EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: UZZ32 on July 15, 2015, 12:39:21 am
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G'day Lads.
I've been doing a lot of capacitor replacement in various modules in my car from the ECU, Wiper control, to the stereo units, literally 100s of caps have been replaced.
I've been using a mixture of Panasonic FM, FC, SU, ADX caps and Nichicon, PW, PM, ST, EP, ES, FG, PA capacitors as well as a few Rubycon YXFs.
However recently while comparing spec sheets, I saw the panasonic FM cap is stated as "not applicable for automotive use" It's quite a vague statement. Yet the similar FC cap doesn't state such.
http://industrial.panasonic.com/lecs/www-data/pdf/ABA0000/ABA0000CE108.pdf (http://industrial.panasonic.com/lecs/www-data/pdf/ABA0000/ABA0000CE108.pdf)
Can anyone share their thoughts on this?
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Panasonic FM has an aqueous electrolyte (same with Panasonic FR), FC doesn't, it uses a different electrolyte solution.
That may explain why FM and FR aren't advertised for automotive use, maybe the electrolyte doesn't like large deviations in temperature. Or maybe Panasonic just didn't bother to certify them, run the tests, pay for the approvals etc?
ps.
FC temp range –55 °C to +105 °C
FM/FR temp range –40 °C to +105 °C
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Interesting note about the electrolyte. Thanks for that!
I had assumed it was to do with the possible temperature changes a car can experience.
All the caps I've been working with are in the interior or boot so avoid the extremes of engine bay heat which is what their statement could be referring too.
I'm down in New Zealand so at worst the cars exposed to 0 degrees Celsius to a typical 10-25 degree ambient temperature and possibly a peak of 35-50 in summer if left outside in the sun but that's quite rare.
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Two obvious differences shown on the FM and FC datasheets:
- FC is "AEC-Q200 qualified" (a quick search shows that AEC-Q200 is an automotive industry standard)
- FC is certified to a lower temperature - colder than any of my cars have ever been exposed to
(FC datasheet is here (http://industrial.panasonic.com/lecs/www-data/pdf/ABA0000/ABA0000CE22.pdf))
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Ah ha!
Thanks for the clarification Len. I didn't even think to google that standard. :palm:
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I'm down in New Zealand so at worst the cars exposed to 0 degrees Celsius...
Clearly you don't live in Timaru... ;D
(https://www.eevblog.com/forum/projects/panasonic-'fm'-capacitors-not-for-automotive-use/?action=dlattach;attach=161093;image)
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Heh, nope! Soft Aucklander here.
Got some frost the other morning, nasty.
So with the caps, I guess the FMs are stated as not applicable because they aren't tested??
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Consider also modern designers allow for very little voltage headroom as a standard practice these days. :palm:
Then take this knowledge to application: the spikes and nasties, don't forget the voltage fluctuations from auto charging systems will put industry standard 16 V caps at risk. Too little headroom.
So if you are consevative on voltage selection and stick with 25 V or higher caps there should be no problem.
Rule of thumb from Govt deparment designers from years ago: subject no component to more than 62% of any of its ratings, electrical, mechanical etc.
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Valid points.
Ive ended up doing just that in certain systems because of the lack of availability of lower caps so ended up going 25v+
Fortunately this 1991 Toyota Soarer was the high point of engineering back then so I'm sure they would have decent tolerances in the electrical designs. All of the components are Panasonic, Denso and Toshiba. Everything still works, apart from those with bad caps, change them and its like new again.