Choosing the right Solar Panel


Benefits of Solar Panels when Camping

  • Solar power is free. All you need is good sunlight and you will have power to use your appliances.
  • Take it anywhere and charge your batteries anytime.
  • Get off the grid and travel to remote and unpowered locations while still being able to use your appliances.

Which Solar Panel should you get?

Solar Panels power generation is commonly given in Watts e.g. 120 Watts. To calculate the energy it can supply the battery with, divide the Watts by the Voltage of the Solar Panel, this should help you in picking the one that is right for your needs.

Please note Solar panels need to be worked out at Watts x 18V, some common options are:

  • 100w Panel = 5.5 Amps
  • 150w Panel = 8.3 Amps
  • 200w Panel = 11.1 Amps
  • 300w Panel = 16.6 Amps
  • 400w Panel = 22.2 Amps
  • 450w Panel = 25.0 Amps
  • 600w Panel = 33.3 Amps

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How do I calculate the Watts, Amps and Volts of the Solar Panel?

It stands to reason that a larger Solar Panel will collect more energy in less time, but just how big does the solar panel need to be?

The power consumption of appliances is given in Watts. To calculate the energy you will use over time, just multiply the power consumption by the hours of use. For example: 10 watt device used over 3 hours equals 10 x 3 = 30 Watt

How to convert Amps to Watts
The energy in Watts is equal to the electric charge in Amps times the voltage in volts: Watts = Amps × Volts

Example
If your device doesn’t have the Watts labelled on it, then it should at least have the input Volts i.e. 240V and the Amps AC it draws such as 240V – 1.5A. You can then use the equation Watts Volts x Amps so 240v x 1.5amps = 360 Watts.

How to convert Watts to Amps
The electric charge in Amps is equal to the energy in Watts divided by the voltage in volts (V): Amps = Watts / Volts

Example
Find the electric charge in Amps when the energy consumption is 300 watts and the voltage is 240 volts. 300 Watts / 240 volts = 1.25 Amps

MPPT Solar Controllers

What is MPPT?
MPPT or Maximum Power Point Tracking is algorithm that included in charge controllers used for extracting maximum available power from PV module under certain conditions. The voltage at which PV module can produce maximum power is called ‘maximum power point’ (or peak power voltage). Maximum power varies with solar radiation, ambient temperature and solar cell temperature.

How MPPT works?
The major principle of MPPT is to extract the maximum available power from PV module by making them operate at the most efficient voltage (maximum power point). That is to say: MPPT checks output of PV module, compares it to battery voltage then fixes what is the best power that PV module can produce to charge the battery and converts it to the best voltage to get maximum current into battery. It can also supply power to a DC load, which is connected directly to the battery.

MPPT is most effective under these conditions:
Cold weather, cloudy or hazy days: Normally, PV module works better at cold temperatures and MPPT is utilized to extract maximum power available from them.
When battery is deeply discharged: MPPT can extract more current and charge the battery if the state of charge in the battery is lowers

What battery do I need?

Battery capacity is measured in Amp Hours (e.g. 100Ah). You need to convert this to Watt Hours by multiplying the Ah figure by the battery voltage (e.g. 12V) – see calculations above.

AH refers to amp hours. This rating is usually found on deep cycle batteries. If a battery is rated at 100 amp hours it should deliver 5 amps of power for 20 hours or 20 amps of power for 5 hours.

When choosing a deep cycle battery, keep in mind the equipment you will be powering and the time in which they will be running. Theoretically a 100Ah battery can deliver 5 amps over a 20 hour period (and so on). Taking into account the average small campsite - with a small 45W fridge running for 6 hours, 3 hours of 15W lighting and 20W of other electronic equipment - the minimum consumption to be expected is 335W. Take this wattage and divide it by the voltage, 12V, gives 28Ah. With the aim of leaving 50% in the battery brings the requirement to 56 Ah per day.