Please note: All our kits will be sold via The Curious Electric Company from now on. This page is for information only. Please visit our shop to see our current range of kits or contact us to discuss your project and how we might be able to help.

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).

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:

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:

Download the PDF file .

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:

Download the PDF file .

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:

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

2 responses to “Battery Voltmeter

  1. Hi. This voltage display can show voltages within the range of 5-33V DC. This means it would work to check the battery voltage of the majority of power tools. The problem would be actually connecting the display to the battery packs, as they are all slightly different from different manufacturers.
    I would suggest that a simple multimeter with a voltage meter setting and test probes would be a better solution and useful for testing lots of other things. One such as this:
    The voltmeter presented here is designed to be attached to a battery system (car battery or off-grid battery bank) and used to easily monitor the battery voltage.
    Hope that helps.

    Quoting Guest:Hi, This tester can test the powr tool battery( voltage?

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