Use this forum to chat about hardware specific topics for the ESP8266 (peripherals, memory, clocks, JTAG, programming)
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By dkdileep
#22385 Hi,
Hope my analysis will help those who are designing with batteries and to help choose the apt power supply.
Please see the attached waveforms for a better insight.
Peak current at startup: approx 320mA @3.3V, so your power supply must be able to handle this. I use a large cap (470uF SMD) as the peak only comes up periodically.

Normal operation with AP connected: 35mA average. Note the peaks of 290+mA during packet operations. Interesting point is that when AP is not connected there is a constant drain of 70mA. (wifi.stat.disconnect()), so I guess for better battery usage you better be connected to an AP :)

In wifi.ap mode the drain is significantly more: approx 80mA

In deep sleep (node.dsleep(xxx,nnn)) it is about 0.1 mA. During wake up the power usage goes bat-crazy, so keep your deep sleeps far between to counter wakeup drains. For deep sleep you must connect RST to GPIO16 + Pullup with 10K or else the module will not wake up. For ESP-V7 you can leave the GPIO0 and GPIO2 floating.

To summarize in my experience a typical 2500mA AAx3 will give you approx 30hours of continuous service. Obviously you do not want that, so the typical 59 minute deep sleep and 1 minute wakeup pattern of 50 minute will get you around 15-20 days

PS: Please note that I removed the red LED before doing the analysis saving me 5mA constant drain
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Last edited by dkdileep on Sat Jul 04, 2015 7:45 am, edited 1 time in total.
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By Eyal
#22401 1) 2xAA does not directly provide enough voltage. What is your power conditioning setup? What kind of batteries used (I assume NiMH)?
2) Are you measuring current at the battery or at the esp (assuming there is some regulation between the two)?
3) How about annotations on the x/y of the graphs?

cheers
User avatar
By tve
#22404 I posted a graph that shows the power consumption in more detail at http://jeelabs.org/book/1526f/
What I'm seeing all makes more or less sense to me. The real open question I have is how to convince the SDK to go into light-sleep mode (~1mA) and whether it's possible to use a UART interrupt to wake it up again...
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By dkdileep
#22419 @Eyal: Thanks for pointing it out. I have corrected my posts with proper annotations.
I also merged it for easier comparison. You're right. 2xAA is not enough for long term use, I used 3xAA alkaline for the actual project. With 2xAA Duracell, the node just about works (boots up, accepts some Lua commands). ESPV7 works even at 5V and it has been running for 30+days on 3 cells now.
I am using 470uF + 100nF at Vcc. I am measuring the current by measuring the voltage drop at Vcc using a 1-Ohm precision resistor. I ran a simple script that cycles through various modes.

@tve. Thanks for the excellent and detailed analytics on your site.

My question is. I am using NodeMCU 0.9.5 firmware. When the node is disconnected why is it consuming 70+mA. Does the default Lua interpreter do any background work? Are modem sleep states not implemented in the firmware?