ESP32 Forum

The ESP32 is intended to be suitable for low power applications - in other words, running on batteries.

The optimal voltage for the ESP32 is 3.3V. The nominal voltage of a Li-ion battery is 3.7V but it can be anywhere between 3V and 4.2V.
Many of the development kits come with the AMS1117, which has a drop out voltage which is far too big for a Li-ion battery.

What is the recommended solution? A LDO regulator? A buck–boost converter? Something else?

There are a lot of boards that support batteries and charging and publish the schematics, check them out.

WiFive wrote: ↑

Fri Dec 14, 2018 4:12 am

There are a lot of boards that support batteries and charging and publish the schematics, check them out.

Thanks. All the ones that I reviewed use LDO linear regulators. They are inefficient because of the power loss for regulation AND the relatively high required battery voltage. Do any boards that are especially power efficient come to mind?

I use Texas TPS62136 buck switching converter and I am very happy.
The full solution with caps and resistors needed is a bit large (7x7 or 8x8 mm), but it is extremely efficient, the best option I know of right now. Cost is around 2-3 eur for the entire solution.

Anyone using a better option?

I use xc6203 LDO regulators with LIPO batteries. These have a drop out of around 150mV at the normal supply currents and also a fairly low quiescent current of around 8uA to minimise battery drain.

As the modules will work happily down to 3.0V this means the batteries are good down to about 3.3V which is pretty much fully drained.

There are even better ones but the xc6203 are pretty cheap.

XC6203 is a good option, I didn't know about TorexSemi, thanks.
Quite SMALL actually (3x3mm plus 2 capacitors) and easier to solder by hand and quite GOOD for deepsleep because dropout and supply current at low output current are very small.
BUT bear in mind that it has a maximum output of 400mA, below the minimum recommeded by Espressif of 500mA, so you will need more capacitance in power line in order to avoid ESP32 brownout when using Wifi/BLE, and you shouldn't power anything else with it.
Plus, at 100mA dropout is only 150mV, which means 4-5% losses, that's fine, but as soon as you increment output current, those losses go quite fast to 10-20 % or more... and suddenly your battery lasts 20% less than what it could if using CPU+Wifi/Ble.



From my experience and actual products made, I find it more important to have higher efficiency at higher current than at lower, because lower is already quite good, and it doesn't make much a difference if consuming 20uA total or 40uA total, but consuming 240 mA instead of 200mA when active is a lot. Of course if your product is in deep sleep 99% of the time, then maybe it is the other way around.

I find this topic very interesting, anyone else has any other alternatives?

This is effiency of TPS62136



From 0.5mA to 2.5A it is above 90%, with a maximum of 96% at 500mA. But at 20uA it is only 40%.

For example
M5stack uses http://www.everanalog.com/Product/Produ ... lInfo.aspx
Odroid-go uses https://www.monolithicpower.com/cn/mp2161.html
Olimex ESP32-DevKit-LiPo uses Silergy SY8089

You can use LiFePO4 battery instead of Li-ion without any LDO.

loboris wrote: ↑

Fri Dec 14, 2018 10:58 am

You can use LiFePO4 battery instead of Li-ion without any LDO.

Thanks for the idea. Even a LiFePO4 battery has a voltage which is too high while it is charging.