Onyehn 4pcs for Wemos D1 Mini Battery Shield Micro USB Single Lithium Battery Charging Boost Module with Pins LED Indicator 5V 1A DC

Although the description does say that both LED's (charging and standby) are red, I've used other Wemos shields where this isn't the case. So, I spent some time trying to determine why my configuration never reached "Charge" stage. Turns out, both LED's are the same color, so when the battery attached is charged to capacity, the LED does indeed change, but since they are the same color it's not intuitive. I ended up soldering a green LED in place of the one used to indicate that full charge has been achieved and all is well. Would be nice for the manufacturer to use a different color LED for 'full charge' to make it obvious. (I used a PL703048 1000 mAh battery pack to connect - it has a JTS 2.0 connector - but if you look, the pins line up so you can just push it onto the battery connection. I'm certain an 18650 battery would work just as well with a holder soldering the leads to the pads on the battery shield)

I used this charger circuit to create a solar-powered, cloud-connected Wemos temperature sensor with OLED display. My lithium battery's connector didn't match the one on the board so I just cut the connector off and soldered the wires to the connecter pins. For the solar panel I used a 2.5W 500mAh solar panel and soldered the negative side to ground and the positive side to the end of R330 closest to the USB connector. This saved me attaching a USB connector to the solar panel wires. The board already has Schottky diodes to prevent the battery from discharging back to the solar panel, so no need to install any. This setup keeps the 2000mAh battery charged and the device runs 24hrs a day. Note that there is a jumper on the board which if bridged, increases the charge current from 500mA to 1000mA. I don't think my solar power puts out that much current but I wanted to ensure maximum current for charging the battery. The only downside of this board is the "charging" and "charging complete" LEDs are both red and are next to each other, making it hard to tell when the battery is fully charged.

These battery shields get very hot within seconds of plugging in an 800 mah 3.7v lipo battery. They seem to charge the battery okay, and the wemos runs about 24 hours without using any low power modes.