Add a battery and a solar panel to your caravan and break the 240 volt power connection permanently. Peter Jackson shows you how.
We were recently looking to upgrade our caravan, however we found that the vans set up with solar panels and batteries were top of the line and out of our price range. Instead I bought an affordable van and added the things that I thought were missing. Here’s what I did in case there are any other (crazy) people who would like to take on a similar project.
Measure power use for a day
I measured the current drawn by each piece of 12 volt equipment (all the appliances and van fixtures that would be used while we are camping away from 240 volt power). This can be measured with either a clip-on ammeter or by inserting an ammeter temporarily into the circuit (most cheap multimeters have a 10 amp DC range). Or you can simply calculate the current by using the wattage marked on the 12 volt appliance or light globe i.e. current = power in watts divided by 12 volts, e.g. the current drawn by a 24 watt light globe connected to a 12 volt battery is 2 amps.
I estimated how long (in hours) each of these appliances will be used each day and entered it in a table. Minutes can be converted into fractions of an hour by dividing them by 60, e.g. 10 minutes = 10/60 = 0.17 hours. To calculate the amp-hour (Ah) usage for each item listed, multiply the current drawn by each appliance by the hours (or fractions of an hour) you expect to use the appliance each day. Finally, add up the ‘Approx Amp-hours usage each Day’ column to give the estimated total daily amp-hour usage figure for each day.
In the sample table (p 25), the ‘Total daily Ah usage’ came to 29Ah per day, which is rounded up to 30Ah per day. The total power required for a 14 day stay would be 30Ah x 14 days = 420Ah. In a domestic caravan it would be impractical to try and carry enough batteries to last that long because of the weight and the cost.
Finding power when bush camping
The best option was to solar power my caravan. There are some down sides to solar; most caravan systems aren’t large enough to run a microwave oven or air conditioner, so you must ask yourself ‘Can I live without those items?’ You also need a back-up system very occasionally for long stretches of cloudy or rainy days.
Knowing that we needed 30Ah per day I selected a 12 volt, 80 watt solar panel, which will supply us with around 30Ah per day (i.e. approx 5 amps x 6 hours = 30Ah) and a bit more on good sunny days. To harvest this much power from an 80 watt solar panel I found that I needed to track the sun rather than just sit the panel in one position and have the sun pass over it daily. I manually move the panel three to four times per day to maximise the power output from the panel. (For an automatic solution, check out www.campatracka.com—Ed.)
If your choice is to use a fixed panel then you may need to buy a higher wattage solar panel than I used or otherwise reduce your daily power usage. My BP 80 watt panel cost approximately $800 a few years ago, although prices have possibly come down now. Discuss what will best suit your application with the solar panel supplier.
Cloudy and no sun?
I chose a 130Ah battery. It weighs 30 kilograms, which is light enough to carry around and lasts me 4.3 days using 30Ah per day before the battery fully discharges—normally enough time for the sun to return. I typically only rely on my battery for two days and then I reduce our daily power consumption because discharging batteries below 50% of their capacity shortens their life. To cut back on power usage we don’t use anything powered by the inverter (unless essential), don’t read so long in bed and don’t use the laptop or television as much. By following these simple steps we can easily halve our daily usage.
If it’s still cloudy after three days then I charge the caravan battery from my tow vehicle. I have installed a 12 volt MotorMate charger in my caravan next to the battery and it delivers 13.8 volts at 20 amps directly into the van battery. By running my tow vehicle motor for 30 minutes I can put another 10Ah back into the van battery, giving us enough power to last almost another day on our reduced power rations. In nearly 200 nights that we have bush camped with this set-up, I’ve only had to use this method of charging four times.
This 12 volt charging system does require quite heavy cabling and Anderson plugs between the vehicle alternator and the van charger. This is because currents of over 30amps can be required, although voltage drops aren’t very important as the charger will work with input voltages as low as 8 volts. I spent a lot of time researching this subject because I wanted to know it would work before spending $240 on a charger.
Read the full article in ReNew 111This entry was posted on Thursday, April 21st, 2011 at 3:09 pm