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Docs Power & Battery Sleep Current

Sleep Current

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The deep sleep current budget: which parts keep drawing after the ESP32 sleeps, and how to get a clean microamp-level sleep.

Sleep Current

Deep sleep current is the most lied-about number in ESP32 builds. The chip’s datasheet says microamps; your board’s regulators and LEDs say otherwise. This page walks the real budget.

The ESP32’s contribution

The ESP32 in deep sleep draws roughly 10 - 150 uA depending on which RTC features stay enabled. The ULP coprocessor, RTC memory, and the RTC timer all add small amounts. In this project the RTC timer and RTC RAM are used, so expect the upper end of that range.

The board’s contribution

Most dev boards add far more than the chip:

Board partExtra draw
Always-on LDO regulator50 - 200 uA
Power LED0.5 - 2 mA (a killer)
USB-UART chip1 - 5 mA unless reset
Charger circuit0.1 - 1 mA

A board with a power LED and a live UART chip can sleep at 3 - 8 mA, which would eat a 2500 mAh cell in under two weeks even with zero beaconing.

Getting under 0.2 mA

  1. Remove or cut the power LED trace.
  2. Put the UART chip on an enable pin that the firmware drives low during sleep.
  3. Use a board with a proper low-quiescent regulator.
  4. Disconnect the GPS power during sleep (see GPS Power Saving).

Measuring

Multimeters lie at these levels: a cheap meter reads 0.0 mA below ~50 uA. Use a meter with a uA range or put a 10 ohm resistor in series and read the millivolts across it.

Why it matters

Sleep current multiplies by the hours the beacon is not transmitting. Cutting it from 5 mA to 0.05 mA turns a 20-day battery into a 2-year one for the same beaconing. The Power Budget and Runtimes table shows the effect.