Measure internal resistance of a battery with LCR meter? - Page 1
Forum section: electronics / general

author: shadowless
author_rank: Regular Contributor
timestamp: February 11, 2012, 08:24:04 pm
content: Hi,I can use my multimeter to measure the internal resistance of a battery. I have no experience with LCR meters, wonder if it can measure the impedance of a battery?

author: Rerouter
author_rank: Super Contributor
timestamp: February 11, 2012, 09:31:12 pm
content: shadowless, how per-say are you measuring it with a multimeter?the resistance range on a multimeter works by feeding through a constant current for the range and measuring the voltage drop for that current, and ususally doenst like a voltage being fed into it while measuring,while if you inject current into a battery positive - positive, it should absorb most of it as a charge, or if the multimeter can only supply less than the voltage of the battery, may begin sinking current from the battery, (bettter multimeters generally can survive it, but still not good for them)

author: IanB
author_rank: Super Contributor
timestamp: February 11, 2012, 09:53:39 pm
content: Although you can't use the resistance range of a multimeter directly, there are many ways to measure the internal resistance of a battery. Google is your friend. Here is one link with a short introduction:http://www.buchmann.ca/Chap9-page2.asp

author: kripton2035
author_rank: Super Contributor
timestamp: February 11, 2012, 10:30:23 pm
content: you need to measure the resistance while injecting an ac voltageyour multimeter injects a dc voltage to measure the resistance, it won't workthis esr meter can also give a good idea of the health of a battery:http://kripton2035.free.fr/digital%20esr/esr-kaspars.htmlexplanations here :http://www.electronicslab.ph/forum/index.php/topic,8863.msg209251.html#msg209251(scroll down to reply #508)other esr meter habitually cannot measure battery resistance.

author: robrenz
author_rank: Super Contributor
timestamp: February 11, 2012, 10:39:41 pm
content: Can a LCR meter with ESR measure the internal resistance of a battery? I have IET DE-5000

author: Unknown
author_rank: Unknown
timestamp: February 11, 2012, 10:56:09 pm
content: Some can. Protection diodes (designed to protect against charged caps) across the inputs will cause problems, however.

author: IanB
author_rank: Super Contributor
timestamp: February 11, 2012, 11:01:11 pm
content: Quote from: kripton2035 on February 11, 2012, 10:30:23 pmAlthough you can do that, you will then measure the AC voltage impedance of the battery. This won't necessarily correspond to how the battery performs unless it is supplying an AC voltage of the same frequency used to measure.If you want a truer measure of how the battery will perform in a circuit it is more accurate to measure the DC voltage internal resistance using one of the suitable methods for that purpose.

author: sorin
author_rank: Frequent Contributor
timestamp: February 12, 2012, 12:31:28 am
content: You cant measure it with LCR meterhttps://www.keysight.com/main/editorial.jspx?ckey=2045153&id=2045153&nid=-11143.0.00&lc=eng&cc=US

author: shadowless
author_rank: Regular Contributor
timestamp: February 12, 2012, 03:36:29 am
content: Can the agilent U173xC series with ESR function do the job? Seems like ESR meter is what i need.Have yet to see Daves review on the Agilent and how it compared with IET DE-5000.

author: Rerouter
author_rank: Super Contributor
timestamp: February 12, 2012, 03:58:25 am
content: to measure the esr of a battery, all you need is a load resistor, compare the unloaded voltage to the loaded voltage, and you can calculate the value of its esr by V=IR, or in your case ESR = Vdroop/I,really thats the best way to do it, batteries esr is also dynamic, so if you really wanted to characterise it, you would need to record it at points across its discharge curve, as the lower the voltage the higher the ESR (because its based on a chemical reaction)

author: IanB
author_rank: Super Contributor
timestamp: February 12, 2012, 04:05:43 am
content: Quote from: shadowless on February 12, 2012, 03:36:29 amAs I hinted above, Google is your friend. It is trivial to measure the internal resistance of a battery using any multimeter using the appropriate experimental technique. Just follow the link I pointed you to or any one of a dozen others.Even if you did measure some impedance using an ESR meter the result would be of little value since it wouldn't correspond to normal battery usage.

author: shadowless
author_rank: Regular Contributor
timestamp: February 12, 2012, 04:16:29 am
content: I will definitely give the DC load test a try. How far out will the result be from the ESR measurement?

author: IanB
author_rank: Super Contributor
timestamp: February 12, 2012, 04:22:39 am
content: There are two industry measures of battery resistance. One is the AC impedance (often measured at 1 kHz) and the DC resistance. The AC impedance can differ from the DC resistance by a factor of 2 or more. The AC impedance is usually lower than the DC resistance.

author: Rerouter
author_rank: Super Contributor
timestamp: February 12, 2012, 04:23:46 am
content: it only comes down to what values you pick, and how accurate your multimeter is, if you pick something like a 10R high wattage for a 1.5V battery, your going to see quite a decent voltage drop, e.g. dropped to 1.26V on my own, with that, you work the math and it ends up being a 1.9 ohm ESR, just for reference this was a dollar bin AAA, so such horrible ESR's can be expected,

author: IanB
author_rank: Super Contributor
timestamp: February 12, 2012, 04:30:33 am
content: There are two reasons to know the internal resistance of a battery. One is to know the voltage sag under load, and the other is to know the heat dissipated inside the battery when loaded (usually with big loads). In both cases the DC internal resistance is the most valuable number.To get a good measure of DC resistance it is best to use a two resistor technique, alternating between two loads. If you compare loaded and open circuit voltage you can get a false reading due to an accumulation of "surface charge" on the battery giving a higher apparent EMF than the more realistic value under load.

author: shadowless
author_rank: Regular Contributor
timestamp: February 12, 2012, 05:15:08 am
content: I am measuring lead acid battery impedance for matching purpose. Definitely doing 2 load dc i think. What type of load is recommended? Will light bulbs be appropriate?

author: Rerouter
author_rank: Super Contributor
timestamp: February 12, 2012, 05:25:47 am
content: a light bulb is not a static resistance :/ it drops like a brick as it heats up enough to give of light,

author: IanB
author_rank: Super Contributor
timestamp: February 12, 2012, 05:27:04 am
content: Yes, light bulbs will work, but you may need to measure both current and voltage at the same time needing two meters. With fixed resistors of known value you have the advantage that you can use Ohm's law to find the current just by measuring the voltage drop across the resistor(s).

author: SeanB
author_rank: Super Contributor
timestamp: February 12, 2012, 12:29:58 pm
content: A better method is to measure all the batteries after charging ( and leaving overnight to stabilise voltage) and then measure the voltage as you connect first one then 2 lamps across them. Use the same lamp and connections in all the measurements for the first and second connection. Then measure the current on the second lamp when in use across one battery to get the current. This saves measurements, as you just use the voltage difference between the first and second lamps, and assume that the current is the same in all cases ( will be close enough that you can disregard it, internal resistance will be a variable anyway, and depends on state of charge) to calculate ESR.If you are doing this to use the batteries in a series and want to match the capacity then it is better to fully charge all the cells and then discharge them all with a load, and measure the time it takes to reach the defines low voltage level for the cell type. Then you match cells by discharge time into the same load, which will give a reasonable matching.

author: Slobodan
author_rank: Regular Contributor
timestamp: February 12, 2012, 01:28:23 pm
content: http://batteryuniversity.com/learn/article/how_to_measure_internal_resistanceAlso, someone commented:Quote

author: siliconmix
author_rank: Frequent Contributor
timestamp: February 12, 2012, 01:50:39 pm
content: contact the battery manufacturer

author: drkirkby
author_rank: Newbie
timestamp: April 07, 2015, 10:35:20 am
content: Quote from: shadowless on February 11, 2012, 08:24:04 pmI know this is an old thread, but I thought I'd reply, as there seems to be a lot of inaccurate information from some responses.Youcanmeasure the internal impedance (and so resistance) of a battery with an LCR meter. I know it can be done with LCR meters which are fitted with 4 wire Kelvin test leads, although I am not so sure about meters with just two wires - I suspect not. The Keysight Impedance handbookhttp://literature.cdn.keysight.com/litweb/pdf/5950-3000.pdfcurrently in its 4th edition, describes the method in section 5-11, which is page 5-31, or its easier to find if you just go to page 117 in the PDF file.Apparently there's some "standard" that dictates the measurement is performed at 1 kHz, but just about any decent handheld or bench LCR meter should be able to operate at 1 kHz (the HP 4284A I have here works between 20 Hz and 1 MHz). In order to measure at 1 kHz, you need a couple of capacitors of at least 32 uF to isolate the battery from the LCR meter, as most LCR meters will not want to see DC. The capacitors need to be rated for a voltage at least equal to the battery voltage. Personally if doing this, I would put two capacitors of at least 64 uF in series, in case one fails short circuit, as a short-circuit failure of a capacitor will almost certainly damage the LCR meter.Dr. David KirkbyKirkby Microwave Ltd

author: dannyf
author_rank: Super Contributor
timestamp: April 07, 2015, 01:27:10 pm
content: It can be done: I used an esr meter to measure the internal resistance of a 9v battery (about 10ohm).Whether you need a dc-blocking cap will depend on the meter's design.

author: dannyf
author_rank: Super Contributor
timestamp: April 07, 2015, 02:03:04 pm
content: QuoteProbably not.

author: wiss
author_rank: Frequent Contributor
timestamp: April 07, 2015, 03:27:11 pm
content: Won't high current DC fry the DE-5000 pretty bad?

author: macboy
author_rank: Super Contributor
timestamp: April 08, 2015, 01:10:41 pm
content: Quote from: wiss on April 07, 2015, 03:27:11 pmI absolutely do not recommend connecting a battery directly to the inputs of the DE-5000.I can, however, see how it would be possible to use an LCR in ESR mode to measure theACESR of a battery at a specific frequency. This does not, however, have any real bearing on what is actually wanted: the internal resistance of the battery for a DC load.The technique to measure the internal resistance of a battery is quite simple. Apply a small load and measure that current and the battery terminal voltage. Then apply a larger load (about equal to the expected working load of the battery) and measure the current and battery terminal voltage. Then RBAT= (V2- V1)/(I2- I1). Basically the drop in terminal voltage is caused by the increased current flowing through the internal resistance of the battery. Note that for some battery chemistries, internal resistance increases as the % charge decreases.

author: Shock
author_rank: Super Contributor
timestamp: April 09, 2015, 10:28:38 am
content: Quote from: robrenz on February 11, 2012, 10:39:41 pmYou will need to translate these from Japanese to English.http://blogs.yahoo.co.jp/tek2465/7968952.htmlhttp://blogs.yahoo.co.jp/tek2465/8112100.htmlhttp://blogs.yahoo.co.jp/tek2465/7968954.html

author: oldway
author_rank: Super Contributor
timestamp: April 09, 2015, 03:14:20 pm
content: You have to discharge the capacitors before testing them with most of the LCR meters.For this reason, you can't apply a DC voltage from a battery on their terminals.Use an low cost ESR meter who can test charged capacitors as this project:https://www.eevblog.com/forum/projects/esr-meter-adapter-design-and-construction/I make one and it is very easy to use ...Fluke 500 series battery analyser use the same principle: the measurement is based on AC injection method of 100mV 1Khz.http://www.farnell.com/datasheets/1842852.pdf

author: mikerj
author_rank: Super Contributor
timestamp: April 09, 2015, 08:22:20 pm
content: Quote from: dannyf on April 07, 2015, 02:03:04 pmIt might have a carbon filament...

author: reagle
author_rank: Unknown
timestamp: April 10, 2015, 01:49:51 am
content: It may be simpler to get one of these cheap Chinese meters:http://www.ebay.com/itm/20R-Internal-Battery-Resistance-Impedance-Meter-Tester-/331466623559?pt=LH_DefaultDomain_0&hash=item4d2cf34a47They work reasonably well and go up to 20 Ohm

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2015, 03:23:09 pm
content: You can use an LCR meter to measure the impedance of a battery. You'll need to add DC blocking capacitors if the LCR has no way to deal with a DC bias and depending on what kind of battery it is you'll need a 4 wire connection. Li-ion batteries for example have an internal resistance in the milli-Ohm range. The internal resistance also depends on the frequency. Usually the impedance at DC and 1kHz are specified.

author: mos6502
author_rank: Frequent Contributor
timestamp: March 01, 2016, 04:20:27 am
content: Quote from: Shock on April 09, 2015, 10:28:38 amHoly crap, that is amazing.Has anyone tried this? Maybe with larger lead acid batteries?And yes I know it's an old thread.

author: Shock
author_rank: Super Contributor
timestamp: March 04, 2016, 01:15:26 pm
content: I've also seen a purpose built OLED Chinese meter from XYZ studios (not to be confused with their USB power meters) about $60 and I recall it being suitable for RC hobby type batteries, milliohm resolution perhaps, I cannot find it anymore.

author: quarks
author_rank: Frequent Contributor
timestamp: December 30, 2017, 01:28:39 pm
content: just in case anyone is still looking for thisI meassure battery internal resistance with my LCR meter, you only need a suitable capacitor to block DC from H-current Input of your LCR Metere.g. as described in IET Application Notehttps://www.ietlabs.com/pdf/application_notes/035048%207600%20Battery%20Measurements.pdf