I have a lot of experience with solar panels for camping, caravans and travel vehicles generally. People often ask me what panels they need for their particular situation so I thought I would pass on some general information to help those looking to set up travel vehicles with Solar.
Solar Panels, in an outdoor scenario, are designed simply to recharge 12 volt batteries. You need enough panels to charge the batteries during the day so that the power is stored and used overnight, then recharged the next day. For most people this means using a 12volt compressor fridge, led lights, 12volt phone charging, water pump for taps, and perhaps a television. You then need enough battery bank to get you through the night so that the voltage early morning gets only to around 12volt. Batteries will work lower, but this is not good for the batteries and harder for the solar to recharge during the day. Often you will need to use the batteries during the day whilst at the same time recharging with the solar panels.
For this (except for the fridge as below) then about 100 watts of solar together with a 100 amp hour deep cycle battery is sufficient. However, adding a fridge is a little more complicated.
I always say that you need to allow at least 100watts of solar per 50L of fridge and 150watts of solar per 50L of freezer. Likewise you need at least 100 amp hours of battery per 50L of fridge and perhaps a little more for 50L of freezer. This is assuming that you are remaining outdoors, and not just going away for the weekend and can afford a slow loss over a couple of days. There is always the odd cloud in the sky, or a hotter day when the fridge is opened more often – or someone drops by for happy hour and the fridge gets used a little more. For this reason, I say at least. Always, a little more is beneficial.
There are basically two types of solar panels. Fixed and Portable. Fixed panels, as the name suggests, are permanently mounted onto a vehicle and are always connected, via a regulator, to the battery. Unless, it is extremely hot you will need to find sun, or more particularly light, and park your vehicle accordingly. It means that the panels are set and forget which is always helpful. However, you would be surprised how many roads in Australia have trees along them placing your panels in the shade whilst traveling….. However, this is still a very good option. However unless you have a large system with small power draw this needs to be supported by some sort of supplementary charging. This could be folding panels, dc charging, generator or plugging into the mains somewhere…
Portable panels, are generally folding with their own regulator on them, and can be put out when stationary and hooked into your battery bank. They can work alongside fixed panels and if you have more than one battery (which if you have two sets of panels is most likely) then you can connect each panel to different terminals in the battery bank. (Your battery bank should be set up in parallel rather than as two separate units ) This means one solar set goes to positive of the first battery and negative of last battery in the bank and the other panel set goes to the negative of the first battery and positive of the last battery.
Unless you have a large roof there is limited space to place panels. Some people like me, have a bus, truck or large motorhome and can place panels on the entire roof. This then means that you can have larger battery banks, more panels and large inverters to run more appliances off the batteries. I have this, with 800 amp hours of battery and a bit under 2,000 watts of solar and run most of my motorhome on 240v including a large 500 litre household fridge freezer. And yes, there are times when I need to charge my batteries with my generator. I also have a dc battery charger, so I charge the batteries whilst driving.
When selecting a panel, check out the warranty. Most of the good brands have a warranty of 20-25 years. This is a good indicator of the expected lifespan of the panel. Although technology will definitely change in this time, the longer the warranty the better you can expect the quality to be.
The other thing to be careful of is that there is 36volt crystal for houses and 21-22 volt crystal for camping. Whilst both may be good quality, 36 volt regulators usually don’t start charging until the voltage on the panel is higher. Therefore, for camping you can get less charge time during the day – which can mean you may need more panels to do the same job. With most vehicles, you are limited for space so I highly recommend 21-22 volt crystal for charging your 12volt system.
Solar is a very good way to charge your batteries, but like all systems it is not the only answer unless you simply want to go without a 12volt fridge, tv, technology, and use battery operated lights. Most of us have done this in the past, lighting fires and the like. However, if you wish to travel anywhere and stay traveling then solar is definitely worth the money.
Hope this was helpful.
In my previous post, I mentioned some other camping issues that may be helpful as well.