Which is best? An installed dual-battery system, or a portable unit?

Dual-battery systems generally come in two formats:

  1. Installed units that are permanently mounted within your vehicle, or…
  2. Those packaged within a portable power pack / battery box.

If you’re having trouble deciding which solution is right for you, here’s a closer look at the pros and cons of each setup using National Luna’s 25A DC-DC charger, versus the 25A DC-DC portable power pack (aka: The Green Box).

Both systems are identical in terms of charging performance, however, the Green Box does boast some added functionality.



Mobility around camp

If your vehicle is forced to park in direct sunlight, you may want to remove your camping fridge and place it inside your tent. Of course, in order to do so, you’re going to need mobile power.

Similarly, a portable system provides mobile power to 12V lights, as well as the ability to recharge your cellphone or camera anywhere in your campsite.

Household use

There’s no denying the benefits of having back-up power in your home for emergency lighting, and/or cellphone charging.

Ease of installation

Because the National Luna Green Box comes “prewired”, the only installation requirement is a heavy-duty cable that installed from the vehicle’s cranking battery, directly to the portable power pack.

Mobility with solar

In some cases, the best source of sunlight may not be accessible to your vehicle. Alternatively, the cable length of your solar panel may not allow you to park your vehicle in the shade, while your solar panel sits in the sun. Having the ability to move your dual-battery system to where your solar panel is situated, can offer greater flexibility and solar-charging performance.

Mobile jump-start

Although it’s not advised to use a deep-cycle battery to jump-start a vehicle, the need may arise in emergency situations; particularly if the road is narrow and the recovery vehicle is unable to gain side-by-side access to the stricken vehicle. A portable power pack may prove helpful in these circumstances.

Note: Do not attempt this with a lithium-ion battery.

Trailers and caravans

A portable dual-battery system is an easy way to add auxiliary power to a trailer and/or caravan.

Easily removed

When the time comes to sell your vehicle, simply unplug the dual-battery box and move it to your new ride.



The greatest threat to any lead-acid battery is inadequate charging and maintenance. Leaving your portable dual-battery system in a partially discharged state will significantly affect its performance and life expectancy.

That said, maintaining your portable system requires a conscious effort, and preferably, a 220V Intelligent Maintenance Charger that’s left connected to the power pack when it’s not being charged in your vehicle.




Save space

Some travellers opt to have their dual-battery system installed within their vehicle’s engine compartment. Naturally, this frees up much needed packing space in the cargo area, while reducing some of the wiring / installation requirements of the charging system.

Low maintenance

Because built-in units are permanently connected to the vehicle’s charging system, there’s no need to worry about battery maintenance or upkeep. The auxiliary battery will recharge while you drive.


Built-in dual-battery systems are typically cheaper than portable units. In the case of the NLDC25 and the Green Box, the NLDC25 may be up to 30% more affordable.


Selling your vehicle

Selling your vehicle may inadvertedly mean the sale of your dual-battery system, too. Of course, you can potentially remove the system before you sell the vehicle, but you’ll have to clear that with the new buyer beforehand.

Engine bay heat

A 10ºC increase in the operating temperature of a lead-acid battery can more than half its lifespan. Needless to say, under-bonnet temperatures can be between 20ºC or 30ºC hotter than the surrounding ambient conditions, thus, radically reducing the auxiliary battery’s life. I

f possible, it’s best to install your auxiliary battery inside your vehicle’s cabin. However, doing so may negate the space-saving benefits of installing a built-in unit in the first place.

Complex Installation

While the installation of a built-in dual-battery system isn’t overly complicated, the job may involve additional brackets and/or drilling work. So although a built-in system may offer a cheaper upfront price, the installation fee may be higher than a portable system.