NOTE: Please note this point while calibrating. If the above steps are successful your circuit is ready to serve the battery.
#Battery guard diy serial#
The calibration for this battery over discharge protection circuit must be done carefully you need a variable power supply, a good multimeter and a screw driver for adjusting the pre-set resistor.ġ) The completed setup is connected to variable power supply without load.Ģ) Set the 13 volt on the variable power supply, verify this using multimeter.ģ) Open the serial monitor and rotate the 10k preset resistor clock or counter clock wise and bring the readings close to the readings of multimeter.Ĥ) Now, reduce the voltage of variable power supply to 12V, the multimeter and serial monitor must read same or very close value.ĥ) Now, reduce the voltage to 11.80 V the relay must trigger on and LED must light up.Ħ) Now, increase the voltage to 14.00V the relay must trigger on and LED light up.ħ) If the above sets are successful replace the variable power supply with a fully charged battery, the readings on serial monitor and multimeter must be same or very close to same.Ĩ) Now connect the load, the readings on both must remain same and synchronized. It is recommended not modify these values unless you are working with different battery voltage. You can change the cut-off, nominal and overvoltage by changing the above values.
#Battery guard diy full#
The nominal voltage in the program set as 12.70 V which is full battery voltage of typical 12V SLA batteries (Full battery voltage after disconnecting from charger). The above stated mechanism is done because the battery voltage rise after disconnecting from load and this must not trigger the relay ON at low battery state.
The nominal voltage is normal operating voltage of the load. When the battery goes below 11.80V, the relay disconnect the load, the relay will reconnect the load to battery only after when the battery voltage attains above nominal voltage which is set in the program. When the battery voltage goes below 11.80V, the relay gets turned on and disconnects the battery from load and LED indicator also turns on, this happen same when the circuit reads overvoltage from the battery, you can set the overvoltage cut-off in the program.
The transistor drives the relay on/off and a diode is connected across the relay for arresting high voltage spike generated from relay, while switching it on/off. The 10k pre-set resistor is used to calibrate the readings on arduino these readings are used by arduino to trigger the relay, the calibration of this setup will be discussed later part of the article.Ī LED indicator is utilized for indicating the status of the relay. The discussed over discharge protection circuit for 12v battery consists of a voltage divider which is responsible for stepping down the input voltage and reduce to narrow range where arduino can read the voltage.
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