George van Deventer of Trans Africa Self Drive Adventures and Tours talks weight and power while overlanding.
Overlanding is defined as “a form of self-reliant adventure travel in which the journey is prioritised over the destination”. In other words, overland adventure is more about challenging yourself to live comfortably in an unconventional manner than it is about where you decide to drive and camp along the way. None of us like to struggle or have problems and issues on what is supposed to be a “holiday”. Over many years of doing tours and many solo trips, I have learned a few valuable lessons from some painful and costly experiences. These tips could mean the difference between a successful or failed adventure. In this edition, we take a look at weight and power management.
Do I Look fat?
Weight can be your single worst enemy when it comes to overlanding. There is always the struggle between what I really need and what I want. Some adventurers have travelled around the world for a decade on a motorcycle, so a limited payload is not the problem. You just need to pack less stuff. However, most of us don’t have motorbikes, we have big 4x4s, and we want to take along all our home luxuries when going to the bush.
The most important number to know is your vehicle’s GrossVehicle Mass (GVM). This refers to the maximum your vehicle can weigh when fully loaded as specified by the manufacturer. You will usually find this figure on the vehicle’s weight placard(generally found in the driver’s door opening) or in the owner’s manual. It is important to note that the GVM is the Kerb Mass plus all accessories (bull bars, roof racks, canopies, winches etc) and payload. If you’re towing, the GVM figure includes the tow ball load.
The problem usually starts with the accessories. Loading to capacity (call it overloading) puts serious strain on your vehicle’s axles, wheel bearings, tyres and braking performance. You need to upgrade these to stronger specs, which usually means additional weight. In the end, weight is really about safety – for you, your family and others on the road. For improved safety and performance, I do not recommend exceeding 85-90% of the GVM. Less, in this case, is in fact more (or rather better!).I speak for myself and many others I know when I say it’s time to put our 4x4s on a diet. I started ditching items a long time ago. As I mentioned last month, if an item is not used for two tours, it is removed.
Bear in mind that you could face some serious legal ramifications such as fines, citations, denied insurance claims, and even criminal negligence charges if it can be determined that the vehicle was wilfully overloaded and this resulted in the death or dismemberment of a passenger, another motorist or a pedestrian.
Making and storing power
Even when we’re roughing it, we can’t seem to live without our electronic devices and our fridges and freezers. The means to keep your beers cold, have ice, and a supply of fresh meat and veggies, has become a priority. To achieve this, you need power.
Most people grossly overestimate how much power a compact solar panel can produce, and under estimate how much power they need. When deciding how to best manage your power draws, you must first calculate how much power you use every day. This is tricky science, and you need to know what the usage of each appliance is per hour and the number of hours this appliance will be drawing power. In summer, with ambient temperatures around 35 degrees, your fridge draws power for almost 24 hours in a day. Let’s take a National Luna fridge that uses 3.9 amps per hour. In 20 hours it consumes a whopping 78 amps. If you have a 105Ah deep-cycle battery, that means 75% of the battery capacity is gone!
One of the major challenges with solar is time. Generating power from the sun takes hours to be of any practical use. To make things worse, solar panels must be aligned with the sun to achieve maximum efficiency. The only way to speed up energy production is to use bigger panels and tend to them constantly to keep them aligned. This is why many overlanders have massive solar panel arrays. They know they can’t always be perfectly positioned, so they compensate by adding extra surface area. This is not terribly convenient for most travel situations and adds to the weight problem.
Let’s do some maths. Assuming a perfect situation with no clouds on a sunny day, you will consume 100 Amp hours with the draws from your fridge, lights, chargers, and other electrical devices in 24 hours. Let’s say you have a 160 watt solar panel and have aligned it perfectly the whole day to get maximum wattage. If the solar panel is rated at 160 watts and the voltage at maximum power (VMP) is given as 23.6V, then the current will be 175 watts divided by 23.6V, which is equal to 6.77 amps. This is current produced by the solar panel at full power each hour during the seven hours of optimal charge time from 09:00 to 16:00. That calculation then goes: 7 hours x 6.77 amps = 47.39 Amp hours.
Given you have used 100Ah over 24 hours to run that fridge and lights, etc, this is not even close to putting back what you have used plus the power draw while charging. Bring cloudy days into the calculation and you have big trouble. If you intend on parking up for more than a day in a spot without electrical points, you need to add more solar panels. As a rule of thumb, take your maximum usage and multiply that by at least three to calculate how much solar power input you need. At least the technology is improving, and the new flexible panels on the market are light, compact, and very easy to use.
Luckily for us overlanders we do a lot of driving, and you can supplement your charging capacity with a DC to-DC charger that works off your alternator. This is a smart charger that runs off 12 volts. They take the power output of your vehicle’s alternator and create an output voltage and current that’s ideally suited to charging and/or maintaining your auxiliary battery. Alternators are not good at this, as they are not dedicated chargers. I would recommend at least a 30 Amp DC-to-DC charger. Then, of course, we have all the different types of batteries. Lead-acid batteries, and specifically Absorbent Glass Mat (AGM) types, are best suited for solar applications because they require zero or almost zero maintenance. They also recharge faster, hold a charge for longer and can be cycled more often than a more sensitive gel type lead-acid battery. They are also more cost effective than lithium batteries.
One of the key advantages of lithium-ion batteries is their ability to handle repeated high discharges without damage. Lithium-ion can generally discharge around80-90% of total capacity, while a lead-acid battery is damaged by discharges in excess of 50%of capacity. This means that, at any given moment, a lithium-ion battery has a 30% larger operating range. They also recharge much faster than AGM.
There are many different makes and models of chargers and batteries to choose from, but I have found the “blueones” work the best for me. To summarise: know what your usage will be and calculate the worst-case scenario for putting back that usage. Remember that you can never have too much power, but you will always struggle and suffer with too little. Speak to a solar agent and your 4x4fitment centre to help you calculate your needs. Make sure you always clean and store your gear properly between uses so you can ensure it lasts as long as possible. There is nothing worse than putting up your tent after a winter of storage and finding it is mouldy on the inside from not being properly dried out. Always check your gear and repair or service where necessary before itis re-packed for a trip. This way you will get full use of the product.