When it comes to power management, you will find there are lots of choice and equally, lots of opinions too.  Thankfully, we have had the time to get to know many of these options over the years and really drill into what is and isn’t needed.

This offering from National Luna is the bigger brother of the two.  Providing a huge 40amps of DC-DC power and up to 40amps for Solar power.  Here’s our simplification of the product;

First of all, it acts as a DC-DC charger.  It will connect up your starter battery and leisure battery together, meaning they will both charge, when you drive.  It will only charge when you drive, so you don’t need to worry about your starter being flat.

This isn’t like the relays you can get, there is a bit more to this.  It can charge at a rate of 40amps per hour.  It does this in a smart way, working out what charge the batteries need and prioritising appropriately, using 6 different stages of charging.  It is also designed for smart alternators, meaning this will provide the performance, when your “Smart” alternator goes into energy conservation mode, unlike the other options.

Secondly, this is a MPPT solar regulator too.  Again, in simple terms, this enables you to connect solar power into this one device.  It is most efficient up to 600W of solar power, with voltages up to 42V.  This is considered a lot of off grid power, it’s more than you could fit on a westy roof, but with solar blankets and fold out panels, you could really begin to have enough power to be parked up for as long your supplies last.   The simple way to understand this product is to appreciate it that it does two things, charges while you drive and charges when you park.  This is one box, with less cable management and everything controlled via one panel.

Here’s some extra information provided by National Luna, with specific details;


The NLDC-40 from National Luna is a DC to DC battery charger and isolator for a dual-battery system.  It will charge an auxiliary or service battery from a vehicle alternator, Solar panel or auxiliary DC source up to 40A output current.  Traditional 12V and 24V vehicle alternators, as well as variable voltage alternators, are supported.

Item number BMS-30401


  • True 40A output current
  • 6-stage intelligent charge algorithm
  • AGM, Gel, Wet, Calcium, Lithium-Ion batteries supported
  • Alternator input up to 32V
  • 40A, 600W MPPT solar regulator
  • Supports solar panels up to 42V
  • Separate auxiliary DC input up to 32V
  • Smart-alternator compatible
  • Battery temperature compensation for safe charging
  • Sealed to IP67 rating (waterproof)
  • Replaceable terminal block
  • Short-circuit protected
  • Reverse-polarity protected
  • Over-voltage protected
  • Over-temperature protected

In the box:

  • NLDC-40 DC-DC charger
  • Universal mounting plate & fixtures
  • In-line fuses & holders
  • Temperature compensation probe
  • Ferrite ring (further reduces radio interference)
  • Installation kit including lugs and screws
  • Installation manual