uF capacitor.
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Consider using a BR2032 rather than CR2032, the chemistry is similar but offers better low-temperature performance.
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Consider using a BR2032 rather than CR2032, the chemistry is similar but offers better low-temperature performance.
I am not a battery expert. I am following this thread because I have a temperature/humidity sensor that has a solar cell and can also use a battery when the solar cell has not sufficiently charged an on board cap. I outfitted it with a CR2032. It works ok but not so well with the coldest temperatures on the darker days (or getting through the night). Not really the point, but mentioned by way of why the thread interests me.
I looked at the temperature data for both the CR2032 and BR2032 - both data sheets for Panasonic products. The attached graphs are from those data sheets.
BR2032 link https://www.mouser.com/datasheet/2/315/3610_fileversion-1889684.pdf (https://www.mouser.com/datasheet/2/315/3610_fileversion-1889684.pdf)
CE2032 link www.cr2032.co/cms/prodimages/panasonic_cr2032_datasheet.pdf (http://www.cr2032.co/cms/prodimages/panasonic_cr2032_datasheet.pdf)
Look at the two graphs from these data sheets...
BR2032
(https://www.eevblog.com/forum/projects/coin-cell-performance-in-low-temperatures/?action=dlattach;attach=1342355;image)
CR2032
(https://www.eevblog.com/forum/projects/coin-cell-performance-in-low-temperatures/?action=dlattach;attach=1342349;image)
Again, I am not a battery expert, but it looks like the CR2032 has much better LOW temperature performance than the BR2032. I realize that there is a small difference in "normal" voltage, but I am addressing the relative temperature performance.
Am I reading these graphs wrong, or did you make an error or something else?
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When I looked at it before BR2032 was much better in my application, but I was looking at a much lesser load and rather colder temperatures, more like a few microamps and -30 C. Your graphs are perhaps more appropriate for electr_peter's application unless he can provide "burst power" from a capacitor.
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The data sheets often specify a maximum current in the single mA range, even though a new cell in the bench might happily drive a 50mA peak radio transmitter.
I can’t say too much, but…
- the open circuit voltage of a Li coin cell doesn’t drop too much with discharge and/or temperature. Maybe 10%-20% voltage drop
- measuring a coin cell voltage with a DMM is pretty useless there’s some load because of the 10Meg input resistance. If you add a little discharge resistor in parallel with your DMM (10k - 100k) you’ll get some more useful results
- internal resistance is a killer when driving a pulse load (eg radio transmitter) because the terminal voltage dips enough to mess up circuit operation. So your equipment might crap out even thought the cell is still technically half full
- internal resistance goes up as the battery gets discharged
- internal resistance goes up as temperature drops
- internal resistance could go up by 100x when battery is discharged and cold.
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Am I reading these graphs wrong, or did you make an error or something else?
I don't think that you are reading it wrong, and most cases the cr will be better than br.
This might clear things up a bit
https://www.master-instruments.com.au/files/knowledge-centre/engineering/guides-and-selection-charts/panasonic___selecting_the_right_lithium_battery_br_or_cr_series.pdf (https://www.master-instruments.com.au/files/knowledge-centre/engineering/guides-and-selection-charts/panasonic___selecting_the_right_lithium_battery_br_or_cr_series.pdf)
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I made some detailed measurements of remote control activity during transmission. Setup: external PSU set to 3.2V at 70mA. Currents is measured with scopemeter in series (mA range, ~1.6 Ohm, insignificant voltage drop).
Remote transmits (also beeps and lights LEDs) for ~975ms at 48mA with 3.2V supply. See screenshots 1, 2, 3 below. This is 150mW power and 0.042 mWh or 0.013 mAh energy. CR2032 capacity is ~200 mAh, so in theory it could last for 15k times (excluding idle drain).
When measured with CR2032, voltage on idle was 3.04V and 2.64V during transmission. See screenshot 4. Voltage drop is ~0.4V, which gives 8.3 Ohm internal resistance (assuming it reaches 48mA with partially discharged CR2032). This is a ballpark of CR2032 IR according to datasheets (~10 Ohm IR).
Conclusion: remote control requires ~50mA short current pulses and it really pushes CR2032 possibilities. This likely creates problems with any temperature variations. LEDs and buzzer on board are pretty weak, RF and MCU are most likely power hogs.
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Yes, this is a lot of power for a CR2032, and too much to buffer with a capacitor. Most new, good-quality CR2032s will manage it at room temperature, but part-discharged ones with higher internal resistance may not, and even new ones will struggle in the cold.
It's not really a good design. I wonder how much power you'd save disabling the LEDs, or if a larger cell could be made to fit.
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Yes, this is a lot of power for a CR2032, and too much to buffer with a capacitor. Most new, good-quality CR2032s will manage it at room temperature, but part-discharged ones with higher internal resistance may not, and even new ones will struggle in the cold.
Larger cap would do nothing with such long pulse duration. Extra battery could improve things if there was enough space.
It's not really a good design. I wonder how much power you'd save disabling the LEDs, or if a larger cell could be made to fit.
LEDs and buzzer were not measured. I do not see how one little SMD LED would consume much current, maybe buzzer is too powerful? I will look into it.
Battery is held in soldered cage, case limits battery size as is (or would require significant modifications).
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It wouldn't surprise me if the LED were driven at 10-15 mA if it is meant to be visible outside the case in strong sunlight. A 20% load reduction would be significant.
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Remote transmits (also beeps and lights LEDs) for ~975ms at 48mA with 3.2V supply. See screenshots 1, 2, 3 below. This is 150mW power and 0.042 mWh or 0.013 mAh energy.
Because F = As / V, if you allow 0.5V voltage drop during the peak, required capacitor would be
0.013mAh * 3600 s/h / 0.5V = 93600µF.
Not going to happen.
Standard electrolytic, tantalum and high energy density MLCC capacitors are good for peaks up to some 1ms.
Now if this was 1ms instead of a full second, a 100µF 4V part would work. This would still be smaller than the battery itself.
This is why many communication devices really require low-impedance battery sources, unless the packets are really short. Power density of capacitors is great, but energy density is like 5-6 orders of magnitude behind batteries.
Still people often solder capacitors as cargo cult attempts to solve these issues, without performing simple napkin calculation first. The result is obviously disappointing. For the same reason, you may see unpopulated capacitor footprints on the PCBs.
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I isolated power usage from LED and buzzer on PCB. LED draws <1 mA. Buzzer (piezoelectric disk element) draws 4-6 mA max, so there is no point in disabling it.
System architecture is pretty complex with 2 main chips onboard - CC110L (TI Sub-1 GHz wireless transceiver) and STM8L151G6 (ST 8 bit MCU, 16 MHz).
Only options to increase battery performance are to add 2nd battery or upgrade CR2032 to something bigger.
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Redesign of the firmware would likely be the right thing to do, why does it have to transmit non-stop for a second, is this transferring tens of kilobytes or what? But obviously, this isn't a realistic option.
Software is everything in low-power wireless. Do the minimum required, in minimum time, and go to sleep.
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- measuring a coin cell voltage with a DMM is pretty useless there’s some load because of the 10Meg input resistance. If you add a little discharge resistor in parallel with your DMM (10k - 100k) you’ll get some more useful results
Yeah, that's why I have one of those cheap dedicated battery testers. They do put a small load on the battery while testing. Can't remember for sure, but I believe it was like 10K
Also more convenient to hold when you have only 2 hands like me (as opposed to holding two probes, a dmm and a battery)
Anyway, so far the 106 capacitor I added works. Already 2 frozen morning without problems.
Now I only hope the leakage of the capacitor leakage does not drain the battery too soon.