FYI - Most 9V batteries I've dismantled contain 6 cells that are
close (about 2mm shorter) to AAA cells. 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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