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Subject: Re: Reducing contact resistance for low volt use?
References: <email@example.com> <firstname.lastname@example.org> <email@example.com>
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Date: Wed, 11 Dec 2002 19:39:09 -0800
NNTP-Posting-Date: Wed, 11 Dec 2002 19:39:08 PST
On Wed, 11 Dec 2002 05:51:15 GMT, jmuchow@SPAMMENOTcamlight.com (John
>>>>Perhaps you could use an active discharge circuit or place a massive
>>>>power supply with current limiting in series with your cell. No need
>>>>to worry about contact and wire resistance. It's a great way to
>>>>reverse charge your cell, just like series connected cells. Beware of
>I may be misunderstanding you but the circuit I have will be active (I
>think). It's a constant-current discharger using linearly-biased
>MOSFETs as the load.
>Hmm...I don't know enough to understand how to use a power supply to
>sink 100A from the cell. If it's a way to avoid having to worry about
>contact and wire resistance, I'm all ears regarding any sources of
>Wait a sec...are you saying that I can place the cell in series with
>the output of a power supply (and thus increasing it's open circuit
>voltage by 1.2V and then shorting the series connected sources
>together? The 1.2V from the cell will discharge through the output
>stage of the power supply (if it can handle the heat)? Or should the
>cell be put in "backwards" so the cell's POS terminal is connected to
>the power supply's POS terminal?
>If the cell will not start reverse charging until it's completely
>discharged, that's OK. It will get so hot above 40A discharge current
>that we'll never be able to use for anything else anyway....a
>destructive test this definitely is. We have a box-withn-a-box test
>jug to hold the cell while discharging. To date, no cell has done
>more than just "pop" a little, with zero projectile electrolyte. But,
>we're not taking any chances. Thanks for the warning.
The dots are wire connections so they don't get confused with the
minus terminals. If you find a beastly power supply with adjustable
current limiting, the power supply will force your desired current
thru the battery and all those milliOhms of cabling and contacts. You
can find some really nice ATE power supplies on E-Bay for cheap. ATE
supplies have remote programming capability which makes this
relatively simple to connect to an PC data logging system. This is
what I meant by active - your load is basically a power supply. The
problem with this setup is it will reverse charge your cell, perhaps
utilizing your safety box.
Santa Barbara, CA
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