When installing a solar panel, making sure you select the right solar charge controller can be a vital aspect. Functioning similar to regular battery chargers, these controllers go in between a solar panel and a deep charge battery and are what ensure batteries do not overcharge in the day or get drained at night.

By selecting the proper controller for your needs, you can know that your batteries are healthier, your lights will turn on and off when they are supposed to, and you’ll always have a proper display of voltage and state of charge. In most cases, you’ll find solar charge controllers effective for setting up off-grid systems or setting up panels on vehicles like boats.

For most regular homeowners with solar panels, charge controllers aren’t needed as much on account of batteries usually just directing excess energy to the grids themselves. If you are worried about battery overloads, however, a charge controller could be the best option.

Different Types of Charge Controllers

There are two main types of solar charge controllers, PWM (pulse width modulation) and MPPT (maximum power point tracking) and the kind you get can make a huge difference.

PWM Controllers

PWM controllers make a direct connection from your solar array to your battery bank. These controllers are the most common and usually the cheapest options. If you are intending to use a PWM controller in your system, you need to ensure that your batteries and you solar panels have the same voltage. PWM controllers are good options for people with smaller systems where efficiency isn’t a critical factor.

MPPT Controllers

MPPT controllers, on the other hand, draw out power at maximum voltage, which usually leads to more energy. They will convert the higher voltage from solar panels down to the lower voltage batteries need to keep charged. MPPT systems will, therefore, extract the most amount of power they can, as compared to PWMs which have a fixed voltage. When batteries are deeply discharged, MPPT systems can extract more power and charge the batteries efficiently.

For larger systems that take more energy, and where solar array voltage is significantly higher than battery voltage, MPPT systems are usually the best options.

How to Fit Your Needs

To know which solar charge controller is right for you, your situation is the key indicator. For smaller batteries and lower output solar panels (in the range of 5-10 watts) a PWM controller will be more than enough to make sure your batteries are safely charged. For higher outputs and larger scale setups, you’ll find much greater efficiency using an MPPT system. Keep in mind when checking your voltage that many outside factors can have an effect on your current output. For example, cold weather in the winter will have an increase in your voltage compared to summer months. The distance from your array to your battery bank will have an effect on your voltage as well.

Typically, an MPPT system will cost more than a PWM controller, but this is usually offset by the fact that using an MPPT will create greater returns for you as your voltage increases. For example, the most common 60 cell panels are built with MPPT controllers in mind, so using a PWM controller on those will produce you half the potential power output. This is because a 60 cell panel will run at an average of 30 volts, and connecting those to a 12-volt battery using a PWM controller will only run the panel at around 15 volts.  When batteries are deeply discharged, MPPT systems can extract more power and charge the batteries efficiently.

Most solar charge controllers usually come with extra features that make your setups more efficient. These could include temperature sensors for your battery to know if they’re getting too hot or Bluetooth connectivity to remotely monitor your system through your mobile devices. For most average homeowners and consumers, a solar charge controller isn’t something they’ll require to keep their renewable energy setups running as well as they can, but for those with off-grid systems, or those requiring more output power, selecting the right solar charge controller can be a worthy investment.