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Tech briefing: Stay in Charge


Why your dual-battery system is incomplete

With the Easter holidays just weeks behind us, there’s a good chance that your auxiliary battery is in desperate need of maintenance, and an even better chance that permanent damage is happening to the battery as we speak. But don’t fret; there’s still time to save your battery and prolong its life. This is what you need to do …

A lot can be said about battery life and how it relates to recharge rates, but in the interests of simplicity, here’s the gist of it: a deeply discharged battery must have enough TIME to recuperate.

There’s a popular misconception that a battery can rapidly recharge in a short space of time. This is simply not true for most batteries. Unfortunately, very few battery manufacturers and fitment shops are conveying this message, and, as a result, overland travellers are paying the price… literally.

The graphs below highlight a few critical lessons about Why your dual-battery system is incomplete dual-battery ownership, using a popular 105Ah (wet cell) deep-cycle battery as an example:

Discharge graph

Discharge graph

This graph shows how much (useable) energy can be drawn from a 105Ah deep-cycle battery. The highlighted region depicts the safe operating area, and equates to a 70% depth of discharge. In other words, you don’t get 105Ah from a 105Ah battery!

Generally speaking, you can draw between 70 and 75Ah of useable energy before entering the deep discharge area where battery damage is accelerated and the life of the battery is shortened.

Note that leaving a battery in a discharged state will accelerate degradation and cause permanent damage to the battery.

Automotive Recharge graph

Whether you’ve fitted a solenoid system (see orange line), or 20 amp DC-DC system (see red line), the fact remains: it takes more than four hours of driving time to restore that 70%. This graph shows the recharge rates of both a solenoid system and a DC-DC charger where the alternator is pushing out 13.9V.

Recharge graph

Now what?

Generalisations are a dangerous thing to make when it comes to dual-battery systems, purely because there are so many options (and variables) in play. However, it remains true that most dual-battery users are unaware that their auxiliary battery is partially discharged, and that because of this, the performance and lifespan of their battery is compromised. This results in frequent battery replacements, or the inability to power a camping fridge throughout the night.

Of course, the simple solution to this problem is to drive more, but most holiday travellers would not find it practical to drive four to eight hours a day in order to recharge the auxiliary battery. Even with this kind of driving time, there’s a good chance that your auxiliary battery is not fully recharging, especially if it was deeply discharged the night before.

It’s an exponential problem: for each day that the battery is not fully recharged, the risk increases of taking the battery into a deeply discharged state from which it is more difficult to recover.

Now what? Well, whether you’re a 4×4 enthusiast, boat owner, or biker, the thing to remember is that if you own an auxiliary battery (regardless of application), there’s an excellent chance that you will need a 220V maintenance charger to restore (full) capacity and ensure that the battery is kept at optimum health − ready for your next adventure.

National Luna’s new Intelligent Maintenance Charger ensures that your battery gets what it needs in terms of time and energy to reach a fullyrecharged state. How it goes about doing this is a critically important feature.

During its many years of battery-charging and MYTH BUSTER Trickle chargers VS Regulated Maintenance chargers Non-regulated (220V) trickle chargers can often do more damage than good. This is because a non-regulated charger will not account for (mains) power surges, and may expose the battery to excessively high voltages and subsequent gassing. This is why it is important that you use only an Intelligent Maintenance Charger that self regulates the input and desired output voltage. maintenance experience, National Luna’s onsite laboratory has conducted a series of comparison tests on almost every battery charger on the market. These tests have culminated in the launch of an affordable battery charger that gives a battery exactly what it needs.

It all starts with an eight-step recharge program that includes a diagnosis of the battery’s health, and an automated sequence of recharge rates to recover, restore and enhance battery life. Best of all, the charger is self-regulated, so that it can be connected to your battery for an indefinite period of time without the risk of damaging the battery or overcharging it.

The Intelligent Charger is suitable for wet, AGM, GEL and Calcium batteries from 1.2Ah to over 120Ah. The reduced-power mode is ideal for small batteries such as those in your motorbike or jet-ski; and a selectable “boost” mode is useful for periodic maintenance of calcium batteries or batteries that have been severely discharged and are showing signs of reduced capacity.

The National Luna charger also features two cable options, allowing you to choose how to connect the unit to your battery.

The National Luna Intelligent Maintenance Charger carries a five-year guarantee and retails for R1595 at all leading outdoor and 4×4 stores. For more information on the National Luna Maintenance Charger, visit

National Luna is a 30-year-old South African company that produces the world’s largest selection of commercially available 12V fridge/freezers. It is also the preferred supplier to most major off-road trailer and caravan manufacturers, and a global distributor of more than 200 outdoor products and accessories. | 011 452 5438