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camping off-grid - power, batteries, solar, fridges


  • one of the main issues when camping off-grid for an extended period is power supply to run fridges and other devices
  • for short periods, lithium ion batteries or lead acid battery may suffice but for extended periods these need to be re-charged and one does not want to rely upon running the car to re-charge them.
  • caravans often have gas powered fridges

Basic set up for a 12V car auxiliary battery system

  • 12V battery - usually 100Ah deep cycle to fit a standard battery box (preferably LiFePO4)
    • NB. these CANNOT be used to jump start the car!!
  • battery box with voltmeter and various plugs including at least 2x Anderson plugs (these are bidirectional 50A)
  • Anderson plug cables to your devices with an inline fuse in the system to avid short circuits damaging your battery or starting a fire
    • optionally have Anderson plug cable with cig lighter female port on other end (or two of them)
    • optionally have one plug to two Anderson plug cable
    • optionally an amp meter with Anderson plugs on either side to measure voltage, current and total power used (or supplied) through the cable
    • optionally a connection from boot to externally mounted Anderson plug at rear of car to provide power to your tent, etc via an Anderson plug extension cord
  • battery charging systems such as:
    • 240V AC battery charger for your type of battery (usually 15A or 25A)
    • DC-DC charger if charging from your car's alternator
      • need to connect this to the car battery with an inline fuse
      • need to connect to auxiliary battery via cable with Anderson plug
      • may need to connect a wire to the car ignition system
    • solar panel and solar regulator (this may be included in your DC-DC charger) with Anderson plug

12V vs 24V vs 48V

  • general rule:
    • 12V best for small systems with less than 300Ah
      • easier and safest to use
      • plenty of accessories available
      • can be charged from your car alternator using a DC-DC charger
      • not great for high wattage devices over 500W
    • 24V best for RV's where you need more power
      • cheaper as has half the amp requirement and thus less copper needed than 12V
      • more efficient as less voltage drop across long wires
      • can still use 12V accessories via a 24 to 12V converter and these generally have 90% efficiency
      • BUT solar panels need to be at more than 24V to charge them hence you may need group parallel panels into pairs of series panels to overcome shading issues etc whilst still giving the needed voltage
      • cannot be charged via your usual 12V car alternator
      • still relatively safe as under 30V so 24V is a nice sweet spot for larger more demanding systems
      • you need to connect two 12V batteries in series to get 24V - not all 12V batteries allow that
    • 48V is best for solar power homes or cabins
      • when you need lots of watts, 48V is much better at achieving it

wires for DC currents

  • red is positive
  • black is negative / earth (connect black wires before red wires to a charged system)
  • 6 BSB / AWG is rated for over 50A and has resistance of 1.3mOhm/meter
    • this is used when wire lengths need to be longer than 5m with high currents
  • 8 BSB / AWG is rated for around 40-50A and has resistance of 2.1mOhm/meter
    • this is the most common wiring for main car battery to DC-DC converter
    • 5m with cross section 8.37mm2 at 15A 12-14V will result in a voltage drop of 0.3V along the wire (0.5V if 25A)
  • 10 BSB / AWG is rated for around 30A and has resistance of 3.3mOhm/meter
    • this is a common wire gauge for solar panels
  • 12 BSB / AWG is rated for around 20A and has resistance of 5.2mOhm/meter
  • 14 BSB / AWG is rated for around 15A and has resistance of 8.3mOhm/meter
  • 18 BSB / AWG is rated for around 10A and has resistance of 21 mOhm/meter
  • 22 BSB / AWG is rated for around 3A and has resistance of 53mOhm/meter

portable car fridge/freezer

  • these are generally DC and 240V AC powered and should have a 3 stage battery protection system to turn the fridge off in the event the vehicle battery is going flat (if the fridge is being powered by the main vehicle battery)
  • most have a digital interface which allows user to dial in the desired temperature from 10degC down to minus 10degC
  • some have dual compartments - one as a fridge and the other as a freezer
  • the best size for most families is a 60L capacity but 45L may suffice for a couple
  • a 45L model will generally draw 1A to maintain contents at 5degC in 32degC ambient temperatures
  • fruit and veges are generally placed in the warmer upper parts to avoid spoiling by freezing
  • a 45L model will cost $AU399-$AU699 - check to see if it will fit a wine bottle standing up if this is important to you
  • Dometic CF models are budget level fridges which are more likely to have issues including failure of the lid lock mechanism
  • Dometic CFX models tend to be the favored models for their better build quality but are more expensive
    • my tests of a Dometic CFX 45 on a hot 37degC summer day in the shade:
      • fridge had been filled with drink bottles in main compartment and kept cold in fridge running overnight prior to tests
      • lid not opened
      • fridge set to minus 4degC:
        • probe amongst the bottles in main compartment remained -4 to -5degC
        • probe in empty top section steady at 5.5degC
      • fridge then set to 0degC:
        • probe amongst the bottles in main compartment increased to -2degC by 1.5hrs
        • probe in empty top section steady at 7.5degC at 1.5hrs!!
    • my tests of a Dometic CFX 45 at average 25degC summer day in the shade fridge set to 0degC:
      • probe amongst the bottles in main compartment averaged minus 0.5degC range minus 0.2 to minus 0.7degC
        • probe in empty top section averaged 7degC with range 5.7 to 7.5

Off-grid power supply

  • there are a variety of components required

solar recharge battery system

main options

  • fast charge, high capacity but heavy and expensive
    • eg. 120AH LiFePO4 battery (~13kg) or 55Ah 8kg in a high end battery box (~4kg) with BMS with 20-100A charge rate
  • fast charge, medium capacity
    • HardKorr Heavy Duty Battery Box $AU219 3.2kg
    • 15A battery charger designed for LiFePO4 with Anderson plug connection modification $AU250-300
    • Drypower 12.8V 55Ah Lithium Iron Phosphate (LiFePO4) 8kg $AU799 or a 100AH battery for same price but 13.5kg
  • slow charge, medium capacity, light weight and compact power station
    • eg. Companion 40Ah Rover (~7kg) but only 5A charge rate which limits solar charging

choice of battery and battery box / power station

Charging your auxiliary battery from your car alternator

solar panels

sockets and other miscellaneous issues

  • MC4 connectors
    • weathersealed single wire connectors usually used on solar panels
  • Anderson 12/24V socket
    • a specialized socket designed to handle a high, continuous load which allows charge from your car battery or solar panel to flow to your accessory battery in dual battery systems and hence can be used to connect car to caravan
    • can also be used powering high-draw 12-volt accessories such as fridges and air compressors
    • they come in different current sizes eg. 50Amp
    • tow bar extension wiring:
  • Merit 12/24V plugs
    • similar to cigarette lighter plugs BUT smaller in size and have the advantage of a superior rugged construction and higher current carrying capability
    • can be converted to cigarette lighter plugs

petrol power generators with AC inverters

  • these are important particularly if you need to run higher current draw appliances such as heaters and microwaves
  • they can also be used to re-charge your batteries if the solar is not adequate
  • make sure you get one with pure sine wave inverter to give clean AC outputs that won't damage your electronics
  • also check how noisy it is as they are perhaps the most hated accessories at camp grounds due to their noise (as well as exhaust fumes)
  • some have parallel stacking capability to combine units for greater power output
  • examples:
    • Ryobi RIG2000PCB 2000W Petrol Digital Inverter Generator $AU999 - 24.4kg 2 x 15A sockets and 2 x USB outlets
    • DeWALT DXIG2200 2200W Inverter Generator $AU1299 - 22.5kg
    • Full Boar SD2200I 2200W Inverter Petrol Generator $AU798 - 21kg, 61db
    • Yamaha EF1000iS 1000W 1 KVA Silent Inverter Generator $AU1299 - 12.7kg, 47-57 dBA/7m

more powerful lithium ion off-grid solar kits for homes or sheds

    • Victron 12v 1200w pure sine wave phoenix inverter
    • DCS 12v 200Ah lithium battery storage
    • 31.5A Votronic solar controller
    • Trina solar panels (2 x 310w mono)
    • Victron Battery Protect (low battery voltage protection)
    • 333Ah 48V dual lithium battery system (2 x DCS PV 10W LFP batteries which provide total 15kW continuous load) = 198kg, $AU17,999 for batteries alone (cw 900kg of lead acid cells)
    • Selectronic 7.5kw SP PRO solar controller
    • Fronius 8.2kw Primo inverter
    • 10 ~ 12kw of solar PV panels - should provide around 19kWh even on the most cloudy days in lower latitudes and average winter evening usages for a house runs at around 10kWh.
    • +/- 5kVa diesel backup generator


  • battery packs wired in parallel (reds to reds and blacks to blacks)
    • red wire of 1st battery to main fuse which connects to shunt which connects to distributor box
    • black wire of last battery to shunt then to distributor box
  • distributor box (eg. Victron Lynx Distributor)
    • earth wire to chassis ground
    • red and black wires to the DC fuse box in the AC-DC distribution panel to supply DC outs
  • inverter charger (eg. Victron Multiplus Inverter Charger 3000 W 12V)
    • red and black to distributor box DC in
    • earth wire to distributor box earth
    • 3 wires (active, neutral, ground) from Shore power to AC in
    • 3 wires (active, neutral, ground) from AC out to AC-DC distribution panel with a breaker
    • thus the inverter charger can:
      • combine amps from Shore power AC (eg. 30A) with the amps from the batteries if usage exceeds the Shore Power amperage
      • if power usage is less than the incoming Shore Power AC, then unit can use this to charge the batteries via the same cable to the distributor box
      • provide AC outlets
  • MPTT solar controller
    • red and black “battery wires” to distributor box
    • earth wire to inverter charger earth
    • red and black “PV” / solar wires“ to solar circuit breaker
  • solar panels are wired in series (or 4S2P pending requirements) and wired to a circuit breaker which is used as a disconnect

those with off-grid homes or sheds - consider biogas

  • capturing methane produced from food waste and using it for cooking is a developing concept which may be attractive for many who live off-grid
  • see! which suggests a household could generate enough methane for average 38 minutes cooking per day (it may take 4 years to pay for itself at 2019 gas prices), and in addition, generate compost and fertiliser

consider pico hydro-electric system

  • NB. the following are my theoretical calculations - see an expert before embarking upon such a system!

fast flowing stream without a waterhead

river or stream to provide a continuous water head

  • this is relatively easy just need a pipe from the waterhead source and a pico hydro-electric turbine and this can produce a continuous 230V AC output
  • 750W turbine requires 18m waterhead and a flow of 5-8L/sec using 75mm pipe and may cost $15000-25000 to buy and install

no river stream to provide a continuous water head

  • most people don't use their solar power when it is generated during the day
  • storing your solar power is problematic, one solution is expensive batteries as above, another potential solution for those whose properties reside on a steep hill is a pico hydro-electric system
  • a large water storage is held at BOTH top and the bottom of the property
  • during the day the solar power drives the pump to send the water from the bottom tank to the top tank
  • at night as required, the water can be released from the top tank to pass through turbines to generate hydro-electric power
  • the amount of hydroelectric power able to be generated in this way is:
    • Change in potential energy of water = mass water x g x height difference
    • Power assuming 100% efficiency = change in PE per second
    • thus Power in Watts = efficiency factor x density water x water volume flow rate x gravity constant x water drop in meters
      • efficiency factor is 0-1 (pico turbines are generally rated at 70%)
      • water density = 1000kg/m3
      • water volume flow rate in m3/sec
        • can use the Hazen-Williams equation for a gravity fed pipe system:
          • velocity in m/s = k * C * R0.63 * S0.54
            • C = roughness coeff of pipe = 100 for cast iron, 110 for concrete, 140 for copper, 150 for plastic
            • R = hydraulic radius in m = the proportion between the area and the perimeter of your pipe = radius / 2
            • S = Slope of the energy line (frictional head loss per length of pipe). It is unitless, but sometimes expressed in m/m; = height drop / pipe length
            • K = Conversion factor dependent on the unit system (k = 0.849 for the metric system)
        • water volume flow rate = pipe area x velocity water
      • gravity constant = 9.8 m/s2
      • thus combining the above gives: Power in Watts = efficiency factor x 4444 x r3 x C x height2 / pipe length
        • example:
          • 30m drop with a 45deg slope requires pipe length of 30/Sin45 = 42m, assuming 75mm plastic pipes would result in flow rate of 0.58m/sec = 0.00256m3/sec = 9.2m3/hr = 9200L/hr
            • power assuming 40% efficiency = 300W
          • 30m drop with a 60deg slope requires pipe length of 30/Sin60 = 35m, assuming 100mm plastic pipes would result in flow rate of 0.94m/sec = 0.0073m3/sec = 26.2m3/hr = 26200L/hr
            • power assuming 70% efficiency = 1500W
            • to get this 1500W for 4 hours each night you need a 100,000L top and bottom tank
            • assuming you can get 8 hours solar panel output each day, you would need to generate around 1500W*4/(0.7*pump efficiency factor) of solar power
              • assuming your pump solar power system is 40% efficient, this gives a total daily solar energy need of around 21kWhrs or 2700W for each of the 8hrs daylight
      • HOWEVER, you do need:
        • a top and bottom tank with sufficient capacity to provide the flow rate required for the desired time period,
        • a pump output and return pipe optimised to use the expected solar power output to return the water to the top tank

off-grid wind turbines

  • you can get cheap Chinese pole mounted small units (excl. pole or MPPT controller) at:
    • 800W output which are about 1m diameter in lantern style, 11kg for around $AU500
    • “3000W” but actually more like 1500W 1.25m diameter 5 blade propeller style for around $AU400
      • starts at 7kph, at 20kph you get only 150W, you need 50kph to get 1500W!
  • for larger systems, these require a rural property of at least 1 acre and mounted on a tall tower
    • costs start around $AU28000 for a 3.3kW system and require specialist installation and annual maitenance

12V electrical wiring tools

  • cutters
    • Hakko-CHP-170 Micro Cutter - for trimming smaller wires, etc
    • Triplett TT-242 CablCut Multi-Wire Copper Cable Cutter (but best use a dedicated stripper instead of the one included on this)
  • strippers
  • crimpers
    • IWISS AP-50BI Cable Crimper for Copper Cable Lugs from 8-2AWG
    • Titan 11477 Ratcheting Wire Terminal Crimper Tool for Insulated Terminals
    • Klein Tools 1005 Cutting / Crimping Tool for 10-22 AWG Terminals and Connectors, Terminal Crimper for Insulated and Non-Insulated Terminals
  • soldering iron
    • Hakko FX601-02 Adjustable Temperature Controlled Soldering Iron
  • AC/DC current clamp meter
    • NB. the clamp current only works on a single line - you will get a net zero result on power cords with active and neutral or pos and neg wires
    • most also have a thermometer to 1000degC
    • Klein CL390 $AU120 on Amazon
  • multimeter
  • insulated ratchets for socket sets to work with battery terminals without shorting them
australia/camping_offgrid.txt · Last modified: 2022/08/12 22:18 by gary1

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