Rafael Vidal Aroca wrote:
>     i'm playing with these great ZigBee modules from Maxstream (XBEE). 
> They are really interesting and powerful..
> 
>     My problem is related to battery life.

1. Are you sure the XBee is in deep sleep, not... whatever they call it, 
shallow sleep?  (Don't have the data sheet in front of me.)

2. If your alkaline batteries are putting out anything over 3.0 V, note 
that the XBee increases its current usage rapidly as you go over 3.0 V. 
  3.0 is great, 3.15 is not good; 3.3 is right out.

>     Some engineers suggested me 9v batteries with a voltage regulator.
> 
>     Is it a good idea? Won't i loose too much in the voltage conversion 
> (9-3=6v). At 50mA i'll spend 300mW just to drop the voltage???

Yeah, a linear regulator on a 9V will have a theoretical maximum 
efficiency of 33%.  Not great.

Your best bet is to use a switcher, but of course that's not a simple 
solution.

Maybe 3xAA = 4.5V nominal with a 3.0V linear regulator wouldn't be too bad.
-- 
Timothy J. Weber
http://timothyweber.org
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