12V Low Voltage Cutoff


Download design files:


Files are provided under the open source MIT License.
A copy is included in the ZIP archive.


Many EV builders opt to use a smaller auxiliary battery, often Lithium chemistry, for their 12V systems to save space and weight. Unfortunately this means they tend to go flat more quickly if the vehicle is left unattended, which can damage cells.

This device will automatically isolate your 12V battery when its voltage gets low to protect it from further discharge - but with enough charge left to allow the vehicle to get going again when you return. It has low power consumption when monitoring, and by switching its own power off upon low voltage detection, zero current draw once tripped to avoid further discharging your battery.

An onboard LED indicates whether the 12V battery is enabled (on) or disabled (off). The reset input will re-enable the battery for 10 seconds when pressed, giving you enough time to start the vehicle.

The device is simply spliced into the positive wire from your battery, typically using 6mm ring terminals (included). There are also M3 terminals for low power wires to ground and reset (via momentary switch to ground).

Note: Due to the one-way nature of the switch, this device can only block discharge current. Charge current will not be stopped, even if the low voltage threshold has tripped.


Voltage range: 8-20VDC
Power consumption: 5mA when active, 0mA when tripped
Current rating: 50A continuous, 100A intermittent
On-resistance: 1mohm
Dimensions: 71x42x18mm
Weight: 35g

Datasheets & Manuals:



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