Powering your auxiliary batteries with solar has been something that many campers have known about for a while now, and here at REDARC, it has been extensively covered. From why it’s good to why you should, we have demonstrated how you can get the most of your set-up using solar.
But what’s less understood is knowing how much solar you need for your set-up. In this blog, we break down what you need to know to get started and how to calculate how much solar power is required for your next off-grid adventure.
Now no two set-ups are the same and your needs are going to differ from your neighbours from either side of you. Added to this are the many different sized panels available on the marketplace, and it can get pretty overwhelming where to begin.
The first thing you need to know is that all electric devices, like your fridge, lights, and charging equipment is measured in Amps. Amps is a measure of how fast an electric current flow. The bigger the current, the more electricity is flowing.
So, you need to figure out how many electrical loads you have or will have and how many amps they will draw from your battery. This information can be found in the product manual or on the label of every device.
Next, you need to determine how long you will be using each item over a 24-hour period, as this will give you the total amp hours used per day. Amp hours is a measure of stored power. Amp hours is the number of Amps drawn, for the amount of time in hours that you draw that current. Amps x hours = Ah
So, you need to know three things:
- The number of electrical loads to be run and their amps
- The duration of each item to be run over a 24-hour period
- The size of your battery
Therefore, the number of solar panels you require will be determined by the amount of charge that needs to be returned to the batteries during the sunlight hours of each day.
How many solar panels do you need
It is best to compare solar panels by their power rating or watts. Watts is the basic unit of power and is a measure of how much electricity it can provide. In other words, the wattage of a solar panel determines the rate at which you can deliver charge back to your batteries. Volts x Amps = Watts.
Say for example you have a 12v system and you need replace 75A/h of charge back into your batteries each day. You have 6 hours of sunlight each day. You will need:
75Ah x 12V = 900Wh
900Wh/ 6h = 150W of solar panels
In reality it is recommended that you always overrate your requirements by at least 20%, therefore you would need 180W of solar panels.
A real life example
Let’s run a scenario to gain a better understanding.
The total loads used per day is 102 Ah, therefore this needs to be put back into the battery each day. In order to maximise efficiency and extend the life of a battery, it is recommended that the battery is only discharged to no more than 50%. Therefore, you would need around a 204Ah battery.
Assuming you only get 6 hours of optimal sunlight each day, you will need this many watt of solar:
102Ah x 12V = 1,224Wh
(1,224Wh/6h) * 0.2 = 244.8W of solar panels
It’s not uncommon these days to see 4WD’s with a fixed 150W solar panel and then supplementing it with an additional solar panel or blanket to provide more sustainable power when using more devices/appliances at camp.
Generally speaking and providing the weather conditions are suitable (not overcast) a 150W solar panel when paired with an in-vehicle battery charger will allow 24/7 use of a modern 60L fridge.
Although the concept can be quite technical, once you get your head around the calculations and different scenarios, you will find it’s not that complicated at all. All it requires is just a bit of your time and sitting down with a pen and paper to work it all out.
But we’ve made it simple. Our solar calculator does all the work for you and provides an indicative measure on how much power will be needed per day depending on the size of the auxiliary battery bank and appliances used whilst touring.
To get started on your journey, click on the button below.