Re: Highest energy cap that's available in hobby volumes .. maybe a few hundred pieces

On 29 Jun 2006 08:21:06 -0700, fpga_toys@xxxxxxxxx wrote:


Paul E. Schoen wrote:
Maxwell has BCAP1200-E270 which is 1200 farads at 2.7 VDC, for about $45.40
in quantity of 1 to 99. That's 4374 joules. A bank of 27 in series will
provide 33 farads at 72 VDC, which is enough energy to absorb (or supply)
13 kW for 5 seconds (for EV acceleration and braking) at a cost of $1226.
Still not a replacement for batteries, but perfect for high current surges.
These ultracaps (BoostCaps) have an ESR of only 0.8 uOhms and peak current
of 3750 amps. They are about 3" long and 2.5" dia, and weigh about 3/4 lb.
I received this quote recently.

Check www.maxwell.com for more info. They have 650 to 2600 farads in this
series.

I sent the Maxwell sales link a request for price and availabilty in
hundreds a little over a month ago, and never got a response. Did a
distributor respond with that quote?

I've since been looking at surplus high voltage caps in the fractional
farad range that are also kilojoule, but are about the same cost and
volume. The only advantage is that they can be connected in parallel,
and not have to worry about the balancing voltage divider.

A big array of series/parallel electrolytics, like photoflash caps,
doesn't need equalizing resistors. Electrolytic leakage is nonlinear
enough to balance the voltages nicely. 'lytics don't fail suddenly
like film caps, they just start leaking more.

Check the surplus houses for electrolytic, film, and oil-filled caps.
Cost per joule will be a fraction of new stuff. Around a few
kilojoules, things start to get interesting.

John

.

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