# ESP deep sleep battery math

Hi all, hoping you guys can help me guess my way through this.

I'm trying to calculate how long I expect a 18650 battery will last when powering my ESP8266 if I'm putting it into deep sleep for 10 seconds, then waking it to do a WiFi scan, then putting it back to sleep for 10 seconds, etc.

According to the technical docs, ESP8266 deep sleep draws 20 microamps, and the 18650 battery I'll be using advertises that it has a capacity of 2500 mah. What I can't seem to find good documentation on is how much juice a single scan of the nearby SSIDs will consume. Anyone have any experience or know something I don't here? How long can I expect this battery to stay afloat?

Thanks!
Matt

20uA? I doubt that. My Wemos Mini draw about 170uA in deep sleep. They are not as efficient as a bare esp module, but even if the bare module draws half that, that is still ~80uA.

My weather station runs for around 12weeks on a 4,200mAh 2,600mAh 18650 Li-ion battery. It only wakes every 15 mins for around 5~10 second and draws around 80mA when awake and around 500uA when asleep. An ATtiny85 monitors the wind & rain sensors when the esp is in deep sleep. The esp in deep sleep + ATtiny awake use around 500uA.

Not sure if the 20 microamps is realistic or not, pulling that from table 1-1 here:

Follow-up question (exposing my ignorance here): how is everyone finding out how much their controllers are drawing during operation? Then I could do some real world tests to see how much the bare unit takes during a WiFi scan.

Do you have a multimeter ?

You should do, then you could measure how much current your 'ESP8266' and the bits you have connected actually consume.

Datasheets might give you an indication as to what to expect, but if you really want to know how long the battery will last, you need to be using that multimeter to do real world measurements.

This is how you post a link on this forum.