Solar Charge Controller: Everything You Need to Know

solar panel converts sunlight into energy via the solar charge controller

Those new to the wonderful world of solar power may be feeling a bit bamboozled as to where to begin and everything they need to do/buy to have the ideal solar set-up. It is likely you’ll already be aware of the basics: the panels, the battery, generators, and so forth. But one of the most pivotal pieces of solar kit is your solar charge controller. Without this little ditty, you could be putting the rest of your equipment at risk.

What is a Solar Charge Controller?

Sometimes known as a solar regulator, a solar charge controller is a charging gadget that connects the solar battery to the panels and acts as a modulator between the two to ensure the battery is being charged accordingly.

The solar charge controller regulates the battery while it’s charging to ensure it’s charging properly and doesn’t overcharge (which will wear out the battery). They also protect the battery from plate damage, electrolyte loss, and gassing.

But that’s just the basic idea behind the controller. Nowadays, they are more advanced and have other purposes too. For example, you can find solar charge controllers with DC loads, which can generate lighting, particularly for small homes/buildings, RVs of all kinds, and off-grid homes.

Types of Solar Charge Controllers

There are two types of solar charge controllers. These are the PWM (pulse width modulation) and the MMPT (maximum power point tracker) .

PWM Solar Charge Controllers

These controllers function via a rapid switch (which is a transistor), which is what regulates the battery while it’s in charge mode. This does so until full absorption charge voltage is achieved, in which it will then open and close rapidly, which modulates the current and conserves the constant battery voltage.

While this is a simple way of modulating your battery, there is a drawback. The PMW will pull the solar panel voltage down to match that of the battery’s voltage, meaning the panel voltage won’t achieve maximum operating voltage. This will reduce the panels’ power and efficiency, which can sometimes be problematic (particularly for those who have zero grid power).

Generally speaking, PWMs are best-suited for smaller solar power needs (i.e.: setups that require only one or two panels) and work just fine for RVs, vanlifers, caravans, small houseboats, etc. This option is the cheaper of the two.

MPPT Solar Charge Controllers

MPPT solar charge controllers are the more advanced and oftentimes favoured option of the two because they allow your panels to operate at maximum power point (hence the name), as well as optimum voltage and current, enabling maximum power output. Because of this, this option is largely considered the more efficient and reliable of the two.

For those with a larger, higher-power solar power system (as in multiple panels), or if the panel operating voltage (Vmp) is above 8V, this option is the best.

How Your Solar Charge Controller Works

The exact specifics of how a solar charge controller works depends on whether you’re using a PWM or MPPT. But the general gist is this:

The solar charge controller monitors the battery’s voltage to regulate the charging current from the PV array (photovoltaic array, which is the system’s module that absorbs solar rays), which then prevents any overcharging.

The controller will gradually reduce (tapering) the energy flow from the panels to the battery to ensure a full charge. Many modern solar charge controllers also contain a built-in warning feature that warns against low voltage and may have a disconnect feature that kicks in when the battery becomes low to prevent excessive discharge.

MPPT controllers will accelerate the charging process by up to 30% per day too, which makes it particularly useful for those whose power needs are exclusively from solar panels.

How they work is they will switch off or redirect the array (either in part, or all of it) to either reduce or stop the energy flow from the panels to the battery. They are essentially the middle-man that keeps tabs on the battery’s wellbeing.

Each battery has a specified low voltage level (preset point), and once reached, a partial or full disconnection will kick in to prevent wasted energy or possible battery damage. It does this by detecting the battery’s present point to understand when energy should be limited to disconnected (i.e.: when the battery has fully charged).

Why Do I Need a Solar Charge Controller?

As well as the above reasons (protecting the wellbeing of your battery and limiting excess discharge), the key reason solar charge controllers are important is because the voltage level in your panels will be higher than that of your battery, which is beneficial for batteries that need regular charging, but also comes with the risk of overcharging.

If you are heavily reliant on solar power (some people use it on par with their grid power to lower utility costs and monitor their carbon footprint, whereas others - particularly those off-grid - may be fully reliant on it), having a solar charge controller is a crucial part of your battery’s maintenance.

All-in-one BLUETTI Battery with MPPT Solar Charge Controller

BLUETTI EP500Pro PV200 is an exceptional product that combines advanced technology with superior performance. This power station is equipped with MPPT (Maximum Power Point Tracking) technology, which optimizes the solar charging efficiency. The presence of MPPT ensures that the battery captures the maximum available power from the solar panels, resulting in faster and more efficient charging. This feature enables the EP500Pro PV200 to harness solar energy effectively, maximizing its power output and extending the runtime of connected devices. With MPPT, users can enjoy the benefits of faster charging, increased energy conversion, and enhanced overall performance.

bluetti ep500pro

Solar Charge Controller Ratings

Each make and model will be different, and there is a wide range of input/output voltage and output current options when it comes to solar charge controllers.

More simple models will have a rating range between 12 - 24 volts, whereas larger, more complex options, will go as high as 72 volts. Folks living off-grid will need to go higher in order to cover all their needs.

Naturally, the smaller the solar power system, the smaller the rating needed. Choosing the right one for you depends on your individual needs and set-up, but a small scale set-up (such as one or two panels) can work fine with a rating of 24.

The lower the rating, the cheaper the cost as well, so rating needs to be especially considered for those on a limited budget.

Solar panel voltages also differ and typically range from 24 to 250 volts.

Solar Charge Controller: Top Tips

While ultimately your best bet when scouting for solar products is to speak to a professional, there are some nifty tips to keep in mind:

  • When setting up your solar charge controller, always connect the batteries BEFORE the solar panels.
  • Make sure your solar charge controller is in an area that is well-ventilated to prevent overheating.
  • When it comes to solar charge controllers, you very much get what you pay for. This means a cheap and cheerful jobby may do more harm than good (especially to your finances) because they’re known to damage batteries.
  • When considering your solar charge controller’s capacity, always aim for at least 50% higher than you think you need, as this will enable expansion.
  • Again, avoid a cheap option. Instead go for one that detects both the panels and the battery’s voltage.

solar panels power house

Solar Charge Controller: FAQs

Do I need a solar charge controller for my solar panel/s?

It is always best to invest in a solar charge controller, whatever your needs and set-up is, because it acts as damage control, which can save you both money and hassle. Having said that, the smallest panel option (1-5 watt trickle) can function fine without a controller.

However, if you’re considering going off-grid (i.e.: opting for a situation that is fully dependent on solar power), it is imperative you hook yourself up with a (good-quality) solar charge controller.

What size solar charge controller do I need?

That depends on the solar set-up you have/are planning to purchase. To estimate this, you will need to note the total watts of the solar array and then divide it by your battery bank’s voltage.

The sum you get will be the output current of the solar charge controller you need.

Can I just connect my solar panel to my solar battery?

No. Remember that your solar charge controller is the middleman. You will need to connect the battery to the solar charge controller first, before connecting it to your panels.

Connecting it just to the battery can damage the battery or the controller.

What are the drawbacks of a solar charge controller?

The pros of solar charge controllers far outweigh the cons, but nothing is perfect. Depending on what type of solar charge controller you opt for, there will be drawbacks.

The main drawback of the PWM, as we mentioned earlier, is that they are the less reliable, efficient option of the two, and the main drawback of the MPPT is that they can come with quite a hefty price tag. They can also be more complex and may require professional installation (which will likely add to the overall cost).

What happens if you connect the solar panel before the battery?

As we mentioned above, you will need to connect your battery to your controller first. Connecting the panel always comes SECOND. Failure to do so will damage the controller.

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