Adjustable Li-Ion Battery Level Indicator I needed a lithium-ion battery level indicator for my hybrid tube amplifier project. The goal was to show the battery levels of batteries at once and needed the min/max voltage to be adjustable. After searching the internet for ages, I came across a LM3914 circuit that looked promising, the result came from an image search of LM3914, it appeared to come from an obscure Chinese website which I can no longer find. The circuit diagram was very poor quality and the writing was not in English. So I looked up the LM3914 specs again and noticed different types of circuits in the document and was able to guess some of the component values. The end result was a working battery level indicator based on the LM3914 that was powered from the battery being measured.
Just some random circuits that I've built.