I just started on a research team where the system is powered by two 12 V batteries that are charged using a solar regulator, but need the circuit to be powered by grid power when the batteries drop below 23 V. I have the 24 Vdc grid power, but need something to switch between the two when the battery voltage drops below 23 V or charges back to 24 V. I also cannot have any loss of power during the switching process. Any help on what sort of device I could use would be greatly appreciated.