It’s usually this time of year that overlanders are deep within the planning of their summer adventure camping trip. One item that is now required for most modern travellers is a charging point for those modern electrical gadgets that we all have become so reliant upon.
So here we’re taking a closer look at solar panels, the basic in’s & out’s.
Solar Panels, they sound pretty easy in principle just plug them in and we will have eternal electric. When we’re using our trucks as portable bases, travel pods or merely have a thing for electrics, solar panels do sound an attractive addition. The first silicon solar cell was built in 1954 and the technology has progressed hugely since then, but what’s what. Here are some basic facts to help guide you towards the sun-powered eternal power point.
First thing that needs to be clarified is Solar Panels work on UV rays so they will work on an overcast day.
Solar cells come in three types, Poly-crystalline, Mono-crystalline and Amorphous. Rigid panels usually support the crystalline cells poly or mono.
Poly-crystalline covered solar panels lose a percentage of output performance in temperatures over 25C /77F. These are the larger and least efficient cells needing a larger surface area for the same output as it’s competitors. Crystallines are more effective in full sun as they loose power in shade and heat.
Mono-crystalline solar panels suffer only slightly less from heat then the Poly so they are classed together for a coefficient pMax rating of -.45%/-.50%. pMax rating is measured as increased temperature versus output power efficiency. This means the hotter it gets over 25˚C the more output would decrease. Mono cells are made from a higher silicon grade and need the least space for the same output. They are also the most popular with manufacturers for technology advancements.
Amorphous solar panels measure a favourable -.20%/-.25% pMax making them a better option in higher temperatures and shade. This makes them more favourable if you’re touring all day and placing the solar panel out in the evening when light quality is less. These cells have flexibility so don’t require a heavy frame so can be rolled out like a blanket for use anywhere. They do need twice as much space as a Mono for an equivalent output but can be folded away when not in use.
For our purposes build quality needs to be a major factor. We want to be able to hit our tracks and not worry about damaging the solar panel. If the Mono-crystalline fixed panels are best for your needs ensure it’s protected with a tempered glass coating and a sturdy aluminium frame. Fixed panels are great for just fitting to the roof and not thinking about again but they can also be used the same as the Amorphous blanket and just placed out when stationary.
Regulators /Charge Controller are required to control power between a solar panel and the battery. Without a regulator you risk frying the battery by overcharging or worse frying your electrical items.
Judging how much power you will need requires some maths, but isn’t over complicated once you have the formula.
Look at all the 12V electrical items you wish to use in a typical day, fridge, phones, sat nav, everything. On the bottom of each item or in the handbook will be a Watts number indicating their consumption. If this is marked in AMPs then multiply the number by 12 (Volts). ie: 6 amps x 12V = 72 watts per hour needed.
Next calculate a daily total of Watts per hour. How often and long will each electrical item be used? Multiply the Watts by the hours of use for each item. ie: 65W TV x 4 hours = 260W. Now add all these hours of use for each item together to give an average daily.
Now the Solar panel size required can be calculated. How much usable light will be available where you are traveling? If you have 6 hours of usable light then divide the average daily 260W by 6 the hours of available charge equals 43W solar panel needed.
Is the battery big enough? This is a vital link in the chain and needs to be up to your demands. Multiply your needed daily Watts by 7 to equal a weekly requirement. Then divide this by 12 (volts) to convert back to Amp hours (battery measurement) and multiply by 2 to give the battery size needed. ie 43W x 7 = 301 divide 12 =25 x 2 =50 amp battery.
That is the basics we all need to know to get us up and running in the solar charging field, but already new technologies are heading to the market to give us more flexible and refined charging options.
Happy charging & travelling.