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A discussion about the charge current of the MPPT solar controller

  • Author:I-PANDA
  • Source:Engineering
  • Release on :2016-03-09
Hello everyone, 

This is Mr Chen, a sales engineer from I-Panda. Here is the summary of the answers to some questions asked by our customers towards the charge current of the controller when it is working. Hope it could do something to help through my explanation to these practical issues.

Q1: How could I know whether I got the real MPPT solar charge controller ? Why the charge current is very small all the time?

A: The easiest way to check whether it is the real MPPT solar controller is to check whether the output current is bigger than the input current. Meanwhile, you can check whether the PV voltage could track the voltage of maximum power point. You can also check it by checking the conversion efficiency,etc.

Q2: Sometimes the charge current of your controller is smaller than PWM or the controller of other suppliers under the same condition, why ?

A: Firstly, the function of the MPPT solar charge controller is to make full use of the solar power when the battery is empty and to charge the battery with high efficiency. Secondly, to charge the battery with small charge current when the battery is almost full or fully charged. So that it could protect the battery and extend the lifespan of the battery. In this situation, it will not charge the battery even the solar radiation is very strong.

The ordinary PWM controller will not be so intelligent as MPPT one. For PWM controller, it will still charge the battery with big current even the battery is full. Even some MPPT controllers from other suppliers will be the same. If you want to make the comparison among different suppliers and different models, please do it when the battery is empty. The charge current of MPPT controller is not always bigger than PWM one.

Q3: I have 48V battery system and 2000W solar panel, but the maximum charge current is just 20A and the maximum charge power is about 1000W, what’s wrong ?

A: Please confirm the following questions:

1.Please check whether the power of the solar panel is sufficient. Besides, the power of the solar panel will be reduced after using.

2.The maximum power generated by the solar panel is under the maximum radiation intensity, how about the radiation intensity at that moment ?

3.Please check whether the battery is fully charged at the moment. What is charging mode?  Constant current, constant voltage or floating charge? If the battery is fully charged, the charge current will be smaller and smaller with time goes on. The maximum charge current of MPPT controller is under the condition of constant current. Please remember that the battery has to be used safely and the lifespan of the battery is quite important. So, when the battery is fully charged, our goal is to protect the battery with small charge current regardless of the solar radiation.

Q4. The charge current of my battery gets smaller very quickly from big charge current. When we restart it, it will be the same, what’s going on ?

1.If the quality of the battery is good, with the increase of the battery capacity, the charge current will become smaller gradually. Otherwise, the battery will be damaged easily.

2.The features of the damaged battery is to get fully charged very quickly. Meanwhile, it will get empty quickly too. So, please check whether the battery has been damaged. Here is the picture of the comparison of good and damaged battery under the same condition, did you get the answer from the picture ?

3. When the solar controller is restarted, it will check the status of the battery automatically and work from CC to CV and then CF. So, when you restart it, it will charge the battery with CC mode and the charge current will be very big. If the battery is fully charged, it will move to next step very quickly and get back to the state before restarting.