Motorhome Solar Power

Free power from the sun

A mains 240 volt producing solar system basically consists of 4 main components, namely solar power production, power regulation, energy storage, and the 240 volt inverter

1 - Solar Panels

These are the energy producing part of the system. Solar panels come in 2 silicon flavours, mono-crystaline and poly-crystaline. We prefer to run a 50-50 mix of poly and mono panels to both preserve the dollars and to gain optimum power production in the southern and northern areas of Australia

Mono Panels

Mono panels are cheaper to buy as they contain manufactured silicon cells. Mono panels produce less power at higher temperatures and lower sunlight levels

Poly Panels

Poly panels are dearer to buy as they contain cells manufactured from silicon poly-crystaline substrate. Poly panels produce more power at higher temperatures and lower sunlight levels.

2 - Power Regulating

An essential part of any solar power system is a quality regulator that will ensure the correct charging voltage and current limiting for your storage battery bank.

Solar charge regulators come in many different types and shapes, some with built-in metering and charge indicators, others with basic LED indicators, but all have differing current ratings.

Remember to buy a regulator that is larger than the amount of charge / discharge current you are requiring. ie: A 5 amp regulator will handle 1 x 80 watt solar panel, and 1 x 60 watt compressor fridge/freezer. So if you have 4 x 80 watt solar panels then you will need at least a 20 amp regulator. If you are drawing 360 watts from the batteries then you would need at least a 30 amp regulator. Watts = Volts x Current. So 360 watts divided by 12 volts equals 30 amps.

3 - Energy Storage

The only way we can store the solar energy we produce is with a deep-cycle storage battery.

The amount of storage or the size of our batteries will depend upon the amount of power we need stored during periods of no sun.

For example, if we have a 12 volt system and a 120 watt light that we will run for 6 hours a night, then using the formula above 120 watts / 12 volts = 10 amps or 10 amps per hour. Therefore the light will consume 10 amps x 6 hours = 60 amp hours or 60 ah.

Ok, so now we know that we need a minimum of a 60ah storage battery to run our light at night. However, our gel storage batteries should never be discharged below 50% of their capacity to extend life, so our 60ah power requirements really means we need a minimum of a 120ah battery.

No this is fine if the sun should shine every day, but during rain periods of no sun we will get little to no charge at all, so in reality we need to allow for a week of no sun, so we can multiple our 120ah battery by 7 days, so we ideally should have 7 x 120ah batteries in our bank for a total of 840ah of storage.

Remember - The bigger the battery bank - the bigger our array of solar panels must be to recharge them. A 12 watt solar panel would only return around 5 amp hours of charge a day in sunny conditions, so that is a long way short of our weekly 420ah consumption from our light in a wet season.

4 - Power production

To convert our stored 12v DC power back up to 240v AC mains power we need to use a power inverter.

Basically, the inverter operates of the DC battery supply and electronically boosts the voltage to 240 volts and produces an AC or alternating current.

The relationships

So now that we can identify the 4 components of our remote area power system, we can see that the size or rating of each component is directly proportional to the load we are using. ie: We cannot run a 15 amp electric welder from a 300 watt inverter coupled to a 20ah battery via a 5ah regulator, recharging from 200 watts of solar panels.