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'SCRs'
1998\10\27@160622 by Andy Kunz

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I asked this a few weeks ago, and got some excellent input, but I still
need more:

I need to discharge a large cap (4000uF charged to 100V) into a nicad cell
(1.2V 2000mAH) in a real short time (< 500mS if possible).

Anybody have any pointers?

Thanks.

Boy, this is strange asking for the help instead of giving it!

Andy

==================================================================
Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
==================================================================

1998\10\27@185024 by g.daniel.invent.design

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pointers:
mercury float switch (manual control), low E.S.R. capacitors, paralleled
capacitors, watch for ultra low resistance remote control power pack
batteries.
regards,
Graham D.

Andy Kunz wrote:
{Quote hidden}

1998\10\27@201346 by Dwayne Reid

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>I asked this a few weeks ago, and got some excellent input, but I still
>need more:
>
>I need to discharge a large cap (4000uF charged to 100V) into a nicad cell
>(1.2V 2000mAH) in a real short time (< 500mS if possible).

Hi there, Andy.  I'm assuming you already tried a (some) SCRs or triacs -
did they work or did they die?  How hard are you hitting the gate?

I regularily discharge 20,000 uF @ 35 Vdc into nicads using a stud mount 40A
triac from years ago.  I hit the gate with about 1 Amp to turn it on - no
failures in over 10 years.

I'd think that gate drive (or lack thereof) may be behind failures you may
have had.

dwayne


Dwayne Reid   <spam_OUTdwaynerTakeThisOuTspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(403) 489-3199 voice     (403) 487-6397 fax

1998\10\30@011828 by kypros.vassiliou

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Andy Kunz wrote:
>
> I asked this a few weeks ago, and got some excellent input, but I still
> need more:
>
> I need to discharge a large cap (4000uF charged to 100V) into a nicad cell
> (1.2V 2000mAH) in a real short time (< 500mS if possible).
>
> Anybody have any pointers?
>
> Thanks.
>
> Boy, this is strange asking for the help instead of giving it!
>
> Andy
>
> ==================================================================
> Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
> ==================================================================
Hi Andy,
I do that my self to break the fusible link (internal short) insite NiCd
batteries in order to make them usable again.
In my case everything is done manually, I discharge the capacitor via a
thick cable to the cell. It works fine.
I haven't read your previus messages but you are mentioning an SCR, I
believe you may need a large one due to the high discharged currents
(mayby a 20 or more amps SCR). Also the gate current needed to turn it
on must be high (I don't know the exact value).
So why don't you use a condactor (the type used to turn on electrical
appliances-motors etc.) It needs to drive its coil from a known source
only.

Regards
Kypros

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