Tuesday, 31 March 2015

Where it all begins...

Cindy and I started camping with our boys a few decades ago in a 12-man tent, huge tarp and many poles and ropes. We had a break for a few years but have recently purchased a 12' camper trailer so we can do it all again with our youngest, Emily.

Our newly purchased camper trailer
Our previous camping trips relied on using an esky and ice to keep the beer cold (ok, food too). Now, however, we've decided to buy a portable fridge / freezer and tackle the energy requirements using solar. When the suggestion was first made by Cindy I was somewhat hesitant, but only because I knew nothing about it. I've had plenty of (hobby) years experience with electrical stuff so figured it was time to take on the challenge and learn everything I needed to know.

The first step was to try and understand just what I needed in a solar panel. Through much reading, however, I discovered what I really needed to know was what sort of power consumption I could envisage being used by a portable fridge / freezer and anything else that could potentially be used, such as lighting.

We went shopping....and bought the Engel 80L fridge / freezer (model MT80F-G4C-S). The decision was made mostly on the basis we wanted both a fridge and freezer. The combined unit would give is the volume we required in the least amount of space. The specifications indicate power usage can vary from 0.5A to 4.5A. The actual usage will naturally depend on the environmental conditions, how many times the lid is opened, how long it has been running for (initial run will use more energy as it needs to reduce the internal temperature).

Our new 240W panel and ArkPak
My next purchase was a 100AH deep cycle battery. I also bought an ArkPak (AP730) as it not only houses the battery but provides 2x 10A cigarette lighter outlets, external battery terminal connectors and an Anderson plug connection. Another attraction for me was the LCD display which allows me to not only see the state of the battery but also shows me the net difference between power going in (from the charger) and what's going out (from the fridge and anything else connected).

I played with the fridge on different settings to see what would give me the best compromise of fridge / freezer temperature and power consumption. At this stage I use a thermostat setting between 3 and 4 (it ranges from 0 to 5). Over a period of 12+ hours I've determined the fridge consumes an average of around 2.0A - 2.2A / hour (sitting in my garage).

The next step was to start looking for a solar panel; but what should I buy!

There's a number of factors that determine the required panel size (in Watts), such as:
  • The capacity (AH) and number of batteries being used;
  • The total energy requirement;
  • The efficiency of the regulator;
  • The quality of the cable being used, especially over long runs;
  • The number of hours of available light;
  • The temperature and altitude;
  • The number of days expected to be without an alternative power source;
  • and more...
Apart from the fridge / freezer and possibly some LED lighting I don't expect to have great energy requirements so I settled on a 240W panel and a 100AH battery. This was based on the following:
  • The fridge / freezer requires approx. 2A x 24 hours = 48A. On the basis the battery will be without sun for 18 hours, and it is recommended to not let the battery fall below 50% before re-charging, the minimum battery requirement = 48A * (18 / 24) hours / 0.5 = 72A. To allow for any extras such as phone charging and LED lighting I decided on a 100AH battery (rather than a 75AH).
  • On the basis that it's recommended to assume 6 hours of sunlight and 80% efficiency from a panel, the minimum panel size required to fully re-charge the 48A consumed is 48A / 6 hours / 0.8 efficiency * 12 volts = 120W. Rather than go with the bare minimum I chose to go with a 240W panel to cater for less than ideal weather conditions.
After a little searching on EBay I chose a 240W panel provided by Outbax Camping. A link to the official site is provided below.

Heading off to our first trip with the camper and solar gear
With this basic setup we ventured off with some good friends (the Johnson's) to a nearby campsite which is so good I'm not telling where it is ;-)

The plan was to spend 4 days away from everything and just relax - and play with our new toys.

The weather conditions weren't too bad but we did find ourselves chasing the sun a fair bit for the first few days. It turned out to be too much trouble so my good friend Stuart and I sat by the water and drank a few beers....all day.

Catching some early morning sun rays
Stuart and I spent a bit of time comparing the relative output of our panels. My panel was using the original 15A regulator supplied, whereas Stuart has his panel connected to a Ctek 250S Dual 5-stage charger. This charger is truly awesome, capable of delivering up to 20A to a 12v battery (40-300AH). Not only does it safely delivery a stable current based on the battery's current state, but it can take the excess voltage provided by a solar panel, reduce it to 14.4v and increase the current.


Having seen the Ctek 250S Dual in action I wanted one. So I bought one !

I spent a day making up cables (a story for another blog) and as you can see I was able to achieve a maximum output of 196.5W - how awesome is that (remember, 80% efficiency is 192W).

Yes, I'm stoked.

This is where the adventures now begin. We're off on another 6-day trip in a few days time. I finally get to play with all my new toys and work out just how well everything performs. The current weather is crap so it's going to be interesting.

Some useful links:


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