Upgrading the temperature measuring gear for battery testing

[Mooch]

I “stole” the trustworthy Omegaette HH306A temperature meter from my day job testing station and have been using to measure vaping cell temperature during testing. It’s time to move it back permanently. It’s just too annoying moving it back and forth when needed. The other meters I have can be used but aren’t quite as accurate.

This gave me an opportunity to upgrade though to the Fluke 52 II, an incredible two channel meter. Especially when paired with tight tolerance thermocouples (temperature sensors) and an extra NIST-traceable calibration done before the Fluke was shipped to me. In the photo you can see two different sensors showing the same 26.8°C ambient temperature...just what I want to see.



You can see one of the temperature sensors on the upper right, with its “bead” tip circled in red. It’s this tiny tip that makes these thermocouples so great for measuring cell temperature. It responds very quickly to the changing cell temperature, it thermally couples itself well to the cell using a dot of thermal paste or thermal epoxy, and it’s easy to isolate from the effects of cooler ambient air using Kapton tape to mount it to the bare cell (wrap removed).

Exciting stuff? No, not really.
Just another step to ensure that the results I give you are accurate.

 

[Baditude]

Exciting stuff? No, nott really.

You might as well have been speaking in Mandarin considering how much I understood what you said above. If it excites you, Mooch, I'm happy. Measure to your heart's content.

As always, thank you for what you do for our community.

 

[CMD-Ky]

I “stole” the trustworthy Omegaette HH306A temperature meter from my day job testing station and have been using to measure vaping cell temperature during testing. It’s time to move it back permanently. It’s just too annoying moving it back and forth when needed. The other meters I have can be used but aren’t quite as accurate.

This gave me an opportunity to upgrade though to the Fluke 52 II, an incredible two channel meter. Especially when paired with tight tolerance thermocouples (temperature sensors) and an extra NIST-traceable calibration done before the Fluke was shipped to me. In the photo you can see two different sensors showing the same 26.8°C ambient temperature...just what I want to see.

View attachment 823945

You can see one of the temperature sensors on the upper right, with its “bead” tip circled in red. It’s this tiny tip that makes these thermocouples so great for measuring cell temperature. It responds very quickly to the changing cell temperature, it thermally couples itself well to the cell using a dot of thermal paste or thermal epoxy, and it’s easy to isolate from the effects of cooler ambient air using Kapton tape to mount it to the bare cell (wrap removed).

Exciting stuff? No, not really.
Just another step to ensure that the results I give you are accurate.

I am not sure what all that is or what it means. I do know that when you roll out the results those results will be worth reading.

 

[Tabac man]

It might not be exactly exciting for you mate but we appreciate your efforts. I have just ordered my first removable battery mod having used built in jobs for years. I had to do the obligatory reading about chargers and batteries, which battery I should use etc, and most of that information came from...you. So thank you.

 

[sonicbomb]

 

[Heartsdelight]

We’re always grateful for all you do!

 

[ecffred]

I've been evaluating the use of 18650s for use in cubesats (in space) and been following all your testing.
Thanks for all you do!
The area that I am having problems finding testing information about is low-temperature discharge.
I've done some informal testing myself to -40c using dry ice, and all the batteries I tested seemed fine at 4 amp draw.
But I'm using a cheap meter and visual recording.
Would you be interested in doing some low-temperature, high amp discharge testing?
tia,
Fred

 

[Rossum]

I've been evaluating the use of 18650s for use in cubesats (in space) and been following all your testing.
Thanks for all you do!
The area that I am having problems finding testing information about is low-temperature discharge.
I've done some informal testing myself to -40c using dry ice, and all the batteries I tested seemed fine at 4 amp draw.
But I'm using a cheap meter and visual recording.
Would you be interested in doing some low-temperature, high amp discharge testing?
tia,
Fred

$219 will get you a tester that will do up to 40A or 150W:
West Mountain Radio - CBA IV - Computerized Battery Analyzer

I'm scratching my head though, wondering why anyone would use 18650s in a satellite application where every gram of weight matters. Wouldn't pouch cells be lighter for the same capacity?

 

[Mooch]

I've been evaluating the use of 18650s for use in cubesats (in space) and been following all your testing.
Thanks for all you do!
The area that I am having problems finding testing information about is low-temperature discharge.
I've done some informal testing myself to -40c using dry ice, and all the batteries I tested seemed fine at 4 amp draw.
But I'm using a cheap meter and visual recording.
Would you be interested in doing some low-temperature, high amp discharge testing?
tia,
Fred

I wouldn’t have the time to test that for you but even just power resistors and an inexpensive voltmeter will allow you to compare different cells at different temperatures.

Soaking the cells overnight in a freezer and then adding the dry ice (finely crushed) and putting it all back in the freezer and not testing until the temp stops dropping might work.

I agree with @Rossum, 18650’s have low power and energy density and low volumetric efficiency versus flat pouch cells. Those characteristics are critical for your application. It might be worth checking some pouch LiPo (LCO chemistry) cells out.I don’t have any recommendations though.

Different battery chemistries are better at those low temperatures. Most li-ion cells are spec’d down to -20C but, IIRC, Molicels are rated down to -40C. They’re 18650, 20700, and 21700 size though. Check the temperature ratings for LiFePO4. Different voltages but I seem to remember something about great cold weather performance.

Ultracaps in parallel with your cells can help a LOT if you draw current in bursts.

Another option is to add some reserve capacity to use for low level heating of the cells (packaged in an insulated container). They don’t need to be warm, just not below their rating. In fact, operating the cubesat right after launch might prevent from ever getting too cold if they are well insulated.

Try checking Tadiran and Saft to see if they have application notes for low temp operation. They should at least mention which chemistries are best. If you don’t need to recharge your cells then you have a lot more choices since you can also use different chemistry primary cells.

An exciting application!

 

[AngeNZ]

Mooch you are our Batman

even on New Zealand vape sites they quote you, so you are also world famous