I've got an application where the environment provides infrequent,randomly-spaced bursts of intense power (think 20V at 300A or more,for 25ms every minute or two), that I'd like to store in a gel-cell topower my device. The average power available from the source is wayway more than the continuous load requirements of my device, but thedesign of a charger circuit to exploit this energy source is notsomething often encountered. Simply putting a linear regulator on thesource and letting it deliver a couple of amps (safe charging current)into my battery won't cut it; I need to capture more of the energy ineach burst and trickle it out to the battery, basically extending theduty cycle at lower current.Searching for circuits that allow the use of intermittent energysources (solar, wave, etc) finds me a lot of things like peak powertrackers, circuits to prevent reverse voltage into unilluminated PVcells, etc. Not really what I'm looking for.I'm thinking vaguely of a bank of low-leakage supercaps charged fromthe environmental input, with some kind of clamping to prevent themfrom being overcharged, powering a switch-mode charger to deliver anamp or two into the [fully discharged] battery, more or lesscontinuously.This is in the nature of a back-of-the-envelope thought processthough. Has anyone encountered a similar situation? Am I missing areally obvious solution?

Farad level caps are probably your best bet.I found they have got quite a bit cheaper/more available,and with tens of milli ohm impedance.-jg

"Pulse" gel-cell charge strategy?

Nov 26, 2009 29 Replies

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larwe 16 years ago

There's nothing wrong with that plan, except that it involves many more moving parts

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lowcost 16 years ago

larwe ha scritto:

why not a peltier cell, heated by a small single flame burner ?

regards

lowcost

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larwe 16 years ago

Because the burner requires fairly precise gas flow control and has a strong potential of becoming clogged and corroded. The explosive method is little more than a funnel turned upside-down, with a spark plug at the narrow end of the cone.

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Mark Borgerson 16 years ago

Certainly true. However, you can replace a lot of generators for the cost of the copper in a system that has to collect the=20 energy in a few milliseconds.

Mark Borgerson

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Mark Borgerson 16 years ago

Is the range of combustible mixtures wide enough to guarantee ignition, or do you have to monitor the fuel/air mixture?

Mark Borgerson

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larwe 16 years ago

I think I said above someplace - no it is certainly not guaranteed. If it fails, we try again.

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Meindert Sprang 16 years ago

Lewin,

I just came across some interesting supercaps from Wima available up to

400F/2.5V. They store 1250J and the pulse current may be 600A. They can be connected in series. Datasheet here:

formatting link

Meindert

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invalid 16 years ago

What was known in the trade as an FGC.

GC = Great Capacitor. F = unprintable

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Paul Carpenter 16 years ago

Aka a BMF capacitor

BM = Big Mother F = ....

Paul Carpenter | paul@pcserviceselectronics.co.uk PC Services Timing Diagram Font GNU H8 - compiler & Renesas H8/H8S/H8 Tiny For those web sites you hate

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larwe 16 years ago

And here is a real BMF complete with Ms.

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