What is it?

A shield for the D1 Mini that includes a battery holder for a LIR2450 rechargeable battery, a charging circuit for the same, and a power switch. Designed to fit on the underside of the D1 Mini.

How does it work?

With the power switch in the ON position, it powers your D1 Mini through the 5V pin, by connecting the battery to it through a Shottky diode (to protect the battery from 5V coming from USB). Despite the name of the pin, it doesn't provide 5V — instead it gives something between 3.3V and 4.2V, depending on the battery charge — so if you need actual 5V for your device, you have to use something else. There is no over-discharge protection.

With the power switch set to OFF, the shield will charge the battery from the 5V pin of the D1 Mini. The charging is indicated by a red LED, and stops automatically once the battery is full.

What do you get?

You get a single assembled shield, with the battery holder, charging circuit and power switch. The pin headers and the LIR2450 battery are not included.

Usage notes

The shield goes under the D1 Mini, with the battery holder facing down — make sure to pay attention to the pin markings on the shield and the board, the GND and 5V pins have to match.

There is no over-discharge protection, so you have to monitor the battery voltage yourself to prevent damaging the battery.

The battery only charges when the switch is in the OFF position, and the device is powered from an external power source.