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Re: Powering the Sound Devices MP-2

Subject: Re: Powering the Sound Devices MP-2
From: Walter Knapp <>
Date: Sun, 08 Dec 2002 22:33:25 -0500
DeafinONEear wrote:
> wow. I had no idea they ran that hot! I have actually had the MP-2 die at
> the near end of a 3 hour session using two 451's and two new AA's. I
> believe that two NSS workshops ago, I was using Dan's MP-2 and it too was
> going low on power with the AA pair. I'm not going to be using this out i=
n
> the woods, this is purely for location recording in chuches, theater, etc
> where the pre isn't near any outlet, so weight really isn't going to be a
> concern of mine-- I'm strictly going for longevity.
> My concern for using some of those suggestions you listed are about
> charging. I have no way to charge an RC pack, I can't seems to find a NIM=
H
> charger for less that $100 (or is that lithium) and it seems that a pack
> with 5 C's in it is going to be about the same bulk/weight as a lantern
> battery. And how would you charge those puppies?=20

The NIMH I'm using are much more capacity than alkalines, I'd estimate
double or so but it's not clear as the Alkaline manufacturers don't
provide capacity ratings. And they are not the highest capacity. There
are some 2000mAh NIMH AA's available. You can get discharge curves for
the alkalines at http://www.duracell.com/  for their brand. Those curves
show that Alkalines drop rapidly in voltage as they discharge. NIMH hold
near full voltage through over 80% of their charge. I'm working on
trying to use the AA's as I carry them anyway, and want the load to be
lighter. I also try to always avoid disposables.

The RC car ones are the easiest to find chargers, almost any hobby shop.
Though the NIMH versions of those batteries are fairly new. The very
high speed chargers the hobby folks use are fairly expensive, lower
speed fast chargers are not as bad. And they are easier on the
batteries. The biggest cap RC flat pacs are something like 3000mAh.
There are 7.2 volts standard or some 8.4 volt pacs. It's a attractive
choice because of availability.

The 5 C pac is on Ebay as a discontinued item, originally designed for
railroad lanterns of some kind that were discontinued. The cells inside
are standard ones and new, but they don't want to bother taking the pacs
apart, so lots of them are being auctioned. For me I'd charge that one
with my Maha MH-C777plus charger. That's a fancy charger with metering
for evaluating the battery's condition. It's also a universal and can
charge a very wide range of batteries. Handles Nicad, NIMH, or lithium
from 1 cell up to 12. I paid about $80, the version without all the
bells and whistles is less. If you are charging AA's there are lots of
excellent choices for much less. I use the Maha MH-C240F older model and
recently got a couple of the latest MH-C401FS chargers. They do a pulsed
charge system that heats the batteries less, and will charge 1 - 4
cells. The older charger the minimum is two cells.

Running off a battery holder using AA's would be the easiest for
charging. Since you could use one of the AA chargers. The ones I use
will all work off a car battery as well as plugin.

The 5C pac is 2.5 x 2.5 x 2 inches, 14 oz. I grabbed a couple of them
off auction thinking of using them with the MP2 if I decide to use a big
pac. Otherwise they will probably power a playback amp I'm working on.
They have not yet arrived, so I can't describe them much more. There are
all kinds of configurations, basically all they do is take some tabbed
cells and string them together and shrink wrap them to make a pac. And
there are all kinds of cell sizes. If I use those pacs for the MP2, I'll
probably open them up and reconfigure them as 6 C's. I have the Porta
Brace case for the MP2, and the battery section of that is for a NP1
video camera Nicad pac. The chunk pac would probably not fit. A 6C pac
with two rows would be about 6 x 2 x 1 inches and would fit. And it
would be a 7.2volt 4000 mAh.

Walt




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