FAQ's on WPTO solar charge controllers
Adding an MPPT (Maximum Power Point Tracking) solar charge controller to an existing system is a very popular upgrade these days as people improve and expand their systems. MPPT controllers will get the most out of your PV array, and actually are more beneficial in off-grid applications because they produce the most benefit in the cold winter months when the batteries tend to be at a lower state-of-charge—right when you need the energy the most!
1.MPPT solar charge controller schematic (What is MPPT?)
Solar arrays have a power curve with a maximum power point and the device that sets this point is called a Maximum Power Point Tracker.
Solar arrays have a power curve with a maximum power point and the device that sets this point is called a Maximum Power Point Tracker.
A MPPT, or maximum power point tracker is an electronic DC to DC converter that optimizes the match between the solar array (PV panels), and the battery bank or utility grid. To put it simply, they convert a higher voltage DC output from solar panels (and a few wind generators) down to the lower voltage needed to charge batteries.
A maximum power point tracker (or MPPT) is a high efficiency DC to DC converter which functions as an optimal electrical load for a photovoltaic (PV) cell, most commonly for a solar panel or array, and converts the power to a voltage or current level which is more suitable to whatever load the system is designed to drive.
2.Main features of MPPT solar charge controller
In any applications which PV module is energy source, MPPT is used to correct for detecting the variations in the current-voltage characteristics of solar cell and shown by I-V curve.
MPPT solar charge controller is necessary for any solar power systems need to extract maximum power from PV module; it forces PV module to operate at voltage close to maximum power point to draw maximum available power.
MPPT allows users to use PV module with a higher voltage output than operating voltage of battery system.
For example, if PV module has to be placed far away from charge controller and battery, its wire size must be very large to reduce voltage drop. With a MPPT solar charge controller, users can wire PV module for 24 or 48 V (depending on charge controller and PV modules) and bring power into 12 or 24 V battery system. This means it reduces the wire size needed while retaining full output of PV module.
MPPT solar charge controller reduces complexity of system while output of system is high efficiency. Additionally, it can be applied to use with more energy sources. Since PV output power is used to control DC-DC converter directly.
MPPT solar charge controller can be applied to other renewable energy sources such as small water turbines, wind-power turbines, etc.
3.The benefits of MPPT solar charge controller
The benefits of MPPT solar charge controllers are greatest during cold weather, on cloudy or hazy days or when the battery is deeply discharged. Solar MPPT can also be used to drive motors directly from solar panels. The benefits seen are huge, especially if the motor load is continuously changing. This is due to the fact that the AC impedance across the motor is related to the motor's speed. The MPPT will switch the power to match the varying resistance.
The benefits of MPPT solar charge controllers are greatest during cold weather, on cloudy or hazy days or when the battery is deeply discharged. Solar MPPT can also be used to drive motors directly from solar panels. The benefits seen are huge, especially if the motor load is continuously changing. This is due to the fact that the AC impedance across the motor is related to the motor's speed. The MPPT will switch the power to match the varying resistance.
4.Compare to the traditional solar charge controller
Maximum Power Point Tracking solar charge controllers (MPPT) are different than the traditional PWM solar charge controllers in that they are more efficient and in many cases more feature rich. MPPT solar charge controllers allow your solar panels to operate at their optimum power output voltage, improving their performance by as much as 30%.
The most traditional charge controller simply monitors the battery voltage and opens the circuit, stopping the charging, when the battery voltage rises to a certain level. Older charge controllers used a mechanical relay to open or close the circuit, stopping or starting power going to the batteries.Traditional Solar Inverters perform MPPT for an entire array as a whole. In such systems the same current, dictated by the inverter, flows though all panels in the string. But because different panels have different IV curves, i.e. different MPPs (due to manufacturing tolerance, partial shading, etc.) this architecture means some panels will be performing below their MPPT, resulting in the loss of energy.
A photovoltaic (PV) array is a constant current device. The current (amps) from a PV module remains relatively constant over a wide range of voltage. For example a typical 75-watt module delivers 4.45 amps at up to 17 volts when the sky is clear and temperature is cool. Traditional PV controllers connect the PV array directly to the battery until it reaches a full charge voltage. When this 75-watt module is connected directly to a battery in a low state of charge it will begin charging at 12 volts. The PV panel still provides about the same current, but, because PV output voltage is lower, it can only deliver 53 watts to the battery. This wastes up to 22 watts or 30% of the available power. MPPT charge controls use this extra voltage to boost charging amps to the battery.
5.Compared with normal solar charge controller by Schematic Diagram
MPPT solar charge controller Schematic Diagram: Picture 2 shows typical 12V battery solar charge system V-A curve.
Normal Solar Charge Controller: Solar Panel works at point A state, the solar panel working voltage is a little higher than battery voltage.
Charge Voltage: UA=13.2V
Charge Current:: IA=9.8A
Charge Power: PA=13.2*9.8=129.36w
Area in drawing: ①＋③
MPPT Solar Charge Controller: Solar Panel works at point B state, the solar panel working voltage much higher than battery voltage.
Charge Voltage: UB=18.4V,
Charge Current:: IB=9.3A
Charge Power: PB=18.4*9.3=171.12w
Area in drawing: ①＋②
MPPT Schematic Diagram
Comparison: The power B is more than power A.
△P/ PA =（PB— PA）/ PA＝32.3%
As a result of different manufacture of solar panels, different solar illumination intensity, different temperature, different efficiency of solar charge controller and so on. The effective power increase rate is 30%.
△P/ PA =（PB— PA）/ PA＝32.3%
As a result of different manufacture of solar panels, different solar illumination intensity, different temperature, different efficiency of solar charge controller and so on. The effective power increase rate is 30%.
6.The price of MPPT solar charge controller
MPPT charge controllers are more expensive that PWM charge controllers, but the advantages are worth the cost. If you can afford it, you should definitely use an MPPT charge controller.
MPPT charge controllers are more expensive that PWM charge controllers, but the advantages are worth the cost. If you can afford it, you should definitely use an MPPT charge controller.
7. WPTO MPPT Technology
The WPTO utilizes Maximum Power Point Tracking technology to extract maximum power from the solar module (s). The tracking algorithm is fully automatic and does not require user adjustment, WPTO technology will track the array maximum power point voltage (Vmp) as it varies with weather conditions, ensuring that maximum power is harvested from the array through the course of the day.
- Current Boost
In many cases, WPTO MPPT technology will “boost” the solar charge current. For example, a system may have 8 Amps of solar current flowing into the WPTO and 10 Amps of charge current flowing out to the battery. The WPTO does not create current! Rest assured that the power into the WPTO is the same as the power out of the WPTO. Since power is the product of voltage and current(Volts×Amps), the following is true:
- Power Into the WPTO-Power Out of theWPTO
- Volts In×Amps In=Volts Out×Amps Out
* Assuming 100% efficiency. Losses in wiring and conversion ignored.
If the solar module’s Vmp is greater that the battery voltage, it follows that the battery current must be proportionally greater than the solar input current so that input and output power are balanced. The greater the difference between the maximum power voltage and battery voltage, the greater the current boost. Current boost can be substantial in systems where the solar array is of a higher nominal voltage than the battery.
An Advantage Over Traditional Controllers
Traditional controllers connect the solar module directly to the battery when recharging. This requires that the solar module operate in a voltage range that is below the module’s Vmp. In a 12V system for exemple, the battery voltage may range from 11-15Vdc but the module’s Vmp is typically around 16 or 17V.
Figure 4-1 shows a typical current VS. voltage output curve for a nominal 12V off-grid module.
If the solar module’s Vmp is greater that the battery voltage, it follows that the battery current must be proportionally greater than the solar input current so that input and output power are balanced. The greater the difference between the maximum power voltage and battery voltage, the greater the current boost. Current boost can be substantial in systems where the solar array is of a higher nominal voltage than the battery.
An Advantage Over Traditional Controllers
Traditional controllers connect the solar module directly to the battery when recharging. This requires that the solar module operate in a voltage range that is below the module’s Vmp. In a 12V system for exemple, the battery voltage may range from 11-15Vdc but the module’s Vmp is typically around 16 or 17V.
Figure 4-1 shows a typical current VS. voltage output curve for a nominal 12V off-grid module.
Current VS. Voltage in 12V system??? ??????? Output power in 12V system
The array Vmp is the voltage where the product of current and voltage (Amps×Volts) is greatest, which falls on the “knee” of the solar module I-V curve as shown in Figure4-1. Because Traditional controllers do not operte at the Vmp of the solar array, energy is wasted that could otherwise be used to charge the battery and power system loads. The greater the difference between battery voltage and the mp of the module, the more energy is wasted.
WPTO MPPT technology will always operate at the Vmp resulting in less wasted energy compared to traditional controllers.
WPTO MPPT technology will always operate at the Vmp resulting in less wasted energy compared to traditional controllers.
- Conditions That Limits the Effectiveness of MPPT
The Vmp of a solar module decreases as the temperature of the module increases. In very hot weather, the Vmp may be close or even less than battery voltage. In this situation, there will be very little or no MPPT gain compared to traditional controllers. However, systems with modules of higher nominal voltage than the battery bank will always have an array Vmp greater than battery voltage. Additionally, the savings in wiring due to reduced solar current make MPPT worthwhile even in hot climates.
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