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Re: Powering the Sound Devices MP-2

Subject: Re: Powering the Sound Devices MP-2
From: Walter Knapp <>
Date: Mon, 09 Dec 2002 03:13:42 -0500
DeafinONEear wrote:
> Whoa! Thanks for the load of info! I wasn't expecting that.
>
>
> Walt wrote:
>
>>The only other issue is that if using NIMH, because their voltage is not=

>>dropping much, the power indicator light on the MP2 will be of little
>>use. When it warns you it's often only a minute or two until shutdown.
>>So you will have to figure out other ways to track how used up the
>>batteries are.
>
>
> I could just check the voltages on a multimeter before I go out. Simple.

Nope, won't tell much. The difference between nearly charged and 80%
discharged is 0.1 volt, and that's under load, the voltage recovers
some. I've tried doing that with mixed results. Mostly I work on
remembering how long since charged and if in doubt I charge. It also
helps that NIMH don't have a problem being charged at any time, unlike
NiCads. So, I normally just charge them before each time. And if on a
long trip periodically well before discharged using my car charging
setup (same chargers, different cords, or a small inverter for some).

Since I maintain my kit in ready to go condition year round, I have all
my spare batteries organized in small ziplocs with a little card slip in
them giving the charge date. From time to time I go through and
recharge. The remaining NiCads are almost always near dead in a week or
two and I mostly just charge them before a trip, they are always charged
using the discharge cycle first. The NIMH are still going pretty good
for 3-4 weeks or more. And the LiOn ones for my digital camera are good
for a couple months. I recharge the Telinga's internal NIMH battery
about once a month using a 9 volt rechargable battery to do that. (more
often if used)

In order to do this all easily, I have two sets of chargers, several in
each set. One set is plugged in inside, the other is the car set,
normally lives in the Ranger most of the time. I can charge quite a few
batteries at once. If I've not got everything charged in time to leave,
it just gets transferred to the car chargers and I leave, charging as I
go. Since I mostly record in the dark of night, batteries are a
important part of it all. The recording is not the big user, lights are.
Though I'm experimenting with using a LED setup in my dual brightness
headlamp for the low beam, and it's much less battery hungry than the
bulb was. I also use LED lights for lanterns when camping for the night.

I did send a note off to Sound Devices this evening suggesting a three
color power LED so as to indicate the discharged points for both NIMH
and Alkalines. It's fairly simple in concept. Don't know what problems
it would have in implementation. If the LED turned Yellow at 2.4 volts
that would be the 80% point with NIMH and time to gracefully change
batteries (and about 40-50% for alkalines), then keep the red as is to
indicate for alkalines (and for NIMH that would be the "you are now
dead" indicator). It would sure be nice to see that implemented, even if
I'd be stuck with a old one.

> One question I have is where can you get a sled? It looks like a great id=
ea
> to have a 4 or 6 C cell sled of rechargeables, and I could find a way to
> make a detachable wrap for it all, even if I have to sew.

Radio shack has some sizes. You can also get some here:
http://www.thomas-distributing.com/battery-holders.htm
And probably lots of other places.

It would probably also be possible to make your own depending on what
tools you have. I could probably make something pretty fancy with the
lathe and milling machine. But even slots in wood could be set up to
work. Main thing is to make sure it gets dependable contact.

If making up a permanent set the easy way is to wire it all up and then
shrink wrap it. You have to find a source for fairly large diameter
shrink wrap. And this will require you have a charger that can be hooked
to the pac as a whole. Or wire in charging leads.

If making a permanent pac you will probably want the cells with solder
tabs. The place above has some, and a internet search will find others.
And Ebay has a number of regular battery sellers.


Walt





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