The ten unbreakable rules for motorhome and caravan electrics
Here is a list of what I consider the 10 most important rules when designing, building and using a motorhome or caravan electrical system
1.SYSTEM VOLTAGE – Keep the vehicle system voltage and the house system voltage the same. If your vehicle is 12 volt – then make sure the house system is also 12 volts. For larger motorhomes 24 volt is much better – but do not mix voltages! I know that there are mixed systems out there – but these are complex and very difficult to fault find when they have a problem.
2.AIR CONDITIONING – You cannot run Air Conditioning (normal compressor type) from a solar powered system. Aircon uses far too much energy to practically be powered from a battery/solar system. You will need a large generator if you intend to run aircon. (That is not to say that you can not use solar for the 10 months of the year when you don’t need aircon).
3.CHARGING – There are no “free lunches”. Whatever energy you take out of a battery, you must put back (with a little interest). If you take 25 amp/hours out of your battery system overnight, you will need to produce and put that back during the day (in addition to whatever you use during the day) .
4.FUSES – Fuse EVERYTHING! When a fault occurs in a circuit that is correctly fused, the fuse blows. When a fault occurs in unfused circuits things melt and fires start. I know which I would rather deal with! Make sure you know where all the fuses are and be sure they are correctly labelled – Murphy’s 3rd law states that “lighting fuses will only blow at night when your torch batteries are flat”.
5.APPLIANCE VOLTAGE – Run everything you can at the native voltage. If your house system is 12 volts – your lights, fans, TV, fridge and every other electrical item should also be 12 volt if possible. This is the most efficient configuration. It costs energy every time you convert it – the very best inverters approach 90% efficiency. Even these are throwing away 10% of the energy that your poor solar panels are working hard to produce each day.
6.WIRING SIZE – Use the correct sized wiring. You may save $10 by fitting a cable with less copper in it – this is insignificant when compared to the issues you will have when the fridge stops (and the beer gets warm) due to voltage drop in the cable or the solar array does not produce what it should. (Don’t listen to auto electricians recommendations regarding cable size – do the math yourself or find someone who knows about this stuff).
7.PHANTOM LOADS – Make sure you do not have “phantom loads”. Phantom loads are appliances that use a small amount of power all the time. 24 hours times “a small amount” is a lot of power to throw away. For example a phantom load of just half an amp will consume 12 amphours every single day. This is enough power to run our microwave for 15 minutes each day!
8.WIRING DIAGRAM – Always carry an up-to-date “as built” wiring diagram. Even if you cannot resolve an issue yourself, it is about 100 times easier for a tradesman to find a fault if you have a diagram. If something gets added or changed, make sure the diagram is updated.
9.MAINTENANCE CHECKS – Make a list of routine maintenance checks: Battery water, terminal tightness etc. Discovering a problem BEFORE it happens is one of the most joyful things ever.
10. BATTERY LIFE – Be kind to your batteries – avoid deep discharges. Flattening lead acid batteries is almost the worst thing you can do to them. Remember – a 100aH battery should not be expected to regularly deliver 100aH – it may do it once or twice – but this kind of abuse will surely kill the battery almost as fast as driving a 6 inch nail into it.
Have I missed any?
Have you broken any of these rules – what happened?
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