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measured values in bold - other values from datasheet or calculation
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MeasurementValueUnitsNotes
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18650 battery voltage4.0V
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Current draw while charging empty battery-186,000uAif battery is empty
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totally off - haven't even pressed PMU on button60.00uA
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deep sleep CPU, lora on but in sleep mode, GPS off, screen off, LED off2,300.00uA
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full on CPU (10ms delay() in loop), lora on, GPS on, screen on, LED on118,000.00uA
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expected cpu power consumption awake with BT100,000.00uAper datasheet and https://lastminuteengineers.com/esp32-sleep-modes-power-consumption/
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expected cpu power consumption modem-sleep mode20,000.00uAalso need to lower cpu speed to get this level
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expected cpu power consumption light-sleep mode800.00uAcpu is off, but bluetooth keeps working
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rf95 radio in sleep mode0.20uAper datasheet
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in idle mode1.50uA
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in standby mode1.60uA
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in receive mode (boost on)11,500.00uAmeasured by me
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in transmit mode +20 dBm boost120,000.00uA
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SSD1306 display in sleep mode10.00uA
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SSD1306 while on7,000.00uAmeasured by me
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NEO 6m GPS, average current while tracking40,000.00uAmeasured by me
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average current during acquisition47,000.00uA<3 secs to acquire lock if using an assisted acquision mode (needs a bit of sw work - currently I only listen to the GPS, no talking to it)
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eco mode tracking (1 Hz update)12,000.00uAFIXME - at least use this mode for an easy savings of 29mA, even better, just do one aquire each wake and then shut the whole thing down (needs <3 s to lock)
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Easy power savings to apply57,000.00uAleave OLED screen mostly off, leave GPS mostly alseep, and use modem-sleep mode on the ESP32
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case 1: Expected average current draw (100% awake CPU & radios, but screen only on rarely)61,000.00uA
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0.24W
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case 2: Expected average current draw (CPU light sleep, LORA radio powered, GPS occasionally powered)15,000.00uAIn this mode messagages & position would always be promptly available on the device, and when a message arrives it promptly forwards to the phone.
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0.06W
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Low power mode duty cycle1515= 1 min out of 15 min awake, 5 1 min out of 5 min awake. It might be possible to shrink the wake time to something more like 30 seconds
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case 3: power mode: wake only 1 minute out of every X minutes to exchange messages with mesh, phone, GPS0.02WIf wireless mesh is chatty when we wake, we could agree to keep the mesh alive longer
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18650 capacity3,000.00mAh
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12.00Wh
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time between charges case 1: 100% awake2.05days
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time between charges case 2: lora powered always, cpu mostly sleeping8.33daysThis is the best case to shoot for
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time between charges case 3: super low power mode30.74days
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super low power mode with tiny 600mAh battery6.15daysFor reference if someone wanted to build up a tiny version, possibly a little longer because we'd be wouldn't need to power the GPS (use phone's instead)
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New measurements 10/8/20 with firmware 1.1.1 on a ESP32+SX1272 TBEAM, 4VFIXME update predictions above based on these measurements
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max current draw with gps, screen, lora tx200.00mA
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with gps, screen, lora rx110.00mA
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with screen, lora rx49.00mA
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with lora rx (dark mode)32.00mA
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light sleep with GPS in sleep mode15.00mA
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light sleep with GPS power disabled 11.00mA
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light sleep with GPS in sleep mode, but actively receiving a packet (because CPU wakes)30.00mA
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Therefore
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GPS current draw while acquiring/active60.00mA
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Current draw for tlora xmit90.00mA
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Current draw for screen17.00mA
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Current draw in light sleep15.00mA
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New measurements 10/16/20: ttgo eink nrf52840
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GPS off + BLE on + CPU DarkState + lora on (normal low power mode with BLE)13.00mA
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