My 18 volt Milwaukee compact Li drill kit has a "battery fuel" gauge on the batteries, with a button that you press to see how full the battery is. Anyway, A few days ago I needed to take a gable vent off, which involved taking out 6 construction screws and putting them back in. It was on 3 (out of 4) when I started, and I even brought the drill in a warm place while I did my work, When I went to put the louvered vent back on, my drill was dead after I put one screw halfway in. By the way, it's pretty cold here. Li is lighter and more powerful (could have zipped in many dozen screws in warmer weather)
That drill has the same amount of power up until the battery becomes too discharged, and the drill's electronics senses it and shuts off. The last light blinks telling you it's time to charge up.