Under Bonnet Dual Battery Kit for Isuzu DMAX 3.0L Turbo Diesel (2012–2020)

Running a fridge, lights and a comms setup off your cranking battery is how you end up stranded at the far end of a track. This under bonnet kit gives the D-MAX a proper second battery, charged intelligently while you drive, with every bracket, fuse and length of cable cut to suit the vehicle.

At the centre is the REDARC BCDC1225D, a 25A DC-DC charger that takes your alternator output and delivers a full multi-stage charge to the auxiliary battery, something a simple isolator or VSR cannot do. It accepts a 9 to 32V input and handles both standard and smart variable-voltage alternators, with charge profiles for LiFePO4 lithium, AGM, gel, calcium and standard lead acid.

An MPPT solar regulator is built into the charger, with REDARC Green Power Priority. When solar is available it draws from the panel first and eases off the alternator, saving fuel and taking load off the vehicle. Add a solar blanket later and it plugs straight in, there is no second regulator to buy.

The mounting side is what makes this a kit rather than a box of parts. The 304 stainless steel charger bracket is pre-drilled for the D-MAX and positions the charger for engine bay airflow. The powder-coated tray bolts to factory mount points, with no drilling and no modifications. Six metres of 8 B&S twin core cable, midi fuses, holders, lugs, heat shrink and conduit are all in the box.

Suits the 3.0L turbo diesel 4JJ1-TC engine, 2012 to 2020, automatic or manual. The Isuzu MU-X shares the same engine and engine bay, so this kit suits it too.

The battery is not included, and case size matters more on this kit than on the LandCruiser and Hilux versions. The tray is rated by the manufacturer to a maximum battery of 265 x 174 x 220mm and 19.6kg.

For lead acid, the Century Overlander DIN65LHHDMF 4x4, 650CCA, 120RC, 70Ah → is Australian built and made for off-road work, with the heavier plate construction and vibration resistance that engine bay duty asks for.

For AGM deep cycle, the SSB HVT50D 12V 60Ah 600CCA Dry Cell AGM Deep-Cycle → measures 238 x 172 x 188mm, and the sealed dry cell handles engine bay heat and vibration well.

On lithium, the only lithium battery we will fit under a bonnet is the Invicta Xero, which is built to take engine bay temperatures. No other lithium belongs in an engine bay regardless of whether the case fits the tray.

The charger is solar-ready out of the box. To run a panel or blanket into it you will also need:

• 6mm twin core cable →
• SB50 Anderson plug →
• SB50 cover →
• Solar input bracket → Mounts the plug neatly in the engine bay.