EG4 6500EX...PV1 and PV2... number of panels?

[TOU47]

While we are building our off grid home, I currently have a single EG4 6500EX, 4-Lifepower4's, 8-Canadian Solar 390W bifacials hooked up to PV1. We run a 30 amp chord to my 5th wheel which uses only electric for its fridge/freezer, hot water heater etc as well as a residential fridge freezer in our solar room from this. (We have a DC disconnect both at the panels & in my solar room before going to the panel.)
The past 10 days have been kinda rough with low, thick dark rain clouds & a ton of rain...hence low solar production. Which is starting to concern me for the winter's shorter as well as overcast days.

That all said, we have another 46 identical panels in storage & want to add some more to cushion for these kinds of days. How many more panels can I add to PV1? Do PV1 and PV2 need to have equal number of panels? What else do I need to add to PV2...2 more DC disconnect switches? Thank you?

 

[Adam De Lay]

Each 6500 has 2 independent mppts. You don’t have to have the same configuration on both.

Your maximum string would depend on the temperature coefficient for your panels. The colder it gets, there’s more potential for your Voc to go up.

If you’re concerned about production, if you have the panels, I would duplicate what you have on PV1 for PV2.

 

[ChillnGrill]

If it was me I would put 9 on pv1 and 9 on pv2 that would give 421v on each string. 10 on each string would give you 468v per string to close for me to max. Somebody on here will have a better answer than me.

 

[TOU47]

Each 6500 has 2 independent mppts. You don’t have to have the same configuration on both.

Your maximum string would depend on the temperature coefficient for your panels. The colder it gets, there’s more potential for your Voc to go up.

If you’re concerned about production, if you have the panels, I would duplicate what you have on PV1 for PV2.

Thank you so much.

As this is my temporary home while we are building this year... nothing is permanent (arrays) & I am only using temporary array scenarios. That said, I have 8 of these permanently affixed to a solar trailer we built & was looking to maybe put 2 more attached to it & then 4-5 more temporarily to PV2.

 

[TOU47]

If it was me I would put 9 on pv1 and 9 on pv2 that would give 421v on each string. 10 on each string would give you 468v per string to close for me to max. Somebody on here will have a better answer than me.

Thank you...9 max per string seems to be the concensus.

 

[Adam De Lay]

Thank you so much.

As this is my temporary home while we are building this year... nothing is permanent (arrays) & I am only using temporary array scenarios. That said, I have 8 of these permanently affixed to a solar trailer we built & was looking to maybe put 2 more attached to it & then 4-5 more temporarily to PV2.

90v is the startup voltage but I’ve heard the mppt really doesn’t start working well till you get past 120v. So 4 should be fine on pv2.

What’s the coldest temp you might see in the winter?

 

[TOU47]

Your maximum string would depend on the temperature coefficient for your panels. The colder it gets, there’s more potential for your Voc to go up.

I have heard this before but didn't understand the why. Probably dumb questions but why does the VOC go up when it's cold? How cold does it have to be to affect it?

 

[TOU47]

90v is the startup voltage but I’ve heard the mppt really doesn’t start working well till you get past 120v. So 4 should be fine on pv2.

What’s the coldest temp you might see in the winter?

Thx again Adam. Usually 5-10⁰F positive but last year we saw -5⁰F to -10⁰F for a few weeks. Farmer's Almanac is again predicting cold.

 

[Adam De Lay]

I have heard this before but didn't understand the why. Probably dumb questions but why does the VOC go up when it's cold? How cold does it have to be to affect it?

I’m gonna be perfectly honest. I don’t understand how it affects it, but I’ve seen it happen at my home during the winter. The panels can over-produce when they get super cold and then the sun hits them.

This resource might help though: https://diysolarforum.com/resources/adjusting-solar-panel-voc-for-temperature.219/

 

[TOU47]

I’m gonna be perfectly honest. I don’t understand how it affects it, but I’ve seen it happen at my home during the winter. The panels can over-produce when they get super cold and then the sun hits them.

This resource might help though: https://diysolarforum.com/resources/adjusting-solar-panel-voc-for-temperature.219/

Thank you Adam...great link.

I'm not sure this is related but my 390w bifacial panels were pulling 450w regularly last winter when it was cold & snow covered. For short periods, I even pulled over 500w. This summer I'm lucky if I pull the 390w. Go figure.

 

[TOU47]

I’m gonna be perfectly honest. I don’t understand how it affects it, but I’ve seen it happen at my home during the winter. The panels can over-produce when they get super cold and then the sun hits them.

This resource might help though: https://diysolarforum.com/resources/adjusting-solar-panel-voc-for-temperature.219/

So looking at that chart, I technically could run 10 panels until it gets to 50⁰F. Once it hits the 40's, l'm potentially in trouble.

That said, according to that article, if you run too high voltage, you risk messing up your MPPT charge controller, correct? I had thought if the voltage was too high, that these inverters protected themselves & would shut down. No?

Either way, starting tomorrow morning, I'm going to run 1 more panel for a total of 9 panels in series as advised for now. One more panel is one more panel & should help.

Then as soon as I can get the other 6 panels mounted & wired to PV2, I'll pull that one into that series for an additional 7 new panels & for a total of 15 panels.

In think that should get me through the winter, even on cloudy days. Even better when the ground is covered with snow. (Bifacials)

 

[Adam De Lay]

So looking at that chart, I technically could run 10 panels until it gets to 50⁰F. Once it hits the 40's, l'm potentially in trouble.

From what I've seen, most people just tend to set for the coldest temperature they experience so they're not having to remember to micromanage their arrays.

That said, according to that article, if you run too high voltage, you risk messing up your MPPT charge controller, correct? I had thought if the voltage was too high, that these inverters protected themselves & would shut down. No?

Some do and some don't. I've seen too many cases though where going over max voltage just cooks the mppt. In most cases you can go over wattage and over amperage, but voltage seems to be a hard and fast limit.

Either way, starting tomorrow morning, I'm going to run 1 more panel for a total of 9 panels in series as advised for now. One more panel is one more panel & should help.

Then as soon as I can get the other 6 panels mounted & wired to PV2, I'll pull that one into that series for an additional 7 new panels & for a total of 15 panels.

In think that should get me through the winter, even on cloudy days. Even better when the ground is covered with snow. (Bifacials)

Good luck!

 

[TOU47]

From what I've seen, most people just tend to set for the coldest temperature they experience so they're not having to remember to micromanage their arrays.

Some do and some don't. I've seen too many cases though where going over max voltage just cooks the mppt. In most cases you can go over wattage and over amperage, but voltage seems to be a hard and fast limit.

Good luck!

?... I'm not going to push the envelope. 9 panels to stay safe for now but then shortly will go with:
8 panels --> PV1
7 panels ‐-> PV2

Thx again for your input, much appreciated. ?

 

[TOU47]

The 9th panel is working out great... just enough.

On another note... yesterday I took advantage of the trade in program on the EGR 6,500ex's in favor of an 18kPV for the new house. Nice part is I'm keeping the 6,500's. Kind of pumped...

Interestingly the 18kPV has 600 VOC & 3 MPPT's which means I can go to 11panels x3 on just the one inverter. Question is... will it play nicely with a 6,500ex?

 

[Adam De Lay]

What do you mean “play nicely”? Since the inverters won’t be in sync between each other, you can’t hook them up together on the same panel.

You “might” be able to get creative on the AC In side, but it would take some playing around to see if it would even work out.

 

[ChillnGrill]

The 9th panel is working out great... just enough.

On another note... yesterday I took advantage of the trade in program on the EGR 6,500ex's in favor of an 18kPV for the new house. Nice po part is in keep the 6,500's. Kind of pumped...

Interestingly the 18kPV has 600 VOC & 3 MPPT's which means I can go to 11panels x3 on just the one inverter. Question is... will l it play nicely with a 6,500ex?

You will love the 18kpv. I did the same thing with 2x 6500ex have not looked back since.

 

[TOU47]

What do you mean “play nicely”? Since the inverters won’t be in sync between each other, you can’t hook them up together on the same panel.

You “might” be able to get creative on the AC In side, but it would take some playing around to see if it would even work out.

I guess I really don't fully know how multiple inverters work together as I have never used more than 1 together yet. I will keep using my 1st 6500EX as is. I will then use 18kPV as my house is finished, then as needed I will add the 2nd 6500EX...which I want to eventually swap it out in favor of a 2nd 18kPV.

 

[TOU47]

You will love the 18kpv. I did the same thing with 2x 6500ex have not looked back since.

Looking forward to it. What batteries are you using?

 

[ChillnGrill]

Looking forward to it. What batteries are you using?

I have 6 x lifepower4 batteries