Defender Off Grid Camper For Extended Touring
To live off the grid independent of powered caravan sites while touring Australia, I installed an additional 310 Watts of solar panels on my Defender. Thus with a 130W and 2x 155W panels I have 440 Watts of solar. 2 AGM batteries provide 250ah of power to run my laptop, fridge, camp oven, lights and other accessories or 240V inverter.
Two Giant Power 155W Monocrystalline panels were purchased on sale. It is ideal to purchase top branded panels if you have the money, but as I can’t afford the luxury, these cheaper Chinese panels will hopefully survive the abuse. My previous 130W panel mounted on the roof has to date coped very well without any issues.
- Max Power: 155W
- Max Power Voltage: 18.6V output
- Max Power Current: 8.35A
In my opinion there are a lot of cheap solar regulators on the market today. Some may very well be high quality units, but as I’ve invested significant money into my vehicle I don’t want to endanger it with a cheap regulator by an unknown brand which could fail and burn out. Hence I invested in a Morningstar regulator, one of the major solar brands. With a 5 year warranty and estimated 15 year lifespan Morningstar regulators are top notch reliable units.
I chose the Morningstar PS-30M Prostar PWM 30 Amp regulator with LCD display so I could monitor the battery health without needing external gauges. It is sufficiently rated to handle the nearly 17 amps output of the 2 panels allowing plenty of spare room for occasional over rating or future additions. An MPPT (Maximum Power Point Tracking) regulator would have been preferred but the significant cost of top branded MPPT regulators forced me to stick with PWM (Pulse Width Modulation).
A Giant Power 130ah AGM deep cycle battery was chosen as my second house battery. This is mounted in the rear passenger footwell. The whole system is independent of the vehicles wiring.
The depth of discharge cycling of the battery should give me many years of service as I’ll only skim the top 30-50% of the available amps.
- 30% DOD 39A = 1650 cycles
- 50% DOD 65A = 700 cycles
- 100% DOD 130A = 300 cycles ie. Dead in under a year.
A cycle can be interpreted as one day of discharging then charging. During the day however, the solar is powering the accessories so the battery capacity won’t begin to drop until nightfall.
For cables I used 6.5m of 6mm² solar cable and 2 T branch MC4 connectors and added appropriate fuses to the battery and solar inputs for protection.
Home Made Roof Rack
Designed to match my 2 pre-existing roof bars, the roof rack mounts the 2 panels flat on top. When additional solar is not required, the modular design allows the rack to be removed from between the roof bars. As the panels are not directly facing the sun due to flat mounting I’ll lose around 15-20% of potential output due to inefficiency. However the benefits compared to a fold out panel which can be adjusted to follow the suns path is the panels are always charging the battery even while driving and can not be stolen easily.
The rack was manufactured from 2mm x 40mm angle and 2.5mm plate steel.
Required Power Calculations
To determine the power usage a multimeter measured the amps drawn while operating my accessories. I then guesstimated the number of hours each day I would typically use that item to calculate my daily power requirements.
- Laptop – 8 a/h x 5 to 8hours = 40 – 64 amps/day
- 240v Inverter – 2 a/h x 2 hours = 4 amps/day
- Lights – 2 a/h x 4 hours= 8 amps/day
- Total load 52 – 76 amps/day
The “Max Power Current” rating written on the rear of the panels determines daily output.
2 panels x 8.35A = 16.7A/hour
Solar hours are the number of hours in a day that the sun is at peak radiation, usually between 9 to 3pm. It various throughout the year and in different regions. The panels will continue to generate power outside of these times as long as there is light on the panels, it’s just that the output will be much less then during peak hours.
5 – 7 solar hours day x 16.7A = 80 – 112 amps/day output
De-rating the system by 20% provides a more realistic estimate accounting for the flat mounting of the panels, voltage drop in the cables and losses from the regulator.
80 – 112 amps/day minus 20% inefficiency = 64 – 90 amps/day estimated output
Thus I should have 12 – 14A excess each day with an estimated output during solar hours of 12.85A.
Real World Results To Date
I took my Land Rover Defender tourer out for a week camping to test the system.
- Peak output observed with full midday sun 16.8A
- Full midday sun with battery under load 13.6A
- Shady campground with panels partly covered 6A
- Overcast or late afternoon 2A
This solar system will hopefully allow me to save money while travelling as I will no longer need to pay an extra $10 to $15 per night for a powered caravan site when I want to run my laptop for long hours. I will also be able to continue editing videos and photographs when I’m in remote outback locations.
310W Solar System Cost
- 2x 155W Monocrystalline Solar Panels (on sale) $606
- Morningstar ProStar 30A Regulator $275
- 130AH AGM Battery $295
- Cables/Bolts/Steel/Shipping $300
- Approx. $AU1476