The basic components of a solar power system:

        Sunlight   (power source)
        Solar Panel   (collection)
        Solar Regulator   (control)
        Battery Bank   (storage) 
        Appliances (power drain)
        Recharging

To view or print this information sheet in full click the link "How Solar Works - A Guide" (see left hand column).

When sun shines on a solar panel, the light, NOT heat is converted into electricity.
Sunlight for solar power purposes is measured in sun hours. A sun hour is a cumulative total rather than a specific length of time. The duration of a sun hour is affected by our latitude, the weather, the season, etc.

EG. On an overcast day in summer a solar panel can accumulate 1 sun hr even if the sun never breaks through. OR, on a very sunny day in the deep south a panel may accumulate only 2 sun hrs over a full day because the sun’s rays are weak at that latitude.

In NZ (based on North of North Island figures) we average 3-4hrs sun hours per day over the year, that’s around 4.5sun hrs/day in spring/summer and 1-1.5 sun hrs/day in autumn/winter.

A solar panels’ size is measured in Watts. The higher the Wattage, the greater the panels’ capacity to gather power per sun hour. 

EG.  An 85W panel can collect around 5 Amps per sun hour, a 130W around 7.5 Amps per sun hour

A Solar panels’ performance is reduced by heat, shade (partial shade), rain, clouds, leaf litter and general grime. Peak performance comes from a clean panel in full sunlight, angled toward the sun.

Electricity from the solar panel is transferred through cables to a solar regulator and then on to the battery for storage. A good quality, 3-stage solar regulator has a voltage range which allows the battery to fully charge. Lesser regulators which operate at one set voltage don’t allow for maximum charging.
When the battery is full the regulator diverts the power so the battery isn’t overcharged.
The size of the regulator is dictated by the total wattage of the solar panel/s. The more solar panels, the larger the regulator needs to be.

EG.    A 15 Amp Regulator can run a single 130W panel but  it’s too small for 2x130W panels.

Solar regulators can come with or without a meter. Meters show how much power is coming in, going out and what the battery voltage is – this indicates the battery level of charge. This information allows for basic monitoring of the system performance and power consumption.  Separate battery monitors with more complex functions can be purchased if a greater level of control of the system is required.

The storage capacity of a battery is measured in Amp Hours. Often batteries are set-up in groups or ‘banks’ to increase the amount of power which can be stored. A battery not fully recharged on a regular basis will begin to sulphate and lose capacity.

The ‘house’ battery is separate from the engine ‘start’ battery and does quite a different job.  ‘House’ batteries are deep cycle batteries and perform best when they have relatively small amounts of power drained and are recharged regularly. They work well with solar panels because the panels allow for daily recharging. To get the best life from deep cycle batteries, manufacturers recommend they be regularly recharged prior to being drained to 50% of their total power capacity. Though, it is okay to occasionally drain a deep cycle battery more deeply than this.

EG. A battery bank totalling 100Amp Hrs should not regularly be drained more than 50Amp Hrs before being fully recharged.

Deep cycle batteries are available as AGM, GEL or WET (Lead Acid) composition. Depending upon the vehicle layout and owners requirements WET batteries are not always appropriate and AGMs may be more suitable as they require no messy maintenance, there is no exposure to acids & chemicals, they can be used in any position so are easier to fit into small spaces, and don’t create any gases so they’re safe to store inside.

Transfer of electricity is never 100% efficient. All along the way from collection to output there’s electricity wasted. When making calculations allow for 20% power loss across the system.
If you need to carefully assess or monitor power use it’s recommended that a specialised battery monitor be used.          
Your  appliances consume the power stored in your battery bank.  In simple terms, if you ran a 2Amp light for 20 hours it  would use 40Amp/hrs of power.

Other examples of  power use include:
  -  Halogen light :  1Amps per hr of use(or 1 Amp/hr)
  -  Water pump : 5Amps per hr (running time 1hr/day)
  -  Electric fridge : 2 –6Amps per hr (running time 10hrs/day)
  -  TV& Booster : 2-6Amps per hr (.7Amps/hr in standby mode)
Depending upon the mobile home set-up, daily power consumption can range from 15 – 70Amps/day (or more).

If you drain more power than your solar panels collect you’ll be operating in a deficit and your batteries will eventually need recharging or they’ll go flat. The larger the deficit the more quickly your batteries will be emptied.

Eg.    Joe has a 100Amp Hr battery and a 130W solar panel. With 3 sun hours per day he’s adding 25Amp Hrs to his battery but he’s draining 40Amp Hrs daily to run his various appliances. With a 15 Amp hr deficit daily it’ll be 3 days before his battery gets down to 50% and needs to be properly recharged.

Aside from power input from solar panels, batteries can be recharged by:         
  - Battery charger
  - Alternator charging
  - A generator

A battery charger is the simplest and most common form of recharging and the more Amps the charger is, the faster it will recharge the batteries. But, the charger  size should be relative to the battery bank – It’s best to stick with a charger that’s amp rating is 8-10%  of the Amp Hr rating of the battery bank.
A 3-stage battery charger is best because it operates at the range of voltages which a battery needs to become fully charged. A single-stage charger runs at a single set voltage level so can only charge a battery to say 70-80% of capacity.

Alternator charging (via the engine) is a good option if you move on a regular basis but the vehicle usually needs to be modified for an alternator charging system to be more than 70% efficient. On average, alternator charging may result in 10-25Amps being added to the 'house' battery per hour of driving and the emptier the battery the more effective the charge. So, to add 50Amp hours back to the battery bank could take up to 5 hours of driving.

The 12V outlet of a generator is not suitable for recharging ‘house’ batteries and needs to be used in conjunction with a 3-stage battery charger to be efficient and effective. A 1KW generator can run up to a 25Amp battery charger.