I'm confused on victron mppt 150/45 solar limits

[sunshine_eggo]

And remember name plate PV watts output is only a tested value that’s hard to achieve for time that’s worth while.

I’d much rather have 1.5 PV name plate going into my SCC knowing that I’d be leaving 10-20% peak output on the table (for an hour or two a day) and capture more power over the course of the entire day.

Yep. While I've seen some nutty performance in special case situations - crazy cold cells, cloud-edging - where output is 20% OVER rated, the vast majority of the time, I'm < 90% rated.



2710/2970 = 91.2% rated.

I'm currently using only half of my existing 250/100 output, but I'll eventually add E/W arrays to ~50% over-panel Watt-wise, but actual simultaneous Isc will still be under 70A.

 

[Benjamin Yang]

49.5Voc * 3 (in series) = 148.5V
10.5Aisc * 3 (in parallel) = 31.5A
Your calculated values for voltage (148.5V) exceed the maximum input voltage of the controller (150V). Even with intentional voltage drop, it's risky to exceed the maximum specified voltage, especially considering potential temperature fluctuations.

Given these considerations, it's recommended to stick with the 2s4p configuration (8x 440W panels) to ensure that you stay within the specified limits of the Victron SmartSolar MPPT 150/45 controller. This configuration should provide you with good performance while staying within the controller's safe operating range.

 

[oregonsun]

49.5Voc * 3 (in series) = 148.5V
10.5Aisc * 3 (in parallel) = 31.5A
Your calculated values for voltage (148.5V) exceed the maximum input voltage of the controller (150V). Even with intentional voltage drop, it's risky to exceed the maximum specified voltage, especially considering potential temperature fluctuations.

Given these considerations, it's recommended to stick with the 2s4p configuration (8x 440W panels) to ensure that you stay within the specified limits of the Victron SmartSolar MPPT 150/45 controller. This configuration should provide you with good performance while staying within the controller's safe operating range.

Sounds good but I don't have space to face 8 panels the same direction, so now what? Can I connect panels facing different directions to catch sun at different times of the day to the same combiner box and SCC?

 

[Q-Dog]

Sounds good but I don't have space to face 8 panels the same direction, so now what? Can I connect panels facing different directions to catch sun at different times of the day to the same combiner box and SCC?

Each string of panels needs to face the same direction. So, if you have a string of 3 panels, those three need to see the same sun.

 

[740GLE]

Sounds good but I don't have space to face 8 panels the same direction, so now what? Can I connect panels facing different directions to catch sun at different times of the day to the same combiner box and SCC?

Find new panels or a higher voltage SCC.

Pretty easy to find panels with VOC of 40-45v

 

[RoadTurtle]

You can over-panel to your heart's content as long as you don't exceed either of those numbers.

I've seen the number 30% thrown out a lot, including some people claiming to have been through Victron training program. For the 100/50 cite you posted, that's only 20%. I have also seen people multiply the numbers together, which you have warned people to not do. Thank you for the citation.

 

[sunshine_eggo]

I've seen the number 30% thrown out a lot, including some people claiming to have been through Victron training program. For the 100/50 cite you posted, that's only 20%. I have also seen people multiply the numbers together, which you have warned people to not do. Thank you for the citation.

The 30% is also referenced on that page just above the rules I quoted:

Oversizing a PV array​

Oversizing a PV array means installing more peak power (Wp) than the maximum charge power of the chosen MPPT charge controller. A common reason to oversize is to cater for winter time when the sun is not as powerful.

The MPPT solar sizing calculator will allow for a 130% PV array oversizing when recommending a charge controller.

The design logic is that panels RARELY spend much time at their peak rated output capacity, only maybe an hour in the middle of a sunny day. The rest of the time they are derated below their spec maximum, and less than the maximum capacity of the charge controller.

Some installers don’t like to do this however, and will override it so that the panel output is never constrained. The best choice will depend on the installation, and may take into account a limited roof area, or limited solar window (due to shading).

Another reason to oversize panel to charge controller capacity is that PV panel output degrades over time, as they get soiled, dirty, PID, etc.

Generally total energy harvested from a 130% panel oversizing results in less than 1% annual energy loss.

 

[Brucey]

Did they study the annual energy loss when overpanelling more (say 150-200%)?

 

[sunshine_eggo]

Did they study the annual energy loss when overpanelling more (say 150-200%)?

I don't know. Did they?

 

[oregonsun]

Find new panels or a higher voltage SCC.

Pretty easy to find panels with VOC of 40-45v

I wish.

I live in a tiny town in a rural area where I can't sell my current panels, I have what I have and am stuck with them. Even if I bought different panels I am space limited by my city lot and roof shape/size as to where I can fit them, they won't all fit facing the same direction no matter what size panels I choose or where I put them.

I received the 150/45 today, wow way bigger than the 100/20's I have. I think I am going to get another 150/45 and sell at least one 100/20, those I can ebay but not so with huge panels.

 

[740GLE]

I didn’t know you had already decided on panels.

Used market for victron SCC is prob taking it hard with recent price drops.

For what I paid for my 100/15 in 2022, I could almost get a 150/35 today.

 

[oregonsun]

I didn’t know you had already decided on panels.

Used market for victron SCC is prob taking it hard with recent price drops.

For what I paid for my 100/15 in 2022, I could almost get a 150/35 today.

I just bought the two 100/20 used after the prices dropped so only paid $75 ea.

Won't lose much selling them. Before going victron I was using a growatt 3000, still am using that to charge from generator but want to stop using it for winter where the idle consumption is just too high. Currently using just a little phoenix 1200 inverter for my minimal needs and just turn on the growatt temporarily to run a microwave.

The growatt has been great in summer, but in winter it's hard to bring in enough power to cover it's own idle consumption.