Split Charge - Merlin Voltage Sensing for Vehicles without Smart Alternators



This kit is Habitation Check compliant for total peace of mind! (what this means)

This is a traditional split charge system built around a modern voltage-sensing relay. 

Non-Smart Alternators

It is suitable for vans without a smart alternator (usually pre-2013 vehicles, although that varies). If you have a Euro cat 5 or 6 engine you will definitely have a smart alternator.

The rollout of smart alternators was very piecemeal so if you're in doubt the best option is to call your main dealer and ask their parts department which one your van has.

For vehicles with smart alternators, check out our Battery-to-Battery Split Charge kits.

Why This Relay?

Older or cheaper alternatives required the relay to be wired into the van's ignition circuit so the relay would only be on when the van's ignition is on. This worked well except when the main battery was ageing and not holding a charge well, as the split charge could still drain it and leave you stranded.

This relay is smarter than that. The voltage sense relay detects the rise in voltage from your vehicle's charging system when it exceeds 13.3v to allow you to charge your leisure battery(s) while your engine is running. When your engine is switched off, and the battery voltage drops below 12.8v, the relay will isolate your leisure battery(s) from your main starter battery, so it does not drain your main starter battery.

Choosing a Kit Length

The kits are sold based on the length of red cable required. This is the cable that is run from the main battery to the location of your leisure battery. It is made to the length you pick with 2 x 250mm cables and the rest of the length as 1 long cable. This allows you to put a fuse between the main battery and the relay, and another between the relay and the leisure battery.

It's always worth slightly overestimating the length required as the kit comes with pre-made cable ends. Run a length of string along the path you intend to run your cables then add a metre (or two if your run is complicated with lots of turns).

Kit Details

  • 12V 140amp M-Power Voltage Sense Split Charge Relay.
  • 1 x 250mm 70amp Red Starter Battery to fuse box lead. (8mm to 6mm terminals)
  • 1 x Main Cable Run 70amp Red Relay to fuse box lead (6mm to 6mm terminals). This comes in the length selected minus 500mm (which is the 2 x 250mm cables made separately to allow for the inline fuses).
  • 1 x 250mm 70amp Red Fuse Box to Leisure Battery Lead (6mm to 8mm terminals)
  • 1 x 1000mm 70amp Black Earth Cable. (8mm to 10mm terminals)
  • Spare terminals + Heat shrink pack for modifications if required
  • Positive & Negative 8mm post type battery terminals
  • 2 x Fuse Holders & 60amp Fuses including a spare.
  • 15 x Cable ties + fixings to keep everything tidy.
  • 1mtr Split conduit to protect cables in the engine bay.
  • Screws to fix fuse boxes & cable tie bases
  • High-Quality HSS Drill Bit
  • Easy to understand Fitting Instructions.

Delivery Details

These kits are made to order so please allow 2-3 days for delivery. Since COVID, this has sometimes taken longer due to issues with couriers.

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