sunny boy inverter?

[nwdiver]

thanks, it is under 1% difference in amps, so should work well in series, thanks

Yep; I added 2 310s into a string of 295s. Worked fine. The current was almost identical the 310s just had a slightly higher operating voltage.

[mudhole]

thanks, it is under 1% difference in amps, so should work well in series, thanks

[inetdog]

so its a 2% difference for 3 panels, so not that big of a deal i guess, if it reduces those panels to the lower panel voltage/current, then i lose less than 1% over the entire string.

To mix panels in series (with the mixed string on its own MPPT input) you want the Imp to be within 5%. The Vmp of the panels can be very different.
To mix panels in parallel you need the Vmp to be within 5%. The Imp of the panels can be very different.

[mudhole]

so its a 2% difference for 3 panels, so not that big of a deal i guess, if it reduces those panels to the lower panel voltage/current, then i lose less than 1% over the entire string.

[SunEagle]

so i am expanding my solar array to overclock the inverter, however the company i got the great deal on the solar panels are out of those, but can get the same manufacturer but the solar panel is 5 watts less than the 3 i have left over to make a new string of 8, will this just cause the 3 panels to perform at 5 watts less? not that big of a deal?

It really depends on how you plan on wiring those panels to the inverter. If they are less than a 5% Vmp or Imp difference they can draw down the higher output panels.

[mudhole]

so i am expanding my solar array to overclock the inverter, however the company i got the great deal on the solar panels are out of those, but can get the same manufacturer but the solar panel is 5 watts less than the 3 i have left over to make a new string of 8, will this just cause the 3 panels to perform at 5 watts less? not that big of a deal?

[Ampster]

........... if i got micro inverters, how would i tie that into my current set up?, can i just tap the AC out line from my sunnyboy 5.0 inverter?

No you would tie them into a separate breaker on your breaker panel. They need their own circuit. If you want to measure the output of both use a CT around both circuits. There are lots of devices that can do that starting with Sense, which is one of the most expensive but is feature rich.

[nwdiver]

i guess the how much solar answer is ,the most bang for my buck, i guess that would be 10 more 275 panels, that would get me around 7KW. ?

Oh... that's perfect! And honestly the additional cost of a 7kW inverter vs 5kW would barely be worth it with ~7kW of Solar. Yes, you can logistically add solar with micros but it wouldn't be worth the additional cost vs just adding more solar to your 5kW string inverter. 7kW on 5kW is only oversized by 40%. I have two systems that are oversized by ~50%.

[mudhole]

How much solar are you trying to install? I have a similar problem with a customer that has a 3.8kW inverter. He started with 4.4kW of solar and expanded to 5.6kW. It would have been worth the $70 to upgrade to a 5kW had I known he would want more but he's only losing ~5% of production from clipping. 7kW on a 5kW inverter would be fine.

i guess the how much solar answer is ,the most bang for my buck, i guess that would be 10 more 275 panels, that would get me around 7KW. ?

the way our emc meters it is i get roughly $.049 per kw-hr when in excess, i pay $.085 when deficit. so my initial thought was that the most bang for my buck was to get enough panels to offset during the day as much as possible. what i didnt take into affect was the labor to install 5kw is basically the same to run 7kw, and the cost for the last 2kw is cheaper....live and learn i guess

the question about micro inverters was to see logistically how it can be done...i assume i could just tie into the ac out at my ac disconnect.

[nwdiver]

i will just put it on the separate mppt input, just a little extra work and cost for pv wire.

I am mad at myself for boxing myself in with just a 5 kw inverter, for just a few hundred extra i could have gone 7 or 10 kw...Here is my thought, if i got micro inverters, how would i tie that into my current set up?, can i just tap the AC out line from my sunnyboy 5.0 inverter?

How much solar are you trying to install? I have a similar problem with a customer that has a 3.8kW inverter. He started with 4.4kW of solar and expanded to 5.6kW. It would have been worth the $70 to upgrade to a 5kW had I known he would want more but he's only losing ~5% of production from clipping. 7kW on a 5kW inverter would be fine.

[mudhole]

i will just put it on the separate mppt input, just a little extra work and cost for pv wire.

I am mad at myself for boxing myself in with just a 5 kw inverter, for just a few hundred extra i could have gone 7 or 10 kw...Here is my thought, if i got micro inverters, how would i tie that into my current set up?, can i just tap the AC out line from my sunnyboy 5.0 inverter?

[inetdog]

Are you referring to the 'Shadefix' white paper? That was debunking the idea of module level optimization not independent MPP channels for each string. 'String level optimization' was in the title. I think it is plausible that the losses are minimal if there's no shading but IMO it's worth putting each string on its own MPPT.

If the cost is low, independent MPPT channels for each string will also keep problems with one panel from bringing down the output of the array by more than just the direct contribution of the damaged panel.

[nwdiver]

An experimental paper by SMA shows that as long as the strings are the same length and neither of them have partial shade during their peak production hours there is no need to have separate MPPT channels. The less insolated string will produce less current at its MPP voltage then the higher insolated string, but the VMP values will be close enough that any power loss will be in the low single digits percentage.

Are you referring to the 'Shadefix' white paper? That was debunking the idea of module level optimization not independent MPP channels for each string. 'String level optimization' was in the title. I think it is plausible that the losses are minimal if there's no shading but IMO it's worth putting each string on its own MPPT.

[inetdog]

Yes, that is enough of an angle difference that you do not want to combine then into one series string. If they have the same number of panels and the voltage is high enough, you could put them in parallel into a single MPPT input though.

[mudhole]

would have been a lot easier if i could have got my picture to upload without error!!!, i will give it a try, the array i have set up is facing 190 degrees, with a 10 degree angle , the new site is parallel, but comes off another roof line, which make it landscaped facing 280 degrees at 25 degrees.


i think from what you said, i would be better off using another site, it is the same azimuth and angle, but it gets the sun 1 hour later in the morning and stays sunny 1 hours longer.


probably the best scenario, is to just use the same angle and azimuth roof and just run it on a separate mppt input, it just extends the run to the inverter.