ESP8266 Community Forum

- Tue Jan 13, 2015 1:26 pm #7212 Yes, your calculation are correct. I am sure that the idle comsumption can be optimized further - right now I am quite busy but I plan to check if some floating pins (inputs) could add to the consumption.
Another test would be to pass the power supply of the SPI flash through a jumper or switch, and then to bring the module in deep sleep, turn the switch off (or unplug the jumper). At this point I can separate measure the SPI flash consumption and the ESP8266 consumption.
Without proper documentation we have to be prepared that those chinese modules might have some leakage somewhere.
Another good test will be to measure how the chip consumption in active mode is affected when CPU is clocked to 160MHz.

- Tue Jan 13, 2015 2:37 pm #7218 Keep in mind also that your battery will have a self discharge current... dependent on battery technology, temperature and remaining capacity. I believe 50 uA is normal for a LiPo, much worse for LiMH and NiCd.

- Tue Jan 13, 2015 4:11 pm #7225 You are right, this is important point to keep in mind. My plans are to use non-rechargable batteries, here is my list of preffered ones:
- CR123A
- lithium AA variants (15-20 years shelf life, > 2500mAh)
- SAFT batteries (if I convince myself about the price)
- and why not "regular" alkaline - like energizer max, with 10 years shelf life?

Rechargable batteries that have low enough self discharge are rare. Currently I don't see a good use case of them.

Another thing to keep in mind is the filtering capacitor - electrolitic (Al) might get higher leakage than the ESP idle current (at some extreme temperatures).

But I logged in to give some results from my tests of the current consumption. My setup uses 5V/3.3V switching DC/DC supply (chinese one with MP1584 chip) to feed the ESP module from Olimex.
In line with the 3.3V I put parallel group of one resistor (1K) and one shottky diode. The purpose of the 1K is to allow me to measure the ESP idle consumption, it gives me easy way to read out values down to 1uA with generic multimeter. The purpose of the shottky diode is to bypass large current spikes that appear while ESP is active.
This seems to work fine for deep sleep measurement, but it is not suitable for active currents ( > 1mA, 70-150mA typical).

The results: first trials were made with 1000uF capacitor on the supply pins of the ESP (after the measurement group). This way I got 150-160mV readings that corresponds to 150-160uA. I think that slow ramp down of the supply voltage tricks the ESP to behave bad and leads to this high readings.

Update: too good to be true ... when I disconnected the usb-uart converter my consumption climbed to 40uA, steady. Not happy.
.

- Tue Jan 13, 2015 6:30 pm #7243

Rechargable batteries that have low enough self discharge are rare. Currently I don't see a good use case of them.

If the consumption is around the 200uA mark - even if deep sleep were 1uA then this would still only drop to ~150uA - any device needs to plan to get recharged rarely. At 200uA a pair of AA's with 2800mAh capacity would last 2800/.2=14000h!! that's nearly 2 years!!

So I'm probably making another late night maths error - but if not - then I think low self-discharge rechargeables would be useful in this case.

Is it the enerloop type that you are referring to as low self discharge rechargeable type? They are quite expensive ....