Powering ESP32 with AA or NiMH Batteries

[lecandas]

Hello, this is my first post to the forum hoping for recommendations about powering ESP32 from regular batteries.

I am using ESP32-WROOM-32D development boards at this moment so I am simply powering the system through USB.
But I want to design my own PCB using just the ESP module.

In my project,
I am only using a single lux sensor that consumes 1.8V 300uA. The consumption of the sensor is so small that I feed the sensor from ESP DAC and it works fine. Also, the sensor is able to tolerate 3.6v on i2c so no special conversion is required to connect to the ESP.

I only use BLE communication to report sensor readings.
After powering up, the device waits for a BLE connection for 5 minutes then goes into sleep until a wake-up signal from a GIO pin is received. When a device is connected, until disconnect ESP keeps reading the sensor and sending GATT notifications to connected devices.

Everything works well for now.
But I am really confused about building the power supply.

I am planning to put a physical on/off switch not to drain the batteries while sleeping.
I am expecting a user to interact with the sensor daily for 1h. I guess a week of battery life is acceptable as long as batteries are easy to reach. Like AA/AAA Alkaline or NiMh. I have space but I don't want to exceed 3 cells. If possible 2 cells are preferred.

While ESP32 is in sleep, the sensor will not be powered up, so consumption will only be ESP32 itself.
While a device is connected, I assume the system will draw 3.3 around 150mA with peaks to 300mA-500mA.

Considering

2 cell Alkaline -> 3.2V to 1.6V
2 cell NiMh -> 2.5V to 1.6V

Is it possible?

[Remyhx]

I don’t really understand the whole post, but its possible yes. Maybe better use 4 AA or the 9V alkaline. The closer you are to the desired voltage, the less loss. Also consider lithium AA’s (the not rechargeable ones).

I use a LTC3440 in a project and select with an output pin connected to de mode pin of the LTC between the energy friendlier mode and the normal one. You can switch power users if needed with a mosfet.

While the batteries are draining the current used will rise. Take that in mind. Deepsleep can be very effective and maybe even measurements with the ULP processor (assembly language) or the bootloader stub. Its possible to fall back to deepsleep without starting the complete processor routine.

Physical on off switch are the things i dont like, but ok. Thats up to you. Try to combine wireless sends, better to send once an hour instead of per minute.