To measure the deep sleep current draw of the D1 Mini, I hooked up 4 NiMH AA batteries in series (~5.2V) to its 5V and GND pins. The sketch uploaded to the D1 Mini was a nominal: void setup() { ESP.deepSleep(60)*60*1000000UL, WAKE_RF_DEFAULT); } void loop() { } The current draw was a pretty steady 0.8mA, or 800uA. That's a obviously a far cry from the sub-100uA reportedly achievable with the barebones ESP-01 due to all the extra components on the D1 Mini. Reported deep sleep current draw for the D1 Mini is all over the place, from 0.21mA (5V) , to 0.3mA (3.3V) , to 6mA (USB) ! Notes: 1. Connecting a 18650 battery (~4V) to the 5V pin did not work. In theory, the MC6211 LDO used by the D1 Mini means anything higher than 3.56V should work . But when connected, the onboard LED started to flash in a slow but erratic fashion, I suspect it is randomly resetting (because each time the D1 Mini powers up, the onboard LED flashes briefly). 2. Connecting a 18650 battery to