Introduction
The efficient use of solar energy systems depends significantly on the ability of the charge controller to extract the maximum possible power from solar panels under varying conditions. This process is known as Maximum Power Point Tracking (MPPT). The ZK-SJ30 is a versatile solar charge controller designed for small to medium-sized projects due to its excellent price-performance ratio. It offers a wide input voltage range of DC6-80 V and an adjustable output voltage range of DC1.3-78 V with a maximum output current of 30 A. Additionally, it features anti-backfilling protection and over-power protection up to 700 W, making it well-suited for various applications.
While many solar charge controllers automatically track the MPPT, the ZK-SJ30 requires a manual adjustment of the MPPT voltage to achieve optimal performance. This article provides a step-by-step guide to manually determining the MPPT point using a laboratory power supply, a resistive load, and an electronic load.
This guide aims to deliver a comprehensive method to test and optimize the ZK-SJ30 solar charge controller, ensuring operation at peak efficiency in diverse solar energy setups.

Experimental Setup
Components Used:
- Laboratory Power Supply (adjustable voltage and current, ensuring it can support the voltages and current ratings of your solar panels)
- ZK-SJ30 MPPT Solar Charge Controller
- Electronic Load (operated in Constant Resistance Mode)
- Resistive Load: Two 4-Ohm resistors, each rated for 100 W
- Multimeter for voltage and current measurements
- Connecting Wires
Configuration:
The experimental setup simulates a solar panel array using a laboratory power supply. In this specific case, we use two 100 W solar panels in series, each with a maximum power voltage (Vp) of 20 V, to charge a lead-acid battery with a target voltage of 13.9 V.
Key Parameters for This Setup:
Component | Specification |
---|---|
Solar Panels | 2x 100 W, 20 Vp (in series) |
Total Vp | 40 V |
Target Battery Voltage | 13.9 V |
Resistive Load | 2 Ohms (achieved with two 4-Ohm resistors in parallel) |
Adapting for Other Solar Panel Configurations
If your solar panels have different maximum power voltages (Vp) or wattage ratings, you will need to adjust the resistive load accordingly. The resistive load value should match the expected current draw and voltage range of your solar array to simulate realistic conditions.
How to Calculate the Appropriate Resistive Load:
- Determine the total Vp of your solar panels. For example, if you have three 150 W panels with a Vp of 18 V each in series, the total Vp would be 54 V.
- Estimate the target current draw (I). Divide the total power of your solar array by the expected operating voltage:Example: For a 450 W system and a 13.9 V battery, the expected current would be:
- Calculate the appropriate resistive load (R) using Ohm’s Law:Example: For a target voltage of 13.9 V and a current of 32.4 A:
In practice, you would round the resistance value to a commonly available resistor rating, ensuring the resistors can handle the power dissipated.
Adjusting for Different Panel Configurations:
Panel Configuration | Total Vp | Recommended Resistive Load |
2x 100 W panels (20 Vp each) | 40 V | 2 Ohms |
3x 150 W panels (18 Vp each) | 54 V | 0.43 Ohms |
4x 200 W panels (24 Vp each) | 96 V | 0.86 Ohms |
Important Considerations for the Power Supply
Ensure that your laboratory power supply is capable of delivering the necessary voltage and current for your specific solar panel configuration. For example, if you are simulating a system with a total Vp of 54 V and a maximum current of 10 A, your power supply must be able to provide at least 54 V at 10 A.
If your system requires higher voltage or current than your power supply can deliver, consider splitting the simulation into smaller sections or using a power supply with sufficient capacity.
Measurement Procedure for My Experimental Setup with 2x 100 W
Step 1: Setting Up the Laboratory Power Supply
- Configure the laboratory power supply to 40 V output voltage and 5.5 A current limit.
- Connect the positive terminal of the power supply to one end of the 2-Ohm resistive load.
- Connect the other end of the resistive load to the PV input of the solar charge controller.
Step 2: Configuring the Electronic Load
- Set the electronic load to operate in CR Mode (Constant Resistance).
- Adjust the resistance value to 2 Ohms.
- Connect the electronic load to the output terminals of the charge controller.
Step 3: Connecting Measurement Instruments
- Place a multimeter in parallel at the PV input terminals of the charge controller to measure the input voltage after the resistive load.
- Insert a multimeter in series between the power supply and the resistive load to measure the input current.
Step 4: Setting the Output Voltage and Current Limit
- Adjust the output voltage using the potentiometer under load to match the target voltage of your battery (e.g., 13.9 V for a lead-acid battery).
- Turn the current limit potentiometer to maximum to ensure the charge controller can handle the peak power demand from your solar array without restricting current.
Manual MPPT Adjustment
The MPPT point is manually adjusted on the solar charge controller by varying the input voltage while monitoring the input power.
Step 5: Adjusting the MPPT Voltage
- Start with a low MPPT voltage setting on the charge controller.
- Gradually increase the MPPT voltage (turn the potentiometer clockwise) while observing the input voltage (V) and input current (I).
- Calculate the input power (P = V × I) for each adjustment.
- Identify the point at which the input power is at its maximum. This point represents the Maximum Power Point (MPPT).
Example Measurements
Input Voltage (V) | Input Current (A) | Input Power (W) |
30 V | 4.5 A | 135 W |
32 V | 5.0 A | 160 W |
34 V | 5.2 A | 176.8 W |
36 V | 4.8 A | 172.8 W |
Important Considerations
- Ensure that the laboratory power supply is current-limited to prevent overloading the charge controller.
- The resistive load should be rated for at least the maximum expected power to avoid overheating.
- The electronic load must be configured correctly to simulate a realistic load, such as a lead-acid battery.
Conclusion
The ZK-SJ30 solar charge controller is a popular device due to its excellent price-performance ratio. However, the available documentation is often lacking in detail, leaving users unsure about how to properly configure the controller to achieve optimal performance. This comprehensive instruction manual aims to fill that gap by providing a clear, step-by-step guide for setting up and manually adjusting the ZK-SJ30 to find the Maximum Power Point (MPPT). By following this guide, users can ensure that the controller operates at maximum efficiency for their specific solar system setup, even in scenarios where automatic MPPT tracking is not available. This reliable and reproducible method will help users optimize the performance of the ZK-SJ30 using common laboratory equipment.
List of Material
ZK-SJ30 MPPT Solar Charger
https://amzn.to/4gKJ0ZM
4 Ohm, 100 W Resistor
https://amzn.to/3Py4MEb
Lab Power Supply
https://amzn.to/3WfsMQg