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The battery voltmeter is a plug-in voltage monitor for 12V battery systems. This could be used in a car, caravan, on a boat or for your off-grid renewable energy system.

The kit includes a switched 4 digit LED display to accurately show the battery voltage, an enclosure for displaying the voltage in an appropriate place and a 'cigar lighter' style socket to plug in and power the display.

Accurately knowing the battery voltage is very important for managing lead acid battery based systems. See our battery worksheet for more information on batteries and their state of charge.

The Battery Voltmeter is available as a kit for £12 (including P&P within the UK).

Or it is available fully built for £18 (including P&P within the UK).

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Above is the new design, with the switch sandwiched between levels 4 and 5 of the enclosure. This design holds the switch better and looks nicer.

Kit Information

This is a relatively simple to put together kit. The kit includes these parts:

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Note: You will also need: wood glue, solder and soldering iron, hot melt glue gun and glue, posi-drive screwdriver.

Buy It Now

The Voltage Display Unit KIT is available to buy here via paypal. Please click on the link below:

The Voltage Display Unit is also available as a ready built unit. Please click on this link:


The construction instructions are available here:

This has also been written up as an instructable here.

Parts List

Reference Description Reference Description
Plug 12V cigar lighter plug with 3A fuse LED 4 digit LED display
Cable 2m of 0.75mm twin cable Bolts 2 x M3 15mm Machine screw
Enclosure Laser cut 5 piece casing Nuts 2 x M3 nuts
Switch On/off switch    

Enclosure design

The enclosure for this kit is laser cut plywood:

You can download the .dxf file for the enclosure design here.

Voltmeter in action

Here are some photos from people who have used the voltmeter in their projects:

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Added to give voltages from two different batteries using the switch above.