Amp MPPT Solar Charge Controller
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- Automatically detects 12V or 24V DC system voltages.
- Compatible with various deep cycle battery options: Sealed, Gel, Flooded, and Lithium.
- Innovative MPPT technology with high tracking efficiency up to 99% and peak conversion efficiency of 98%.
- Electronic protection against reverse polarity, overcharging, over-discharging, overload, short-circuiting, and reverse current.
- LCD screen and multiple LED indicators for displaying system operation information, customizable parameters, and error codes.
- Features diverse load control; also capable of charging over-discharged lithium batteries.
- Die-cast aluminum design allows for efficient heat dissipation.
- RS232 port to communicate with BT-1 Bluetooth module.
|Rated Battery Current:||40A|
|Rated Load Current:||20A|
|Max. PV Input Short Current:||50A|
|Max. Battery Voltage:||32V|
|Max Solar Input Voltage:||100VDC|
|Charge circuit voltage drop:||≤ 0.26V|
|Discharge Circuit Voltage drop:||≤ 0.15V|
|Working Temperature:||-35°C to 45°C|
|Max Terminal Size:||8AWG|
|Rated Load Current:||10% to 90% NC|
|Overall Dimension:||9.37 x 6.81 x 2.85 in|
|Net Weight:||4.41 lb|
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Charge your 36v or 48v Golf Cart with almost any solar module!
Increase your range and battery life using the power of solar and the Solar EV MPPT Solar Boost Charge Controller.
Run your golf carts longer, with less maintenance using solar.
The Solar EV MPPT-Boost Solar Charge Controller is specifically designed for adding solar panel(s) to a golf cart. With the ability to use lower voltage (12V to 24V) solar panels with 36V or 48V batteries, our MPPT-Boost Controller is the industry’s most efficient voltage-boosting solar charge controller. With a powerful panel and sunshine, you will be able to drive up to 10 miles per day on the sun. You may never need to plug your cart in!
325-350W 8A input 36/48V MPPT Controller
- 99% Peak Efficiency
- Continuous MPPT
- Advanced electronic protections
- 5-Year Warranty
- MADE in the USA
Boosting Panel Voltage Saves Money
Most solar charge controllers move power from a higher voltage panel to a lower voltage battery bank. These golf cart solar charge controllers will take almost any solar panel and boost the voltage to charge a 36V or 48V battery pack. Because these controllers feature true MPPT, no configuration is necessary; the controller will automatically adapt to your panel and not to forget the Four-Wire installation.
Running circles around the Competition
You have a limited amount of space on the roof of your golf cart. Advanced electronics in the our controller extract more usable power from your panel than any other controller. These solar charge controllers are fully waterproof, which makes them ideal for golf carts and other applications where the controller will be exposed to moisture.
High-Speed MPPT: Always on Target
Not all Maximum Power Point Tracking controllers were created equally. Most use a sweep and sleep method that scans the entire voltage range every 30-60 seconds. That’s okay for a clear day, with a stationary panel. But moving vehicles, and changing Cloud cover requires a faster, more advanced controller. The Solar EV controllers adapt to changing light conditions 15 times every second. They are always on target, capturing every bit of available sunshine. Simply put, other controllers can’t keep up.
Computer Controlled, Temperature-Compensated 3-Stage Battery Charging
Precise computer controlled charging ensures the optimal charge cycle for your battery. This increases the battery life and maximizes battery capacity. Our controllers for lithium batteries feature industry-standard Constant-Current Constant-Voltage (CC/CV) charging for widest battery compatibility. Please call us for Lithium Chargers Pricing!
Made in the USA
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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.
What is a Solar Charge Controller
A solar charge controller manages the power going into the battery bank from the solar array. It ensures that the deep cycle batteries are not overcharged during the day, and that the power doesn’t run backwards to the solar panels overnight and drain the batteries. Some charge controllers are available with additional capabilities, like lighting and load control, but managing the power is its primary job.
A solar charge controller is available in two different technologies, PWM and MPPT. How they perform in a system is very different from each other. An MPPT charge controller is more expensive than a PWM charge controller, and it is often worth it to pay the extra money.
PWM Solar Charge Controller
A PWM solar charge controller stands for “Pulse Width Modulation”. These operate by making a connection directly from the solar array to the battery bank. During bulk charging, when there is a continuous connection from the array to the battery bank, the array output voltage is ‘pulled down’ to the battery voltage. As the battery charges, the voltage of the battery rises, so the voltage output of the solar panel rises as well, using more of the solar power as it charges. As a result, you need to make sure you match the nominal voltage of the solar array with the voltage of the battery bank. Note that when we refer to a 12V solar panel, that means a panel that is designed to work with a 12V battery. The actual voltage of a 12V solar panel, when connected to a load, is close to 18 Vmp (Volts at maximum power). This is because a higher voltage source is required to charge a battery. If the battery and solar panel both started at the same voltage, the battery would not charge.
A 12V solar panel can charge a 12V battery. A 24V solar panel or solar array (two 12V panels wired in series) is needed for a 24V battery bank, and 48V array is needed for 48V bank. If you try to charge a 12V battery with a 24V solar panel, you will be throwing over half of the panel’s power away. If you try to charge a 24V battery bank with a 12V solar panel, you will be throwing away 100% of the panel’s potential, and may actually drain the battery as well.
MPPT Solar Charge Controller
An MPPT solar charge controller stands for “Maximum Power Point Tracking”. It will measure the Vmp voltage of the panel, and down-converts the PV voltage to the battery voltage. Because power into the charge controller equals power out of the charge controller, when the voltage is dropped to match the battery bank, the current is raised, so you are using more of the available power from the panel. You can use a higher voltage solar array than battery, like the 60 cell nominal 20V grid-tie solar panels that are more readily available. With a 20V solar panel, you can charge a 12V battery bank, or two in series can charge up to a 24V battery bank, and three in series can charge up to a 48V battery bank. This opens up a whole wide range of solar panels that now can be used for your off-grid solar system.
The Key Features of a Solar Charge Controller are:
- Multistage charging of battery bank. changes the amount of power set to the batteries based on its charge level, for healthier batteries.
- Reverse current protection. stops the solar panels from draining the batteries at night when there is no power coming from the solar panels.
- Low voltage disconnect. turns off attached load when battery is low and turns it back on when the battery is charged back up.
- Lighting control. turns attached light on and off based on dusk and dawn. Many controllers are configurable, allowing settings for a few hours or all night, or somewhere in between.
- Display- may show voltage of battery bank, state of charge, amps coming in from solar panel.
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