WHAT IS A SOLAR CHARGE CONTROLLER, AND WHY DO YOU NEED ONE?
IT’S THE CONTROLLER BETWEEN YOUR SOLAR PANEL AND YOUR BATTERY (OR BATTERIES)
The sun’s intensity varies throughout the day, the season, and of course with the weather. So the output from your solar panel isn’t constant either. The voltage from an average solar panel can vary as much as 200% from morning to midday, and at night, it can actually drain power from your battery!
This not only is wildly inefficient; it can wreak havoc on your expensive battery (or batteries). With the voltage swinging up and down, you can rapidly destroy them or shorten their life.
It’s therefore critical to have a solar charge controller installed between your solar panel and batteries, to ensure they are neither under- or over-charged.
SOME SOLAR PANELS HAVE A CONTROLLER BUILT IN
Many of our portable solar panels already have a charge controller built in, so you don’t have to worry about this at all. However, for all “raw” solar panels, it’s a critical piece of equipment to add to your system.
TYPES OF SOLAR CHARGE CONTROLLERS
There are two primary charging technologies currently used for solar power management. They connect to your system in the same way, but inside they’re fundamentally different.
PWM
Pulse Width Modulation (PWM) controllers are a high quality yet cost effective way to manage your solar charging. PWM essentially pulses the power into your batteries while monitoring the state of charge. It’s simple way to manage power delivery, reasonably efficient and the hardware is quite robust. The biggest limitation is that panel voltage always has to match the battery voltage. For example, you need 24 Volt panels to charge 24 Volt batteries.
MPPT
Maximum Power Point Tracking (MPPT) is a more advanced charging method. It’s designed to better handle the power fluctuations from solar panels and wind turbines, allowing the controller to run more efficiently and deliver more of the available power to your batteries. Most importantly, it allows you to have the solar panel voltage much higher than the battery voltage, so for example you can charge 12 Volt battery from a 36 Volt panel. The hardware itself is very robust, however the units themselves are more complex and heavier. You’ll therefore pay a little more for an MPPT unit, however you’ll charge your batteries more efficiently under just about all conditions.
BATTERY COMPATIBILITY
Not all chargers can appropriately charge different battery chemistries. You’ll need to ensure the charge controller is compatible with your batteries, or your system will underperform, or destroy your batteries.
LEAD ACID
Lead Acid (sometimes sealed lead acid or SLA) batteries are common, fairly cheap, and very popular. Great bang for buck.
AGM
Absorbed Glass Mat are able to handle deeper discharge than a traditional lead acid battery. Perfect for house battery type scenarios, or systems where batteries could be heavily discharged.
LITHIUM
The most advanced battery option. They’re usually less than half the weight of a lead-based battery, and can deliver more usable power for the same capacity rating.
ADDITIONAL CONSIDERATIONS
MULTIPLE BATTERIES
While you can wire two or more batteries in parallel, there are many instances where you would prefer to keep batteries separate. Some controllers offer multiple charge outlets so you can independently charge more than one battery while keeping them electrically isolated.
MULTIPLE INPUTS
Some charge controllers will offer management of multiple power input sources. In addition to solar, you may have a generator, vehicle alternator, or shore/site mains power. Having this integrated into the one system is generally the best method for simplicity of system design, and efficiency.
REMOTE MANAGEMENT
A few of our controllers now feature remote management interfaces either via a remote, or using your smartphone. These systems can provide great insight into your system’s behaviour and your power usage.