Is there a way to evaluate the charge left on a 3V Lithium Button Cell Battery - Page 1
Forum section: electronics / testgear

author: Pascalken
author_rank: Contributor
timestamp: August 18, 2013, 01:59:59 pm
content: Hi,Is there a way (simple) to evaluate the charge left on a 3V Lithium Button Cell Battery, e.g. CR2016.Thank you,Pascal

author: Tita
author_rank: Contributor
timestamp: August 18, 2013, 02:03:50 pm
content: Buy a cheap multimeter(DT830B) and test the battery !Or you could buy an universal battery tester!

author: Pascalken
author_rank: Contributor
timestamp: August 18, 2013, 02:10:05 pm
content: Hi,As I understand it, the voltage remains constant over the entire lifespan, and therefore is not representative for the remaining charge.Of course the voltage drops when fully discharged.So if you mean something else than a voltage check then please elaborate,thank youPascal

author: dr.diesel
author_rank: Super Contributor
timestamp: August 18, 2013, 02:11:22 pm
content: Quote from: Tita on August 18, 2013, 02:03:50 pmOr just replace the battery!Pascal, are you simply wishing to test the battery one time, or what's the overall goal/project?

author: Pascalken
author_rank: Contributor
timestamp: August 18, 2013, 02:40:32 pm
content: Well, I left my garage remote control in the rain. I had just replaced the 2 batteries.I cracked it open and after I dried it it still worked.During the period it was wet it was consuming current because the LED faintly burned.It works with the old batteries. However since I have to break the remote open and glue it all together again to replace the batteries, I was wondering if it were not better to buy new ones.That is why I started to ask myself if there was a way to measure the left charge.Of course you are right. Just replacing them is the best way to go, but the unanswered question remains....ThanksPascal

author: digsys
author_rank: Unknown
timestamp: August 18, 2013, 02:45:00 pm
content: The short answer is NO. - and why BMs are mandatory on all Lithium packs. They measure the total charge going in,and subtract the charge going out to give a good indication of status. They will also look for the "elbow" at the topand recalibrate (or even the "knee" at the bottom). As most the energy curve is pretty much a flat line, there's notmany other choices. Sometimes we fire very short high current pulses and try to determine the internal impedance,usually comparing it against a profile for that battery, but that isn't that accurate and involves more complexity.With 10-20C+ rated Lithiums, even that isn't easy. For 1 to a few simple cells, you wouldn't bother with "other tricks".Edit: Just got beaten by your last post. For non-rechargeable, the answer is definitely NO.

author: Pascalken
author_rank: Contributor
timestamp: August 18, 2013, 03:39:52 pm
content: Hi thank you for the answer,I immediately understood the short answerBy BM you mean Battery Management I presume."the "elbow" at the top and recalibrate (or even the "knee" at the bottom)"Do you mean that the battery management system is looking for an "elbow or knee" in the discharging curve over time, to determine if at least one cell is completely discharged?Interesting, thank you,Pascal

author: HKJ
author_rank: Super Contributor
timestamp: August 18, 2013, 03:45:06 pm
content: Quote from: digsys on August 18, 2013, 02:45:00 pmFor lithium-ion you can use the voltage as a charge indicator.For primary lithium batteries you cannot use the voltage as charge indicator.There is nothing called rechargeable lithium batteries, the rechargeable is lithium-ion or LiIon.

author: robrenz
author_rank: Super Contributor
timestamp: August 18, 2013, 04:10:22 pm
content: Does the internal resistance change enough from fresh to depleted to be an indicator?

author: SeanB
author_rank: Super Contributor
timestamp: August 18, 2013, 04:20:23 pm
content: Internal resistance change is going to increase when cell is nearly dead, but is quite constant till that point, or varies more with temperature than with SOC. I have done quite a few upgrades on remote fobs by simply adding a 10uF 16/25V tantalum chip capacitor across the supply rail, and the battery life then is about 5 times longer in the pulsed draw typical of them. Only drawback is that EOL detection on the KEEYLOQ chipsets then does not work reliably, it will go from working to a dim flashing low battery in about 10 presses, instead of flashing for about 100 presses. Having a life though that is about 3 years though is a good advantage, and as I use A123 12V cell packs a lot it is not a hassle to change them. For coin cells like in a car fob this also works well.

author: saturation
author_rank: Super Contributor
timestamp: August 18, 2013, 11:23:08 pm
content: What others have said is true, but if you are doing it for aqualitativequick test of a simple CR2016 the answer is yes. If the battery is at end of life, the discharge voltage will be in or past the knee of its discharge curve unloaded, so the lower it is past 3V the more worn it is. A better test is load the cell briefly with 400 ohms and check the voltage simultaneously. A good cell will not drop below 2.5V at room temp under load, its easily seen in a typical discharge curve for 2016. A new cell will drop its output voltage and remain flat, but a very worn cell can also be pushed to the knee of the curve for an easy diagnosis and may not stabilize and drop continuously.http://data.energizer.com/PDFs/cr2016.pdfhttp://www.sony.net/Products/MicroBattery/cr/pdf/cr2016.pdfFor a steady output, the lower the pulse voltage is the more worn it is. You can't really say what itsquantitativemAH is, but you can say the tested battery is less than brand new.Note, a similar thing can be done to high mAH cells like 123A, but its far more risky to do given the battery's higher capacity so you need to know what you're doing fairly clearly.Quote from: Pascalken on August 18, 2013, 01:59:59 pm

author: nukie
author_rank: Frequent Contributor
timestamp: August 19, 2013, 12:44:08 am
content: There's a lot of EE experts here but the person you really need to talk to is battery specialists. Get this ZTS made in the USA battery tester.http://www.amazon.com/gp/aw/d/B000FQG1XEIt has profiles and characteristics of most batteries types and brands stored in the Pic Microchip that powers the device. It may not be 100% accurate, it doesn't tell me exact state of charge but it gives me a good picture so I don't get caught out by flat cells.The ZTS mini mbt is a better seller but the bigger brother does button cells.

author: IanB
author_rank: Super Contributor
timestamp: August 19, 2013, 01:26:36 am
content: Quote from: Pascalken on August 18, 2013, 02:40:32 pmThat doesn't make sense. Are you sure you haven't missed a screw somewhere?All batteries run down, they can't last forever. So unless they intend you to buy a new remote when the batteries are empty, there must be a way to replace the batteries.The remote control key fob on my car has the tiniest of screws you wouldn't recognize without a magnifier, but you can definitely unscrew it with a watchmaker's or jeweler's screwdriver and replace the battery non-destructively.As to the original question, the best way is to do a loaded voltage test on the battery, but unless you are very familiar with the characteristics of the battery it is going to be difficult to perform the test and interpret the results.The general answer with button cells or coin cells, if in doubt, is to replace the battery. Even at the seriously inflated retail prices often charged, this is not usually going to break the bank.

author: leafi
author_rank: Regular Contributor
timestamp: August 19, 2013, 04:25:14 am
content: I have an idea, try to drop it on the table and measure how it bounces vs a fully charged one and fully depleted one.... lol jk (referencing the video Dave made recently)

author: saturation
author_rank: Super Contributor
timestamp: August 19, 2013, 12:21:06 pm
content: Just get one of these, it works similar to what I described:http://www.radioshack.com/product/index.jsp?productId=3795405#Its not the best accuracy but its easy.

author: Corporate666
author_rank: Unknown
timestamp: August 19, 2013, 07:41:03 pm
content: To all those saying there is no reliable way to know the charge remaining in a lithium battery - nonsense!Hook it up to an electronic load and run it to death. You will get a pretty accurate idea of what the remaining charge was.Of course, that doesn't help the OP

author: nukie
author_rank: Frequent Contributor
timestamp: August 20, 2013, 10:30:25 am
content: Hello, can you proof that battery tester such as the ZTS doesnt work? I have it for years it has served me well. I standby that this product works as advertised. The pulse tester is patented and they even make version for the military.http://www.ztsinc.com/

author: saturation
author_rank: Super Contributor
timestamp: August 20, 2013, 01:28:56 pm
content: Yes, because those loads are for estimating applications, not for capacity, their test loads are in kiloohms. Also that datasheet is very incomplete.For Button cells, you need to pulse test with 400 ohms or less. Pulsing must be sufficiently fast to avoid wasting a primary cell, an eload is preferred.To test a 'new' cell's capacity insure pulse loading is at or above the load line of the curve. Below it the cell is used or rejected.At 1kohms or greater, the curves are ~ flat and will be mostly useless, however you can still detect drops in voltage in > 1kohm loads with a 6.5 digit DMM but the bigger issue is internal resistance vary by the quality of the battery, so detecting small changes depends highly on the quality of manufacture. Pulsing at 400 ohms or less and insure Vo > 2.5 works for most new cells, of acceptable quality.These are often done for QC checks in production, not for calculating the spec sheet data.http://www.evergreencpusa.com/PDF/Lithium/Button_cell/CR1616.pdfHowever, recent studies suggest the actual shape of the curve and pulsing intervals could generate spec sheet data far more efficiently than previously:http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=4458229&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F60%2F4505383%2F04458229.pdf%3Farnumber%3D4458229Quote from: mojo-chan on August 20, 2013, 10:41:43 am

author: nukie
author_rank: Frequent Contributor
timestamp: August 20, 2013, 02:15:44 pm
content: Dear mojo-chanIt seems that your so called 'research' is only limited to contant load discharging. The datasheet you linked doesnt even show you graphs of pulsed discharging characteristics. It's a poorly implemented datasheet. Try a better datasheet from Energizer. The internal resistance of a lithium coin cell behaves differently when it is pulsed discharged.Here is another very good PDF on state of discharge when lithium coin cell is pulsed discharge.http://www.renata.com/fileadmin/downloads/designersguide/DesignersGuide-2011_FAQ.pdfIn Figure 2, you can clearly see the voltage curve of the voltage drop V2 when pulsed discharge as the battery charge depletes.Next, have a good read at this patent and the circuit is easy to make with a microprocessor. All you need is to record the pulsed battery voltage profile as it is discharged. The more data you have, the more accurate. Then use that data to compare with the battery under test.http://www.google.com/patents/US6823274Like I said it is not 100% accurate but it gives you a good picture of the battery state of charge.

author: nukie
author_rank: Frequent Contributor
timestamp: August 21, 2013, 02:31:05 am
content: To the OP, here's a nice video showing the versatile ZTS battery tester, there's 10 test points for different types of battery chemistry.

author: IanB
author_rank: Super Contributor
timestamp: August 24, 2013, 08:47:53 pm
content: Quote from: mojo-chan on August 20, 2013, 02:36:11 pmI'm not entirely convinced that "industrial" cells are significantly different in their internal construction from "consumer" cells. In many cases the differences are more around packaging and distribution channels. (It is not efficient for the manufacturer to increase the number of product variations in their factory unless there is a commercial advantage to doing so, such as higher margins or increased sales volume for particular product specs.)

author: peter.mitchell
author_rank: Super Contributor
timestamp: August 25, 2013, 03:03:30 am
content: Quote from: IanB on August 19, 2013, 01:26:36 amOften they use tiny plastic tabs to retain the housing, which can easily break when replacing the battery, thus requiring you to glue it back together, I assume this is the case at hand.