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Solar Power Guide

These days more and more people are finding it simple and convenient to take solar panels with them when they go camping. You can keep a surprising amount of power going in your campsite with a foldable panel that stows away in a bag, and not have the noise and hassle of running a generator. But people often have lots of questions about what exactly they should get, so we have put together the following guide. And if all the numbers start messing with your head, we have also made a handy calculator so you can work out what you will need!

Camping Solar Power Calculator


12v vs 240v
All the appliances in your house run on 240 volts. You can think of this as like water under very high pressure - it works very efficiently but can be dangerous and needs installation by a qualified electrician. The electrics in your car, caravan or camper run on 12 volts. (Unless you have a specialised 24v setup, in which case you probably already know what you are doing and can skip this bit!) This is like water with a much lower pressure - it still works just as well but more safely. The main downside is needing bigger pipes to get you the same amount of water.

So when you go camping, you ideally want to take 12v appliances which have been designed to work with this voltage. Camping and auto stores readily supply 12v fridges, lights, phone chargers etc. and you can even get 12v TVs, hairdryers and microwaves if your idea of camping is a bit more glamorous. If you don't want to have to get special equipment just for camping, it is also possible to buy an Inverter, which is a transformer which will take your 12v power and ramp it up into 240v power. This lets you take your appliances from home, which is great but it comes at a cost. The inverter itself is not 100% efficient, and most 240v appliances will demand more power than 12v ones which are designed to be efficient, so you can find yourself using up a lot of your hard-earned electricity very quickly.


Storage
Once you have decided to run a 12v system, you need somewhere to store all your electricity - a battery. You can use your car battery, but we strongly suggest you don't because it is very easy to drain it too far by mistake and then find you can't start the car. So most people will have a second battery, either in their car or in a caravan or trailer. You can run this completely independent of your car's electrics, but it is generally a good idea to buy a kit that will allow it to charge from your car when you are driving. Again these are readily available from camping and auto stores.

There are a number of different types of batteries, but most people recommend getting a deep cycle battery. Car batteries are very good at supplying large amounts of power in short bursts to fire up the engine, but they are not so good at sustained power and they don't like being discharged too far. Deep cycle batteries are designed for caravans/boats etc. and will supply ongoing power very happily and you can use much more of their power without ruining the battery.

One more thing on batteries. The amount of power they can hold is measured in Amp Hours or Ah (Amps or A is a measure of how much electricity they are producing). So a 100Ah battery can produce 100A for 1 hour, or more likely 10A for 10 hours. BUT you should never let them discharge completely. In fact the less they discharge, the longer they will last. So a battery that generally only drops to 80% capacity before being recharged will last twice as long as one which is discharged to 50% regularly, which in turn will last twice as long as one which is discharged to 20%. There are no hard and fast rules here - you can use up to 70-80% of your battery if you want to, but they are not cheap things to buy and most people seem to think using them down to about 50% is the best way to go. That means if you want to be able to store 80Ah of electricity, you should consider getting a 160Ah battery.


How Much Power
The next question is, 'How much power do I need'? To answer that, you need to think about what you are going to use it for. Most people will want, as a minimum, to take a fridge and some lights. You might also want to charge your phone or computer. You might want to run a pump or compressor, or a TV, microwave, etc. So you need to look at the appliances you have and see how many Amps of power they draw. And you need to estimate how many hours a day you want to use them. A 12v TV, for example, might use 5A. If you are going to use this for 2 hours a day, then you will be using 5 x 2 = 10 Amp Hours. A 12v oven might use 10A. If you use this for 1 hour a day, you will be using 10 x 1 = 10 Amp Hours. Lights will generally use 0.25-1A each, so running 4 lights at 0.5A each for 3 hours you would use 4 x 0.5 * x 3 = 6 Amp Hours.

The biggest power draw, and the hardest to predict, is probably your fridge. Some fridges use a lot more power than others, and they will all vary greatly depending on the outside temperature and whether you are using them to cool down warm food or maintain temperature in food that is already cold. A small, new, efficient fridge in reasonable temperatures might only draw 1.5A, whereas a large, older inefficient one on a hot day might draw 10A. So it is worth doing your research!

Once you know what you have, make a list like this:
Fridge: 24 hours @ 3A = 72Ah
Lights: 3 @ 0.3A for 3 hours = 2.7Ah
Charging iPad: half charge = 2.5Ah
12v TV: 2 hours @ 5A = 10Ah
TOTAL: 87.2Ah

So you are going to use 87.2Ah per day.


What size solar panel and battery?
Batteries and panels both cost money, so traditionally people have tried to find the best trade-off for their needs. As solar panels have got cheaper, though, you are generally better off getting a bigger panel and a smaller battery.

In a perfect world you would be able to camp forever and be self sufficient. So carrying on from the example above you would buy a big enough solar panel that you can be confident of getting more than 90Ah every day out of it even if the weather isn't perfect. You would then estimate that 60Ah of that would be during the night when the panel isn't charging, and buy a big enough battery that you can use that 60Ah every day without draining the battery by more than 50% (see Storage section above). That means a 200W panel and 120Ah battery and all things being well you could keep going indefinitely.

The trade-offs look like this: if you knew that you only needed your setup to last 5 days without some external charge, you could buy a smaller 160W panel which only produces 75Ah a day. Your power use is now exceeding what you are generating by 15Ah per day, so after 5 days your battery has run down by 75Ah. As long as you have a big enough battery to cope with the loss, then it doesn't matter. But by the end of that last night you have used 60Ah of power for the night, plus 75Ah loss for the holiday = 135Ah of power. You might be happy dropping below 50% charge for the last night or two, but you would still want a 160Ah battery instead of a 120Ah one, and these days the bigger solar panel is a cheaper investment.


Solar Panels
The first thing to be aware of is that no solar panel setup is 100% efficient. In theory a 120W panel connected to a 12v system will produce 10A. Give it sunlight for 8 hours and it should produce 80Ah of power. This doesn't really work in practice - you need to make allowances for weather, for loss of power through the controller, cabling and connections, and for your 12v battery in reality working at 13v or more. So on a good day you might want to base your calculations around 70-75% of that to give you a margin for loss. These figures will obviously vary a lot with different conditions and setups, but we would work on something like this:
100W panel: 45Ah per day
120W panel: 55Ah per day
160W panel: 75Ah per day
200W panel: 90Ah per day
240W panel: 110Ah per day


Regulators/Controllers
A solar panel needs to get power to your battery in a form it can use. Most panels in their 'raw' form produce power at around 17-18v, so you need to be able to step this down to the correct voltage for your battery. This is usually a maximum of about 13.5-14.4v (a bit more than 12v so it can 'push' the power into the battery, but not so much more as to damage it). For this reason, you need a solar panel that comes with a Controller or Regulator (these are two words for the same thing!). There are a number of different types, but most commonly you will see PWM and the more modern MPPT controllers. These take the power from your panels, look at the state of your battery, and then feed that power through to the battery in the best way that it can use it. They will generally supply a lot of power when the battery is empty, and then ease off to a trickle charge as it gets full.

We have done a lot of testing on different controllers. You will see everywhere the prevailing wisdom that MPPT controllers are up to 30% more efficient than PWM controllers. For our purposes here, this is extremely misleading! While it might be true with large power setups, in practice with portable camping systems we found very little difference (between 2-5% depending on conditions). In fact in full Australian sunshine we found the cheapest PWM controllers we sell to be more efficient than the name brand MPPT ones we were testing against. (This does sound counter-intuitive, but there are some good reasons for it!) So we would recommend making your purchase decision based on the features of the controller rather than any idea that a more expensive one will be much more efficient and give you extra power. If you want better screens and indicators and logging functionality, get the more expensive controller. If you want more power, put the money into a bigger panel.


Camping Setups
There is not too much to say here. Many people will have a camper trailer, van or caravan with a dual battery system already set up. In which case all you need to do is buy a solar panel (with a controller if you don't have one) and clip it onto the battery or plug it into your Anderson socket. If you are wanting to create your own system, the simplest way is to buy a deep cycle battery and put it in a box. If you want a little more sophistication, you can get battery boxes from auto stores with various combinations of power lights/meters, cigarette lighter sockets, USB sockets already installed. This makes it much easier to attach leads from whatever lights or appliances you are wanting to use. Some of these are inexpensive but they can get quite sophisticated. Or you can make your own up fairly easily. And again, adding solar is as easy as clipping the leads onto your battery or plugging into the battery box.


Baier Solar Panels
Finally, a word on our Baier solar panels. We worked quite hard with the manufacturer to come up with the setup which was most efficient and most cost-effective. The panels themselves are very high quality, with A grade monocrystalline solar cells sourced from the world's top manufacturers. (There is another kind of solar cell called polycrystalline, which historically has been considered of much lower quality. In truth these days they are pretty good, but they are still considerably less efficient so you need a bigger area and more cells to generate the same amount of power.)

They come with long cables so you can set them up 10m away from your battery if you need to. This also allows you to put the controller near the battery, not near the panel, so you can run a higher voltage through the long stretch of cable and minimise any power loss that way. They come with Anderson plugs. If you are going to create your own camping setup we highly recommend using these - they are generally considered to be the best and most robust connectors for use in vehicles. If you prefer not to use them, the kit also contains an adapter cable with crocodile clips (alligator clips) so you can clip directly on to your battery.

And if you don't have a controller already, we offer a range of controllers which represents the majority of what you will find on the market today. As described above, we have done a lot of testing and for a small camping setup there is no point spending money on an expensive controller to gain efficiency - you won't get much back and you should spend the money on a bigger panel instead. Having said that, the bigger controllers do have some nice features if you want them!



CALCULATOR
To help you work out what the best system would be for your needs, we have created a Camping Solar Power Calculator - click here to see

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