user7831: I am working with a ArduinoUNO - 2100 mA battery, and a solar Charger shield. I use a temperature reader that sends info every half hour with GPS-GSM shield called LONET (http://www.seeedstudio.com/wiki/LoNet_-_GSM/GPRS/GPS_Breakout for more info).
I want to save all the energy i can, i am trying to put Arduino UNO and LONET on Sleep mode.
LONE has its own mode via “AT+CSCLK=1”. 
But for Arduino UNO i haven seen a library called Narcoleptic (https://code.google.com/p/narcoleptic/ for more info) wich can solve the problem.
My question is:
Is there any other method that can help me to save Battery with Arduino uno? is it a good approach to use Narcoleptic or there is another method to do it?
Thanks for your time/help and sorry for my English.
Any feedback could be welcome.

user7631: There's a great article on that topic: https://www.openhomeautomation.net/arduino-battery/

user6740: There is an even greater article on this topic: http://www.gammon.com.au/power
It shows how to reduce your power usage for the Uno from about 50mA to 350nA (0.000350mA) - at this point, you need to factor in the natural drain of batteries.
Also, I have had good success with a project that was activated by a pushbutton, by using a latch - the push button turned the power on; once the power is on, it latched. Then the Arduino can switch itself off, using one of it's pins. As far as I can tell from a simulator, there is no leakage (while it is off, to within the accuracy of the simulator, assuming a perfectly spherical transistor in a vacuum ;) ). 
Just in case anyone is interested, my latch circuit can be seen at: http://i.imgur.com/sDvW4rd.png - the two resistors and the switch at the bottom represent the Arduino - +5V coming in the top, GND at the bottom, and one of the pin to switch it off is the switch - this pin should be INPUT to keep the power on; when you are ready to switch of, set it to output -> high. You should get switched off immediately. The switch at the top will switch it on. In the startup part of your sketch, set the pin to INPUT first.

7831: <p>I am working with a ArduinoUNO - 2100 mA battery, and a solar Charger shield. I use a temperature reader that sends info <strong>every half hour with GPS-GSM shield</strong> called LONET (<a href="http://www.seeedstudio.com/wiki/LoNet_-_GSM/GPRS/GPS_Breakout" rel="nofollow">http://www.seeedstudio.com/wiki/LoNet_-_GSM/GPRS/GPS_Breakout</a> for more info).</p>

<p>I want to save all the energy i can, i am trying to put Arduino UNO and LONET on Sleep mode.</p>

<p>LONE has its own mode via “AT+CSCLK=1”. </p>

<p>But for Arduino UNO i haven seen a library called Narcoleptic (<a href="https://code.google.com/p/narcoleptic/" rel="nofollow">https://code.google.com/p/narcoleptic/</a> for more info) wich can solve the problem.</p>

<p>My question is:</p>

<p>Is there any other method that can help me to save Battery with Arduino uno? is it a good approach to use Narcoleptic or there is another method to do it?</p>

<p>Thanks for your time/help and sorry for my English.</p>

<p>Any feedback could be welcome.</p>
 7631: <p>There's a great article on that topic: <a href="https://www.openhomeautomation.net/arduino-battery/" rel="nofollow">https://www.openhomeautomation.net/arduino-battery/</a></p>
 6740: <p>There is an even greater article on this topic: <a href="http://www.gammon.com.au/power" rel="nofollow noreferrer">http://www.gammon.com.au/power</a></p>

<p>It shows how to reduce your power usage for the Uno from about 50mA to 350nA (0.000350mA) - at this point, you need to factor in the natural drain of batteries.</p>

<p>Also, I have had good success with a project that was activated by a pushbutton, by using a latch - the push button turned the power on; once the power is on, it latched. Then the Arduino can switch itself off, using one of it's pins. As far as I can tell from a simulator, there is no leakage (while it is off, to within the accuracy of the simulator, assuming a perfectly spherical transistor in a vacuum ;) ). </p>

<p>Just in case anyone is interested, my latch circuit can be seen at: <a href="https://i.imgur.com/sDvW4rd.png" rel="nofollow noreferrer">http://i.imgur.com/sDvW4rd.png</a> - the two resistors and the switch at the bottom represent the Arduino - +5V coming in the top, GND at the bottom, and one of the pin to switch it off is the switch - this pin should be INPUT to keep the power on; when you are ready to switch of, set it to output -> high. You should get switched off immediately. The switch at the top will switch it on. In the startup part of your sketch, set the pin to INPUT first.</p>
