Our Camper trailer electrical and solar upgrade

Setting up a decent 12V system in a 4WD or Camper Trailer takes time, money and a bit of knowledge. I knew when we purchased our Outback Expedition Deluxe Camper trailer, I’d have to do a few upgrades to get it the way we wanted.

We currently run a 55L Evakool Fridge/Freezer in the Land Cruiser, which has been fantastic, but its always a fine balance trying to keep some things frozen and others not. On top of that, you can never have enough fridge/freezer room!

With a 9 day trip to Steep Point on the cards, we had to be 100% self sufficient, and had to get something organised. I wanted a camper trailer battery setup with solar that would reliably run and not require significant intervention.

Self sufficient camping
The aim of the game is fully self sufficient camping, including a 55L fridge and 55L freezer

Existing electrical system

The existing camper trailer 12V setup on the Outback camper trailer was reasonable, but not big enough for our needs. It was a 100 amp hour deep cycle battery connected to a few LED lights, water pump and had plenty of cigarette/Anderson plugs around the place.

There was a little 40W panel on the front toolbox which wasn’t working, along with a small Projecta solar regulator and Projecta DCDC battery charger (DC20). The battery would charge from the vehicle, but we often stay in one place for a long time, so an upgrade was required. In a vehicle you’d get away with moving around a bit, but as the camper stays put, you need another method of keeping the batteries topped up.

For the rest of our 12V posts, check out our Electrical page.

Camper Trailer soft floor
Our camper trailer when we first bought it

A new freezer

We decided it would be brilliant to be able to split our fridge and freezer completely, and picked up another 55L Evakool Fridge Freezer (GFM55)with digital thermostat for $800 on one of their ‘seconds’ sales. The idea was to use the new one with digital controls (as you don’t have to keep adjusting the temperature knob) as the fridge, and make the old yellow one (FM55) into the freezer.

The FM55 is supposed to be slightly more economical, and also runs the genuine Danfoss Compressor.

Huge power consumption from a freezer

I like to do things properly the first time around, and thought I’d work out how much power was required before committing to any solar panels or batteries. I did several tests on the Evakool FM55 as a Freezer with an inline amp meter, and was quite surprised at how much power it consumed.

To maintain items at below -15 degrees, it would use anywhere from 55 – 85 amp hours over a 24 hour period (2.3 – 3.5ah on average). For those of you who know 12V gear, you’ll understand that’s a lot of power. Looking around, it appears this is fairly normal for most 12V fridges, so something to be aware of.

Of course, you can dramatically reduce the consumption by keeping items at only -3 degrees – they are frozen, but -18 is the standard recommended, and one we’d like to stick to for fresh fish. 

This consumption was the ultimate kick to create a camper trailer power setup that would be significantly larger than I’d first considered.

55L Evakool yellow fridge/freezer
The 55L Evakool, relocated from our 80 series and into the camper trailer

Working out what to buy

With the above results, I knew I was going to have to spend a small fortune setting up the electrical system we wanted. You don’t want to run your batteries down below 50% charge, and ideally 2 – 3 days without charge is recommended l in case of overcast weather, so I’d need to have at least 240 amp hour of batteries, and a substantial camper trailer solar setup.

I did the measurements, and worked out I could fit two 135 amp hour deep cycle batteries into the side of the camper trailer with some modifications. They suggest 2 watts of solar per amp hour of batteries (which I believe in most cases is overkill), so I decided on two 200 watt solar panels from eBay, which I’d mount semi permanently on the boat loader.

Running 400W of panels means you need a big, quality regulator and I wasn’t about to skimp on a cheap one. I ended up choosing a Victron 100/30, which has some great features and a great reputation. I looked into removing the Projecta DCDC battery charger and replacing it with a newer one that has a solar input, or a Redarc 1240 BCDC, but wasn’t convinced it was the best way about it. Several people confirmed this on various forums too.

Handy calculators and links

Solar panel angle and pitch

When I was looking at mounting panels permanently, I was curious to know how much power I would lose. The ideal scenario in terms of efficiency is to have portable panels that you move around, following the sun throughout the day.

However, that’s a pain and after finding this table, I reckon its not really worth it! Solar quotes made this, and all you have to do is find your location within Australia, pick the angle the panels are going to sit at, and the direction they will face (0 degrees being north) and you have a figure. Check it out here – Solar Quotes Panel Angle and Pitch.

Redarc cable size

Getting the right size cable is imperative. Get it wrong and things will run inefficiently (if they do at all), and you’ll be pulling it out and doing it again. Redarc have a fantastic PDF which can be used to determine the correct cable size. Simply align the length of the run with the current drawn, and you have your cable size somewhere in the middle.

Buying all the gear

Evakool GFM55L Fridge

Evakool released their new grey plastic fridges some time ago, which normally retail for $1200. However, from time to time they have a ‘seconds sale’ at $800 including shipping, and I managed to grab one. At the time I didn’t realise they run off an EK25DC compressor, which is a copy of the well known Danfoss.

That was initially concerning, but after a bit of research it seems this is becoming common practice; even Waeco are doing it. 

Installing 12V electrics
The new Evakool Fridge/Freezer for the fourby

200 watt mono solar panel x 2

Solar panels have dropped in price significantly. 10 years ago, you’d pay a small fortune for 400W of solar panels. I picked up two 200W panels from Low Energy Developments on eBay at $174 each (now $161.50), with shipping to Perth ($61).

Buying solar panels from eBay is not a new thing; there have been thousands sold in the last year alone, and many more before that. I believe in finding a product that has solid reviews, and that’s economical. I’ve had a 100W solar panel from eBay for about 5 years now which is still going strong, and another 190W folding panel that’s a few years old.

To give you an idea, a 150W solar panel from Redarc retails for $578. They sell great amazing quality gear, but there’s no way I could justify that sort of money. I got a bigger panel with a 10 year warranty for 30% of the price.

That said, be very wary of panels that are cheap; a huge majority of what is on eBay is falsely advertised, and they are selling panels that are not able to generate their claimed wattage. Have a read of this – eBay solar panels; how to avoid getting ripped off.

Camper trailer solar
400W of solar pumping the power in

Victron 100/30 MPPT regulator

I did hours and hours of research on solar panel regulators. If you are running a decent sized panel, you want to look for one with MPPT functionality. Victron have an amazing reputation, and they sell the bigger units for house PV systems, so know what they are doing. I picked mine up from Low Energy Developments off eBay at $270.

Victron MPPT regulator
The new Victron MPPT regulator

If I didn’t already have the Projecta DC20 on the camper trailer, I might have considered a Projecta DC25 which has the solar input as an option. The Redarc 1240 BCDC is also another great option, but I heard mixed reviews from those using them primarily as a solar regulator, and that’s what its main purpose will be.

Parallel or Series panels

One of the other benefits of the Victron is that you can run your panels in parallel and series. In other words, you can have the power coming in at 18V (normal for a 12V panel), or 36V, all the way to 100V. On the other end though, the Victron will convert it back to the voltage that your batteries are running at.

I did way too much research on whether to run the panels in parallel or series, and ended up deciding on series, with the option of easily being able to swap it back. Essentially then, I’m feeding 36V into the regulator, and its putting out about 14V into the batteries.

The intention is to have the Victron unit permanently mounted, so the panels are charging all the time; whether we are driving or not.

Victron bluetooth dongle lead

One of the shortfalls of the Victron unit is you can’t tell what its doing in detail without a bluetooth dongle adaptor. It will tell you whether its charging in bulk, absorption or float, but you can’t tell how many watts or anything.

For $76.50 from Low Energy Developments I picked one up, and its amazing. I can access the regulator through the Victron app, which tells me what mode its in, how much its charging, and it logs the total generation for the day for a full month.

Victron app on my phone
Using the Victron bluetooth app on my phone

Power AGM deep cycle battery 135AH  x 2

Deep cycle batteries are a difficult thing to buy. At one end of the scale, you have Full River, which are very high quality, and the other end lies a whole heap of no brand name ones imported from overseas. I got pricing from Goodchild Enterprises in Cockburn (who are fantastic) for Bosch 120 and 150 ah deep cycles, and then realised I couldn’t fit a 150 in the camper anyway.

A compromise was found online through Autoelecau on eBay, where you can buy the 135AH Power AGM batteries with a 30 month warranty. I was going to get them online, but needed them quickly and bartered with Power Crank in Welshpool, who delivered two to me for $620. I’ve seen these in various scissor lifts, and a good friend of mine has run a big 210AH unit for several years, and given it a hammering.

These are connected in parallel, giving me 270AH of power at 12V (with realistically 135AH of usable power)

Power AGM batteries
Two new 135aH batteries in parallel. Also note the Projecta 20 amp DCDC battery charger mounted on the side of the camper, and the Victron bluetooth dongle.

MC4 connectors, anderson plugs and lugs, crimps, and various other bits

Last on the list is all the bits and pieces to put it together. I ended up going to the 12V shop in Welshpool who were very helpful, albeit a little pricey. I could have gotten everything from eBay for much cheaper, but it would have come without the advice, and the help the guys gave to crimp bits and pieces for me.

I chose 6 B and S Cable (14mm squared) to handle about 20 amps over 6 metres. Its hefty cable, and was fun to install.

Boat loader system

If you want further information on the boat loader solar system, including close up shots of how it all works, I wrote a new post which covers it in more detail – Boat loader solar panel system.

Overall cost; budget blown out of the water

To be brutally honest, I spent way more than I wanted to, and had I have done more research in the beginning I would have possibly canned the whole idea. However, you can learn from my mistakes, and make your own call!

If you are planning on running a freezer, expect to need a major 12V upgrade.

Camper trailer modifications

I set about installing a second battery tray, and making the existing one stronger on the camper trailer. I see a lot of people put batteries in the front toolbox, but that’s a lot of weight up front, and doesn’t make good use of space. Now, the batteries are balanced over the axle (one in front, and one behind), and they make use of dead space anyway.

I made the panels hinged on one end of the boat loader, so I could tilt them up and sit them flat if required. This means I don’t have to worry so much about facing the panels north – if they are flat they will generate power in any direction the camper is facing. Yes, not as much as if they were perfectly angled, but having oversized the panels it doesn’t really matter.

I found a great document (see handy calculators and links above) that shows the power loss in various parts of Australia at different pitches and used that to do some figures. In Perth, the optimum angle is 30 degrees, and facing north. However, if the panels sit at 60 degrees, you lose 11% of power, and that’s the angle the boat loader sits at when open. Pretty insignificant in the scheme of things!

Testing it all out

I have to admit I was pretty excited to see how it all ran, and connected the regulator up to the batteries. Even late in the afternoon, it was comfortably pumping 200 watts into the batteries. We’ve used it over 12 days in the mid north west touring Lynton Station and Ellendale Pool as a freezer, and it works beautifully.

It’s awesome to see that something which took a fair bit of time and a lot of money works as it was designed and intended to. I might be poorer as a result, but we can now take frozen fish and crays home, whilst taking frozen meals for our little bub and ourselves, making camping even easier.

On average, the batteries were fully charged by 12 – 1PM with the panels facing roughly north, and locked at 60 degrees. The system would generate roughly 1000 watts every day, with some cloud each day. If we used more power, the panels would easily replace it by the end of the day.

Very shortly we leave for 9 nights at Steep Point, where it will run everything required to be entirely self sufficient. To say I’m keen is an understatement!

Camper trailer solar
12V power for days

The cruiser setup

The only modification I did to the Land Cruiser was to run 6 B and S cable from the second battery to a fuse and then through the chassis to an Anderson plug on the rear. This is where the DCDC battery charger on the camper plugs into and takes power from.

Asides from that, the system is the same; a 66AH yellow top Optima battery that is the main, cranking battery and which the winch runs off. Every other ancillary accessory runs off a 105AH calcium deep cycle battery. This includes the new GFM55 Evakool Fridge, LED strip lighting, an LED flood light, various 12V chargers and a 300W Dick Smiths inverter for charging some camera batteries.

The batteries are separated by a Redarc battery isolator, which has been brilliant.

I run a 100 watt panel on the roof racks which is permanently mounted, and have a 190W folding panel that is put out if we are in one spot for a long time. This panel is major overkill, and frankly a pain in the behind to move around and take with us.

It’s rare for the battery voltage to drop below 12.5 volts even early in the morning; this system is stand alone from the camper trailer and is well proven.

You can read more about the 80 Series here – 80 Series Land Cruiser Build up by 4WDing Australia.

Land Cruiser solar on the roof racks
100W panel on the roof of the Land Cruiser
Dual battery monitor by Projecta
Our Projecta dual battery monitor

Important points for you to consider

Too many 12V systems are built on guess work. I knew very, very little about 12V electrics before starting this, but took the time to read and learn. There’s so much information online; you just need to take the time to find and read it!

I’m not one to build something and then re-build it when it doesn’t work; I’d rather put the time, effort and money in and do it right the first time. This stuff might look complicated from a distance, but its really not. If I can learn it, I promise you can too.

Battery size

The battery, or batteries are the heart of your 12V system. Working out how big they need to be is actually very simple. Every accessory you have (fridge, LED Lights, water pump etc) has a rated power consumption, and you just multiply that by how long it runs for each day. When you know how many amp hours you need each day, think about how long you want to be without any charge. Solar panels are fantastic, but if the sun doesn’t shine you can be in trouble really quickly. Allow 2 – 3 days without charge if possible.

So, lets say you use 50 amps every 24 hours, and you want to last two days without charge. That’s 100 amps, and given you should never run your deep cycle batteries below 50% state of charge, you need a minimum of 200 amp hours of batteries. Bigger is better, but its also heavier and more costly. You have to weigh it up for your individual situation.

If you want to know more, check this out – Are you damaging your 12V deep cycle batteries?

Deep cycle battery state of charge

Panels vs generators

Generators are still fairly common, mainly for those with caravans who run camping air conditioners and bigger electrical appliances. However, panels have become so economical that there’s a massive switch. If you can get away with panels then do it; they are silent, free once set up and greener.

Panel size

The next thing to decide is your panel size. I see the general rule is 2 watts of panels to every 1 amp hour of batteries, but I reckon that’s overkill for most situations. Your panel size can be worked out by the number of daylight hours, the ambient temperature and how much power you need to generate. Have a think about where the panels are facing, as this also plays a big role.

12V Solar farm while camping
Lots of portable panels too

Permanent or portable panels?

You’ll get all sorts of answers on this, and the end result is simple. It needs to suit your requirements, end of story. The ideal situation is probably a combination of both, but that’s not always possible. Permanent panels will generate less power than portable ones that are moved around to follow the sun.

That is a given. However, its also time consuming, and a pain to move panels around. I’ve got both, and decided I didn’t want to be moving camper trailer panels around every couple of hours. I’d rather be relaxing by the beach!

One of the issues we have with panels that are big and semi portable is if the camper is set up under trees, we don’t have much option for charging the batteries. However, there’s no way I’d be moving 400W of panels around to chase power!

If you want to know more, check this out – Portable vs permanent 12V solar panels.

Usable daylight hours

This is an interesting concept, and one you need to have a quick think about. The length of days in Australia varies a lot from one location to another, and we aren’t talking about the second the sun shows its face to the second it disappears.

Usable solar power hours are much shorter than that – generally around 6 hours a day is normal in Australia. You can check this on the Bureau of Meteorology page for your specific location. If you bank on having 9 hours of sun generation and you only get 6, you could be in trouble!

Ambient temperature dramatically affects power consumption and generation

Solar panel efficiency drops considerably as the temperature rises. It’s along the lines of 1% less power generated for every degree the temperature rises. This is why on a cold winter or spring day, you will generate much more power at any one time than you would in the middle of summer, when its scorching hot. It’s also why so many people find their solar systems don’t cope when they head north.

A double whammy is this; your fridge or freezer (which is usually the highest energy consumer) also has to work much harder in warmer weather. I’ve heard figures of 5% more power consumed for every degree rise. If you’ve got a fridge in a hot toolbox on the front of your camper trailer, you may easily use double the normal power!

MPPT regulator

Maximum power point tracking is relatively common in household solar system installations, but not always for 12V systems. They are more expensive, but are much more efficient, and generally well worth the purchase. One thing to note is that some eBay panels come with ‘MPPT’ regulators that are not actually real! If the price seems a bit ridiculous, query it!

12V solar panel regulator
What solar regulator is best?

Cable size

Another major part of a 12V system that is overlooked is cable size. Current flowing through cables makes them warm, and if you try and push a lot of power through a tiny cable, its going to get hot and melt, or it will run very inefficiently. Small cable also suffers badly from voltage drop, which will affect your appliances and make them run less efficiently.

The motoring industry has a stupid way of dictating cable sizes, which confuses everyone. Electrical cables are generally measured in mm2, but the automotive industry uses outside diameter size which includes the insulation thickness. A 3mm diameter cable is only 1.13mm2, and if you get the two mixed up you will be in trouble. Redarc has a great cable size document that allows you to work out what cable to run if you know the power it will move, the voltage and length of cable.

Regulator cabling
Big, heavy cable running to the regulator

Use it

When this post comes out, we will be days away from leaving to Steep Point. We’ve got 9 days up there, and will do a heap of fishing, diving and 4WDing. For those 9 days, we will be 100% self sufficient, and its a good feeling knowing we can take fresh fish home, and frozen home cooked meals up with us.

What’s your 12V system?

I’m always keen to know more about how people run their own 12V systems, so leave a comment below and let me know how yours is set up!

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  1. Hey Freddie,

    Great work, and I’m glad it was useful! Steep Point and DHI are incredible!

    All the best

  2. freddie de cuyper says:

    Great article which I have read many times now,it helped me no end getting our mini caravan set up for self sufficiency with solar.Did all the research a, read your article and the result was outstanding.Off grid for around 9 days,Steep Point and Dirk Hartog,fantastic!Got a Renogy 400w solar panel and controller set up with a 125W lithium battery,brilliant.Thanks again.

  3. Hi Aaron I would not have a clue how to go about this , you mentioned you are in Perth is there anyone you would recommend

  4. Hey Wade,

    We sold this camper trailer a while back, but yep, the solar was charging the batteries and everything running off the batteries.

    All the best

  5. Wade Langford says:

    Great article and thanks, I’ll certainly be using this as a basis for setting up my camper trailer (an MDC similar to yours). I’m just wondering, have you got your discharging elements (fridge, lights etc) connected directly to your battery as well as your charging elements? That is, are your batteries charging (solar) and discharging (fridge etc) at the same time?
    Thansk again.

  6. Ther’s great little app for solar panel angles called Solar Tilt. Amazing how a few degrees either way effects the panels output

  7. Cheers mate. Yep, you’ve got to do it the right way around – too much guess work involved in 12V setups for my liking.

    Doing things twice over gets tiring real fast.


  8. Thanks Aaron. A good piece and a model of planning. The only way to avoid a system that fails to deliver is to do an energy budget and meet it.

    I’ve used systems built by others and learned some hard lessons.

    The biggest draw is the fridge and you can’t believe the consumption figures put out by the manufacturer. My 60l EvaKool is rated at 1.5 Ah at 30 C ambient in fridge mode but in fact it draws much more at times. (See http://12voltblog.com.au/how-much-power-does-12volt-stuff-use/ for some other test figures).

    The other whamee and a related one is that on my setup it can be 20 C ambient but will be 40 in the fridge box when the CT is parked in the sun with the hatch doors closed. Following the 5% rise in draw for every degree warmer rule, that means the consumption will be double at least.


  9. Hey Trevor,

    Cheers for the tip. Sounds useful in the right application. I’m happy for my main battery to lose 20% in the Land cruiser, as its a yellow top optima and easily handles it, whilst giving me a little bit of extra amp hours to run gear off. I can see how it would be an issue though if your main battery wasn’t designed to be cycled.


  10. Great article. Another good thing to look into, new to me, is programmable VSRs (Not related to solar though but dual batteries and aternators). Most VSRs only disconnect at 12.7V, but that is 80% full for most AGM batteries so you’re losing 20% to the main battery before they disconnect from each other. Not great. A programmable VSR lets you set the correct engage and disengage voltages to suit your battery’s specs. Hope that helps.