Re: I am about to add an LED to a charger but need further opinions.

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#473

From: alitonto
Date: Wed, 15 Mar 2006 11:46

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Just to add further:  the battery pack consists of 5 NiMh AA batteries
and the actual charger is just a wall plug with 9 volts dc at .500 mA
max. The batteries are inside a torch and I am wanting to add this LED
circuit inside the torch with a simple diagram.
Will the voltage across the resistor/LED combinatiion adjust itself to
be equal to the voltage across the resistor in paralell for when the
batteries are really flat and therefore higher current will be flowing?
Ali

Pete wrote:
> Ol' Duffer wrote:
>
> >> I have seen some chargers that have the dropping resistor and LED in
> >> series  with each other and then this combination is in parallel with
> >> another resistor of lower ohms which goes to the battery pack
>
> What I've often seen done is a string of three series diodes in the
> output lead with a LED and series resistor in parallel with the diode
> string.  Just make sure that the diodes can handle the maximum charger
> current.
>
> > Some of the makers who have done this have had trouble with
> > blowing out the LED's.  Consider what happens when you plug
> > in a dead battery, or maybe even worse a bad one that happens
> > to be shorted...
>
> Since a nicad charger is supposed to be constant current, I can't see
> that being a problem unless whoever "designed" it didn't know what they
> were doing...
> 
> Peter

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From: "alitonto" <alitonto@hotmail.com>
Newsgroups: sci.electronics.repair,aus.electronics
Subject: Re: I am about to add an LED to a charger but need further opinions.
Date: 15 Mar 2006 03:46:58 -0800
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