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RE: Typical battery size in terms of maH capacity

Chris,

I suspect this is down to the type of voltage regulation you're using.  If it's a linear regulator, you're lucky to be getting 30 seconds - most linear regulators need ~7 volts input minimum to be able to provide 5 v out.  This covers voltage drops across the regulators transistors.  If it's a switching regulator, the minimum input voltage depends upon the design but again the most common types need 7 v or above.  If you're not using a regulator, then you're lucky not to have blown a component.

The easiest solution is to get a battery pack with a higher voltage output although with linear regulators you will "lose" the power associated with any excess voltage above 7 v as waste heat.  A switching regulator should be much more efficient at handling higher voltages and will run cooler as well.

Note that it's possible to put your batteries in series and so get 12v nominal input but get knowledgeable advice before doing this - I think there are some risks associated with putting unmatched cells in series.

Regards,

Philip

> -----Original Message-----
> From:	Pubnix Net Axess [SMTP:]
> Sent:	Tuesday, July 04, 2000 6:01 AM
> To:	
> Subject:	Typical battery size in terms of maH capacity
> 
> 
> Hello, I am building a fairly typical setup, 
> Jumptec LCD6/166/128 ram 
> 3.2 gig laptop drive
> Keyboard
> Twiddler
> M1 (right now, but I will be replacing it b/c frankly I think it is awful)
> Plan to add other things as well.
> 
> Was wondering what type of batter capacity most of you have. I've wired
> two Rat Shack 6v 1800 maH NiMH camcorder batteries (in paralell) and find
> that it will power the rig on only for ~ 30 seconds then power off and
> cycle. (works fine w/ a PC PS, the batteries test out ok with a Multi
> Meter)
> 
> -chris
> 
> 
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