I wanted to power my Raspberry Pi 3B plus some sensors and an additional Huawei modem with a Powerbank. When turned on that's no problem, everything works fine. But I want to measure some enviromental conditions with the Pi over a period of time as long as possible. So I bought a WittyPi wich enables me to set the Pi into a standby mode. This reduces the power consumption dramatically as I've measured. If I connect the Pi to the grid everything works fine, it turns itself on every half hour and send the data it collected to me, but if I use the powerbank it stops supplying energy after a while and the Pi can't boot up again. Do you know how I could solve this? Maybe by switching the circuit in the powerbank with a circuit that doesn't stop the supply? Does such a 'energy controller designed for a Raspberry' exist? And if so do you know any good ones? Or do you have any other idea, I feally don't know what to do.