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MPPT Solar Charge Controller using LT3652. Mcu solar charge controller

MPPT Solar Charge Controller using LT3652. Mcu solar charge controller

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    Solar Charge Controller Types, Functionality and Applications

    A solar charge controller is fundamentally a voltage or current controller to charge the battery and keep electric cells from overcharging. It directs the voltage and current hailing from the solar panels setting off to the electric cell. Generally, 12V boards/panels put out in the ballpark of 16 to 20V, so if there is no regulation the electric cells will damage from overcharging. Generally, electric storage devices require around 14 to 14.5V to get completely charged. The solar charge controllers are available in all features, costs, and sizes. The range of charge controllers is from 4.5A and up to 60 to 80A.

    Types of Solar Charger Controller:

    • Simple 1 or 2 stage controls
    • PWM (pulse width modulated)
    • Maximum power point tracking (MPPT)

    Simple 1 or 2 Controls: It has shunt transistors to control the voltage in one or two steps. This controller basically just shorts the solar panel when a certain voltage is arrived at. Their main genuine fuel for keeping such a notorious reputation is their unwavering quality – they have so not many segments, there is very little to break.

    PWM (Pulse Width Modulated): This is the traditional type charge controller, for instance, anthrax, Blue Sky, and so on. These are essentially the industry standard now.

    Maximum power point tracking (MPPT): The MPPT solar charge controller is the sparkling star of today’s solar systems. These controllers truly identify the best working voltage and amperage of the solar panel exhibit and match that with the electric cell bank. The outcome is extra 10-30% more power out of your sun oriented cluster versus a PWM controller. It is usually worth the speculation for any solar electric systems over 200 watts.

    Features of Solar Charge Controller:

    • Protects the battery (12V) from overcharging
    • Reduces system maintenance and increases battery lifetime
    • Auto charged indication
    • Reliability is high
    • 10amp to 40amp of charging current
    • Monitors the reverse current flow

    The function of the Solar Charge Controller:

    The most essential charge controller basically controls the device voltage and opens the circuit, halting the charging, when the battery voltage ascents to a certain level. charge controllers utilized a mechanical relay to open or shut the circuit, halting or beginning power heading off to the electric storage devices.

    Generally, solar power systems utilize 12V of batteries. Solar panels can convey much more voltage than is obliged to charge the battery. The charge voltage could be kept at the best level while the time needed to completely charge the electric storage devices is lessened. This permits the solar systems to work optimally constantly. By running higher voltage in the wires from the solar panels to the charge controller, power dissipation in the wires is diminished fundamentally.

    The solar charge controllers can also control the reverse power flow. The charge controllers can distinguish when no power is originating from the solar panels and open the circuit separating the solar panels from the battery devices and halting the reverse current flow.


    In recent days, the process of generating electricity from sunlight is having more popularity than other alternative sources and the photovoltaic panels are absolutely pollution free and they don’t require high maintenance. The following are some examples of where solar energy is utilizing.

    • Street lights use photovoltaic cells to convert sunlight into DC electric charge. This system uses a solar charge controller to store DC in the batteries and uses it in many areas.
    • Home systems use a PV module for house-hold applications.
    • A hybrid solar system uses for multiple energy sources for providing full-time backup supply to other sources.

    Example of Solar Charge Controller:

    From the below example, in this, a solar panel is used to charge a battery. A set of operational amplifiers are used to monitor panel voltage and load current continuously. If the battery is fully charged, an indication will be provided by a green LED. To indicate undercharging, overloading, and deep discharge condition a set of LEDs are used. A MOSFET is used as a power semiconductor switch by the solar charge controller to ensure the cut offload in low condition or overloading condition. The solar energy is bypassed using a transistor to a dummy load when the battery gets full charging. This will protect the battery from overcharging.

    This unit performs 4 major functions:

    • Charges the battery.
    • It gives an indication when the battery is fully charged.
    • Monitors the battery voltage and when it is minimum, cuts off the supply to the load switch to remove the load connection.
    • In case of overload, the load switch is in off condition ensuring the load is cut off from the battery supply.

    A solar panel is a collection of solar cells. The solar panel converts solar energy into electrical energy. The solar panel uses Ohmic material for interconnections as well as the external terminals. So the electrons created in the n-type material passes through the electrode to the wire connected to the battery. Through the battery, the electrons reach the p-type material. Here the electrons combine with the holes. When the solar panel is connected to the battery, it behaves like other battery, and both the systems are in series just like two batteries connected serially. The solar panel has totally consisted of four process steps overload, under charge, low battery, and deep discharge condition. The out from the solar panel is connected to the switch and from there the output is fed to the battery. And setting from there it goes to the load switch and finally at the output load. This system consists of 4 different parts-over voltage indication and detection, overcharge detection, overcharge indication, low battery indication, and detection. In the case of the overcharge, the power from the solar panel is bypassed through a diode to the MOSFET switch. In case of low charge, the supply to MOSFET switch is cut off to make it in off condition and thus switch off the power supply to the load.

    Solar energy is the cleanest and most available renewable energy source. Modern technology can harness this energy for a variety of uses, including producing electricity, providing light and heating water for domestic, commercial or industrial applications.

    MPPT Solar Charge Controller using LT3652

    Almost every Solar based system has a Battery associated with it which has to be charged from solar energy and then the energy from the battery will be used to drive the loads. There are multiple choices available for charging a lithium battery, we have also built a simple Lithium battery charging circuit previously. But to charge a battery with a solar panel, the most popular choice is the MPPT or maximum power point tracker topology because it provides much better accuracy than other methods like PWM controlled chargers.

    MPPT is an algorithm commonly used in solar chargers. The charge controller measures the output voltage from the panels and the battery voltage, then by getting these two data, it compares them to decide the best power that the panel could provide to charge the battery. At whatever the situation, whether in good or poor sunlight condition, the MPPT charge controller uses this maximum power output factor and converts this to the best charge voltage and current for the battery. Whenever the power output from the solar panel gets dropped, the battery charge current also decreases.

    Thus, in poor sunlight conditions, the battery continuously gets charged according to the output of the solar panel. This is usually not the case in normal solar chargers. Because each solar panels comes with a maximum output current rating and a short circuit current rating. Whenever the solar panel could not provide the proper current output, the voltage falls significantly and the load current does not change and crosses the short circuit current rating making the output voltage of the solar panel is zero. Hence, the charging gets stopped completely in poor sunlight conditions. But MPPT allows the battery to charge even in the poor sunlight condition by controlling the battery charge current.

    MPPTs are around 90-95% efficient in the conversion. However, efficiency is also dependable on the solar driver temperature, battery temperature, solar panel quality, and conversion efficiency. In this project, we will build a Solar MPPT charger for lithium batteries and check the output. You can also check out the IoT Based Solar battery monitoring Project in which we monitoring some critical battery parameters of a lithium battery installed in a Solar System.

    MPPT Charge Controller. Design Considerations

    The MPPT Charge controller circuit that we design in this project will have the following specifications meat.

    • It will charge a 2P2S battery (6.4-8.4V)
    • Charge current will be 600mA
    • It will have an additional charging option using an adapter.

    Components Required for Building MPPT Controller

    • LT3652 Driver
    • 1N5819. 3 pcs
    • 10k pot
    • 10uF Capacitors. 2 pcs
    • Green LED
    • Orange LED
    • 220k resistor
    • 330k resistor
    • 200k resistor
    • 68uH Inductor
    • 1uF capacitor
    • 100uF capacitor. 2 pcs
    • Battery. 7.4V
    • 1k resistors 2 pcs
    • Barrel socket

    MPPT Solar Charger Circuit Diagram

    The complete Solar Charge Controller Circuit can be found in the image below. You can click on it for a full-page view to get better visibility.

    The circuit uses LT3652 which is a complete monolithic step-down battery charger that operates over a 4.95V to 32V input voltage range. Thus, the maximum input range is 4.95V to the 32V for both solar and adapter. The LT3652 provides a constant current / constant voltage charge characteristics. It can be programmed through current sense resistors for a maximum of 2A charge current.

    On the output section, the charger employs 3.3V float voltage feedback reference, so any desired battery float voltage up to 14.4V can be programmed with a resistor divider. The LT3652 also contains a programmable safety timer using a simple capacitor. It is used for charge termination after the desired time is reached. It is useful to detect battery faults.

    The LT3652 requires MPPT setup where a potentiometer can be used to set the MPPT point. When the LT3652 is powered using a solar panel, the input regulation loop is used to maintain the panel at peak output power. From where the regulation is maintained depends on the MPPT setup potentiometer.

    All these things are connected to the schematic. The VR1 is used to set the MPPT point. R2, R3, and R4 are used to set the 2S battery charging voltage (8.4V). Formula to set battery voltage can be given by-

    RFB1 = (VBAT(FLT) 2.5 105)/3.3 and RFB2 = (RFB1 (2.5 105))/(RFB1. (2.5 105))

    The capacitor C2 is used to set up the charge timer. The timer can be set using the below formula-

    tEOC = CTIMER 4.4 106 (In Hours)

    The D3 and C3 are the boost diode and boost capacitor. It drives the internal switch and facilitates the saturation of the switch transistor. The boost pin operates from 0V to 8.5V.

    R5 and R6 are a current sense resistor connected in parallel. The charge current can be calculated using the below formula-

    The current sense resistor in the schematic is selected 0.5 Ohms and 0.22 Ohms which is in parallel creates 0.15 Ohms. Using the above formula, it will produce almost 0.66A of charge current. The C4, C5, and C6 are the output filter capacitors.

    The DC barrel jack is connected in such a way that the solar panel will get disconnected if an adapter jack is inserted into the adapter socket. The D1 will protect the solar panel or the adapter from reverse current flow during no charging condition.

    Solar Charge Controller PCB Design

    For the above discussed MMPT circuit, we designed the MPPT charger controller circuit board that is shown below.

    The design has the necessary GND copper plane as well as proper connecting vias. However, the LT3652 requires adequate PCB heat sink. This is created using the GND copper plane and placing vias in that solder plane.

    Ordering the PCB

    Now we understand how the schematics work, we can proceed with building the PCB for our MPPT Solar Charger Project. The PCB layout for the above circuit is also available for download as Gerber from the link.

    Now our design is ready, it is time to get them fabricated using the Gerber file. To get the PCB done from PCBGOGO is quite easy, simply follow the steps below-

    Step 1: Get into, sign up if this is your first time. Then in the PCB Prototype tab, enter the dimensions of your PCB, the number of layers, and the number of PCB you require. Assuming the PCB is 80cm×80cm, you can set the dimensions as shown below.

    Step 2: Proceed by clicking on the Quote Now button. You will be taken to a page where to set a few additional parameters if required like the material used track spacing, etc. But mostly, the default values will work fine. The only thing that we have to consider here is the price and time. As you can see the Build Time is only 2-3 days and it just costs only 5 for our PCB. You can then select a preferred shipping method based on your requirement.

    Step 3: The final step is to upload the Gerber file and proceed with the payment. To make sure the process is smooth, PCBGOGO verifies if your Gerber file is valid before proceeding with the payment. This way, you can sure that your PCB is fabrication friendly and will reach you as committed.

    Assembling the PCB

    After the board was ordered, it reached me after some days through courier in a neatly labeled well-packed box, and like always, the quality of the PCB was awesome. The PCB that was received by me is shown below. As you see, both the top and bottom layer has turned out as expected.

    The vias and pads were all in the right size. It took me around 15 minutes to assemble to PCB board to get a working circuit. The assembled board is shown below.

    Testing our MPPT Solar Charger

    To test the circuit, a solar panel with 18V.56A of rating is used. The below image is the detailed specification of the solar panel.

    A 2P2S battery (8.4V 4000mAH) battery is used for charging. The complete circuit is tested in moderate sun condition–

    After connecting everything, the MPPT is set when the Sun condition is proper and the potentiometer is controlled until the charge LED starts to glow. The circuit worked pretty well and the detailed working, setup, and explanation can be found in the video linked below.

    Hope you enjoyed the project and learned something useful. If you have any questions, please leave them in the comment section below. You can also use our forums to get your other technical queries answered.

    Solar Charge Controller Settings

    A solar charge controller has various settings that need to be altered for it to function properly, such as voltage ampere settings. Today you will get to know about solar charge controller settings along with solar charge controller voltage settings.

    Solar Charge Controller

    The amount of power generated from the solar panel travels to the inverter batteries. This power needs to be maintained and regulated. A solar charge controller is used for this purpose. It sends short energy pulses to the battery. The average output produced by an MPPT solar charge controller can be 42 volts. You will require additional batteries to produce higher voltages. Here is the catch: to prevent your batteries from damage, you need to choose the right solar charge controller.

    Solar Charge Controller Settings

    Just installing a charge controller won’t solve all your problems. There are different settings that need to be checked and manually adjusted. Different types of batteries like Lithium Iron Phosphate (LIPO), lithium, iron phosphate, lead-acid, and Absorbent Glass Mat (AGM) batteries have different settings. However, there are only two types of charge controllers.

    MPPT controller or maximum power-point tracking controller

    PWM controller or pulse width modulation controller

    Before starting to set up the solar charge controller, you need to understand its functioning of it. Here are the points that you need to keep a note of while installing and setting up the solar charge controller.

    Once the battery is fully charged, the battery will not hold more solar energy in comparison to the chemical content.

    • If the battery is charged high, it can result in the development of heat and gas inside the battery.
    • Electrolytes inside the battery began to expand. This further led to the development of bubbles.
    • This chemical process leads to the generation of hydrogen gas, which is explosive.
    • An overcharged battery will decrease the capacity and increase the aging process of the battery.

    The Parameters:

    Battery Floating Charging Voltage

    The voltage at which a battery is maintained once it is fully charged is known as the battery floating charging voltage. This voltage maintains the capacity of the battery by self-discharging it. The typical voltage for a 12V system is 13.7V and for a 24 V system, it is 27.4V. 58.4V is the voltage for a 48V system.

    Battery Over-Discharging Protection Voltage

    It is also known as under voltage cutoff voltage and its value should also be in accordance with the battery type. In solar charge controller settings, the voltage value range for a 12V system is 10.8V to 11.4V. For a 24V system, it is 21.6V to 22.8V, and 43.2V to 45.6V for a 48 V system. So, the typical values are 11.1 V, 22.2 V, and 44.4 V.

    Battery Overcharging Protection Voltage

    This voltage value should be set as per the battery type. This voltage is also termed a fully charged cutoff voltage or over-voltage cutoff voltage. This voltage value for a 12-volt system ranges between 14.1 V and 14.5 V. For a 24-volt system, it is 28.2V to 29V and for a 48V system, it is 56.4V to 58V. So overall, the typical value for the voltage is 14.4V, 28.8V, and 57.6V.

    Charge Controller Capacity

    It is the maximum number of amperes that your solar charge controller can handle. It is the parameter on the basis of which a solar charge controller is rated. It can be 10A, 20A, 30A, 40A, 50A, 60A, 80A, or 100A.

    Maximum Charging Current

    It is the maximum output current of the solar panels or solar arrays. It is the output that you receive from the batteries.

    System Voltage

    It is also known as the Rated Operational Voltage of your solar power system which refers to the battery bank voltage (direct current operational voltage). Usually, the value is 12V, 24V, or 48V. However, a medium-scale or a large-scale charge controller system has voltage values of 110V and 220V.

    Solar Charge Controller Voltage Settings

    These are the most critical settings that need to be done carefully for the better functioning of the solar charge controller. A solar charge controller is capable of handling a variety of battery voltages ranging from 12 volts to 72 volts. As per the basic solar charge controller settings, it is capable of accommodating a maximum input voltage of 12 volts or 24 volts.

    You need to set the voltage and current parameters before you start using the charge controller. This can be done by adjusting the voltage settings. Here is the list mentioning the most critical voltage settings for the solar charge controller.

    • Absorption Duration: (Adaptive/Fixed)
    • Absorption Voltage: 14.60 volts
    • Automatic Equalization: (Disabled / Equalize every X Days) Disabled
    • Equalization Current Percentage: 25%
    • Equalization Duration: 4 hours
    • Equalization stop mode: (Fixed Time / Automatic on Voltage) Fixed time
    • Equalization Voltage: 14.40 volts
    • Float Voltage: 13.50 volts
    • Low-Temperature Cutoff (optional): Disabled
    • Maximum Absorption Time: 6 hours to 3 minutes (max) per 100Ah battery capacity
    • Maximum Absorption Rate: 30 minutes per 100Ah battery capacity
    • Manual Equalization: Select start now
    • Maximum Equalization Duration: 3-4 hours
    • Re-Bulk Voltage offset: 0.1 volts
    • Tail Current: 2.0A
    • Temperature Compensation (mV/°C): 27.7 volts / 40° Celsius-25° Celsius

    Note: Settings can be changed manually on the controller or from the PC Software. Follow the instructions of the manufacturer for the best results.

    Steps in Solar Charge Controller Settings

    While you set up your new solar charge controller, you should begin with properly wiring the controller to the battery bank and solar panels properly. Once the wiring is properly done and the controller detects the power, its screen will light up. Other steps are as follows:

    Enter the settings menu by holding the menu button for a few seconds.

    Charge current PV to Battery will be displayed

    Battery Type Selection can be done by pressing the menu button for a long time.

    The battery voltage will be auto-detected by the controller.

    According to the user manual, set the setting for absorption charge voltage, low voltage cutoff value, float charge voltage, and low voltage recovery value.

    If the system has an option for setting up the discharge value for DC, then set it as per the user manual.

    Once the setting is done, the charge controller will instantly start the charging process.

    PWM Solar Charge Controller User Manual

    The user manual of a PWM or a pulse width modulation solar charge controller contains information regarding the following:

    LCD Display or Key

    A solar charge controller has a digital display that displays a number of things on the panel through abbreviations or signs and symbols. Here is the list of those things and what they mean.

    • A panel with a small sun shining indicates the solar panel charge.
    • An arrow near the panel when it is bold black means the system is on Aqualation or buck when the arrow is flicking it means it is on float mode.
    • A square filled with horizontal bars indicates battery.
    • Near the battery sign, there is an arrow indicating the output.
    • A bulb sign indicates the load
    • V% indicates the voltage
    • AH is for ampere hours
    • A square-shaped box indicates a menu. It is used for switching between different displays. You can enter or exit the setting by pressing it for a long time.
    • An up arrow is used to increase the value
    • A down arrow showing a decrease in the value

    LCD Display or Setting

    To browse different interfaces in the solar charge controller settings, press the menu button. The LCD or key display discussed in point 1 is the main display. Next displays in order when you press the menu are:

    • FloatVoltage – The screen shows LIT, voltage, and the battery
    • Discharge Reconnect – Shows LIT, voltage, battery, output (arrow), and load (bulb)
    • Under voltage Protection – Displays LIT, voltage, empty battery symbol, and load (bulb)
    • Work Mode – It displays hours (H), output (arrow), and load (bulb). OH, means dawn to dusk, 24H means load output is for 24 hours, and 1-23H means the load is on after sunset and closed after sunrise hours.
    • Battery Type – LIT and the battery box with horizontal bars, determine the amount of battery charged and the type of battery. LIT is for lithium. After this, you are again on the main display.

    Important: To switch On or Off the load manually on the main display, press the down key.

    mppt, solar, charge, controller, using

    Product Features

    • 3-stage PWM charge management
    • A built-in industrial microcontroller with adjustable parameters
    • A pulse width modulation solar charge controller has the following features:
    • Battery Switching functions between lithium and lead battery. The lithium battery is the default setting and switches it to the battery type interface by holding it for 3 seconds.
    • Dual metal–oxide–semiconductor field-effect transistor (MOSFET) Reverse current protection with low heating dissipation
    • In-built protection for short-circuit open circuits, overload, and reverse

    Safety Instructions

    Every electrical appliance comes with a list of safety instructions that are prepared according to the appliance. A PWM controller has the following safety instructions mentioned in its user manual.

    • Do not connect another charging source with the charge controller. The controller is suitable only for regulating solar modules.
    • For the controller to recognize the battery type, ensure the battery has enough voltage before you begin the installation process.
    • Install the controller on a well-ventilated and flat surface. While running, the controller will be heated.
    • This controller is suitable for lithium batteries. All kinds of lead batteries (open, AGM, and gel) are also compatible with it.
    • To minimize loss, keep the battery cable as short as possible.

    System Connection

    In solar charge controller settings, it contains instructions related to the connection. It tells you which port you need to connect to which wire.

    • Connect the battery to the charge regulator (plus and minus)
    • Connect the consumer to the charge regulator (plus and minus)
    • Connect the photovoltaic module to the charge regulator (plus and minus)

    Technical Parameter

    This section contains all the information regarding the voltage, amperes, input, output, size, weight, etc. of the PWM solar charge controller.

    • Batt voltage – 12 volts / 24 volts auto adapt.
    • Charge current – 10A (KYZ 10), 20A (KYZ 20), 30A (KYZ 30)
    • Discharge current – 10A (KYZ 10), 10A (KYZ 20), 10A (KYZ 30)
    • Max solar input – less than 41 volts
    • Model – (KYZ 10) (KYZ 20) (KYZ 30)
    • Operating temperature –.35 ~60° Celsius
    • Size or weight – 13370355 millimeters or 140 grams
    • Standby current – greater than 10 mA
    • USB output – 5 volts / 2 A Max

    The technical parameters of lithium and lead batteries under certain parameters are mentioned in the table below.

    Type of Battery Equalization Float Undervoltage Protection Discharge Reconnect
    Lithium (LIT) battery 12.8 volts 12.0 volts (default, adjustable range 11.5-12.8 volts) 10.7 volts (defaults, adjustable range 9.0-11.0volts) 11.6 volts(defaults, adjustable range 11.0-11.7volts)
    Lead acid battery (bAt) 14.4 volts 13.7 Volts (defaults, adjustable range13-15V) 10.7V (defaults, adjustable range9.0-11.0 Volts) 11.6 Volts (defaults, adjustable range11.0-11.7V)

    Trouble Shooting

    Every electronic appliance faces some problem that can be easily resolved with troubleshooting. The basic problem and its solution are mentioned under the troubleshooting column in the PWMM user manual. Here I have mentioned the problem – probable cause – solution.

    • Charge icon not on when sunny – Solar panel is open or reversed – Reconnect
    • Load icon off – Battery low – Recharge
    • Load icon off – Mode setting wrong – Set again
    • Load icon slow flashing – Overload – Reduce load watt
    • Load icon slow flashing – Short circuit protection – Auto-reconnect
    • Power off – Battery too low reverse – Check battery or connection

    Solar Charge Controller 24V Settings

    After the solar charge controller settings for a 12V system, the 24V system is the most common charge controller used in residential solar power systems. The basic settings for this are mentioned in the user manual of your charge controller. However, here are a few basic settings that are for a 24V system.

    • Battery Floating Charging Voltage is 27.4V
    • Battery Over-discharging Protection Voltage is 21.6V to 22.8V
    • Battery Overcharging Protection Voltage is 28.2V to 29V
    • Solar charge controller settings for AGM battery

    The solar charge controller setting for an AGM or Absorbent Glass Mat battery is also for 12 volts, 24 volts, or 48 volts. The maximum charge current should be at 50A maximum per 100Ah battery capacity. The absorption voltage should be 14.60 volts and the float voltage at 13.50 volts. Equalization voltage at 14.40 volts and bulk voltage offset at 0.10 volts. Absorption duration should be adaptive, and duration should be between 6 hours to 30 minutes per 100Ah battery capacity. The current percentage for equalization is at 25% and its duration at 4 hours max.

    Solar Charge Controller Settings for Lithium Batteries

    Before you begin setting up your lithium batteries, remember that lithium batteries do not require temperature compensation. Also, if you are replacing lead batteries with lithium batteries and the settings are set at Equalized this needs to be changed. To change this, select, EQE (Master equalizer enable/disable) on the charge controller display. This can also be done by selecting OFF the dip switch in other controllers. Some common settings for a multi-stage charge profile need to be set to the following settings:

    • Charge voltage – 14.4 volts (3.6 VPC)
    • Absorption time – 30 minutes to balance lithium cells
    • Float voltage – 13.6 volts
    • Resting voltage (default) – 3.4 VPC

    Solar Charge Controller Settings for Lead Acid Battery

    The lead acid battery is a classic configuration in a solar power system. Once you convert the battery type from lithium/AGM to lead acid battery, the original set parameters for a lead acid battery will be used. These configurations are already installed in the charge controller system. And sometimes, it is just plugging and using the system.

    Well, today you learned about the alteration in solar charge controller settings in accordance with the type of batteries your inverter has. Also, solar charge controller voltage settings should be carefully done to get the maximum potential output from the solar charge controller.

    Olivia is committed to green energy and works to help ensure our planet’s long-term habitability. She takes part in environmental conservation by recycling and avoiding single-use plastic.

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    2 Комментарии и мнения владельцев

    Hello, very nice article! Could I have 2 questions: 1.) I have the same type controller. Do you know, why my solar controller is changing battery setup from B03 to B01 by itself? Is it damaged? 2.) Now I miss arrow on display between solar panel and battery. Does it mean, that battery is fully charged? Thank you.

    Dear Jaro, Thankyou for reaching out to us. For Query 1: Solar Charge Controller changing battery setup from B03 to B01. We have found that said settings mean as follows: B03 – Battery Over Voltage – This error occurs when Input voltage to battery terminals exceeds 17.5-V B01 – Battery Disconnected – This fault code appears when the Portable solar kit cannot detect a battery bank. The issue you are facing can be due to the following reasons: 1- Automatic Configuration – Some controllers adjust their settings based on the battery type and conditions they detect. Check your controller’s manual to see if it has this feature and disable it, according to instrcutions listed in the manual. 2- Firmware or Software Issue: Glitches in the controller’s firmware or software can cause unexpected behavior. Check for firmware updates or try resetting the controller to its factory settings. If this doesnt work, contact the manufacturer to get the controller checked for damage and for possible repair. For Query 2: Arrow on Display between Solar Panel and Battery It is difficult to determine the exact meaning without knowing your controller’s model. 1- In some cases, the arrow indicates charging. 2- It could also mean the battery is fully charged. 3- Or, there might be an issue the controller requires a reset. Follow steps listed in the manual to do the same. And if the issue is still unresolved, there could be some issues with wiring between the 3 components. Last option is to get the entire system checked by an authorized technician and contact the manufacturer for assistance.

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    Recent Posts

    Teardown, Tested: Generic Kw12x0 “W88” Solar Charge Controller (10/30A Versions)

    It was over a month ago when I decided to embark on a project testing MOSFET Rds using the Rohde Schwarz NGM202 power supply when I got a comment from a reader about the possibility of testing some “cheap” PWM solar regulators as they suspected that they may have some “fake” MOSFETs with high Rds values.

    Needless to say, I decided to take on this challenge as I was interested in it as well. After all, my undergraduate degree is in photovoltaics and it’s a rather big surprise to me to find such controllers now hitting the AU10-20 mark with quite generous current ratings up to 30A. Would such units be any good?

    The Products

    For testing, I decided to order two items – a 10A version and a 30A version to see what the differences between the two are.

    10A Version

    The 10A version cost AU12.86 including postage and GST. As it was shipped from China, it took around 34 days to arrive. The 10A version arrived in a cellophane bag. It contained the unit and the user manual (not seen in the picture above).

    The unit feels quite flimsy and is mostly made of plastic. The front panel label is poorly fitted and the internal LCD is slightly angled. The unit claims “MCU Control, Build-in timer, SET voltage and FULL protect”. Three buttons adorn the front for user input. A row of screw terminal block inputs are provided for solar, battery and load. There are also two USB ports on the front for charging or powering USB devices.

    The ratings are on a label on the top of the unit – it claims to be compatible with 12/24V with a 10A rated current, maximum 50V PV voltage and 130/260W power capability. The unit itself feels rather flimsy and is slightly curved on the rear.

    The 10A version weighs 127 grams, which is exceptionally light for this sort of product.

    30A Version

    The 30A version cost a little more, being AU16.20 including GST and taking an identical amount of time to arrive from China. But instead of being just bundled in a cellophane bag, this one comes in a colour print cardboard box. It claims to carry ISO accreditation, but no mention of manufacturer. It also carries a CE logo, but that’s very dubious.

    The box features a blue, white and black printed design. They don’t seem to have mastered the use of spaces in the title, but also seem to not understand the difference between “C” and “G”, advertising features such as LGD (for LCD) and SOG (for SoC). I do like the rear that says “all necessary protections equipped” – I guess this depends on what you define as necessary, but it’s very non-specific. There’s also a surplus space in the word “parameter” in the next line.

    The side of the box very clearly state that it is Made in China. On one side is an area for a specifications label which is not attached, instead checkmarks are placed in the boxes on the opposite side.

    The same style of rating label adorns the top of the controller. This one has a rated current of 40A with a maximum power of 390/780W.

    The controller visually looks the same as the 10A version. Even the front label has a slight angle to it, although it seems to be better adhered. The user manual is a single page colour fold-out leaflet with Chinese on one side and English on the other.

    It’s not the easiest to understand with a number of typos and poor English expression, but it’s sufficient to understand how to set up the controller. One hint I have is that you need to press and hold the first button to “unlock” the value to be adjusted with the up and down buttons and then press and hold the first button to set. Aside from that, everything is pretty much self-explanatory.

    The terminals themselves are rising clamp type, accessible from the bottom. They are recessed somewhat into the unit, but because of the flimsy construction, tend to be difficult to properly secure as it moves at the slightest pressure applied to the screws. The row of terminals is also mounted at a slight angle in this example.

    The body is relatively flimsy plastic – the design has a “raised” section for the terminal block. There are four mounting holes provided.

    The rear of the unit is made of a black metal plate, secured by four screws.

    The 30A unit weighs 132 grams, or 5 grams more than the 10A version. This suggests to me that there is a difference between the two units.


    Taking apart the two units side by side, it’s clear that the 10A version has just three MOSFETs while the 30A version has five MOSFETs. The internals are, otherwise, very much identical. A look at the oily “splodge” left on the rear plate shows that the thermal pad is only making contact at the edges due to the non-flat angle of the MOSFETs on the PCB. This arrangement doesn’t ensure consistent clamping force and does not ensure good heat dissipation – the rear plate appears to be steel which is not anywhere near as good as aluminium.

    The thermal pad itself is very “thin”, with adhesive on the side facing the MOSFETs and a “greasy” side facing the rear panel.

    The two PCBs are basically identical, although the silkscreen suggests the PCB was manufactured by different plants. The design is known as W88-V3.0.

    Internally, the capacitors used are not of reputable make – Chongx, JEC, Jwco and MT. The main controller resides underneath the LCD and is an unmarked 20-pin chip. Aside from that, there are a pair of LM258 Op-Amp ICs and an ON semiconductor MC34063A switching regulator controller. The input seems to be protected by a 47V MOV, so it’s strange that the maximum input voltage is listed as 50V as that might cause some degradation of the MOV over time. The MOV does not appear to be fused in any way, so if it does “let go”, a fire or shattered hot bits of MOV could be the result.

    The inside of the front casing shows the mold used seems to be quite messy. Nothing unexpected from cheap Chinese electronics, I suppose. No clue as to who actually makes these units though …

    In Use

    To fairly test the unit, I decided to create a basic standalone photovoltaic system using some spare parts left over from my PhD and others which could be adapted for use. In some ways, it’s a demonstration of what not to do if you want to have an efficient setup for long term use.

    Solar input is from two unbranded Chinese 50W PV panels. These were connected in parallel using bullet crimps to 0.75mm^2 mains flex leads with a mains plug (since I have no MC4 connectors or solar cable lying around). The parallel arrangement was had by using some cheap double-adapters to hook the two together into a 10m extension lead, also 0.75mm^2. My calculations suggest that the voltage drop would have only very slightly limited the maximum current when the battery is approaching full, but for demonstration this would be sufficient.

    Snaking the cable through the window, it was hooked up to the 30A version of the PWM solar regulator via another double-adapter (due to gender differences) while the exposed pins were used as a way to measure PV voltage. A Century PS12180 12V 18Ah sealed lead-acid battery with about 10Ah of effective capacity (at five years of age) was used as the storage. Various MR16 downlights were used as a load – initially a 50W incandescent, then a 35W incandescent followed by a 10W LED unit. I added a few small switches to isolate the panel, battery and loads from the regulator to ensure proper sequencing and in case of operational emergencies. The voltage on the PV panels, battery and load were monitored using a BK Precision DAS240-BAT Multi-Channel Recorder.

    Operational Results

    During the first day, the battery state was probably only around 30-40% charge to begin with. For the most part, the regulator was just connecting the panels to the battery – the voltage difference is in the voltage drop in the wiring. The PWM effect is not much seen on the first day which was partly cloudy, but the over discharge protection cut off the load at about 10.8V as expected (midpoint between battery and load voltage is the controller’s view of the voltage due to wiring losses). The second day was full sun, where the PWM was much more active in protecting the battery from excessive voltage, maintaining 14.5V (configurable). Part of the reason is that the 18Ah battery can only accept charge current up to about 5.4A according to the datasheet – its internal resistance was pushing the terminal voltage up. I was not able to determine the timing at which it switches from cycle equalisation charge to float charge – in winter, we might not get long enough periods of sun for this to happen.

    With a smaller 10W LED load, the unit allows the light to run for a lot longer before it cut off. The load can be seen to activate at a PV voltage of about 8V, as stated in the datasheet. On the whole, this seems to be exactly as claimed on the datasheet.

    One thing I learned the hard way was not to reconfigure anything on the DAS240-BAT while recording. In this case, after three days of testing, towards the end I tried to turn on the screen sleep feature. After that, when I went to stop the recording, I was greeted by an error and the recording lost all the data after changing the setting. Just another unfortunate quirk in the firmware on the DAS240-BAT.

    The regulator never really warmed up under such a low current load (estimated at ~8A peak), which is a good sign. Unfortunately, the design of the regulator is a bit strange – the load is automatically switched on as soon as the battery is connected and must be manually turned off before connecting the load. The timer feature is not a clock-type timer, but instead is a “x hours after dusk” timer, detected by the PV voltage falling below 8V. The first time this is configured for 0H for dusk-to-dawn operation, it seems the load may stay on for some reason. I had to configure a certain number of hours and then back to 0H for it to operate correctly. But given the price, it seems to do a good job of preventing the battery from being “cooked” or over-discharged to death even if the accuracy is to about 0.1V.

    Part of the reason I decided to test the regulators in an actual system was because of my testing of the regulator in bench-test situations.

    I decided at first to try and simulate a PV input with the internal resistance feature of the NGM202 on one channel, while simulating a battery on the second channel but also attaching a bank of resistors to cause the virtual battery to “slowly” discharge naturally. Unfortunately, the PWM regulation on the charger is so fast, the NGM202 can’t keep up between charging/discharging of the virtual battery. Adding a capacitor to the load to try and slow things down helped slightly, but not enough as the NGM202’s simulated battery was not properly “accepting” charge. Other results, however, can be obtained from bench testing.

    Low Voltage Disconnect

    Testing the low voltage disconnect on the 10A version, the output load can be seen to be disconnected at almost exactly 10.8V. However if the battery voltage rises, even above the claimed 12.8V reconnect point, the load is not re-energised. This suggests that this regulator is not compatible with external charging that does not come via the PV input as it doesn’t reset the over-discharge protection. Definitely good to know but can cause issues in some special applications.

    USB Port Output

    The unit has two USB ports which seems to be a nice convenience. The datasheet says that they can deliver 2.5A maximum, but they are run from an MC34063A which has a datasheet rating of 1.5A. Somehow, it still didn’t look like it was sized enough to deliver that.

    As the ports are paralleled, I decided to modify the 10A board by soldering wires directly to the battery input and to the pins behind the USB connector. Pairs of wires are soldered to produce a four-wire Kelvin connection so that voltage drop in the wire is cancelled out.

    The port can really only deliver about 580mA before the voltage falls too far. At short circuit, it delivers a hair above 1.1A. Nowhere near the 2.5A claim.

    Efficiency was determined by taking the output divided by the input. To determine the input, the quiescent current without the USB switching converter is taken away from the total input current to accurately determine input power (see next section). The results suggests that the converter has about 75% efficiency, making it very average at best. It is really not good enough to be truly useful.

    Quiescent Current

    But seeing as the USB output is absolutely rubbish, I decided to go ahead and desolder the MC34063A regulator IC entirely. This managed to drop the quiescent current to 9.63mA, which means that the switching regulator costs about 3.28mA when idle. It’s also good to know that nothing inside the regulator seems to be reliant on the switching converter 5V output, so it can be removed without affecting the rest of the operation.

    MOSFET Testing

    Thus we reach the crux of why I was invited to test these regulators in the first place – the MOSFETs used within. Are they real, or are they fake? To try and answer this question, I first extracted all the MOSFETs using the “solder blob” and pull method.

    For those who paid attention during the teardown, it is clear that the MOSFET packages were not all the same. From the rear, differences in the tabbing (notched, unnotched, notch size) are apparent. From the front, things are absolutely bizzare.

    The 30A unit has four MOSFETs claiming to be SM7501N which is a Sinopower part number but it’s clear that there are at least three different types based on the plastic package “dimple” marks alone – the leftmost is operating the load control and is one type, the next two in control of battery reverse flow protection are a second type, while the right-two are a third type and in control of the solar PWM. This is corroborated by looking at the height of the plastic part of the package as well. It seems that the construction of the unit takes this into account – each “parallel” pair of MOSFETs are of the same “visual” type. Even the fonts vary on the markings in a very noticeable fashion. This could happen in some legitimate cases in the case there are multiple plants making the same MOSFETs but to have one product use parts from multiple plants is highly unusual.

    All MOSFETs are surprisingly scratched-looking from the front. This suggests to me that these parts may have been recycled – likely to have been re-marked during this process and are perhaps not well treated. I’ve never heard of Sinopower branded transistors, so perhaps that brand and part number is a victim of a remarking operation, or they could be themselves part of one. I have no idea.

    The MOSFETs on the 10A controller are even more bizzare. There seems to be an attempt to cover up the part numbers by grinding them away, but they did a bad job on the third MOSFET and I can see it’s an FBM80N70P. This MOSFET is actually quite similarly rated to the above, but with a slightly lower Rds. Looking at the dimples, it seems all have central dimples, but the rightmost one seems to have the larger dimple. The texture of the metal surface on the middle one is different, and the hole seems marginally larger. I’ve assumed the three are all the same MOSFET type for test purposes.

    Because these MOSFETs don’t have nice pins I can wedge into a breadboard and because it is expected they will exhibit very low resistance of 6-11mΩ, I decided to build a test board using a bit of strip board and soldering each tested MOSFET for testing. Kelvin four-wire connections were used to the NGM202 and the test current was cranked to the full 3A capability of the unit to try and produce the cleanest readings of Rds vs. Vgs.

    Of note is that the MOSFETs are rated at which is well above what I can achieve with ease. As a result, I can’t actually determine if the MOSFETs are capable of passing the 80A they claim or verify the Rds at 40A, but on the whole if the Rds is high then that should show at lower currents as well.

    Because of the low Rds, another “issue” arises – the resistance of the test board itself may affect the results. It’s not entirely possible to get a “true” zero ohm correction, but what I did was to measure the test board fixture with the drain and source pads solder bridged together to form as close to zero ohms for the test fixture. This is reported in the below graph as “Null”.

    Interestingly, the overall readings show that the MOSFETs are broadly similar, at least at the Rds rating condition of Vgs = 10V. In the case of the 30A controller’s MOSFETs, there were a few that were similar and a pair which were somewhat different, but that is well within expectations for manufacturing variation. The 10A controller’s MOSFETs were a bit different from each other – perhaps there are actually three types in there, but the Rds was actually lower than the MOSFETs used in the 30A controller.

    Zooming in and subtracting the null line from the readings, it seems that all the MOSFETs measured within the expected range. The SM7501 is rated at 9 to 11mΩ – the tested results were about from 8.8 to 10.8mΩ. The FBM80N70P is rated for 6 to 7mΩ – the tested results ranged from 5.4 to 6.5mΩ. These results are probably slightly optimistic, as the null reading that is subtracted is not a true zero resistance – however, even without the null line subtraction, the MOSFETs actually test quite well and survived the torturous desoldering process as well.


    After testing the MOSFETs, it was a bit of a game trying to suck out the very crusty solder from the PCBs. This required a co-ordinated effort with an iron on top and the sucker below … but I managed to re-mount the MOSFETs on both units. All of that soldering and desoldering and it seems that the MOSFETs survived!

    Unfortunately, in the case of the 10A unit, I discovered during testing that I had a tiny scrap of desoldering braid on the load-control MOSFET. It shorted out the gate with the drain – this immediately destroyed the drive transistor and thus the 10A unit has lost its ability to run loads and perform overdischarge protection duties.


    The generic Kw12x0 PWM Solar Charge Controller is a rather inexpensive piece of equipment but it doesn’t do a terrible job of being a basic solar charge controller. On the whole, it behaves as one may expect – protecting the battery from excessive voltage and overdischarge, with an integrated dusk timer function and USB outputs.

    Testing revealed the controller did have some quirks – the load is energised as soon as the regulator starts up, the output is also turned on after configuring the regulator into dawn-to-dusk mode, the output does not reset its overdischarge protection if the battery voltage rises above the reconnection voltage, a quiescent draw a little above the claimed value and USB outputs that are severely anemic with regards to current.

    However, despite all of this, the MOSFETs inside were a surprise. They appeared mismatched, scratched and likely to be recycled in some way. But testing revealed all MOSFETs were able to achieve the datasheet rated Rds at the test current of 3A. While the datasheet rating was made at 40A (and I have no easy, accurate capability to test up to that level), the MOSFETs were definitely well oversized for the application (e.g. parallel pairs of 80A rated MOSFETs in the 30A rated regulator) that it seems likely the regulator would run cool. This matches the relatively “ad-hoc” thermal interface between the MOSFETs and the rear panel which can have a very limited contact area (and hence effectiveness) due to the difference in angle between the package and the metal plate backing.

    The build quality of the unit feels relatively cheap and flimsy, with terminal blocks sometimes mounted at a jaunty angle with screw heads that are easily chewed up, but what do you expect for 10-20? Something that works is already a big surprise to me.

    mppt, solar, charge, controller, using

    The testing was not exactly casualty free, but I was still pleased to have managed to test all of the MOSFETs and reassemble both units, only losing the load-control MOSFET’s driving transistor due to a scrap of desoldering braid shorting out the gate and drain.

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