The post discusses a simple relay changeover circuit for managing a sustained power to the connected battery via a solar panel, and a mains operated SMPS power supply. The idea was requested by Ms Rina.

Technical Specifications

I would like to know how the circuit looks like for the problem that you have explained previously. But the application is little bit different.

There are three parameters:

The solar panel, The battery, And the AC/DC adapter. During day time the solar panel charges the battery and also stays connected to a 1hp air conditioner, pendaflour tube and a computer so that it can be lit through solar panel.

At night, all 3 appliances gets automatically connected to the battery.

And during overcast conditions or in absence of sunlight, if the battery voltage drops, the battery gets connected to the adapter so that it is able to get charged from the AC/DC source....

Thank you in advance Sir.


Illuminating DRL and Turn Lights with Single Common Lamp

The Design

The proposed solar panel, battery and mains relay changeover circuit as shown above may be understood with the help of the following explanation:

Referring to the figure, we can see that the solar panel power is fed to a charger controller, preferably an MPPT circuit, and also to an SPDT relay coil (via a 78L12 voltage regulator)

This relay remains activated as long as the solar panel voltage is persistent during the day, and as soon as darkness falls, the relay contacts change over and switch the mains adapter voltage with the charger controller unit.

An inverter battery can be seen connected across the output of the charger controller, which is continuously charged through the controller either through the panel voltage or the Mains SMPS voltage, depending upon the day/night or overcast conditions.

The battery can also be seen directly and permanently connected to an associated inverter which is able to receive the battery power throughout the day and also during the night time.

However since the battery is consistently kept in the charging mode via the solar panel or the SMPS, its lower discharge level is never reached and the battery finds itself always in topped-up condition, and supplying a 24/7 power to the connected loads via the inverter output mains.

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