I am googling around for ultracapcitors/supercapacitors, and most pages want to sell me a prefab "power module" or "request a quote". Where is the best place to order unit quantities of ultracapacitors of various sizes for prototyping and general farting around with?
You need to go to component distributors. Most google seaches for ultracaps will return results for outfits selling upgrades for in car entertainment systems.
Graham
If you want the kind used for memory backup, try Mouser, Digikey etc. Maybe Jameco or some of the surplus places could have some too.
If you're looking for the kind that have more oomph, you'll probably have more trouble unless you get lucky with surplus.
Best regards, Spehro Pefhany
VCRs, tv sets, likely some digitally tuned AM/FM tuners or stereo receivers to keep the memory alive while the unit is off. Perhaps some other consumer electronic equipment that likewise has settings you want to keep when off.
I know I've found them in VCRs and tv sets.
If you're in the US, Solarbotics.com do some nice ones: 1Farad at
2.5volts.If, like me, you're in the UK, try Total Robotics:
Thanks. I finally found some on Digikey as well, searching on "capacitor" instead of "supercapacitor" or "ultracapacitor".
Does anyone know how much "excess" you need on the voltage rating? If I have a PV module that might provide 12V peak and a load that can run at significantly less than that (voltage regulators, etc.) then what voltage rating do I need on the ultracapacitor?
I am thinking I need about a Farad with a voltage rating of at least
15V; nothing seems to exist in that range. However, at least one manufacturer says that you can string their ultracapacitors in series to get higher voltages (at a lower capacitance, of course). If I were using the ones Tolstoy describes, I would have to put three in series to get a voltage rating of 16.5V and a capacitance of 1/3 of a Farad, then put three of those strings in parallel to get 1 Farad.Does anyone know if it is better to put them in series first or in parallel first? i.e.,
|-C-C-C-| |-C-| |-C-| |-C-|
--|-C-C-C-|-- vs. --|-C-|-|-C-|-|-C-|-- |-C-C-C-| |-C-| |-C-| |-C-|
I am thinking that the latter is more likely to yield uniform voltage across all of the caps. Either one is a nuisance.
snipped-for-privacy@nospam.com (Paul Ciszek) wrote in news:f3232m$f25$ snipped-for-privacy@reader2.panix.com:
I left off posting here till I knew whether you meant these, or the big oomphy things used in car sound systems...
Electric Double Layer caps, GoldCaps (Panasonic brand). I also had trouble once finding some on Digikey till I knew what type they were called by. Now they group those with the aerogel, super and ultra all in one link it's easier.
Regulate before the caps. I think you probably meant that but if not, you'll need to. Some kind of wide-ranging input DC-DC power converter..
Either will do, but I'd favour the second. I've used the 1F and 0.33F
2.5V types in parallel with a laser diode with no problems, the diode maintains a safe voltage of around 2.4, so you can operate close to limit. If you're wanting the full voltage, you might want to use the second network you drew, and across each set, a resistance. The value will have to be chosen by trial and error, I think, but each should be equal, to make sure the voltage is equally divided across the network. I think there is some internal DC leakage with these caps, and if it's unequal, you might get some capacitors seeing more voltage than others. If you omit the resistors, the connections in your second layout will be better, as they'll help to average out differences.
The cap's voltage rating needs at least to equal the peak voltage output.
Graham
Mouser stocks Powerstor Aerogel Supercaps from Cooper-Bussman, with less than 100mOhm esr.
Maxwell Technologies sells small quantities of supercaps in 'D' cell body sizes under the BCap or Boostcap trade name. These offer interestingly simple mechanical possibilities for retrofit.
RL
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