I have a monitoring station in a city in a sunny tropical area. Station power consumption is about 10 W. Station is powered from the grid. As grid is not very stable, I first used an UPS. Indeed, grid voltage is often low and UPS switch to internal battery until it is completely drained even without grid failure. Second, I used a 12V24Ah battery with a bluesmart charger (12V 5 A). Devices are DC power from the battery (with a 12V->5V buck converter for USB powered devices). All went fine until grid deteriorates strongly i.e. with electricity available only a couple of hours a day or even worth. My setup is no more strong enough. BTW, I also a BlueSolar PWM Charge Controller (DUO) LCD&USB 12/24-5 and solar panels up to 30 Wp (and can buy a bigger one) that I only use when going to the bush. So, to improve my powering, can I use grid and solar chargers in parallel?