MPPT Testing

3 Nomura MPPTs with an output voltage of 23-37V was purchased in March, 2017 for testing. The goal is to evaluate them and better understand it's region of operations before committing to purchasing more. 

April 1, 2017

Test setup

Each module of 20 SunPower E60 solar cells left over from MSXI were connected to the input side of the Nomura MPPT. VR1 was then adjusted according to the instruction manual to 1.25V. An output voltage of 27V was decided on, giving a boost ratio of close to 1.9. The output of the MPPTs were connected together in series, then connected to the DC load supply. 

In cloudy conditions (10 - 11AM)

• In total, the modules outputted approximately 20W at peak power in CV mode of the DC load. 

In sunny conditions (2 - 3PM) 

• The three modules combined to output approximately 140W at peak power in CV mode set to 68V on the DC load
  • 68V was chosen based on the equivalent battery configuration. So a peak voltage of 27*3 = 81V is approximately 19 4.2V fully charged Li-ion cells, so at the nominal voltage of 3.6V, 3.6*19 = 68.4V.  
• Covering 1-2 modules decreased the power output significantly (+100W → 60-80W), but output voltage was approximately the same
• Covering more cells produced a voltage drop roughly 1/3 of the total voltage. That is, covering multiple cells in a module will practically turn the MPPT off and put it in through mode. 
• Disconnecting a module on the PV_IN side also allowed the rest of the modules to function despite the MPPTs being in series with each other. So a total failure of a string is not catastrophic enough to turn off the entire array

Bench Testing

• A power supply was connected to the PV in node, set to ~13.2V with a max current of 1.7A. We then used the DC load in CV mode, sweeping the voltage range from 27 - 25V in 0.1V increments while recording the current. The same was done from 25-14V except at 1V increments. The data is as follows.  MPPT.csv