When you need to choose a suitable battery for your next battery-powered IoT design, you could sit down with a DVM and measure the active and sleep current to estimate roughly how long the device will run from a single charge. The design could then be optimised by perhaps altering the ratio of sleep to active mode and maybe by choosing a different battery type and capacity. The BattLab One is a USB-powered device that can do all this at a click of a mouse button. It both powers the device under test and also shows all data relating to expected battery life.