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Re: Powering the Sound Devices MP-2

Subject: Re: Powering the Sound Devices MP-2
From: Walter Knapp <>
Date: Wed, 11 Dec 2002 01:07:30 -0500
Lang Elliott wrote:
> Walt:
> 
> here's the description of the new RayoVac charger:
> 
> http://www.rayovac.com/products/recharge/recharge.shtml

That's not at all like the older one I have, more closely resembles my 
current chargers.

If it's truly charging at the 1C rate, some NIMH are not rated for that 
fast a charge, though most of the newer generation ones are. Expect 
battery temps in the order of 45 degrees centigrade, maybe higher. The 
charge will also not be as complete as slower charges. It will be 
pumping in nearly two amps into a cell to make it in a hour. The cell 
will probably come out too hot to hold. I'll be interested to hear what 
you find.

My older Maha chargers take about 2-3 hours to charge, though that's the 
fast part, it will indicate charged, but a little more can be put in, it 
then switches to trickle charging to finish the last 5% or so of the 
charge. To be absolutely, completely charged takes 3-5 hours total 
depending on the residual charge the battery had. The new one has a 
switch. You can go 1 hour or 4 hours. Four hours will give much better 
battery life than 1 hour. The new Maha has a microprocessor controlled 
pulse system for fast charging that breaks up the gas that forms at the 
plates during fast charge so it gets closer to full charge, and at lower 
temps. It also then switches to trickle. It's unclear if the rayovac is 
doing the same. So many of these chargers have the same thing inside, it 
might. Though the fact it's designed to charge the rechargable alkalines 
would indicate not.

I've never found a need for really fast charging, and have my new 
chargers set on the 4 hour setting. That will give me a longer battery 
life. The two hour fast charge was warm enough. Though with the pulse 
charging the one hour is not that much hotter. The four hour pulse 
charge hardly warms the batteries.

In fact I mostly charge the Portadisc's batteries with it's internal 
charger, which is much slower. I've had no problem keeping up with my 
recording rate.

Walt






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