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Re: [OM] [OT] Calling on the list's electrical engineers

Subject: Re: [OM] [OT] Calling on the list's electrical engineers
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Tue, 02 Dec 2008 20:43:32 -0500
Thanks, but it must be getting late.  I think you must have meant to say 
"alkaline" wherever you mentioned NiMH.

Chuck Norcutt

WayneS wrote:
> I have not read all the replies, but NiCad batteries can delivery very
> high currents compared to NiMh or other batteries. If used in a device
> that assumes limited current capability from the battery could be a
> problem.
> 
> Usually the circuits for electronics is regulated with switching regulators
> but the flash circuits may use a direct connection to the battery. Since 
> the flash voltage needs to generate high voltage, there is no reason to
> use a regulated supply, but simply go direct to the battery. The switching
> circuits of the flash charge pump probably assume a limited battery
> impedance. As such, in order to work with NiMh batteries, the circuits
> are optimized for higher battery resistance. If a low resistance battery
> is then used, the switching circuits could be damaged as they are not
> designed to handle the lower batter impedance and higher surge currents.
> 
> I won't go into the details, but simply put, the switching control circuits 
> are
> minimal in design and control in order to minimize cost.
> That is, the designer assumed NiMh and optimized cost for that battery.
> 
> Wayne - former Linear Tech analog designer.
> 
> 
> 
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