LN2 capacitor testing

[TiN]

Lot of extreme people know about adding extra bulk capacitors for VGA's power convertors, and such. There are great guides online, like Shamino's one. But maybe not all understand why to add them, and which capacitors are good, which are bad for these works.

I'll describe this a bit more in this thread.

There are a lot of capacitor sizes and types manufactured today, and not expiriensed person can easily confuse,what cap to choose.



To make right decision even books was written by experts, but we only stop here on one exact ability of different capacitors to work on extreme low temperatures. Not warmer than 77K of boiling LN2. This is practical lesson, to get idea what happen to caps on frozen hardware.

So I choose cap caps to test



From left to right.

Rubycon MBZ 1000µF/6.3V ---- Nichicon 470µF/6.3V SMD ---- Sanyo OS-CON SVP 1200µF/4V SMD ---- Fujitsu 820µF/2.5V

Nichicon KZG 1500µF/6.3V ---- Nichicon KZE 1000µF/6.3V ---- Sanyo OS-CON SP 510µF/4V ---- Fujitsu 820µF/4V

Tantalum electrolyte caps from EPCOS.

All these caps are low-esr, very often can be found on switching DC-DC convertors, and widely used as good filter/charge store.

Those with caps with shiny metal cans not covered by plastic are solid polymer type, plus violet OS-CON and yellow Fuj too polymer. Most of cases you can see if cap polymer or usual liquid electrolyte, by presents of cuts on top. If top of cap can have cross or star cut - it's 90% liquid. Cuts are there to break hermetic can more easy if electrolyte boil in can due excessive load/voltage or temperature. This prevent cap from destructive explosion. Solid caps don't boil so their can top is flat usually.

Polymer caps better than liquid, have more stable characteristics, and usually much lower ESR, which mean that they can filter ripples better, and feed more current.

There is good basic presentation from Sanyo about their OS-CON's. - 1.1MB.

Pity that OS-CON's now used only in few computer parts (mainly only server hw now), coz greenpeace and such guys found their waste as harmful for environment.

So lets show begin.
I used few caps for test.

Test is simple. Hook up Fluke 87V DMM in capacity mode to cap and read value on ambient temp, and with cap submerged to LN.



Chineese generic axial cap 470u x 16V

Nominal:

Ambient temp photo

Capacity drop fast when cooling started

Light subzero

During cooldown it got malfunction, maybe shorten even. That's because liquid electrolyte in cap frozen.

Short occur deeper subzero

After further cooling, it recovered but almost with no capacity. 15nF is hundreds times less than nominal 535uF measured on ambient. So on LN temps it's just non-existant as capacitor

Cap lost all capacity in LN2

Chineese LowESR 470u 16V

All similar to previous. With same shorted issue.

Ambient temp photo
Same shorts
Lost all capacity in LN2

Sanyo LowESR generic 470u 6.3V

439uF ambient

Ambient temp photo

With frozing almost instantly got to few nF. Same no any use under LN.

No use for LN2

Sanyo OS-CON SP 510u 4V

Ambient 514uF

Ambient temp photo

Frozen...406uF

Dropped to 80% cap, and no worse. Usable!

Holded it for a min in boiling LN, but no less drop. Perfect use for us!

Tantalum smd cap 220u 10V

Ambient 228uF

Ambient temp photo

Frozen 210uF, almost no change

Looks good for LN temps

Ceramic SMD MLCC 10uF

No pics coz i holded it by probes and nobody put shutter
No matter still, it don't change it's cap.

Of course such "testing" don't show all effects present with extreme cold, but can show a bit more to us, even if we don't know ESR,ESL and real work changes.

Maybe later, if people would interest, i'll make special testing curcuit and PCB to test caps with subzero under load.

So now we have the answer, that putting on just any capacitor for modding is NO way to go. If use generic caps, you can ever damage power curcuitry badly.
That's why only good solid caps are best for extreme benching, they loose capacity and bit but doing well in general. Tantalum and ceramic small SMD caps are best, but they aren't much big capacity, so need to use very big amount of them to get sufficient filtering/power storage. (Don't look on Volterra, coz it switching on near 1 to 2.5MHz , this make ceramic enough for nominal use and moderate oc).

Updates, error reports, suggestions are always welcome.

[FatAlbert]

so much helpful information here

I think your Frankenstein G80 will be enough good do show how the capacitors work in very low temp.

[Shammy]

interesting info tin thanks!
what about Nichicon 470µF/6.3V?

[k|ngp|n]

Good stuff TiN Thanx for your contribution and time!

[TiN]

Will test more caps later then No ln2 left now.

Forgot to add later tests too.

Sanyo OS-CON SEPC axial 560uF 4V

495uF ambient.

Ambient

451uF in LN2, ok for extreme

Frozen SEPC

Yellow Fujitsu polymer (with cuts on top,btw), 820uF 4V axial

830uF ambient (no pic)

731uF in after 1 min LN2, ok for extreme

Frozen Fujitsu axial

[Expat GriZ]

Thanks for this!! Great info & testing. Now to find a shop in Belgium.....

[steponz]

Thanks Tin, Very helpful...

steponz

[carpo93]

very nice

[chispy]

Thank you TiN , very informative and useful info and explanation. Appreciated .


Regards: Angelo.

[Putittogether]

Thanks TiN. I learned something