Solar Water Pump Circuit using Battery and Relay

This project is about Solar Water Pump Circuit using Battery and Relay.

It uses one 18V 20W solar panel, two small 12V batteries, one relay and diodes.

The circuit can run a 12V DC water pump.

Battery stores power from solar panel and relay controls when pump run.

It is a very simple circuit and is easy to build.

Good for small garden or fish tank.

Circuit Working:

Parts List:

Solar panel gives around 18V in sunlight.

D1 and D2 are Schottky diodes 1N5819.

They stop reverse current from battery to panel.

Panel charges both batteries B1 and B2 each with 12V 2.5Ah.

Relay coil is 12V and when solar or battery power is available then the relay pulls in.

Relay common pin connects pump to battery.

Normally open NO contact closes and pump gets 12V to run.

D3 1N4007 protects relay coil from back EMF.

Pump runs only when relay pulls in.

When voltage is low then relay drops and pump stops.

This protects battery from deep discharge.

The relay turns the pump ON and OFF automatically based on the solar power or battery voltage.

Formulas with Calculation:

Solar panel current:

Panel = 18V 20W

I = P ÷ V = 20 ÷ 18 = 1.11A

Battery energy:

Each battery = 12V 2.5Ah

Energy = V × Ah = 12 × 2.5 = 30Wh

Two batteries in parallel = 30Wh + 30Wh = 60Wh

Pump power:

Pump load = 12V 3A

Power = V × A = 12 × 3 = 36W

Estimated run time:

Run time = Total battery energy ÷ Pump power

= 60Wh ÷ 36W

= 1.66 hours

Estimated run time 1.66 hours approx.

How to Build:

To build a Solar Water Pump Circuit using Battery and Relay following are the steps required to follow:

• Take all the parts as shown in circuit diagram.
• Connect solar panel positive to diode D1 and D2 anode.
• Connect diode D1 and D2 cathode to B1 and B2 battery positive line.
• Connect solar panel negative directly to battery negative line.
• Connect relay coil pin 1 to battery positive.
• Connect relay coil pin 2 to ground through diode D3 1N4007 reversed across coil.
• Connect relay common pin to battery positive.
• Connect relay normally open NO pin to pump positive wire.
• Connect pump negative wire directly to battery negative.
• Use thick wire for pump because it draws 3A.

Conclusion:

This is very simple and useful project for Solar Water Pump Circuit using Battery and Relay.

Only one relay and few diodes needed.

Solar panel charges batteries and relay controls pump safely.

It is good for small home projects which is easy to build even for beginners.

References:

Relay Switching On and Off Rapidly During High Current Draw [closed]