David VanHorn wrote:
> I need about 10mJ energy storage, with a peak voltage of 16V, that can
> withstand some fairly high temperatures.
> ...
> I need something that works like an electrolytic, tolerates much wider
> temperature extremes, and costs roughly the same.

It's going to cost what it costs, but ceramic capacitors can have much wide=
r
operating temperatures.  10mJ at 16V is only 78uF.  You only need a few 20V
ceramics in parallel to get that.  This is so obvious it's hard to
understand what the problem is.

Of course your circuit has to deal with voltage varying depending on how
much energy is stored, but that is true with any capacitor.  Since you'd be
OK with electrolytics, this poses no additional restriction.

I just checked, and there are 22uF 25V ceramic caps in 1206 package
available for under $.30 each for a reel of 2000.  Five of those in paralle=
l
more than meets your spec.  These are rated from -55 to +85 degC, which
should cover "outside in a metal box".  You'll have a hard time finding
parts for the surrounding electronics to cover that range.


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