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Reviews and information on the best Solar panels, inverters and batteries from SMA, Fronius, SunPower, SolaX, Q Cells, Trina, Jinko, Selectronic, Tesla Powerwall, ABB. Plus hybrid inverters, battery sizing, Lithium-ion and lead-acid batteries, off-grid and on-grid power systems.
What is a solar charge controller?
A solar charge controller, also known as a solar regulator, is basically a solar battery charger connected between the solar panels and battery. Its job is to regulate the battery charging process and ensure the battery is charged correctly, or more importantly, not over-charged. DC-coupled solar charge controllers have been around for decades and are used in almost all small-scale off-grid solar power systems.
Modern solar charge controllers have advanced features to ensure the battery system is charged precisely and efficiently, plus features like DC load output used for lighting. Generally, most smaller 12V-24V charge controllers up to 30A have DC load terminals and are used for caravans, RVs and small buildings. On the other hand, most larger, more advanced 60A MPPT solar charge controllers do not have load output terminals and are specifically designed for large off-grid power systems with solar arrays and powerful off-grid inverter-chargers.
Solar charge controllers are rated according to the maximum input voltage (V) and maximum charge current (A). As explained in more detail below, these two ratings determine how many solar panels can be connected to the charge controller. Solar panels are generally connected together in series, known as a string of panels. The more panels connected in series, the higher the string voltage.
- Current Amp (A) rating = Maximum charging current.
- Voltage (V) rating = Maximum voltage (Voc) of the solar panel or string of panels.
MPPT Vs PWM solar charge controllers
There are two main types of solar charge controllers, PWM and MPPT, with the latter being the primary FOCUS of this article due to the increased charging efficiency, improved performance and other advantages explained below.
PWM solar charge controllers
Simple PWM, or ‘pulse width modulation’ solar charge controllers, have a direct connection from the solar array to the battery and use a basic ‘Rapid switch’ to modulate or control the battery charging. The switch (transistor) opens until the battery reaches the absorption charge voltage. Then the switch starts to open and close rapidly (hundreds of times per second) to modulate the current and maintain a constant battery voltage. This works ok, but the problem is the solar panel voltage is pulled down to match the battery voltage. This, in turn, pulls the panel voltage away from its optimum operating voltage (Vmp) and reduces the panel power output and operating efficiency.
PWM solar charge controllers are a great low-cost option for small 12V systems when one or two solar panels are used, such as simple applications like solar lighting, camping and basic things like USB/phone chargers. However, if more than one panel is needed, they will need to be connected in parallel, not in series (unless the panels are very low voltage and the battery is a higher voltage).
MPPT solar charge controllers
MPPT stands for Maximum Power Point Tracker; these are far more advanced than PWM charge controllers and enable the solar panel to operate at its maximum power point, or more precisely, the optimum voltage and current for maximum power output. Using this clever technology, MPPT solar charge controllers can be up to 30% more efficient, depending on the battery and operating voltage (Vmp) of the solar panel. The reasons for the increased efficiency and how to correctly size an MPPT charge controller are explained in detail below.
As a general guide, MPPT charge controllers should be used on all higher power systems using two or more solar panels in series, or whenever the panel operating voltage (Vmp) is 8V or higher than the battery voltage. see full explanation below.
What is an MPPT or maximum power point tracker?
A maximum power point tracker, or MPPT, is basically an efficient DC-to-DC converter used to maximise the power output of a solar system. The first MPPT was invented by a small Australian company called AERL way back in 1985, and this technology is now used in virtually all grid-connect solar inverters and all MPPT solar charge controllers.
The functioning principle of an MPPT solar charge controller is relatively simple. due to the varying amount of sunlight (irradiance) landing on a solar panel throughout the day, the panel voltage and current continuously vary. In order to generate the most power, an MPPT sweeps through the panel voltage to find the sweet spot or the best combination of voltage and current to produce the maximum power. The MPPT continually tracks and adjusts the PV voltage to generate the most power, no matter what time of day or weather conditions. Using this clever technology, the operating efficiency greatly increases, and the energy generated can be up to 30% more compared to a PWM charge controller.
PWM Vs MPPT Example
In the example below, a common 60 cell (24V) solar panel with an operating voltage of 32V (Vmp) is connected to a 12V battery bank using both a PWM and an MPPT charge controller. Using the PWM controller, the panel voltage must drop to match the battery voltage and so the power output is reduced dramatically. With an MPPT charge controller, the panel can operate at its maximum power point and in turn can generate much more power.
Best MPPT solar charge controllers
See our detailed review of the best mid-level MPPT solar charge controllers used for small scale off-grid systems up to 40A. click on the summary table below. Also see our review of the most powerful, high-performance MPPT solar charge controllers used for professional large-scale off-grid systems here.
Battery Voltage options
Unlike battery inverters, most MPPT solar charge controllers can be used with a range of different battery voltages. For example, most smaller 10A to 30A charge controllers can be used to charge either a 12V or 24V battery, while most larger capacity, or higher input voltage charge controllers, are designed to be used on 24V or 48V battery systems. A select few, such as the Victron 150V range, can even be used on all battery voltages from 12V to 48V. There are also several high voltage solar charge controllers, such as those from AERL and IMARK which can be used on 120V battery banks.
Besides the current (A) rating, the maximum solar array size that can be connected to a solar charge controller is also limited by the battery voltage. As highlighted in the following diagram, using a 24V battery enables much more solar power to be connected to a 20A solar charge controller compared to a 12V battery.
Based on Ohm’s law and the power equation, higher battery voltages enable more solar panels to be connected. This is due to the simple formula. Power = Voltage x Current (P=VI). For example 20A x 12.5V = 250W, while 20A x 25V = 500W. Therefore, using a 20A controller with a higher 24V volt battery, as opposed to a 12V battery, will allow double the amount of solar to be connected.
- 20A MPPT with a 12V battery = 260W max Solar recommended
- 20A MPPT with a 24V battery = 520W max Solar recommended
- 20A MPPT with a 48V battery = 1040W max Solar recommended
Note, oversizing the solar array is allowed by some manufacturers to ensure an MPPT solar charge controller operates at the maximum output charge current, provided the maximum input voltage and current are not exceeded! See more in the oversizing solar section below.
Solar panel Voltage Explained
All solar panels have two voltage ratings which are determined under standard test conditions (STC) based on a cell temperature of 25°C. The first is the maximum power voltage (Vmp) which is the operating voltage of the panel. The Vmp will drop significantly at high temperatures and will vary slightly depending on the amount of sunlight. In order for the MPPT to function correctly, the panel operating voltage (Vmp) must always be several volts higher than the battery charge voltage under all conditions, including high temperatures. see more information about voltage drop and temperature below.
The second is the open-circuit voltage (Voc) which is always higher than the Vmp. The Voc is reached when the panel is in an open-circuit condition, such as when a system is switched off, or when a battery is fully charged, and no more power is needed. The Voc also decreases at higher temperatures, but, more importantly, increases at lower temperatures.
Battery Voltage Vs Panel Voltage
For an MPPT charge controller to work correctly under all conditions, the solar panel operating voltage (Vmp), or string voltage (if the panels are connected in series) should be at least 5V to 8V higher than the battery charge (absorption) voltage. For example, most 12V batteries have an absorption voltage of 14 to 15V, so the Vmp should be a minimum of 20V to 23V, taking into account the voltage drop in higher temperatures. Note, on average, the real-world panel operating voltage is around 3V lower than the optimum panel voltage (Vmp). The String Voltage Calculator will help you quickly determine the solar string voltage by using the historical temperature data for your location.
In the case of 12V batteries, the panel voltage drop due to high temperature is generally not a problem since even smaller (12V) solar panels have a Vmp in the 20V to 22V range, which is much higher than the typical 12V battery charge (absorption) voltage of 14V. Also, common 60-cell (24V) solar panels are not a problem as they operate in the 30V to 40V range, which is much higher.
In the case of 24V batteries, there is no issue when a string of 2 or more panels is connected in series, but there is a problem when only one solar panel is connected. Most common (24V) 60-cell solar panels have a Vmp of 32V to 36V. While this is higher than the battery charging voltage of around 28V, the problem occurs on a very hot day when the panel temperature increases and the panel Vmp can drop by up to 6V. This large voltage drop can result in the solar voltage dropping below the battery charge voltage, thus preventing it from fully charging. A way to get around this when using only one panel is to use a larger, higher voltage 72-cell or 96-cell panel.
When charging 48V batteries, the system will need a string of at least 2 panels in series but will perform much better with 3 or more panels in series, depending on the maximum voltage of the charge controller. Since most 48V solar charge controllers have a max voltage (Voc) of 150V, this generally allows a string of 3 panels to be connected in series. The higher voltage 250V charge controllers can have strings of 5 or more panels which is much more efficient on larger solar arrays as it reduces the number of strings in parallel and, in turn, lowers the current.
Note: Multiple panels connected in series can produce dangerous levels of voltage and must be installed by a qualified electrical professional and meet all local standards and regulations.
Solar panel voltage Vs Temperature
The power output of a solar panel can vary significantly depending on the temperature and weather conditions. A solar panel’s power rating (W) is measured under Standard Test Conditions (STC) at a cell temperature of 25°C and an irradiance level of 1000W/m2. However, during sunny weather, solar panels slowly heat up, and the internal cell temperature will generally increase by at least 25°C above the ambient air temperature; this results in increased internal resistance and a reduced voltage (Vmp). The amount of voltage drop is calculated using the voltage temperature co-efficient listed on the solar panel datasheet. Use this Solar Voltage Calculator to determine string voltages at various temperatures.
Both the Vmp and Voc of a solar panel will decrease during hot sunny weather as the cell temperature increases. During very hot days, with little wind to disperse heat, the panel temperature can rise as high as 80°C when mounted on a dark-coloured rooftop. On the other hand, in cold weather, the operating voltage of the solar panel can increase significantly, up to 5V or even higher in freezing temperatures. Voltage rise must be taken into account as it could result in the Voc of the solar array going above the maximum voltage limit of the solar charge controller and damaging the unit.
Panel Voltage Vs Cell Temperature graph notes:
- STC = Standard test conditions. 25°C (77°F)
- NOCT = Nominal operating cell temperature. 45°C (113°F)
- (^) High cell temp = Typical cell temperature during hot summer weather. 65°C (149°F)
- (#) Maximum operating temp = Maximum panel operating temperature during extremely high temperatures mounted on a dark rooftop. 85°C (185°F)
Voltage increase in cold weather
Example: A Victron 100/50 MPPT solar charge controller has a maximum solar open-circuit voltage (Voc) of 100V and a maximum charging current of 50 Amps. If you use 2 x 300W solar panels with 46 Voc in series, you have a total of 92V. This seems ok, as it is below the 100V maximum. However, the panel voltage will increase beyond the listed Voc at STC in cold conditions below 25°C cell temperature. The voltage increase is calculated using the solar panel’s voltage temperature coefficient, typically 0.3% for every degree below STC (25°C). As a rough guide, for temperatures down to.10°C, you can generally add 5V to the panel Voc which equates to a Voc of 51V. In this case, you would have a combined Voc of 102V. This is now greater than the max 100V Victron 100/50 input voltage limit and could damage the MPPT and void your warranty.
Solution: There are two ways to get around this issue:
- Select a different MPPT solar charge controller with a higher input voltage rating, such as the Victron 150/45 with a 150V input voltage limit.
- Connect the panels in parallel instead of in series. The maximum voltage will now be 46V 5V = 51 Voc. Note this will only work if you use a 12V or 24V battery system; it’s unsuitable for a 48V system as the voltage is too low. Also note, in parallel the solar input current will double, so the solar cable should be rated accordingly.
Note: Assuming you are using a 12V battery and 2 x 300W panels, the MPPT charger controller output current will be roughly: 600W / 12V = 50A max. So you should use a 50A MPPT solar charge controller.
Guide only. Use the new String Voltage Calculator to determine panel voltages accurately.
The charge controller Amp (A) rating should be 10 to 20% of the battery Amp/hour (Ah) rating. For example, a 100Ah 12V lead-acid battery will need a 10A to 20A solar charge controller. A 150W to 200W solar panel will be able to generate the 10A charge current needed for a 100Ah battery to reach the adsorption charge voltage provided it is orientated correctly and not shaded. Note: Always refer to the battery manufacturer’s specifications.
Advanced Guide to off-grid solar systems
Before selecting an MPPT solar charge controller and purchasing panels, batteries or inverters, you should understand the basics of sizing an off-grid solar power system. The general steps are as follows:
- Estimate the loads. how much energy you use per day in Ah or Wh
- Battery capacity. determine the battery size needed in Ah or Wh
- Solar size. determine how many solar panel/s you need to charge the battery (W)
- Choose the MPPT Solar Charge Controller/s to suit the system (A)
- Choose an appropriately sized inverter to suit the load.
Estimate the loads
The first step is to determine what loads or appliances you will be running and for how long? This is calculated by. the power rating of the appliance (W) multiplied by the average runtime (hr). Alternatively, use the average current draw (A) multiplied by average runtime (hr).
- Energy required in Watt hours (Wh) = Power (W) x Time (hrs)
- Energy required in Amp hours (Ah) = Amps (A) x Time (hrs)
Once this is calculated for each appliance or device, then the total energy requirement per day can be determined as shown in the attached load table.
Sizing the Battery
The total load in Ah or Wh load is used to size the battery. Lead-acid batteries are sized in Ah while lithium batteries are sized in either Wh or Ah. The allowable daily depth of discharge (DOD) is very different for lead-acid and lithium, see more details about lead-acid Vs lithium batteries. In general, lead-acid batteries should not be discharged below 70% SoC (State of Charge) on a daily basis, while Lithium (LFP) batteries can be discharged down to 20% SoC on a daily basis. Note: Lead-acid (AGM or GEL) batteries can be deeply discharged, but this will severely reduce the life of the battery if done regularly.
For example: If you have a 30Ah daily load, you will need a minimum 100Ah lead-acid battery or a 40Ah lithium battery. However, taking into account poor weather, you will generally require at least two days of autonomy. so this equates to a 200Ah lead-acid battery or an 80Ah lithium. Depending on your application, location, and time of year, you may even require 3 or 4 days of autonomy.
Sizing the Solar
The solar size (W) should be large enough to fully charge the battery on a typical sunny day in your location. There are many variables to consider including panel orientation, time of year shading issues. This is actually quite complex, but one way to simplify things it to roughly work out how many watts are required to produce 20% of the battery capacity in Amps. Oversizing the solar array is also allowed by some manufacturers to help overcome some of the losses. Note that you can use our free solar design calculator to help estimate the solar generation for different solar panel tilt angles and orientations.
Solar sizing Example: Based on the 20% rule, A 12V, 200Ah battery will need up to 40Amps of charge. If we are using a common 250W solar panel, then we can do a basic voltage and current conversion:
Using the equation (P/V = I) then 250W / 12V battery = 20.8A
In this case, to achieve a 40A charge we would need at least 2 x 250W panels. Remember there are several loss factors to take into account so slightly oversizing the solar is a common practice. See more about oversizing solar below.
Solar Charge controller Sizing (A)
The MPPT solar charge controller size should be roughly matched to the solar size. A simple way to work this out is using the power formula:
Power (W) = Voltage x Current or (P = VI)
If we know the total solar power in watts (W) and the battery voltage (V), then to work out the maximum current (I) in Amps we re-arrange this to work out the current. so we use the rearranged formula:
Current (A) = Power (W) / Voltage or (I = P/V)
For example: if we have 2 x 200W solar panels and a 12V battery, then the maximum current = 400W/12V = 33Amps. In this example, we could use either a 30A or 35A MPPT solar charge controller.
Selecting a battery inverter
Battery inverters are available in a wide range of sizes determined by the inverter’s continuous power rating measured in kW (or kVA). importantly, inverters are designed to operate with only one battery voltage which is typically 12V, 24V or 48V. Note that you cannot use a 24V inverter with a lower 12V or higher 48V battery system. Pro-tip, it’s more efficient to use a higher battery voltage.
Besides the battery voltage, the next key criteria for selecting a battery inverter are the average continuous AC load (demand) and short-duration peak loads. Due to temperature de-rating in hot environments, the inverter should be sized slightly higher than the load or power demand of the appliances it will be powering. Whether the loads are inductive or resistive is also very important and must be taken into account. Resistive loads such as electric kettles or toasters are very simple to power, while inductive loads like water pumps and compressors put more stress on the inverter. In regards to peak loads, most battery inverters can handle surge loads up to 2 x the continuous rating.
Inverter sizing example:
- Average continuous loads = 120W (fridge) 40W (lights) TV (150W) = 310W
- High or surge loads = 2200W (electric kettle) toaster (800W) = 3000W Considering the above loads, a 2400W inverter (with 4800 peak output) would be adequate for the smaller continuous loads and easily power the short-duration peak loads.
ATTENTION SOLAR DESIGNERS. Learn more about selecting off-grid inverters and sizing solar systems in our advanced technical off-grid system design guide.
MPPT Solar Oversizing
Due to the various losses in a solar system, it is common practice to oversize the solar array to enable the system to generate more power during bad weather and under various conditions, such as high temperatures where power derating can occur. The main loss factors include. poor weather (low irradiation), dust and dirt, shading, poor orientation, and cell temperature de-rating. Learn more about solar panel efficiency and cell temperature de-rating here. These loss factors combined can reduce power output significantly. For example, a 300W solar panel will generally produce 240W to 270W on a hot summer day due to the high-temperature power de-rating. Depending on your location, reduced performance will also occur in winter due to low solar irradiance. For these reasons, oversizing the solar array beyond the manufacturers ‘recommended or nominal value’ will help generate more power in unfavourable conditions.
Oversizing by 150% (Nominal rating x 1.5) is possible on many professional MPPT solar charge controllers and will not damage the unit. However, many cheaper MPPT charge controllers are not designed to operate at full power for a prolonged amount of time, as this can damage the controller. Therefore, it is essential to check whether the manufacturer allows oversizing. Morningstar and Victron Energy allow oversizing well beyond the nominal values listed on the datasheets as long as you don’t exceed the input voltage and current limits. Victron MPPT controllers have been successfully used with 200% solar oversizing without any issues. However, the higher the oversizing, the longer the controller will operate at full power and the more heat it will generate. Without adequate ventilation, excess heat may result in the controller overheating and derating power or, in a worst-case scenario, complete shutdown or even permanent damage. Therefore always ensure adequate clearance around the controller according to the manufacturer’s specifications, and add fan-forced ventilation if required.
Warning. you must NEVER exceed the maximum INPUT voltage (Voc) or maximum input current rating of the solar charge controller!
IMPORTANT. Oversizing solar is only allowed on some MPPT solar charge controllers, such as those from Victron Energy, Morningstar and EPever. Oversizing on other models could void your warranty and result in damage or serious injury to persons or property. always ensure the manufacturer allows oversizing and never exceed the maximum input voltage or current limits.
about Solar Sizing
As previously mentioned, all solar charge controllers are limited by the maximum input voltage (V. Volts) and maximum charge current (A – Amps). The maximum voltage determines how many panels can be attached (in series), and the current rating will determine the maximum charge current and, in turn, what size battery can be charged.
As described in the guide earlier, the solar array should be able to generate close to the charge current of the controller, which should be sized correctly to match the battery. Another example: a 200Ah 12V battery would require a 20A solar charge controller and a 250W solar panel to generate close to 20A. (Using the formula P/V = I, then we have 250W / 12V = 20A).
As shown above, a 20A Victron 100/20 MPPT solar charge controller together with a 12V battery can be charged with a 290W ‘nominal’ solar panel. Due to the losses described previously, it could also be used with a larger ‘oversized’ 300W to 330W panel. The same 20A Victron charge controller used with a 48V battery can be installed with a much larger solar array with a nominal size of 1160W.
Compared to the Victron MPPT charge controller above, the Rover series from Renogy does not allow solar oversizing. The Rover spec sheet states the ‘Max. Solar input power’ as above (not the nominal input power). Oversizing the Rover series will void the warranty. Below is a simple guide to selecting a solar array to match various size batteries using the Rover series MPPT charge controllers.
20A Solar Charge Controller. 50Ah to 150Ah battery
- 20A/100V MPPT. 12V battery = 250W Solar (1 x 260W panels)
- 20A/100V MPPT. 24V battery = 520W Solar (2 x 260W panels)
- 40A/100V MPPT. 12V battery = 520W Solar (2 x 260W panels)
- 40A/100V MPPT. 24V battery = 1040W Solar (4 x 260W panels)
Remember that only selected manufacturers allow the solar array to be oversized, as long as you do not exceed the charge controller’s max voltage or current rating. always refer to manufacturers’ specifications and guidelines.
solar charge controller Price guide
The older, simple PWM, or pulse width modulation, charge controllers are the cheapest type available and cost as little as 40 for a 10A unit. In contrast, the more efficient MPPT charge controllers will cost anywhere from 80 to 2500, depending on the voltage and current (A) rating. All solar charge controllers are sized according to the charge current, which ranges from 10A up to 100A. Cost is directly proportional to the charge current and maximum voltage (Voc), with the higher voltage and current controllers being the most expensive.
A general guide to the cost of different size solar charge controllers:
- PWM 100V Solar controllers up to 20A. 40 to 120
- MPPT 100V Solar controllers up to 20A. 90 to 200
- MPPT 150V Solar controllers up to 40A. 200 to 400
- MPPT 150V Solar controllers up to 60A. 400 to 800
- MPPT 250V Solar controllers up to 80A. 800 to 1200
- MPPT 300V Solar controllers up to 100A. 900 to 1500
- MPPT 600V Solar controllers up to 100A. 1600 to 2800
About the Author
Jason Svarc is a CEC-accredited off-grid solar power system specialist who has been designing and building off-grid power systems since 2010. During this time, he also taught the stand-alone power systems design course at Swinburne University (Tafe). Living in an off-grid home for over 12 years and having designed, installed and monitored dozens of off-grid systems, he has gained vast experience and knowledge of what is required to build reliable, high-performance off-grid solar systems.
This is to be used as a guide only. Before making any purchases or undertaking any solar/battery related installations or modifications, you must refer to all manufacturer’s specifications and installation manuals. All work must be done by a qualified person.
MPPT Solar Charge Controller Manual
The MC Series Solar Charge Controller enables maximum energy tracking for solar panels with the industry leading PowerCatcher MPPT technology. This technology allows the controller to quickly and accurately track the maximum power point of the PV array in any environment, obtain the maximum energy from the solar panel in real time, and significantly increase the energy utilisation efficiency of the solar power system.
This product can be connected to an external LCD screen or Bluetooth communication module and a PC master computer to dynamically display operating status, operating parameters, controller logs, control parameters, etc. The user can look up various parameters and modify the control parameters as needed to suit different system requirements.
The controller adopts the standard Modbus communication protocol, which is convenient for the user to view and modify the parameters of the system. Meanwhile, the company provides free monitoring software, which can maximize the convenience for users to meet different needs of remote monitoring.
The controller provides general electronic fault self-test and powerful electronic protection functions, which minimise component damage due to installation error and system failure.
PowerCatcher Maximum Power Point Tracking technology allows the controller to track the maximum power point of solar panels even in a complex environment. Compared to traditional MPPT tracking technology, it has a faster response time and higher tracking efficiency.
A built-in Maximum Power Point Tracking (MPPT) algorithm can significantly increase the energy harvesting efficiency of the PV system, which is about 15% to 20% higher than traditional PWM charging.
It provides an active charging voltage regulation function. In case of battery open circuit or lithium battery BMS overcharge protection, the controller battery terminal will output the nominal charge voltage value.
The MPPT tracking efficiency is up to 99.9%.
Due to advanced digital power technology, the circuit energy conversion efficiency is up to 98%.
Available in multiple battery types and supports charging procedures of various types of batteries, such as lithium battery, colloidal battery, sealed battery, vented battery, Lifepo4 battery, etc.
A current-limited charging mode is available. If the power of the solar panel is too high and the charging current is higher than the rated current of the valve, the controller will automatically reduce the charging power so that the solar panel can operate at the rated charging current.
Supports automatic identification of lead-acid battery voltage.
An external LCD Screen or Bluetooth module can be connected to view the unit’s operating data and status, and the controller’s parameters can be modified.
Supports standard Modbus protocol to meet communication needs in different situations.
Built-in over-temperature protection mechanism ensures that when the temperature exceeds the set value of the device, the charging current decreases linearly with the temperature, thereby reducing the temperature rise of the controller and preventing high temperature damage.
Temperature compensation and automatic adjustment of charge and discharge parameters help to improve battery life.
Solar panel short circuit protection, battery open circuit protection and TVS lightning protection, etc.
|1||Solar panel “” interface||6||Communication Interface|
|2||Solar panel “-” interface||7||Operation keys|
|3||Battery “-” interface||8||PV charging indicator|
|4||Battery “” interface||9||Battery level indicator|
|5||External temperature sampling interface||10||Battery type indicator|
MPPT Technology Introductions
The Maximum Power Point Tracking (MPPT) system is an advanced charging technology that allows the solar panel to produce more energy by adjusting the operating conditions of the electrical module. Due to the non-linear characteristics of solar arrays, there is a maximum power point of an array on its curve.
Traditional controllers (Switching Charging Technology and PWM Charging Technology) cannot maintain the battery charge at this point and therefore the maximum energy of the solar panel cannot be obtained. The solar charge controller with MPPT control technology, on the other hand, can track the maximum power point of the array at all times to obtain the maximum energy to charge the battery.
Take a 12V system as an example. The peak voltage (Vpp) of the solar panel is around 17V, while the battery voltage is around 12V. In general, when the controller is charging the battery, the voltage of the solar panel is around 12V and does not fully contribute its maximum power.
However, the MPPT controller can overcome this problem. It constantly adjusts the input voltage and current of the solar panel to achieve the maximum input power.
Compared to the traditional PWM charge controller, the MPPT controller can provide the maximum power of the solar panel and thus provide a larger charging current. In general, the MPPT controller can improve the energy utilisation by 15% – 20% compared to the PWM controller.
In addition, the maximum power point often changes due to differences in ambient temperature and light conditions.
The MPPT controller can adjust parameters from time to time according to different conditions to keep the system close to its maximum operating point.
The whole process is fully automatic and does not require any adjustment by the user.
MPPT Controller Charging Stage Introductions
As one of the charging stages, MPPT cannot be used alone. It is usually necessary to combine boost, float, equalisation and other charging methods to complete the battery charging process.
A complete charging process includes Fast charge, holding charge and float charge. The charging curve is shown below:
In the fast charge phase, the battery voltage has not yet reached the set value of the full charge voltage (i.e. the equalisation/boost charge voltage) and the controller will perform an MPPT charge, using maximum solar energy to charge the battery. When the battery voltage reaches the set value, the constant voltage charge will start.
When the battery voltage reaches the set holding voltage value, the controller will perform a constant voltage charge. This process will no longer include MPPT charging and the charging current will gradually decrease over time.
There are two stages to the maintenance charge, i.e. equalising charge and boost charge. The two stages are performed without repetition, with the equalisation charge being started once every 30 days.
The default duration of the boost charge is 2 hours. The customer can also adjust the holding time and the preset value of the boost voltage point according to actual requirements. When the duration reaches the set value, the system switches to float charge.
Overcharge and excessive gas generation can damage the battery plates and cause active substances on the battery plate to come off.
Equalisation charging can cause damage if the voltage is too high or the time is too long. Please carefully check the specific requirements of the battery used in the system.
Certain types of battery benefit from regular equalisation charging, which can stir the electrolyte, balance the battery voltage and complete the chemical reaction.
Equalising charging increases the battery voltage above the standard voltage, causing the battery electrolyte to evaporate.
If it is detected that the controller automatically controls the next stage to be an equalisation charge, the equalisation charge lasts for 120 minutes (default).
The equalisation charge and boost charge are not repeated during a full charge to avoid excessive gas evolution or overheating of the battery.
MPPT Solar Charge Controller Installation Instruction
- Take great care when installing the battery. Wear safety glasses when installing the vented lead-acid battery. If you come into contact with the battery acid, rinse with clean water.
- Avoid placing metal objects near the battery to prevent the battery from short-circuiting.
- Acid gas may be produced when the battery is charged. Ensure good ventilation.
- The battery may produce flammable gas. Keep away from sparks.
- Avoid exposure to direct sunlight and rain when installing outdoors.
- Poor connection points and corroded wires can cause extreme heat to melt the wire insulation layer, burn surrounding materials and even cause a fire. Therefore, it is necessary to ensure that the connectors are tightened and the wires are preferably fixed with a cable tie to avoid loose connectors caused by wire vibration.
- In system wiring, the output voltage of the component may exceed the safety voltage of the human body. It is therefore necessary to use insulated tools and ensure that hands are dry.
- The battery terminal on the controller can be connected to either a single battery or a battery pack. The following instructions refer to a single battery, but also apply to a battery pack.
- Follow the battery manufacturer’s safety recommendations.
- The system connection wires are selected according to the current density, not exceeding 4A/mm2.
- Ensure that the controller is grounded.
Wiring and Installation Specifications
Wiring and installation must comply with national and local electrical codes.
PV and battery connection wires must be selected according to the rated current.
Wiring specifications are given in the following table:
Installation and wiring of the unit
Caution! When installing the controller, ensure that there is sufficient airflow through the controller’s heat sink, leaving at least 150mm above and below the controller to allow natural convection for heat dissipation.
If the controller is installed in an enclosed box, ensure that the box provides reliable heat dissipation.
Step 1: Select a location
Avoid installing the controller where it will be exposed to direct sunlight, high temperatures or water, and ensure good ventilation around the controller.
Step 2: Mark the mounting position according to the mounting dimensions of the controller.
Drill 4 mounting holes of the appropriate size at the 4 marks. Insert screws into the top two mounting holes.
Align the mounting holes of the controller with the two pre-mounted screws and hang up the controller. Tighten the lower two screws.
For installation safety, we recommend the following wiring sequence as this wiring guide.
Please connect the battery first and then the solar panel. Please follow the “” first and “-” next method when wiring.
When all wires are firmly and securely connected, check that the wiring is correct and the polarity is reversed. When you are satisfied, connect the battery fuse or circuit breaker and check that the LED indicator lights up. If not, immediately disconnect the fuse or circuit breaker and check that the wiring is correct.
When the battery is correctly energised, connect the solar panel. If there is sufficient sunlight, the charge indicator on the controller will light up or flash and start charging the battery.
Product Operation and Display
There are three indicators on the controller
|1—PV array indication||Indicate the current charging mode of controller|
|2—BAT indication||Indicate the current state of battery.|
|3—BAT Type indication||Indicate the current battery type.|
PV array indication
|No.||Indicator status||Charging status|
|1||Steady on||MPPT charge|
(On:0.1s, off: 0.1s, then, On:0.1s, off: 1.7s, cycle: 0.2s)
BAT Type Indication:
|Indicator color||Battery type|
|Green||Sealed lead-acid battery （SLD）|
|Yellow||Gellead.acid battery (GEL)|
|Red||Flooded lead-acid battery (FLD)|
|Blue||12VLi battery (Default:LiFePo4)|
|Purple||24VLi battery (Default:LiFePo4)|
There is a button on the controller which is used in conjunction with the battery type indicator to select the battery type.
The specific mode of operation is as follows
In the current operating state, press and hold the button for 8 seconds. The battery type indicator (the colour displayed is that of the previously stored battery type) will start to flash (the controller will stop charging and other operations and enter the standby mode).
At this point, each time the button is pressed, the battery type indicator will change to a colour corresponding to a battery type. Once the battery type has been selected, press the button again for 8 seconds or do nothing for 15 seconds.
The controller will then automatically save the current battery type and return to normal operation;
In addition, if you press and hold the button for 20 seconds, the controller will restore the factory default parameters.
Product protection and system maintenance
Input power limited protection
If the power of the solar panel is higher than the rated value, the controller will limit the power of the solar panel within the rated power range to prevent damage by overcurrent, and the controller will enter the current limiting charge.
Reverse battery protection
If the battery polarity is reversed, the system will not operate.
PV input end voltage too high
If the voltage at the PV array input end is too high, the controller will automatically disconnect the PV input.
PV input end short-circuit protection
If the voltage at the PV array input end is short-circuited, the controller will stop charging; after the short-circuit is removed, charging will automatically resume.
PV input reverse polarity protection
If the polarity of the PV array is reversed, the controller will not be damaged and normal operation will continue after the wiring error is corrected.
Night reverse charge protection
Prevents the solar panel from discharging the battery at night.
If the temperature of the controller exceeds the set value, it will reduce the charging power or stop charging.
To maintain the best long-term performance of the controller, it is recommended to carry out inspections twice a year.
Check that the airflow around the controller is unobstructed and remove any dirt or debris from the heat sink.
Check that the insulation of any exposed wires has not been damaged by sunlight, friction with other nearby objects, dry rot, insect or rodent damage, etc. If so, the wire must be repaired or replaced.
Check that the indicators are consistent with the operation of the unit. Remember to take corrective action for any malfunctions or fault indications, if necessary.
Check all wiring terminals for corrosion, damaged insulation, signs of high temperature or burning/discolouration. Tighten terminal screws.
Check for dirt, insect nests and corrosion and clean as necessary.
If the lightning arrester has failed, replace it in time to protect the controller and the user’s other equipment from lightning damage.
|Zero load loss|
|Maximum PV open circuit voltage||92V(25℃)；100V(Lowest ambient temperature)|
|Maximum power point voltage range||（Battery voltage 2V） ～ 72V|
|Rated charging current||20A||30A||40A||50A|
|Maximum PV input power||260W/12V|
Voltage setting principles
Equalising charge voltage ≥ Boost charge voltage ≥ Float charge voltage ≥ Boost charge recovery voltage.
overvoltage cut-off voltage overvoltage cut-off recovery voltage.
Other MPPT Solar Charge Controller User Manual
MPPT Solar Charge Controller User Instruction and Download Links
|Dual Battery Solar Charge Controller MPPT||DOWNLOAD|
|SCF60 60A MPPT Solar Charge Controller||DOWNLOAD|
|EPever Upower Inverter Charger||DOWNLOAD|
MPPT vs PWM Solar Controllers: Pros and Cons Highlighted
MPPT charge controllers are so efficient that some can reach 98% efficiency or better. But that doesn’t automatically make them better than PWM solar controllers. When comparing MPPT vs PWM charge controllers, you need to consider several other factors.
Pulse-Width Modulation (PWM) and Maximum Power Point Tracking (MPPT) are both effective at controlling battery charging and preventing battery damage from overcharging and undercharging, but they’re completely different technologies.
Each type works best under different conditions and deciding which is best for your needs will depend on several factors, such as:
- The size of your solar array (maximum voltage/power produced)
- Local climate conditions—PWMs work best in strong sunshine
- The complexity of the system and any extra features you need
- Budget—MPPT controllers are more expensive than PWMs
If you’re just getting started with solar power or are researching options for an installation, this guide is for you.
Don’t be put off by the high cost of installation. As the Minister for Climate Change and Energy Chris Bowen said,
“Renewable energy is the cheapest form of energy. The more renewable energy we have in the system, the cheaper bills will be.” – Chris Bowen
And don’t worry, this isn’t mind-bending “nerd speak,” even though we work hard on technical accuracy and detail.
This guide explores how PWM and MPPT solar controllers work, their characteristics, as well as their advantages and disadvantages.
We’ll also recommend where best to use either PWMs or MPPTs and where to buy quality models, so stick with us to the end.
Pros and Cons of PWM Charge Controllers
Pros of PWM Charge Controllers
Pulse-Width Modulation (PWM) technology is simple and robust, which makes PWM charge controllers affordable and easy to use.
Pulse-Width Modulation relies on the use of a digital switch (transistor) that controls how long power can flow. A longer “on time” means more electrical energy passes through. If the switch is off, no electricity passes through.
PWM is one of the pioneering solar controller technologies. It is time-tested and highly reliable, and so long as you get a quality model with sufficient cooling (either using a fan or a metal heat sink), you can install it even in extreme conditions, such as the desert.
Cons of PWM Solar Charge Controllers
The simplicity of PWM charge regulators is also their biggest weakness. For one, they can’t regulate the input voltage from the solar panels. For example, a 12 V PWM charges the battery at 12 V regardless of the voltage the solar panel is producing.
Even if you connect 24 V panels to a 12 V PWM charge controller, it will bring down the output voltage to 12 V and the rest of the power will be wasted as heat. This reduces the system’s efficiency and can even damage the controller if the current is too high.
That’s why you must always match a PWM charge controller to the battery voltage and the solar array’s power rating (current and voltage). For example, the Victron PWM Solar Charge Controller below is rated for either 12 V or 24 V panels and 5 Amps of current.
PWM charge controllers lose efficiency in cold temperatures or sub-optimal sunlight conditions.
They produce less power when there is no direct sunshine or if the panels are shaded. PWM controllers can’t adapt to such conditions and may stop charging the battery if the power production falls below a certain voltage.
But, despite their faults, PWM solar controllers have a big price advantage over MPPT controllers. You can usually get a good PWM charge controller for under 150, such as this Enerdrive ePOWER PWM Solar Controller. Also some cheaper portable solar panels you can get from some of the big box discounters often have a PWM solar controller included and whilst the panels efficiency likely isnt’ first rate and PWM controller is basic an inefficient you can still get adequate results if you are a very casual user. For people going camping once a year over a weekend and say to make do with that but for anyone else you are better doing it right the first time.
The table below compares the and main features of some PWM and MPPT charge controllers available at Off Grid Direct.
- Works with and auto-detects 12, 24, or 48 V systems
- Can charge heavily depleted batteries, even at 0 V
- Works with solar array voltage of 150 or 250 V
- Rated for 70 Amps or 100 Amps
- Remote control and configuration over Bluetooth or internet
- Can be connected with other similar units
PWMs from reputable manufacturers are highly capable. But, although they provide a high level of battery protection, they work with low voltages and miss out on advanced features like remote monitoring. Understanding MPPTs will help make these differences clearer.
Pros and Cons of MPPT Charge Controllers
Pros of Using MPPT Charge Controllers
In the video above, a solar specialist from Clean Energy Reviews talks about MPPT charge controllers. He compares common models available in Australia, including their and performance.
From the video, it’s clear that MPPT solar controllers have unique features such as input voltage monitoring and better output control. You can also change the conversion algorithm to match current weather conditions to maximise efficiency.
These advantages can make MPPT charge controllers more economical than PWMs in the long run, despite being more costly.
The way Maximum Power Point Tracking (MPPT) technology works is quite ingenious. MPPTs look at the input voltage from the solar array and the required battery voltage. Then, they run the input power through a transformer and convert it into low-voltage, high-current electricity at a level that best matches the battery’s charging needs.
This way, MPPTs always extract maximum power from the solar panels despite changing sunlight conditions and battery charging requirements.
Maximum power point tracking requires an algorithm that allows the controller to compute all the data it needs to operate efficiently despite changes in the amount of power produced.
Solar panels can produce more or less power depending on factors such as:
- Solar irradiation — the amount of light energy falling on the panels
- Temperature — high temperatures can lower panel efficiency and vice versa
- Roof orientation — solar panels are most efficient when sunlight falls directly on them
- Other factors — weather conditions, shading, type of solar panel, type of roof, and the condition of the solar panels can all affect efficiency
The ability to adapt to changing conditions to optimise charging is what makes MPPT charge controllers so effective. Victron claims its MPPT controllers can exceed 98% efficiency under ideal conditions.
This high efficiency allows MPPTs to continue charging the batteries even when conditions are not ideal. power production means you can recoup your investment costs sooner, especially if you have a grid-tied system.
MPPT charge controllers can also handle solar arrays with a much higher voltage compared to the battery charging voltage. For example, the Victron SmartSolar MPPT below can handle a 150 V solar array to charge a 12, 24, or 48 V battery bank.
The way MPPT charge controllers work allows for a high level of control over input and output power. This makes them ideal for large and complex solar installations.
High-end models also come with extra features that may be useful, such as built-in metering, LED displays, remote connectivity, and programmability. These features offer better monitoring and control for solar experts.
Cons of Using MPPT Charge Controllers
Although MPPT technology was around as early as 1985, it’s only recently that MPPT controllers have become affordable and reliable enough for use in many solar installations. Even then, the price of MPPT controllers can exceed 1,000 for high-power applications.
For example, the Enerdrive ProStar MPPT Solar Controller below is rated for systems of up to 1,100 Watts of power and 40 Amps of current, but it’s quite expensive compared to a PWM.
The technology used to manufacture MPPTs also requires more components, which makes them more likely to fail. MPPT charge controllers generally have a shorter lifespan compared to PWM models.
Since MPPT charge controllers operate above the battery voltage, sizing them for your system is challenging. They require precise calculations for proper voltage and current rating, and special components may be required to deal with the high voltage involved.
Where to Use PWM or MPPT Controllers
The efficiency gain from using an MPPT charge controller, such as the one above, helps them produce maximum power. This makes them more economical than PWMs in the long run.
However, for small solar installations, the efficiency gains might be too little to justify a 500 charge controller. Small installations (below 200 W) in tropical and subtropical regions may be served best by an appropriate PWM controller.
On the other hand, MPPT charge controllers operate at a higher voltage, which means lower current and power losses on long cable runs. Because you use smaller cables, material costs are lowered significantly.
From a technical point of view, the most important factors to consider when choosing between a PWM or MPPT charge controller include:
- Installation size — use an MPPT if the system is high-voltage or exceeds 200 W, such as in solar farms
- Site conditions — use an MPPT if you live in a temperate region, or if the batteries will be installed far from the solar array
- System components — some batteries, such as lithium models, work best with MPPT controllers that can provide the appropriate charging profile
- Type of installation — if your system is grid-tied, you must use MPPT controllers since PWMs are best used in 12 V or 24 V off-grid installations
Budget constraints can also be a major factor. If both PWM and MPPT controllers can work for your installation, buying a PWM controller can save you some money. PWMs can be two to three times cheaper than MPPTs of a similar capacity.
Expert Tip: If performance and reliability are important to you, buy high-quality MPPT charge controllers from a major brand like Victron or Enerdrive. Cheap MPPTs are often made with low-quality components that are more likely to fail.
Which Are Better, PWM or MPPT Charge Controllers?
Even though MPPT charge controllers seem to be superior in many respects, PWMs also perform very well in the right conditions. We can’t say that one type is superior to the other unless we consider the conditions under which they’re meant to be used.
What we can say is that MPPT controllers are more efficient than PWM models. An MPPT charge controller can help you harvest up to 15% more power in winter and 30% more in summer.
PWM controllers might be preferable for their reliability, but their limitations mean you have to use an MPPT charge controller for installations that require the use of three or more panels, or in temperate regions that get inconsistent sunshine.
Get Charge Controllers You Can Trust From Off Grid Direct
You may know by now what type of solar charge controller you need. The important question is, which brand will you buy?
We’ve emphasised the importance of buying high-quality, reliable brands for good reason. A charge controller is the brains of your solar installation, and is responsible for protecting your expensive batteries and other components.
At Off Grid Direct, we take the worry out of the equation by only bringing you solar system components from manufacturers we have tried, tested, and come to trust.
Find your solar charge controller now to take advantage of our price match guarantee, and enjoy free delivery for orders above 300 within mainland Australia.
What Is An MPPT Charge Controller?
The most basic functionality of a solar power system is solar panels collecting energy from the sun and storing it in batteries so that you can use it whenever you’d like. However, you can’t simply connect your solar panels directly to your batteries and expect them to charge. To get the most out of your solar panels, you’ll need a charge controller to charge your batteries efficiently. The most efficient type of charge controller is the maximum power point tracking or MPPT charge controller.
Let’s take a look at how they work and what benefits they provide.
What is Maximum Power Point Tracking?
Before we dive into how MPPT charge controllers work, let’s explain how they get their name.
The voltage at which a solar panel produces the most power is called the maximum power point voltage. The maximum power point voltage varies depending on environmental conditions and the time of day.
MPPT charge controllers get their name because they monitor the solar panel and determine the maximum power point voltage for the current conditions. This function is called maximum power point tracking, or MPPT for short.
Tip: Refresh on Amps, Volts, Watts and their differences.
What Is An MPPT Charge Controller?
Solar panels and batteries have different optimal operating voltages. Not only that, these voltages fluctuate. An MPPT charge controller is a DC-DC converter that maximizes the efficiency of a solar system. It does this by optimizing the voltage match between the solar panel array and the batteries.
For example, depending on the state of charge, a 12-volt battery has a nominal voltage that ranges between just over 10 volts and just under 13 volts. Furthermore, the voltage required to charge a 12-volt battery ranges between 13.5 and 14.5 volts depending on the charging phase.
On the other hand, the optimum output voltage of a solar panel varies depending on the panel’s temperature, time of day, how cloudy it is, and other environmental factors. For instance, under ideal conditions, a 250-watt solar panel may have an optimal operating voltage of 32 volts. As the panel heats up in the sun or on a hot day, the optimal voltage may drop to as low as 26 volts.
The rated panel voltage must be higher than the battery voltage to accommodate for these voltage drops in the panel and the increased required battery charging voltage. Without an MPPT charge controller, this voltage differential leads to a lot of wasted power.
What Is The Difference Between MPPT and PWM Charge Controllers?
To better understand how this voltage difference causes inefficiencies, let’s first examine the other common type of solar charge controller. This controller is the pulse width modulation (PWM) charge controller.
PWM controllers use a transistor switch that rapidly opens and closes as needed to regulate the charge current going into the battery. Since PWM controllers can’t modulate the voltage, they pull the output voltage of the solar panel down to match the battery voltage. Let’s look at an example.
A 250-watt solar panel may have an optimal or max power voltage (Vmp) of 32 volts and a max power current (Imp) of 7.8 amps. (32 volts x 7.8 amps = 250 watts)
Using a PWM controller, your panel will still produce 7.8 amps. But the voltage will drop to match the battery at 12 volts. Now, your panel is only providing 94 watts instead of 250 watts. (12 volts x 7.8 amps = 94 watts)
How MPPT Charge Controllers Work
As we mentioned before, MPPT charge controllers are DC-DC converters. This means they regulate the charge current into the battery like a PWM controller. But, they also convert the voltage coming out of the panel to match what the battery needs. Let’s look at an example of how this drastically improves efficiency.
Using the same 250-watt panel, the MPPT controller allows the panel to operate at the max power voltage (Vmp). Now the power going into the controller is the full rated 250 watts.
The output from the controller to the battery still needs to match the battery at 12 volts. But the current increases to 20.8 amps allowing you to utilize the full 250 watt potential of your panel. (12 volts x 20.8 amps = 250 watts)
For simplicity, these examples assumed a 100% efficient conversion in the charge controllers. In reality, a small amount of power is lost as heat during the conversion.
Benefits of an MPPT Charge Controller
Efficient at Using Power
On a properly sized solar power system, it’s not uncommon to see up to a 30% increase in efficiency by switching to an MPPT controller. This efficiency increase is even more significant on systems where the solar panel voltage is much higher than the battery voltage, like our example above.
Best for Large Systems
Utilizing an additional 20-30% of power out of your system becomes more advantageous as the size of your system grows. For this reason, MPPT controllers are often best used on large systems and may not be worth it on smaller, simpler setups.
Better in Cloudier Environments
The maximum power point tracking feature of MPPT controllers is a huge benefit in cloudy environments where the max power point of the solar panels will be fluctuating all day.
Are MPPT Solar Charge Controllers Worth It?
MPPT charge controllers are more expensive than PWM controllers. The added cost of upgrading your controller may not be worth it on small, basic systems. However, on larger systems or in locations with unstable weather conditions, the increased power and efficiency gained by using an MPPT controller will likely more than makeup for the added cost of the controller.
Nobody likes to waste power. MPPT charge controllers help you get the most out of your solar panels without worrying about changing weather conditions or making sure you perfectly sized your solar panels to your battery voltage.