How to Match Solar Panels with Different MPPT Models: A Complete Guide

At present, MPPT solar charge controllers on the market can be roughly divided into 30A,40A,60A,80A,100A,120A, etc. When choosing different configurations of MPPT and solar panels, it is very important to ensure that the parameters of solar panels match the working range of MPPT. The following will help you how to configure the appropriate number of solar panels from multiple levels.

1.The working principle of MPPT

MPPT is to adjust the working state of the solar system in real time according to the changes of the output voltage and current of the solar panel, so that the output power is always maximized. Different types of MPPT have different input voltage and current ranges, so it is particularly important to correctly configure the number and arrangement of solar panels.

2. Key parameters

When matching solar panels, you need to know several important parameters:

Input voltage range of MPPT: Each MPPT has a minimum and maximum input voltage range, which determines the number of solar panels connected in series.
Maximum input current of MPPT: This input current capacity limits the number of solar panels that can be connected in parallel.
Open circuit voltage (VOC): This refers to the output voltage of the solar panel under no load. The sum of open-circuit voltages of solar panels in series cannot exceed the maximum input voltage of MPPT.
Short-circuit current (ISC): This is the current value output by the solar panel under short-circuit condition, which will increase the short-circuit current under parallel connection condition.
Peak power point voltage (VMP): This is the voltage value of the solar panel at the maximum power output, which is usually lower than the open circuit voltage (VOC).

3. Match the number of solar panels according to MPPT input voltage range

The number of solar panels in series depends on the input voltage of MPPT. There is a formula to determine the number of solar panels in series:

A.Determine the minimum and maximum input voltage of MPPT:

For example, if the input voltage range of MPPT is 150V-500V, you need to ensure that the open circuit voltage of solar panels in series is within this range.

B.Determine the open circuit voltage (VOC) of the solar panel.

The open-circuit voltage is marked on the solar panels. For example, if the VOC of a solar panel is 40 V, then 150V≤N series ×40V≤500V, from which the number of solar panels in series can be calculated:

150V/40V=3.75 (rounded up to 4 boards)

500V/40V=12.5 (rounded down to 12 boards)

Therefore, the number of solar panels connected in series is 4-12.

4. MPPT maximum input current matches the number of parallel solar panels

MPPT has a maximum input current limit, and the number of parallel solar panels cannot make its total current exceed the limit. In parallel, the currents add up, so we need to pay attention to the short-circuit current (ISC) of solar panels and the maximum input current of MPPT. The following is the parallel number formula:

A.Determine the maximum input current of MPPT: for example, the maximum input current of MPPT is 80A.

B.Determine the short-circuit current (ISC) of the solar panel: for example, the short-circuit current of the solar panel is 8A.

C.Calculate the number of parallel connections: =10, so at most 10 solar panels can be connected in parallel.

5. Temperature

Open circuit voltage (VOC) varies with temperature. In low temperature environment, the open circuit voltage of solar panels will increase, which may cause the total voltage of solar panels in series to exceed the maximum input voltage of MPPT. Therefore, in cold areas, it is necessary to calculate and consider the temperature correction coefficient.

Temperature correction formula:
Voc-temp=Voc+Temperature Coefficient of Voltage* （T_standard-T_actual）
Among them: ·
1. Voc-temp is the corrected open circuit voltage

2. Temperature coefficient of voltage is the temperature coefficient in the solar panel data table.

3. T _ standard is usually 25°C, and T_actual is the actual ambient temperature.

6. Practical application examples

Assume the following parameters: ·

MPPT input voltage range: 150V-450V V. ·

MPPT maximum input current: 40A

Open circuit voltage (VOC) of solar panel: 37V.

Short-circuit current (ISC) of solar panel: 9A

Temperature correction coefficient:-0.35%/C.

Steps

1.Calculation of series number:

150V ≤ N × 37V ≤ 450V

150V/37V ≈ 4 boards

450V/37V ≈ 12 boards

So the number of solar panels in series is 4 to 12.

2.The parallel number calculation:

40A/9A ≈ 4 boards

So the number of parallel connections is at most 4 boards.

3.Considering temperature correction:

If the actual temperature is-10 C, calculate the open circuit voltage:

Voc-temp=37V+ (0.35%*(25°C−(−10°C))*37V

=37V+(0.35%*35°C)*37V

=37V+0.12975*37V≈41.8V

Therefore, it should be noted that the voltage in series will become higher in a low temperature environment.

7. System security

In order to ensure the stability and safety of the system, a certain margin is usually left for the current and voltage of MPPT solar charge controller. For example, the total voltage should not be too close to the maximum voltage threshold of MPPT when connected in series, and the current should not be too close to the maximum input current of MPPT solar charge controller when connected in parallel.

8. Summarize

Increasing the voltage in series needs to be within the voltage range of MPPT; The current increased in parallel should be within the maximum input current of MPPT, and beyond this range, the stability and safety of the system will be affected. Moreover, temperature should be considered to ensure the safe operation of the system.

Then take E-Hybrid MPPT Solar Charge Controller as an example.

Features:

1.Using intelligent chip and algorithm, the voltage output is stable.

2.Energy dual-channel accurately distributes the direction of light energy, increasing battery life.

3.Built-in MPPT, the maximum tracking efficiency is greater than 99.9%

4.The maximum charging conversion efficiency can reach 98%

5.Optimize charging management to make the battery life longer.

6.Three-stage charging optimizes battery performance

7.Can work without batteries.

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