Learn how to manage the power generated by your solar panels to ensure efficient charging and long battery life.
Charging from the sun is not as simple as connecting a battery directly to a PV (photovoltaic) array. Solar panels that are rated at 12V tend to generate DC up to 17V or more in practice. Their output also varies in measure of how intensely the sun is shining, and they operate more efficiently in cooler weather.
Get the power under control
Excessive voltage can damage a battery, although many of the latest LiFePO4 units feature intelligent onboard management with over-current protection. In both permanent and portable solar installations, a charge controller fulfils several functions. These include regulating the voltage supplied to the battery and preventing it from discharging through the panel at night.
Pulse width modulation
Charge controllers based on PWM (pulse width modulation) are the simpler and more economical variety. They primarily work on the principle of limiting the voltage supplied to the battery, and progressively reducing it further as the battery approaches full capacity.
Maximum power point tracking
Up to 30% more efficient than their PWM counterparts, MPPT controllers are also more expensive. This type of controller increases the amperage of the current as it reduces voltage, maintaining a stable, optimal charging rate when the combination of temperature and sunlight cause the PV panels to be producing maximum electricity.
See below to learn more about solar power systems.
The sun is still shining bright, even through the short winter days, there's plenty of sunlight to capture using solar panels. Whether you're subsidising your home energy usage or just wanting to create a standalone power unit where there's no grid power available, solar power doesn't need to be intimidating or difficult to manage.
Don't I need a huge installation to use solar?
Sure, you can power your entire house from solar power. You can cover your entire roof in panels (and soon even make your roof from solar tiles), but it doesn't need to be that big to make a dent in your power bills ei-ther. Solar power is an investment that returns over an over again. There's no metering charge, no phone calls to your lovely energy provider, just free energy streaming through your system every day.
Large-scale solar installations are achieved by wiring many individual solar panels together. It is possible to make single very-large panels, but they then become heavy, cumbersome, and a larger single-point of failure if something goes wrong. Therefore, panels are generally kept to a maximum of a few hundred watts each. Even at this size, they're large and weighty - even using light weight Aluminium as a framing material.
It's not all about the big stuff
Sometimes all you want to do is keep a battery charged, a fan blowing, or some other small device running, and don't have access to grid power. It's not unusual to have a shed or garage detached from the main house, which may not have mains power. A small solar installation could be as little as a small lunch-box sized solar panel and some battery clips (usually there will be a simple charge controller in a device like this). It will keep any batteries charged so that electric start fires every time.
What makes up a solar installation?
We're going to assume you're thinking about more than just a plug and play system. The following will apply to virtually any size system, as all components are scalable according to your needs. Indeed, you can often expand it later if you feel the need too.
“Well derrr...” we hear you say, but bare with us. There are various types of solar panels, and they're not all created equal. For a permanent installation, monocrystalline solar panels (usually a lovely bright blue colour) are usually guaranteed for a very long time to give you reliable output over many years. They are the best for rooftop solar and other permanent applications. Amorphous solar panels (generally almost black in colour) are cost effective and work very well, but their electrical output can diminish over time. These are best suited to applications such as charging batteries while camping, and other intermitted uses for this reason. Amorphous panels will still provide an excellent service life and value for money, but monocrystalline panels are worth the additional investment for constant use / fixed installations.
Solar Regulator / Charging Controller
The voltage output from a solar panel will vary based on the available sunlight. A solar regulator levels out the charging voltage to provide a constant voltage to run low voltage appliances, or charge batteries. When charg-ing batteries, many units will also monitor battery condition and levels to make sure you're not over-charging the batteries which can cause overheating and shorten their lifespan. Solar panels themselves can also dis-charge a battery when there's no solar radiation (ie, at night), and the controller will prevent this battery dis-charge too.
Mains Power Inverter
In order to power regular 240V mains devices from your solar installation, you'll need a mains inverter. This takes the low voltage power supplied by your solar panels and creates a close replica of mains power. This means all your standard mains-powered appliances (with a few considerations) can run as though there's standard grid-power applied. Depending on what you would like to run from your inverter will determine what size you require. We can help you select the right inverter for your requirements.
High capacity batteries are cheaper than ever, and still provide the most convenient way to store solar power. While they're not necessarily required for a solar installation to function, it provides a buffer when there's no sunlight, so you can still avoid grid power (providing your storage has adequate capacity). It's also a must-have if you're running a fridge or other motor-based appliance, as the battery can provide much more “startup cur-rent” than your solar installation can on its own. Motors require a lot of energy to overcome their motionless state, and the battery bank will help accommodate this.
Mixing Grid Power with Solar Power
If you want to use grid and solar power together, special inverters provide grid-tie technology allowing you to switch between the two (or leverage power from your solar, while topping it up from the grid). If you're using your solar just to run the pool filter or similar, then you likely won't need any support from the grid (providing you have a suitably sized installation), but for many installations having the flexibility of using energy from the grid overnight then your solar through the day, will still provide fantastic cost benefits.
Additional hardware is also required to wire your solar, batteries, and inverter hardware together. It varies greatly based on your requirements, and we can assist you here. It's important to note however, that any mains-facing wiring such as grid-tie inverters, must be carried out by a qualified electrician. Indeed even low voltage wiring when solar panels and batteries are involved, should be undertaken with great care.
Want to know more?
We have several books available, as well as very knowledgeable staff on getting started with solar. Whether it's a plug and play battery charger, or a full off-grid installation, we're here to help.