[Farmnet] Power supply, ultracaps, etc

Mike O'Dell mo at ccr.org
Sat Oct 7 21:07:57 CDT 2006

i'm actually a bit surprised by the aggressiveness of
the GammaPS design. the switcher seems smaller than
necessary to make the size target - that's only 60 watts.
one can get more watts in the same size package
and that would cause less strain for long
key-down cycles. but the design does reflect current
trends in power system design - combining technologies
to deal with bursty loads. this is particularly important
in cellphones, especially GSM phones given the power
demands of the air interface.

the ultracap space is pretty interesting these days.
the gold standard is Maxwell. they have the highest-performance
ultracaps of any product currently shipping. there is
better technology in various labs but it's not ready
for prime time.

given that almost all of the efficiency improvement in current
hybrid vehicles comes from regenerative braking,
ultracaps play a big role in their design and those
requirements are driving most of ultracap development.
there's a spec that was created by automakers giving
their "dream specs" for ultracaps to use in hybrids.
the energy recovered by regen-braking is stored in the
ultracaps and that is re-used to accelerate the vehicle
again.  beats the heck outa heating brake rotors just
for sport.

at the moment, none of the shipping products hit those
numbers (by a considerable margin in most figures of
merit), but they are the targets people are shooting for.

there's a credible rumor that BMW will be introducing
a hybrid version of the X5 SAV which completely foregos
batteries and does the energy storage completely with
ultracaps.  if this is true, it will be interesting
to see how it does in the market.

the wild-card in all this is the company "EEStor" in Austin.
they claim to have a storage device which will hold enough
energy to run a (small) car 500 miles and recharge in
only 5 minutes.  they have been incredibly tight-lipped
about what they are doing but it is known they are using
barium titanate ceramics of some kind. i've heard various
stories about device geometry and i don't know what to believe.

the issue is that if you do the sums, the amount of energy
they claim to store strains credulity. the overall energy
density (coulombs per liter of volume) and the electric
field strength that would have to exist just boggle the mind.
if it could recharge as fast as they claim, the internal
resistance has to be almost vanishing, so
if the thing ever developed an internal short,
it's hard to see how it could avoid being an electron bomb.
but time will tell. if they do pull it off, though,
it will be world-altering.


"If the power LED goes out in less than 10 seconds after
  hitting the power switch, the filter caps are too small."

A. Maitland Bottoms wrote:
> The item I brought to Tacos is an
> HPS-1a Gamma Hybrid Communications Power Supply
> http://www.gammaresearch.net/
> I've also been playing the peak/average power
> supply game using the PWRgate:
> http://westmountainradio.com/pg40l.htm
> which also seems to allow the use of a beefier
> transmitter with a smaller power supply.
> Lawrence Stoskopf writes:
>  > The Gamma Power supply works well so far.  I popped the top and checked out
>  > the caps:  NessCap 2.7v @ 25 F.  Five in series.  Forgot to look under the
>  > board to check out the voltage equalizing resistors.  Fan runs for 4 minutes
>  > at least after the AC is cut.  Switcher is standard small 5 amp sized.
> http://www.nesscap.com/products_edlc.htm
> scroll down for interesting notes...
> -Maitland
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> Tacos at amrad.org
> http://www.amrad.org/mailman/listinfo/tacos

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