There's no point getting top-notch solar panels if your charge controller isn't up to scratch. We compare three of the best charge controllers on the market and see which comes out on top.
An efficient solar charge controller is an essential part of a worthwhile solar energy system that uses battery packs. It gets the most out of the solar panels and ensures the batteries charge smoothly and safely. In many cases, you can seriously improve the energy efficiency of a solar set-up by upgrading the charge controller.
In today's guide, we take a close look at the most efficient solar charge controllers. These devices all use a technology called Maximum Power Point Tracking or MPPT. These days more sophisticated MPPT charge controllers are preferred over the traditional PWM versions due to their increased efficiency and also their ability to harvest more power in low light conditions.
We've put together a handy buyer's guide where you can learn how to choose the right size of controller. We also compare three of the top models and decide which one is the very best.
If you're new to the world of charge controllers then this is a great place to start. We explain how to choose the right size and also the key features that you should be looking for.
Solar Charge Controllers Explained
A charge controller controls the rate at which a battery is charged. It is essential in a solar installation, as it protects the system against overcharging and power surges.
The problem with solar panels is that they don't deliver the voltage that they are quoted as doing. A 12 Volt solar panel will produce a few volts more than this for example. The reason for this is so that they still output some power when the level of light is low. If they produce 12V as quoted, then when the sun disappears there will be no voltage output. So, the extra voltage is like a reserve supply that ensures a more constant stream of energy.
Furthermore, a 12 Volt battery doesn't charge at exactly 12 Volts. It requires a bit more than this. The input voltage that it requires to charge depends on its current capacity among other things.
The charge controller regulates the voltage/current going from the solar panel array to the battery. It also regulates the discharging of the battery. In doing so, it protects both the batteries and the system.
Why Use MPPT Technology?
Multi Power Point Tracking (MPPT) is the most advanced charge controller technology currently available. It provides more efficient power management of solar arrays than the traditional PWM (Pulse Width Modulation) technology.
As we mentioned in the last section, solar panels produce much more voltage than they are quoted for. MPPT controllers are able to convert this excess voltage into current (Amps) which can then be used to charge the batteries much quicker. This extra voltage is wasted in PWM controllers.
MPPT models can also handle much higher voltages than the competition. This means you can use more solar panels and use more wire without seeing energy losses.
Furthermore, if your system is grid-tied then Maximum Power Pont Tracking solar controllers are the only kind that are able to handle the large voltages involved.
MPPT devices can be as much as 95% efficient. This can be up to 30% more efficient than their PWM counterparts which tend to give around 65%.
But, there are a couple of downsides with MPPT controllers...
They are much more expensive than the competition and they are much bigger in size too. The best MPPT charge controllers cost significantly more than the top PWM models.
Recommended Reading: Don't miss our big guie to the top small solar panel kits.
How to Size a Solar Charge Controller
It's essential that you get a solar charge controller that fits your installation.
There's a simple way to work out what size your installation needs.
- Calculate the total size in watts of your solar array.
- Divide this number by the voltage of your battery bank.
- Add 25% for some extra headroom. The reason for this is that on colder days the open-circuit voltage of the solar cells will increase.
I have 2 solar panels rated at 200 watts each. They supply a 12 Volt battery bank.
2 x 100 = 200 watts
200/12 = 17 Amps
17 + 25% = 21.25 Amps
This is the minimum controller output current
If you need to work it out the other way and wish to know how big a solar array will fit a controller then do this:
Controller size in amps x voltage of the battery bank = maximum solar array wattage
I want to know if a 60 Amp controller will fit my 1200 watt solar array. I use 24 Volt batteries.
60 x 24 = 1440 watts
Yes, a 60 Amp controller is a good size.
The Features You Should Be Looking At
Here we discuss some of the features that set the good controllers from the bad.
1. The Display
Even the most basic of models need to use a system to display the current charge level. It tends to be that as these systems go up in price the more sophisticated their methods of displaying information become.
LED: the most basic of displays is using LED lights. This could be as basic as a few lights showing that you currently have power and you are getting charge. While these interfaces are perfectly functional, they lack the means to give you detailed feedback on the current health of your solar array.
LCD: this is the next step up and this kind of display interface can give much more meaningful information. Icons, numerical values, and text can now all be used to represent the current health of your system. The jump from LED to LCD display usually represents quite a significant leap in price.
2. Data Logging
The most impressive systems have the ability to record and log performance statistics for months at a time. This means you can effectively monitor the health of the health of your solar set-up over long periods. This is a massive help when trying to identify system faults.
3. The Warranty
Like any expensive electronic equipment don't forget to check the warranty. These devices need to be extremely reliable and the warranty should reflect the manufacturer's confidence in their product.
4. Load Control
This one isn't essential for the larger installations but it's a great feature to have for the smaller ones out there.
The load terminal or LVD output is used for small non-critical loads like appliances and even lights. It will automatically turn off to stop the batteries being run down too low.
5. Remote Access
Some controllers can be accessed remotely and the settings changed from the comfort of your living room using an app or a computer. If you plan on being away from home for long periods then this could be a deal clincher.
MPPT Solar Charge Controller Reviews
In this section, we take a look at the three best solar charge controllers currently available. We've only included our MPPT charge controller reviews as these systems are by far the most efficient, and therefore the best solar controller types.
If you want to get the most out of your solar installation then MPPT is the way to go. An MPPT controller gives better performance in times of low light, and also reduces transmission loss. The best MPPT controllers have efficiencies of around 94 - 98% and can save you considerable amounts of money, especially when used in larger solar installations.
Take a quick look at how the top models compare in the comparison table before reading about them in more detail.
OUR TOP PICK
Outback FlexMax FM80
Warranty: 5 years
- Remotely monitor & control
- Low power usage
- 80 character LCD display
- Logs performance data
Warranty: 1 year
- LCD display
- Optional Bluetooth module
- Aluminum body
Warranty: 1 year
- 4 charging options
- Optional PC monitoring software
- Great for off-grid solar
Outback FLEXmax FM80 *Best MPPT Solar Charge Controller*
Features: Flexmax MPPT software algorithm, battery voltages from 12V-60V, +98% peak efficiency, less than 1 Watt power consumption, active cooling, intelligent thermal management cooling, backlit 80 character display, remote monitoring and programming, suitable for virtually any battery type.
FLEXmax charge controllers are some of the best available. The FM80 supports a wide range of battery voltages and also has the ability to step-down high voltage solar arrays to recharge low voltage batteries.
It can deal with up to 150 Volts from a solar array, which is stepped down to between 12 - 60 V (direct current). It's a really versatile device that can handle many battery types and voltages. It's also one of the most powerful controllers around when it comes to customization and programmability. Though the amount of options might seem overwhelming at first, once you get the hang of the parameters your solar array will be running more efficiently than ever.
The MPPT technology increases the power yield of a solar array by up to 30% over traditional methods. Active cooling and thermal management cooling allow the FM80 to operate at the full current rating in ambient temperatures of as much as 104°F.
The system runs extremely efficiently and draws less than 1 watt of power. The self-consumption of power in controllers is a particular issue in smaller solar installations, but the FLEXmax range is designed with this in mind.
The built-in LCD display is backlit and shows up to 80 characters on screen over 4 lines. The display shows the current system status, as well as information regarding the performance over the last 128 days. It can also be remotely monitored and programmed using the MATE system display. Using any internet connected device, the user is able to remotely control the FM80.
A 5-year warranty (extendable to 10) shouldn't be sniffed at either. These devices need to be reliable and Outback obviously have faith in their production.
Bottom Line: The Outback FLEXMax FM80 is a higher end charge controller with a price tag to match. However, features such as internet connectivity and low power consumption make it a worthwhile investment. There aren't many solar controllers that run this smoothly and efficiently. This is the best solar charge controller for those with the budget for it.
Renogy Rover 40 Amp *Great Value for Money*
Features: Auto detects 12/24 Volt systems, error code detection (for self-diagnosis), compatible with multiple batteries (lithium, sealed, gel, flooded), 4-stage charging (Equalization, Boost, Bulk, and Float), LCD display, programmable charging parameters, Die-cast aluminum casing, battery temperature monitor, remote monitoring
The Renogy Rover 40 Amp MPPT controller provides efficiency of up to 99%. It is packed full of great features like the error code detection, which allows you to diagnose the system set-up and prevent any damage caused by mistakes in the installation or by any system faults.
It comes with multiple safety features to protect your operation. These include overcharge, over-discharge, short circuit, and overload protection. The die-cast aluminum body ensures that heat is dissipated quickly and efficiently too.
The LCD display is clear and concise. This is backed up by a series of LED indicators that display critical information like error codes. The LEDs are also used for metering purposes and free up the LCD screen. The unit can be easily programmed and the parameters adjusted as needed.
The MPPT technology extracts the maximum amount of power from the panels at all times. The MPPT tracking algorithm doesn't require any programming and is fully automatic.
The Renogy Rover MPPT has 4 battery charging algorithms, which it is able to switch between. Each has its own special use.
- Bulk charge - this is used for regular day to day battery charging. It uses the full 100% of available solar power and delivers maximum current to the batteries.
- Constant charge - when the battery reaches a voltage threshold, the system will stop using MPPT. This reduces the current and avoids overheating the battery. This also includes Boost charge which maintains the charge for 2 hours (default). This can be adjusted by the user.
- Float charge - the controller reduces the battery voltage. This happens when the battery is fully charged. It maintains a light charge of the battery. The system will revert back to bulk charging when required.
- Equalization - this is the intentional overcharging of the battery. This happens every 28 days in a controlled manner. Some batteries benefit from this as it balances the chemicals. This has the effect of increasing their efficiency and extending their lifespan.
As we discussed in the buyer's guide, this model has a solid load control that helps protect any DC loads that are connected. This prevents the batteries discharging too deeply.
An awesome add-on that is available with the Renogy Rover is the Bluetooth Module. This allows the controller to be paired with Renogy's remote monitoring app. This means you can easily see how your system is running from the comfort of your living room. You can even make changes to the settings with it.
A one year warranty doesn't exactly get me excited, especially when compared to the 5 years offered by the previous Outback model that we reviewed. However, you have to remember that this costs less than a third of that model too.
Bottom Line: This Renogy solar charge controller is well designed and easy to use. It's built to get the most out of a solar installation, and has many automatic safety features to manage the operation. It's also probably the best MPPT charge controller for the money.
SolarEpic MPPT 40A
Features: Supports 4 charging options, multiple safety features, PC monitoring software, max 150V input, intelligent self-diagnosis.
This solar charge controller from SolarEpic is in the mid to lower price range. It is perfect for an off-grid solar set-up and will control the charging and discharging of the batteries. Using MPPT technology it maximizes the energy yield of the solar energy system.
This model is optimized to give long battery life and efficient performance. It has various safety features to ensure everything is always running smoothly. The low voltage disconnect stops the battery from over-discharging while overcharging, over current, and over temperature protection is also included.
It uses intelligent self-diagnostics to monitor the system performance and highlight and prevent mistakes or faults. It also uses the RJ45 communications interface to communicate with external accessories that you may wish to add.
It supports 4 different charging options: flooded, gel, sealed, and user-defined. It accepts a maximum input of 150 Volts.
The lack of an LCD display limits the information that is available, but the LED light system works well enough. This also has the benefit of consuming very little power.
Bottom Line: It's not the flashiest of controllers, but it's durable and efficient. This works well with the smaller solar array set-ups.
You should perform regular maintenance checks on your solar charge controller. Checking at least twice a year is recommended.
Here are some quick checks you should perform to make sure everything is running smoothly.
1. Check to see that nothing is blocking the air-flow around the controllers. These things can get hot and need some space to regulate their temperature. Likewise, make sure everything is dry and there are no water leaks anywhere.
2. Check all the wiring and make sure there is no wear and tear.
3. Make sure the terminals are tight and there is no corrosion or signs of serious wear.
4. If you're using LED monitoring them make sure each LED light is functioning properly. Just one failed light can hide a serious problem with your installation.
5. Check that everything is grounded properly.
You should always consult the user manual for maintenance tips specific to your particular solar controller. These tips are in no means an exhaustive health check, just a good place to start.
If you have any questions then get in contact and we'll do our best to help.
If you are particularly interested in renewable energy then check out our guide to small wind turbines too.
Check back soon as there's a lot more to come from Tiny House, Huge Ideas over the coming months!
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