Author Topic: EEVblog #515 - Battery Ionic Resistance Investigation  (Read 16213 times)

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Online IanB

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #25 on: September 06, 2013, 05:40:32 pm »
I imagine it would be possible to design some small device like the µCurrent to be used as a high impedance front end buffer for a regular DMM? It would echo the input voltage to the output terminals, but it would provide something like a 10G input impedance instead of the regular 10M from a DMM.
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Offline PA4TIM

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #26 on: September 06, 2013, 06:16:59 pm »
Bob Pease has a design for a  meter in his book trouble shooting analog circuits , page 52 It is logarithmic and the scale with a goes from zero in the middle via +/-1pA to +/-1 mA

And to my big shame, I read this book several times, that he also describes the multimeter way from Harvs,  :palm: but to my defence, he used it as part of an other schematic and I did not study itr because I have an electro meter for current.  :phew:
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Offline saturation

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #27 on: September 06, 2013, 08:18:12 pm »
You could make a poor man's differential voltmeter with just a good low noise and stable PSU, like the Power Designs precision supplies or the HP 6114/5a. 

http://www.fluke.com/fluke/usen/community/fluke-news-plus/ArticleCategories/DMMs/Take-the-Lead.htm

A problem with a snap on differential or high impedance front end for any DMM is even if made well, it won't change the inherent accuracy of the DMM.  So if one is measuring uV variations on a 10V scale, it takes at least a 6.5 digit DMM or better to make sensible readings off it. 

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 Saturation
 

Offline KedasProbe

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #28 on: September 07, 2013, 10:41:22 am »
I also played around with a 1.5V battery and my DM3068 and it's clearly the heat transfer that made it change in my case. I couldn't make it move when pressing hard with isolation between it but could easily make it drop with a slight touch and paper between it.

Even breathing above it made it drop. (that's what made me test it, since it changed when I got close to it)

But like in de video the AA battery doesn't recover easily. see picture below:

(if you wonder what caused the 'big' up spike, that's a frozen fry getting friendly with the battery  ;D )
« Last Edit: September 07, 2013, 10:59:10 am by KedasProbe »
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Offline PA4TIM

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #29 on: September 07, 2013, 12:01:58 pm »
Nice, test. Only strange thing is your voltage dropped ? Temp should make it go up. Or do i read it wrong, Seebeck effect can go up or down depending on the metals (if I remember well) So maybe it is thermal EMF of the connection to the battery.

This picture is a result from sunlight. around 8:00 pm (20:00 hour). The sun was going down a a faint light beam was shining through the window at the other side of the room and tought the table my battery was on. I saw it creeping over the battery. It was spring and around 15 degrees outside. So not something like the aussi sun power. But this little bit of light managed to  make a significant voltage jump.

« Last Edit: September 07, 2013, 12:04:02 pm by PA4TIM »
www.pa4tim.nl my collection measurement gear and experiments Also lots of info about network analyse
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Offline KedasProbe

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #30 on: September 07, 2013, 02:31:36 pm »
Yes it seem to be a thermoelectric effect (but not necessary only from the battery), we are in this 10µV range, I removed the battery and replaced it with a wire (on crocodile clips)
And I could reproduce the effect, by cooling one end it went up, by cooling the other end it went down, although one end was more sensitive than the other.

Not everything that counts can be measured. Not everything that can be measured counts.
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Offline thesgoat

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #31 on: September 09, 2013, 03:43:24 am »
These guys has managed to simulate a battery at the atomic level, interesting it seems to mimic very closely much what happens in a real battery.
http://arxiv.org/abs/1308.3424
 

Offline robrenz

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #32 on: September 15, 2013, 04:07:30 pm »
Finally found this pic I had of a 9V cell on high impedance mode on my 8846A. The meter is zeroed out on the 9V to get the high resolution variation over the 7hrs and 37mins. Total vertical scale is the 277.52µV.  What's up with the squiggles? :scared:  (No, its not the meter)

Edit: It helps to actually attach the picture :palm:
« Last Edit: September 15, 2013, 04:14:25 pm by robrenz »
 

Online IanB

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #33 on: September 15, 2013, 06:59:37 pm »
What's up with the squiggles?

Did you have any kind of heating or cooling system running at the time? You could be looking at the effect of ambient temperature cycles on the battery.
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Offline robrenz

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #34 on: September 15, 2013, 07:57:48 pm »
My shop is fairly temperature stable. A shorted input test for drift over 6 days on the 8846A in the same location is a min max span of 1.08µV. I can see daily cyclic external temperature influences as you can see the 2 humps in this 2 day (1 day 23-1/2 hr) trend plot but the total vertical scale here is only 716nV so the actual "centerline of the noise" hump height may be about 50nV.

« Last Edit: September 15, 2013, 08:12:01 pm by robrenz »
 

alm

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #35 on: September 15, 2013, 11:53:37 pm »
That's the tempco of the meter. The tempco of the battery will probably be much higher. Tracking the temperature in parallel to the output voltage would be useful. That's why you need a meter with a scanner option, or multiple multimeters. I think you need at least an many bench meters as precision power supplies ;).
 

Offline robrenz

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #36 on: September 16, 2013, 12:23:21 am »
I think you are right, thanks for that excellent advice as always alm  8)

Offline jh15

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #37 on: September 21, 2013, 05:06:03 am »
What advice, this?: "I think you need at least an many bench meters as precision power supplies ".

That's what you tell the wife when she says "don't you already have one of those?"
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Offline robrenz

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #38 on: September 21, 2013, 02:37:02 pm »
That's what you tell the wife when she says "don't you already have one of those?"

I use "You have way more purses and shoes than I have bench meters and power supplies, and most of my power supplies are cheaper than your purses or shoes"

Offline PA4TIM

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Re: EEVblog #515 - Battery Ionic Resistance Investigation
« Reply #39 on: September 21, 2013, 03:14:05 pm »
And if she does not approve you sneaky  pull a fuse from the TV an hour before the bold and the beautifull begins. Then make sure you are not finnished "repairing" it before the end of the program. And while struggeling to "repair" it, you complain a lot about your multimeter and that you had been ready on time if you had that multimeter.  :-DD
www.pa4tim.nl my collection measurement gear and experiments Also lots of info about network analyse
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