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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 solarcharge controller ? Why the charge current is very small all the time?

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

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

A: Firstly, the function of the MPPT solarcharge controller is to make full use of the solar power when the battery is emptyand to charge the battery with high efficiency. Secondly, to charge the batterywith small charge current when the battery is almost full or fully charged. Sothat it could protect the battery and extend the lifespan of the battery. Inthis situation, it will not charge the battery even the solar radiation is verystrong.

The ordinary PWM controller will not be so intelligentas MPPT one. For PWM controller, it will still charge the battery with bigcurrent even the battery is full. Even some MPPT controllers from other supplierswill be the same. If you want to make the comparison among different suppliersand different models, please do it when the battery is empty. The chargecurrent 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 isabout 1000W, what’s wrong ?

A: Please confirm the following questions:

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

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

3.Please check whether the battery is fullycharged at the moment. What is charging mode?  Constant current, constantvoltage or floating charge? If the battery is fully charged, the charge currentwill be smaller and smaller with time goes on. The maximum charge current ofMPPT controller is under the condition of constant current. Please rememberthat the battery has to be used safely and the lifespan of the battery is quiteimportant. So, when the battery is fully charged, our goal is to protect thebattery with small charge current regardless of the solar radiation.

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

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

2.The features of the damaged battery is toget 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 comparisonof good and damaged battery under the same condition, did you get the answerfrom the picture ?


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