At 4:08 PM -0600 11/26/05, Allen Cobb wrote:
>FYI - Most 9V batteries I've dismantled contain 6 cells that are
>close (about 2mm shorter) to AAA cells.
Of course! Duh,..!$#! So maybe I wasn't too far off target with the
2/3's size AA NiMH's. Mike says we'd need to measure the current of
each cell to match them. Got a link for something cheap to measure
current? After that, I only feel confident about charging NiMh with a
MAHA charger so that could mean four, 12 volt (4 X 10 X 1.2) battery
packs. Mike or Allen, see any problem with using 4 packs serially?
Rob D.
>Of course, some 9V cases
>are more easily ripped open than others... Anyway, that might be
>an approach to getting a set of exactly 40 MATCHED cells in a
>custom sled of some kind.
>
>One can also fab a snap-holder that would allow 7, 6, or 5 9Vs
>to be added in as the voltage droops. With snap-on shorting
>strips, of course, as Mike suggests, for the empty snaps. NiMH
>are nominally 1.2V, but they reach 1.4 (or even 1.45) if very
>fully charged. This "overvoltage" phase is short-lived, and a
>small amount of usage drops them to 1.2 very quickly. Then they
>fade gracefully for a much longer period.
>
>This page has more info on HiMH batts than you probably wanted
>to know:
>
>http://www.thomas-distributing.com/nimhbattery-faq.htm#Question%
>20#1:
>
>
>ac
>
>Allen Cobb
>
>http://acobb.com
>http://shakespeare.acobb.com
>http://timbreproductions.com
>
>
>-----Original Message-----
>From:
> Behalf Of Rob
>Danielson
>Sent: Saturday, November 26, 2005 1:26 PM
>To:
>Subject: Re: [Nature Recordists] DIY 5X9v bat phantom supply
>(was low
>voltage DC phantom
>
>
>At 11:46 AM -0600 11/26/05, Mike Feldman wrote:
>>Rob Danielson:
>>
>>> ... I'll try to pull the collective insights together...
>>
>>I bought a bunch of the 9v battery connectors and
>>hotglued 6 of them into a housing and wired them
>>in series. 5 alkalines and another shorted connecter
>>give you adequate voltage when the batts are fresh.
>>Six connectors lets you use NiMh rechargables that
>>don't generate full voltage.
>>
>>You'll want a good battery tester that actually
>>draws some current (not just a voltmeter) to weed
>>out the weak cells. One cell going bad renders
>>the other 4 or 5 useless.
>>
>>-- Mike
>>
>
>Thanks for this suggestion! I'll up the ante to 6. I'm sending
>you
>and Allen the draft for comments if you like.
>
>The Rolls has a 12 volt external jack so its easy to get around
>pockets full of 9 volt recharge bats (which are not cheap). The
>Rolls has not failed me so the goal for me would be proving that
>the
>battery design produces less noise and then onto the powering
>options. Did your "pure" bat phantom seem to work well/quietly?
>
>I'd like any "pure" battery version to run for at least 12
>hours. I
>bought a bunch of 2/3 size AA's to make a large sled of many
>smaller
>voltage cells to supply ample current, but I didn't stop to
>think how
>I would re-charge such a high voltage pack. Awkward and more
>expense
>to break it into 4 packs for charging.
>
>If Klas's friend's unit provides stable,clean power on 1-9 volt
>battery, likely one could parallel several 9volt cells. Starting
>to
>seem more like a bargain at $250. Rob D.
>
>
>
>
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>"Microphones are not ears,
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>Klas Strandberg
>Yahoo! Groups Links
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>
>
>
>
>
>
>
>
>
>
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
>
--
Rob Danielson
Film Department
University of Wisconsin-Milwaukee
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