I'm doing an experiment for school which involves measuring the temperature of batteries. I'm measuring the temperature using an infrared thermometer, and in order to get an accurate result I need the emissivity value of the surface that I am using the thermometer to measure. To be more specific, I am using a 1.5 volt Duracell battery with the plastic label taken off.

What type of metal is the casing made of? For example, if it is steel, is it galvanised, oxidised, sheet, buffed, polished etc?

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    \$\begingroup\$ What does the datasheet say? \$\endgroup\$ – Ignacio Vazquez-Abrams Mar 29 '17 at 4:36
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    \$\begingroup\$ @IgnacioVazquez-Abrams can you find a single battery data sheet that says it? I tried 5 brands and multiple battery types. The only thing the data sheet says is the battery chemistry, not the casing material. \$\endgroup\$ – Passerby Mar 29 '17 at 4:45
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    \$\begingroup\$ Steel, usually. For example: "The materials of construction for the nickel-metal hydride battery external surfaces are largely comprised of nickel-plated steel, and therefore, are resistant to attack by most environmental agents." and "The preforms are next inserted into a nickel-plated steel can; the combination of the preforms and the steel can make up the cathode of the battery. In a large operation, the cans are made at the battery factory using standard cutting and forming techniques." - Google will help you in finding the sources of those quotes. \$\endgroup\$ – Sredni Vashtar Mar 29 '17 at 4:53
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    \$\begingroup\$ BTW, why don't you put a piece of black opaque tape on the battery and use that to measure the temperature? \$\endgroup\$ – Sredni Vashtar Mar 29 '17 at 5:01
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    \$\begingroup\$ I am glad you are asking this, because getting the correct emissivity is important. I believe it is sheet steel. Consider painting it black prior to the measurement. Another option is to adjust the emissivity to match the temperature when the temperature is known through other means (ice-water bath for 1 hour, for example). \$\endgroup\$ – mkeith Mar 29 '17 at 5:26

After you measure the steel case Temp also measure the ESR or incremental voltage drop for rise in I and then compute Pd from Pd= I² * ESR and not simply V * I...

ESR will be a better indicator of heat loss, Pd and thus the linear temp rise for Pd as V drops and I rises .

Then compute the thermal resistance Rth_ca, Pcase is an indication of the internal Anode temp which is hotter. Thus ESR vs Tcase and then Rth_ca=ΔT/Pd (steady-state) (thermal case to ambient resistance.) Moving air, ice, removing plastic and adding enclosure will each affect this thermal resistance and temp rise .

Hotter batteries also have lower ESR and more power available YET age much faster. (50% life reduction every 10'C rise regardless * mAh consumed)

The same is true for LiPo cells and Lead Acid although LiPo's can have a thermal runaway effect above ~200'C? core temp and explode.

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