The battery shield on top of Arduino UNO
With just a battery shield, your Arduino goes portable by using batteries for power. Of course you can connect your Arduino directly to a battery using a battery clip and 2.1mm power plug, but open-electronics user Boris Landoni shows us how you can use a battery shield to power the Arduino and how to optimize the energy consumption. The optimization is a process that optimizes the power consumption without violating the performance of the board.
A part of the tutorial covers a software technique that limited the main clock frequency. This method, part of the optimization process, is not enough to optimize the power supply, but it can decrease in some cases the power consumption.
The shield used to supply with power the Arduino support a voltage input range of 5 to 12 V. Two important particular features of the shield are the clock and calendar; both features allow you to power the Arduino at fixed intervals, how long to stay on and when to turn off the power.
That said, this battery shield is good enough to optimize the power consumption, but at the same time it increases the cost of your project with up to 16 EUR ($20 USD).