Solar Recharging for your 4x4

SOLAR RECHARGING

There have been significant advancements in solar technology in the past ten years and at last solar recharging is a practical and non costprohibitive method of charging batteries in the bush.

The reason solar has earned a bad reputation is because so many products are sold that simply do not live up to the claims made by those who sell them and the ignorant buyer who gets taken for a ride.

Consider the following:
•Do you want a solar system to lengthen your stay in a camping spot without having to start the engine to charge the batteries?
•Do you want to add 25% on your time there, double your time or stay indefinitely?
•If you want to add 25% to your time, you need to supplement 25% of your power consumption.


•If you want to double your time there, then you require a minimum of 50% of the current drawn to be replaced.
•If you want to stay indefinitely, then your solar system must recover more than 100% of the current drawn.
Powerfilm is a flexible range of solar panels. While not as efficient as rigid panels, Powerfilm is robust and ideal for use in the bush.

A simple exercise

Today I still use the old panel I used ages ago and it has been with me on countless trips. It supplies enough current so I can double the length of my stay in one place.

For example if you are running a 40-litre Engel and two lights, you need to measure the average current consumption over a 24 hour period. If that’s too much stress to measure then try this: How long can you stay at one place without charging batteries? Let’s say it’s three days drawing current from one, 100 amp battery. This means that over one day 33,3 amps is consumed (100 divided by three days). To add one more day you need to add 33,3 amps to the battery and you must do it within three days.

Let’s say you want to double your stay. If your consumption is 33,3 amps per day, then you must put back half of that, 16.65 amps in each 24-hour period. In effect you are halving the current consumption and doubling your stay. In the same way, if you want to stay indefinitely your system must replace 101% of the current drawn – a little over 33,3 amps each 24-hours.

The solar experts will probably baulk at this and what I am about to write, because it is too simplistic. I say, “So what?” It’s my experience that solar experts are the opposite – too technical and often make claims that are relevant in the laboratory but are meaningless to 4x4 drivers like you and I who are looking for a simple solution to a technical problem. They may say, “There is no simple solution”. Nonsense.

Outrageous claims

Sanyo’s massive 180-watt HIT panel. Actually its not that big at 1,44x0.81metres, it easily slides under the average roof-rack. In full sunlight this baby delivers a massive 15 amps. In realistic terms though, during a sunny day, it will probably replenish ±40 amps. That’s enough for most campers to stay in one

Let’s take a 60-watt cell. This is a common medium-sized solar panel. 60-watts means that at the point that the sun is at its highest, and at the moment when it is shining directly at the panel it will, on a good day, when the panel is brand new, produce 60-watts, if you’re lucky. 60-watts translates into 5-amps at 12-volts. The time that panel will spend delivering 5-amps, if it gets there at all is probably, on average, never. It will more than likely top out at 4,5 amps. All the other time the current delivered will be less, far less.

The angle at which the sun strikes a panel reduces the output current significantly, even if it’s just a couple of degrees. So, a 60-watt panel is actually a 28.5-watt panel. Why? With eight hours of sunlight, the first and last two hours the oblique angle means that the panel is only running at an average of 15 watts. That means that for four hours out of the eight it produces just 1.25 amps-per-hour, a total of 5 amps. For the other four hours it produces an average of 3.5 amps per hour, totalling 14 amps. Add this to the 5 amps and the panel is producing 19 amps. That means that with just one 60 watt panel, that delivers 228 watts. Over the eight hours of sunlight the panel delivers 28.5 watts, replacing over half of the current I use over a 24-hour period.

So you see with this example based on what happens at my campsite on a sunny day, this surely gives you comfort that with a simple solar set-up such as I have, solar recharging is possible without spending a fortune. Fact is that I have worked a 60-watt Solarex crystalline panel for over twelve years and have had much joy and success with it.

Types of solar panels

Solar experts will talk about crystalline and amorphous panels and the advantages of both as well as voltage regulators and other devices. I will leave the details of these to them. For most 4x4 users this is not of any real consequence. What does matter is the amount of current they will generate in the environment in which we play and the costper watt.

Strapped to a roof rack, placed on the ground, leaned against a tree or bush with a few wires run down to a regulator and onto the battery system. As long as the meat stays frozen and the drinks are icy, that’s all that really matters. My advice: Keep it simple.

Solar panels and their performance claims:
•Look for panels with good low-light claims.
•Ratings must be measured above 13,8-volts. Some panels boasting high yields boost their figures by lowering the voltage to 12-volts or lower. Don’t be fooled; a 12-volt battery at 12-volts is a flat battery! A healthy battery under load should never fall below 12-volts.
•Look at the ratio of current per cost. E.g. For every unit of currency spent I get X units of current (amps or watts).
•Beware of cheap Chinese trash. So many badly made panels stop working soon after delivery as they are unable to take the vibrations from being mounted on a vehicle. They are also far less efficient.


Solar panels come in rigid and flexible types. Flexible units are more robust and practical for 4x4 use, but they are costly and inefficient for their size. Rigid panels are almost twice as efficient size for size, but are bulky and must be loaded flat on a roof rack and tied down very firmly. If they flex, even a little bit, they will break.

The cables must be heavy multi-core copper. Hand joins, bad connectors and thin cables will severely reduce efficiency. This is VERY important. There are advanced electronics that help the solar panel deliver more current more efficiently, but these are a nice to have and not a must have. For years I have run heavy cable from the panel, via a diode, to the battery. I can measure the battery voltage and can measure the current the panel is delivering. Without fancy electronics I achieve much. With it I could achieve more, true, but do I really want it? It is better to spend the money on heavy cables and the best connectors you can find. I should add, if your solar system has the potential to over-charge your batteries, a regulator is essential.

With our sun at the moment, It could take some time to charge even a phone battery
Great info tho mate

I posted this as i fitted one to my motorhome, and you'd be very surprised at the power even this time of the year

ok rislar......i've taken the hint......i will bring my jump leads up for you....


Interesting topic that Steve ......cheers mate.

Excellent write up....

have you seen the ones maplin electrionics offer from around £14 (the £19 one is sometimes on special at £12) i use one and some of my mate use them for various vehicles and we have all been more than happy with them.

1 watt £14.99
http://www.maplin.co.uk/Module.aspx?ModuleNo=228624

1.5watt £19.99
http://www.maplin.co.uk/Module.aspx?ModuleNo=98358

2.4watt on special £12.99 normal price £24.99
http://www.maplin.co.uk/Module.aspx?ModuleNo=223251

4.8watt from £29.99
http://www.maplin.co.uk/Module.aspx?ModuleNo=115194

Nice one carts, I'll take a look at those, good old Maplin strikes again

Cheers carts/rislar......really good post......

This may well be a good investment for me as the Nav is only used at weekends......being lazy now......are the cig. lighters permanently live even with the ignition off?...................

You know thats a good question that i don't know the answer to well sort of i've 3 of them and the one in the armrest is always live, im not sure on the others so you'll have to jump in yours and check it out

Dave C wrote:Cheers carts/rislar......really good post......

This may well be a good investment for me as the Nav is only used at weekends......being lazy now......are the cig. lighters permanently live even with the ignition off?...................

Just an update for all ....... yes the cig. lighter on the dash is a permanent positive........so the plug in Maplin panels are fine......

I did not check the centre armrest console one....forgot....

Good effort, so another toy to buy

and i just found I have a cig plug laying in the shed, that came with the pannel...

Nice, so you'll be getting your bits out (so to speak )

Rislar wrote:Nice, so you'll be getting your bits out (so to speak )

Something like that

keep it to yourself

Again......lol.....

Dave C wrote:Again......lol.....

Rislar..... How was your shoot.....

In the other thread buddy

Got one of these today......just a small one......only thing is.....never know if it is working.....but hey.......hopefully just enough trickle charge for the alarm/tracker to keep ticking over....

Nice one Dave, you can put a multi-meter on the battery to see if it works!!

Ah right ok ...i will bear that in mind.......just need to get one of them now then.......

Nice signature buddy

You mean you've not got..................................... oh never mind

well i have ......i normally lick my fingers when i am searching for a current.....can never be quite sure of the power though....

you'll come a cropper like that