This device is designed to protect a 12V battery or battery bank from being run down excessively and suffering permanent damage.
The output from this low voltage disconnect is rated to 1 Amp. This can be used to directly power lighting and other devices up to a total of 1 Amp, or can be used to energise a relay which in turn can switch much higher current levels. (see here for information on relay boards to switch up to 10 or 16 Amps, or here for information on automotive relays to switch up to 30 or 40 Amps.
The user can programme the voltage below which the low voltage disconnect will engage (turning off the output and therefore disconnecting the loads to protect the battery), and also programme the voltage above which the output will turn back on again reconnecting the loads.
To ensure brief spikes and dips in voltage are ignored, the measured battery voltage must remain below the low voltage threshold for 10 seconds continuously before the disconnect engages. The voltage must subsequently remain above the high voltage threshold for 10 seconds continuously before the disconnect will be cancelled and the loads reconnected.
The LCD display unit is backlit and shows the measured battery voltage, the system status, and the user-programmed high and low voltage thresholds. The backlight is also used to give a visual indication (by blinking) when the system state may be about to change.
Low Voltage Disconnect Programming Instructions
Connect the controller circuit board to the 12V battery and to the LCD display as shown in the connection diagram above.
To programme in your voltage thresholds, press and hold the black button on the circuit board. The backlight on the display will turn off. If you keep holding the button for 3 seconds, the backlight will turn back on and the display will show PROGRAMMING MODE -RELEASE BUTTON-.
You are now in programming mode, so release the button.
The display will now show Set Low Voltage 12.5 Volts. 12.5 Volts is the maximum value for the low voltage disconnect voltage. You now use the button to reduce this in 0.1 Volt steps until you get to your desired value – i.e. press the button six times to get down to 11.9V. Five seconds after the last time you press the button, whatever value is displayed will be stored in memory as your low voltage disconnect voltage.
The screen will now show Low Voltage Saved XX.XV (where XX.X is the voltage you set).
After a couple of seconds the display will show Set High Voltage 12.0 Volts. 12.0V is the minimum value for the high voltage cancellation voltage. You now use the button to increase this in 0.1 Volt steps until you get to your desired value. Five seconds after the last time you press the button, whatever value is displayed will be stored in memory as your high voltage cancellation voltage.
The screen will now show High Voltage Saved YY.YV (where YY.Y is the voltage you set).
Note that the high voltage threshold must be set to be at least 0.3V higher than the low voltage threshold. Therefore, if after going through the programming steps described above, this condition is not met, the screen will display HIGH V TOO LOW AUTO SET TO YY.Y where YY.Y will be 0.3V above whatever value you had set for the low voltage threshold.
The thresholds you programme in are stored in long term memory and so are NOT lost if/when you disconnect the device from the battery. Therefore you only need to go through these programming steps when you actually want to change the thresholds.
Using the REUK Low Voltage Disconnect with Display
With programming out of the way, everything is very simple. If the voltage falls below the low voltage threshold, the backlight of the display will blink. The system status will change to LOW, but the output will remain on. If after ten seconds the battery voltage is still measured to be low, then the system status will change to OFF, the output will turn off, and the display backlight will stop blinking.
When the battery is recharged or recharging and exceeds the high voltage threshold, the system status will change to HIGH, the display backlight will start to blink, but the output will remain off. If after ten seconds, the battery voltage is still above the high voltage threshold, then the system status will change to ON, the output will turn on, and the backlight will stop blinking.
If when the device is first connected to the battery, the measured voltage is immediately found to be below the low voltage threshold, the device will start in the OFF position – i.e. output off, system status OFF.
If you have any questions about the above instructions please email firstname.lastname@example.org. Similarly email if you have slightly different requirements – for example, if you want a low current relay fitted to the circuit board in place of the 1A output, if you want to have a low voltage disconnect with datalogger, or if you want a 24V low voltage disconnect with display.