Coin Battery Shield for D1 Mini

Some additional battery holders came today, so I soldered a couple of more shields and put them on sale on Tindie. In the process I ran out of the charging chips, so I will make more when those arrive.

Here's a photo with the smaller LIR2032 battery.

As you can see, that version allows stacking, so you can have more shields under it (just the access to the battery will be harder).

UPDATE: Unfortunately this version doesn't have enough power to actually power the ESP8266.

I needed a battery for my #D1 Mini UI Shield, so I revived this project and tried a second attempt. This time I'm using a bigger battery, LIR2450, though I made sure you can solder a holder for the smaller LIR2032 as well. There has been a change in how the charging works — with the switch on, the board is powered from the battery (through a shottky diode, to protect it from USB power you might have connected), with the switch off, the battery is charging.

There is a battery shield for D1 Mini development board, produced and sold by Wemos, but I find it a little lacking for some specific use cases. It wastes power by boosting the battery voltage to 5V and then letting the on-board LDO bring it back to 3.3V. It has a separate USB socket for charging the battery. It doesn't have a power switch. And most of all, it doesn't contain an actual battery — you have to connect that separately. That means it not suitable for some really small and portable projects. So I made this.

It's a very simple shield. It only has the battery itself, behind a shottky diode to protect it from your USB power, a charging circuit connected to the 5V pin, with an indicator diode, and a power switch. That's it.

There are two down-sides for using this design. First, the battery is tiny — only around 40mAh — so it won't last long. Second, it only provides between 3.6 and 4.2V to the 5V rail, so if you have anything that actually requires 5V, it won't work. But I think it's still useful for certain projects.