There are situations when we need to ensure that the radio station can work even in the event of a power outage. There are UPS backup sources available on the market that work as automatically switched 12V DC to 230V AC converters.
Radio stations are mostly powered by low DC voltage. Thus, we can advantageously use gel lead accumulators as a backup source. But how to ensure that the accumulator is always charged when we need it and that it replaces energy from the source in the event of a power grid failure? The solution is very simple and cheap.
The solution to the automatic backup power supply of the radio station is clear from the diagram. It shows the situation in the event of a power outage: TCVR it is powered through a relay contact from the battery. In the presence of voltage from the source, the relay closes and the TCVR is powered from the source. At the same time, the accumulator is charged through a diode and a limiting resistor. The diode prevents the discharge of the accumulator through the source and the switching on of the relay by the voltage from the accumulator.
We determine the value of the limiting resistor according to the capacity of the accumulator so that it is charged. With a considered voltage source of 13.8V and a voltage drop of 0.8V on the diode, the resistance is 4.7 to 33 ohms. When reviving, it is advisable to connect an ammeter to the branch and select such a resistance that the accumulator is charged with a low current.