Making a CTEK charger lead for Discovery 4

Some time ago I bought a CTEK MXS 5.0 in an Amazon ‘Black Friday’ sale. It was originally for the GLR Defender but never got around to fitting the extra tow electrics to allow the remote charging.

The GLR D4 is a weekends and holidays vehicle and not an everyday driver. For that reason, the battery needs to be kept in a topped up condition whilst kept in the garage. I got the wiring details from this article on

I bought the CTEK Comfort Indicator lead and Ring Automotive 12S plug from Amazon (links below). The wiring is as below: –

Pin 3 (31) Ground (Negative)
Pin 4 (R) 12V (Positive)

The lead was covered in some convoluted tubing I had lying around in the garage. Both ends had heatshrink applied to improve the strain relief and longevity of the lead. I also wired a 5A mini fuse in line with the 12v line.

After construction and a continuity check the lead was plugged in. The CTEK Comfort Indicator flashed the yellow LED to indicate that the battery needed charging. The charger was plugged in and it’s currently going through its charging cycle as I type this…


GLR Webmaster & Contributor. In real life I'm a Software Engineer developing embedded software mainly in the automotive industry. Freelander 2 SE TD4 in Tonga Green Discovery 4 SDV6 HSE in Aintree Green Defender XS also in Tonga Green - Gone Freelander Td4 ES TD4 in Epsom Green - Gone Freelander Td4 Kalahari TD4 in Epsom Green - Gone Freelander XEi in Epsom Green - Gone

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