Good morning. I need some advise please. I have a Mercer Axpert 3000VA inverter. According to its manual these are the ratings for its MPPT controller:

• Max PV Array Open Circuit Voltage: 75v
• PV Array MPPT Voltage Range: 30 to 60v

I then have 2 solar panels with the following specifications:

• Optimum operating Voltage (Vmp): 30.6v
• Open Circuit Voltage (Voc): 37.7

If I connect the panels in series I am worried that I might be over the maximum MPPT values and might damage the inverter because:

• 37.7 (panel Voc) * 2 = 75.4v -- MPPT maximum raring is 75v. 
• 30.6v (panel Vmp) * 2 = 61.2v -- MPPT maximum rating is 60v.

I understand that warm weather, cable length, etc will drop the voltage of the panels slightly but I feel I am super close to the upper limits and I am worried I might damage something.

But if I run the panels in parallel , then I am super close to the lower limits again....

I am not sure what will happen if I go over the upper MPPT limits (or below the MPPT limits) and don't want to risk breaking something. I unfortunately only have these 2 panels at the moment and would like to use them if possible. 

Any advise will be greatly appreciated.

 

 

 

17 minutes ago, necrolingus said:

Good morning. I need some advise please. I have a Mercer Axpert 3000VA inverter. According to its manual these are the ratings for its MPPT controller:

• Max PV Array Open Circuit Voltage: 75v
• PV Array MPPT Voltage Range: 30 to 60v

I then have 2 solar panels with the following specifications:

• Optimum operating Voltage (Vmp): 30.6v
• Open Circuit Voltage (Voc): 37.7

If I connect the panels in series I am worried that I might be over the maximum MPPT values and might damage the inverter because:

• 37.7 (panel Voc) * 2 = 75.4v -- MPPT maximum raring is 75v. 
• 30.6v (panel Vmp) * 2 = 61.2v -- MPPT maximum rating is 60v.

I understand that warm weather, cable length, etc will drop the voltage of the panels slightly but I feel I am super close to the upper limits and I am worried I might damage something.

But if I run the panels in parallel , then I am super close to the lower limits again....

I am not sure what will happen if I go over the upper MPPT limits (or below the MPPT limits) and don't want to risk breaking something. I unfortunately only have these 2 panels at the moment and would like to use them if possible. 

Any advise will be greatly appreciated.

 

 

 

You can only use the 2 in parallel. The 75.4V is at 25 deg. As soon as the temp drops this voltage will increase and blow your MPPT. A expensive risky move. 

Never connect anything close to the maximum PV voltage, you will blow the MPPT. Rather get a single 540-550W panel and use that. 

Yeah the caps on the MPPT board are going to suffer if the voltage gets too high... 2 Canadians should be fine if you get the angle right etc. You can try setting the 2 panels up over the course of a couple days to see what the maximum voltage you get is and repeat with slightly different angles to find out what would be the ideal angle to keep the MPPT voltage under the max voltage. For that you will need a couple days of really good sun though and looks like the weather isn't going to allow it for a while...

Otherwise, as per @YellowTapemeasure, you can swap the panels out for a single panel that will stay within the required voltages no matter what which would be much easier and safer to do...

Thanks everyone for your fast and valuable input! I really appreciate it.

Ok cool, then I will connect the 2 panels in parallel and monitor the output voltage. If that does not work I will look into rather getting a single panel with the correct voltage.

1 hour ago, necrolingus said:

Thanks everyone for your fast and valuable input! I really appreciate it.

Ok cool, then I will connect the 2 panels in parallel and monitor the output voltage. If that does not work I will look into rather getting a single panel with the correct voltage.

You will get 30V very early in the day. The MPPT will then start working. Not sure you can lower the voltage by angle in summer. 

In winter you will have to provide a heater to prevent two in series not to increase

Edited December 13, 20222 yr by Scorp007

Thanks Scorp007! I will have to read up a bit about that,sounds rather interesting. But perhaps a single high wattage panel will be best, less hassle in the long run. 

2 hours ago, necrolingus said:

Thanks Scorp007! I will have to read up a bit about that,sounds rather interesting. But perhaps a single high wattage panel will be best, less hassle in the long run. 

Yes those low 75V MPPTs were designed when panels were much smaller than the mega of today. Today the small inverters are around 145V for the MPPT. Values are now increasing very fast. 

Luckily my 145V unit also operates as low as 32V based on what I gave seen on the display. 

Edited December 13, 20222 yr by Scorp007