I usea a voltage divider (simple resistor pair) to bring the max voltage within range of A/D. I then scale the reading from the A/D to the voltage and determine battery state from that.
Larry
> 
> From: "fred jones" <boattow@hotmail.com>
> Date: 2005/11/14 Mon PM 08:08:30 EST
> To: piclist@mit.edu
> Subject: [PIC] How to read Battery voltage with PIC
> 
> 
> Hi all,
> I'm sure this is an easy question for many of you so I hope I don't get 
> flamed.  I searched but can't find the answer in the archives although I'm 
> sure it must be there somewhere.  This is not my strong point so I thought 
> I'd ask for help.
> 
> I am building a device that will run off of a 12V gel cell battery.  It will 
> use a 16F877 PIC powered with a 7805 regulator.  I'd like to be able to read 
> the voltage of the gel cell and display it on the 2X16 LCD display.  I'm 
> sure I can't connect the 12V batter into the A2D of the PIC but I'm not sure 
> what the proper method would be.  Any help is appreciated.
> Thanks for your time,
> FJ
> 
> 
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