AVR-Chat

> -----Original Message-----
> From: Dave VanHorn [mailto:dvanhorn@cedar.net] 
> Sent: Friday, 23 January 2004 9:53 PM
> To: AVR-Chat@yahoogroups.com; AVR CHAT YAHOO
> Subject: Re: [AVR-Chat] NICAD charging cheap and long term.
> 
> 
> At 09:28 PM 1/23/2004 +0800, Kathy Quinlan wrote:
> >Hi All,
> >
> >Need some ideas on charging nicads to get the most life out 
> of them in 
> >low duty cycle pulsed current load and as long life as possible
> >
> >Situation is similar to a smoke alarm.
> >
> >Any ideas ?
> 
> Not the best suited battery for this app.  Lead acid, with the input 
> voltage set to their float spec, are probably best for long 
> term float.

I know, but trying to get a SLA of small enough capacity is hard, we are
talking of the highest load being a pizo sounder IE 50mA max and even
then it will have a duty cycle like 0.25 seconds on 10 seconds off. And
it is designed never to run ;o) only in emergencies (no a life support
or life protection so no need to worry about run durations etc) I would
say if it would run possibly for 4 hours on something like 3 AAA nicads.


> Other than that, keep the nicads charged with <0.1C maybe 
> 0.01C if their 
> delf-discharge spec says you'll be energy positive.

Yeah that is what I was planing, a perminate resistor set at 0.01C
(aprox need to read up on the specs of batteries we use) and then a fet
and lower resistor to do a charge when battery is flat and AC is on.

Regards,

Kat.

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