We build and sell a wide range of low voltage disconnects for use with 12V and (less frequently) 24V battery systems to protect batteries from being overly discharged and therefore damaged.
Pictured above is a device for a slightly different application, but which is based around our REUK Programmable Low Voltage Disconnect with OLED Display.
This Arduino powered device is designed to interrupt a signal line (using an on board relay) when an input voltage is measured to be below a user set value expected to be in the range 0 to 5V. Since the input voltage could be too low to power the microcontroller and display etc, the board is powered by an external 12V supply with a common ground connection to the voltage to be measured.
The user can set the low voltage threshold below which the signal line will be cut (by the relay being de-energised), and then a higher voltage threshold above which the signal line connection will be restored (by the relay being re-energised). Timers are built in to this device so that 10 seconds of consistent low or high voltage is required for a change of state of the relay to occur so any brief input voltage spikes and dips, or interference do not have an effect.
If you need any kind of low voltage disconnect or automatic voltage monitoring device, please email email@example.com with details of your specific requirements.