Battery LVD (low voltage disconnect)

28.08.2017

This is Arduino based voltage comparator which prevents a deep discharge of a car battery during an extended powering of a device.

Battery LVD will automatically disconnect powered device e.g. portable freezing box from your car battery in case voltage falls below preset threshold. This is useful in case when a car ignition is turned off but the device still needs to be powered. Therefore you don't need to care for over discharging your car's battery after you left the car.

Operation basics:


After a period of powering a device the car's battery is discharged. When low voltage threshold is reached, the system will delay for 5 seconds before disconnection occurs. This delay prevents disconnecting powered device during car ignition process which causes a voltage drop far below threshold.
If you want this device to operate properly than a socket with continuous power supply is needed in your car. I don’t have one installed serially in my car so I had to mount additional power socket including a fuse which is wired directly to the car battery. Pay attention to cable resistance regarding the cable length and cross section otherwise undesirable voltage drop or damage can occur at high current loads. Also the device will not be powered appropriately in this case.

Components Required:

About the code:


When reading analog signals on analog pin you will also have to deal with unwanted spikes caused by car electronic system which alternate the measured voltage. These spikes are present only if the car ignition is on. They result in inaccurate controlling of the powered device so we need to eliminate them.
Conventional smoothing methods of analog signals like calculating average from multi readings didn't give satisfying results in my case so I needed to use a library for noise cancelation which I found on the web. You can find a link and credits of this library in my code. After the noise removal the input signal is quite stabilized although some minor unwanted deviation can still be noted.
The voltage of a car battery is being read continuously. But only if a voltage deviation passes over the noise elimination filter the voltage comparison is processed. If the processed result passes the threshold then the powered device is controlled.
The reading voltage and calculated states can be also monitored on the OLED.

Car Cigarette Lighter adapter 2 Port

Arduino pro mini

OLED SSD1306 64x32

MOSFET IRF540

resistor divider for MOSFET (1k, 10k)

resistor divider for reading voltage (220k, 680k)

arduino battery lvd
Project gallery & downloads:
Project gallery & downloads:
arduino battery lvd
arduino battery lvd
arduino battery lvd
arduino battery lvd
arduino battery lvd
arduino battery lvd
arduino battery lvd
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