Off-grid solar car charging technique

4x4electric solar charging off-grid

The innovative charging technique we use to charge our car and a separate battery for cooking and charging our electronics.

Quite a while ago we shared an article about our new car charging technology. As it has evolved and is now ready to use, we decided to write it once again in more detail for you to understand how we will charge our car off-grid directly with solar panels. A technique that has never been used before in this way!

To begin with, we have 2 separate systems to charge the car with solar panels. One system consists of 7 solar panels that are installed on the car, the other system consists of 60 solar panels stored in the back of the car while driving.

Solar charging 4x4electric

Off-grid car charging solution

Solar panels 4x4electricThe car is charged with 60 solar panels stored in the car. They are stored in a custom aluminum drawer system made by Tilbox. The system contains 10 drawers, each containing 6 lightweight flexible solar panels. 3 solar panels on their back as a cascade, and 3 on top also in a cascade. As each solar panel weighs 3 kg, this results in a total weight of 180 kg of solar panels. Therefore, this is the heaviest luggage we have with us, not counting the car itself.

Information about the solar panels:

  • 60 x 180-Watt peak per solar panel
  • Up to 11-kilowatt peak in total
  • The efficiency of the panel is ~18%
  • Brand: DAS Energy

Why DAS Energy solar panels?

We chose DAS Energy solar panels because they are very efficient, lightweight, made of high-quality materials, and made in Europe. They are flexible but we still have to be careful with them as micro-cracks can arise by flexing them too much. In the end, these micro-cracks will decrease their efficiency, something we want to prevent as much as possible.

Our expected charging routine

After some tests, we expect to be able to prepare the setup to start charging the car with solar panels in 20 minutes and break it down in 30 minutes. Once we have done this more often, we expect to find a more efficient way resulting in less time needed for the set-up. The 60 solar panels will be put in two strings of 30 panels each and connected to the charging unit.

A full car battery gives us a range up to 370 km (highway speed of 85km/h). Originally this was 500 km, however, the range is decreased because the car is less aerodynamic due to the rooftop tent and the additional friction of the all-terrain tires. We noticed that the impact of weight is limited due to the fact that we can regenerate energy while braking. As we expect to drive 150 km a day, a fully charged car battery is more than enough to drive for 2 days in a row.

Innovative DC-DC inverter to charge the car directly with solar energy

Venema solar chargerAll the electricity generated, is used to charge the car battery. To do so we use a specially built DC-DC charger made by Venema E-mobility. They have a lot of experience building DC-DC (fast) chargers to charge a car off-grid with a battery. Charging a car with solar panels was new to them, we even believe a system like this has not been built before. Luckily, we met Venema E-mobility early in our process of preparing for this expedition, as we could not have realized it without them.

The DC-DC charger uses 12 volts provided by the car to power the electronics and computer of the charger to check if the set-up is done correctly. Only then we can start charging the car with the energy produced by the 2 solar panel strings. This a valuable safety check.

We charge the car with the usual CCS plug. This is the well-known plug on electric cars for fast charging. While charging, the inverter constantly communicates with the car how much energy is produced by the solar panels. By warning the car how much energy is coming, it accepts the changing power provided. This power will change because of clouds and birds passing by or other shades appearing on the solar panels.

Optimalisation during the expedition

To increase the efficiency of solar panels, it is always better to aim them directly at the sun. Sometimes this means tilting the solar panels a bit. The good thing is that we will have to do this less often as we drive towards the equator where the optimal tilting is 0 degrees. But still, sometimes it might be worth the effort, though it’s only to cool down the panels by letting some wind underneath the panels. To do so we will take special pegs with us. For each panel, we will screw them into the earth, but not entirely. This way we can tilt the panels towards the sun. A lightweight and easy-to-use solution.

In addition, we can use the same pegs to pin the panels down to the ground. This can be a solution on a windy day. Too much wind will be a too high risk to start charging, but pinning them down could help us during windy days.

To charge the car we will look for locations that are not too crowded, as we cannot expect that everybody knows the solar panels are vulnerable. In addition, we want to prevent people from being seduced to steal them. Luckily, we have already found some people that would happily provide a safe place for charging on our route.

What if we lose panels, or they break?

Solar panel check

As we will use the panels quite intensely, it could be that they won’t survive the entire expedition. Of course, we will do all we can to make sure they do. However, as it is an experiment you never know. The good thing is that we can still charge with half the amount of solar panels, 30 in total.

This picture is one of our solar panels showing the UV light that the panel transmits when we put power on it. The picture is taken after we used the panel already multiple times. In this picture, you could see if there were any, microcracks in the solar panels. After a couple of weeks of using the panels, there is not even one (micro) crack in the cells. This tells us that the way we use them actually works!


Solar charging while driving

As we will be driving for a big part of the day, our partner Mito Solar installed solar panels on top of the car; on the hood, on the rooftop tent, and on the rooftop box.

Information about the solar panels:

  • Custom-made solar panels made by Mito Solar. Up until now, they made custom solar panels for solar boats and cars of student teams.
  • 500-Watt peak in total
  • The efficiency of the panels is 24%, which is really high

In this video, we show how they are made and installed on the expedition car. We use these solar panels to charge a separate household battery, as we call it. This is a 2000 Watthour battery of LP Energy, capable of proving 2000-Watt of power. We use this energy for the fridge, induction cooking, and charging our electronics. In addition, we use some energy to charge the 12-volt battery of the car. The result of this separate charging system is that the car battery is only used for driving, to enjoy the maximum range.


Experiment to the max

This charging technique is not used before. Therefore, for us as well as for our partners it is an experiment. We expect to make some adjustments during the expedition, to optimize it further.

We hope to have answered most of your questions about our charging technique in this article. Do you still have a question? Contact us! As we happily answer those as well!

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