Measure internal resistance of a battery with LCR meter?

[shadowless]

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?

[Rerouter]

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)

[IanB]

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

[kripton2035]

you need to measure the resistance while injecting an ac voltage
your multimeter injects a dc voltage to measure the resistance, it won't work

this esr meter can also give a good idea of the health of a battery:
http://kripton2035.free.fr/digital%20esr/esr-kaspars.html
explanations 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.

[robrenz]

Can a LCR meter with ESR measure the internal resistance of a battery?  I have  IET DE-5000

[alm]

Some can. Protection diodes (designed to protect against charged caps) across the inputs will cause problems, however.

[IanB]

you need to measure the resistance while injecting an ac voltage

Although 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.

[sorin]

You cant measure it with LCR meter


https://www.keysight.com/main/editorial.jspx?ckey=2045153&id=2045153&nid=-11143.0.00&lc=eng&cc=US

[shadowless]

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.

[Rerouter]

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)

[IanB]

Can the agilent U173xC series with ESR function do the job? Seems like ESR meter is what i need.

As 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.

[shadowless]

I will definitely give the DC load test a try. How far out will the result be from the ESR measurement?

[IanB]

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.

[Rerouter]

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,

[IanB]

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.

[shadowless]

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?

[Rerouter]

a light bulb is not a static resistance :/ it drops like a brick as it heats up enough to give of light,

[IanB]

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).

[SeanB]

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.

[Slobodan]

http://batteryuniversity.com/learn/article/how_to_measure_internal_resistance

Also, someone commented:

Troy Mikkelson wrote:

To Measure the internal resistance:
Buy a high wattage (10W) precision resistor of low value, say 0.1 ohm.

Put the resistor in series with the battery charger + cable and one terminal of resistor, connect battery charger - cable to battery -, connect second terminal of resistor to battery +, (A) Read the voltage across the resistor terminals.  (B)Read the voltage across the battery terminals.

A) Divide the voltage across the resistor by the value of the resistor (0.1 ohms) to get the exact current flowing into the battery. This value will be used for step B

B) Divide the voltage across the battery terminals by the current found in step A.  The answer will be roughly (a few percent, of a 70% accurate measurement is pretty good) the internal resistance of the battery.

Second Method:  Get an ESR Meter (Equivalent Series Resistance)  ($100-$300), these are essentially AC Ohmmeters with fixed or variable frequency.  Measure resistance of battery (Equivalent Series Resistance) which is a direct reading with no other meters needed.  These meters can be used on batteries from AAA to 9V alkaline with very good indication of health as well.

[siliconmix]

contact the battery manufacturer 

[drkirkby]

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?

I 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.

You can measure 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 handbook

http://literature.cdn.keysight.com/litweb/pdf/5950-3000.pdf

currently 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 Kirkby
Kirkby Microwave Ltd

[dannyf]

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.

[dannyf]

it drops like a brick as it heats up enough to give of light,

Probably not.

[wiss]

Won't high current DC fry the DE-5000 pretty bad?