I have a Wemos D1 Mini ESP8266 module which I'm trying to run from a 2400 mAh Li-Po battery through a MT3608 boost module. The wiring is simple:
Li-Po positive and negative to VIN+ and VIN- of MT3608 respectively;
VOUT+ to ESP 5V, VOUT- to ESP GND.
I also hooked up a multimeter in series to measure the current:
As you can see, when I switch on the setup, my ESP draws 144 mA, and does not boot. For reference, it should be drawing around 70 mA. Battery is properly charged. MT3608 is set to output 5V.
Now, this is where it gets interesting. If I replace the Li Po with NiHm battery pack, suddenly the ESP boots perfectly! No issues whatsoever. But I need it to run from Li Po.
So I tried swapping this 2400 mAh Li Po to 2800 mAh and even 10,000 mAh (single cell) batteries that I have. Same result.
Then, I tried adding 470uF electrolytic capacitors between the 5V and GND. It took 5 (!) capacitors before ESP finally booted correctly.
I strongly suspect that Li Po is not providing enough current to handle the peak of ESP boot cycle. I remember reading that this peak can go up to 437 mA. But then again, my 2400 mAh Li Po is rated at 1C (max discharge current), meaning that it should be able to provide 2.4 A - well above that peak.
I tried swapping every single element of the circuit - ESP, battery, boost module, wires, even the multimeter. Nothing changes.
Can anyone please offer any suggestions as to why ESP gets stuck in boot with Li Po that should easily handle the current peak during that boot? Why do I need to add so many capacitors in order to make it work?