arduino on battery for long time use I have a small project with arduino UNO R3 + RTC clock DS3231, that control through a relay a electrovalve (12V). 

I would like to use the entire circuit on battery. 

The electrovalve (a small motor) has a consumption of 500mA and will be active 4 times a day for 15 second. 

I have a 7Ah battery, and I had calculated that my system will work only around 34 hours with it... is there any way to optimize circuit consumption ? 

Thanks for any suggestion !
You can turn off the entire Arduino and let it wake by your RTC. That way you can conserve a lot of power. (link)

Also you will have losses from the power regulator when powering the Arduino from 12V. You might consider using a Arduino Pro mini with 3.3V powered by two AA batteries. That should last for years.