ESP Low Power Sensor and Battery status

Hi again,
can i make Arduino low power sensor with arduino NANO 5v or i need Arduino Pro Mini 3.3?
If i cant (i've ordered 10 nano some weeks ago) i can use a 4pack AA battery.
Do you think that this battery can support ESP, arduino and for ex. BMP180? for days, months, or years ? (just to have an idea).

And , about BATTERY STATUS, how it works? i've seen it in my sensor... but how we can do it in esp sensors ?

Thanks a lot

Wait wait...ok for battery status, i wait it !

but don't understand exactely if easyiot library doesn't support power save what can i do... i suppose nothing !

Is it a good idea to try how many time stay an arduino nano with ESP8266 and bmp180 with 4 AA battery ? or its useless because can stay on just some days ?
I've seen in serial monitor that when esp is idle easyiot ping all time....

Dario


EDIT : Ok i've tested, a 9v battery goes down after just 1 day !!! Definitively closed !