From the hook up guide
If you want to add your own, larger LED, there’s an unpopulated footprint where you can solder either a 3mm or 5mm LED in the tiny (but bright!) red LED’s stead. Make sure you get the polarity right, though.
I can’t get an external led to work. Do I need to disable the on board led somehow? I hav tried both 3mm and 5 mm led’s. Voltage at leads is 1.7 v. Polarity is correct. Any help appreciated As this is my first project and I want to integrate the power supply and battery into a wooden lamp base. I can’t come up with a configuration that will allow the on board led to be visible to ensure charging is complete.