Growatt SPF5000 with only 3 panels

[PhilUK]

I’ve searched for the answer on this but unfortunately didn’t get anywhere so apologies in advance…

I’ve just built a shed which I want to be off-grid. The roof can only accommodate three panels - does this rule out the SPF5000 because the panels can’t generate 150v to power the inverter?

If I really had to, could I power the SPF5000 with mains power and fill the battery with solar only?

Cheers

 

[sunshine_eggo]

I’ve searched for the answer on this but unfortunately didn’t get anywhere so apologies in advance…

I’ve just built a shed which I want to be off-grid. The roof can only accommodate three panels - does this rule out the SPF5000 because the panels can’t generate 150v to power the inverter?

The spec is ±10V, so I would assume 160V. If your 3S panel Voc is < 160V, no start.

If I really had to, could I power the SPF5000 with mains power and fill the battery with solar only?

If < 160V, no solar ever for any reason. MPPT will not start unless Voc is >160V.

 

[PhilUK]

Thanks Sunshine

So just to confirm, even if the inverter is connected to the mains, I still have to reach 150 VOC?

Thanks

 

[BentleyJ]

The internal MPPT charge controller is a separate circuit and has nothing to do with the mains. If you wish to charge batteries from solar, you would have to purchase a different charge controller with a lower start up voltage. You are basically bypassing the MPPT in the inverter.

 

[PhilUK]

Thanks Bentley, that clarifies things.

So another real newb question…does a panel’s VOC drop in low sun or at night or is the VOC constant? I’ve found four panels that can supply 160v VOC which is slightly more than what the SPF5000 asks for. But will this drop at night and therefore go below the required VOC?

Cheers!

 

[sunshine_eggo]

Thanks Bentley, that clarifies things.

So another real newb question…does a panel’s VOC drop in low sun or at night or is the VOC constant? I’ve found four panels that can supply 160v VOC which is slightly more than what the SPF5000 asks for. But will this drop at night and therefore go below the required VOC?

Cheers!

Voc is zero at night. No light.

Voc does decrease in low light conditions, but will tyipcally stay above Vmp except in extreme cases like dark grey thunderstorms, total eclipse, etc. They will absolutely, positively drop in Voc in full sun due to heating of the cells. Check the NMOT or NOCT rating of the panels for hot Voc.

The target should be decidedly above 160V to be considered viable. Just shooting for 160V is likely going to be a miss.

 

[BentleyJ]

So another real newb question…does a panel’s VOC drop in low sun or at night or is the VOC constant? I’ve found four panels that can supply 160v VOC

First lets clarify, obviously the voltage of a solar panel varies based on irradiation, low sun angle, clouds, hazy Etc. Voc is an industry specification that is determined at specific Standard Test Conditions. 1,000Watts per sq meter of irradiation at a 45 degree angle. Solar module temp at 25 deg. C. It is unique to each model of solar panel and does not change. BTW, panel voltage Increases as temp Decreases. A general coefficient is -0.3% per degree. So you can specify Voc at a different temp but need to note at what temp you calculated at.

If the 4 panels can achieve 160V then the MPPT controller should start up and operate until the sun goes down so far then will shut down.

 

[PhilUK]

So the SPF 5000 says 150v ±10V so I’ve aimed for 160. That’s the best I can do really with the size of the shed roof - four panels at around 40-43 volts.

If the VOC drops at night, how does the charge controller continue to work? Does it rely on a battery? If no battery, does it just stop workng?

 

[BentleyJ]

If the VOC drops at night, how does the charge controller continue to work? Does it rely on a battery? If no battery, does it just stop workng?

Do you have an expectation that solar panels work at night? Perhaps you are confusing the MPPT solar charge controller with the built in AC charger, which is a separate item. It will charge your batteries at night as long as there is utility or generator power and your settings allow it.

 

[PhilUK]

Haha, no, definitely not expecting them to work at night. I think my main concern is that I go and buy the Growatt inverter, four panels and a battery and find out that on a really cloudy or winter’s day, the panels can’t power the charge controller.

The shed has mains power which I’m fine with powering the fridge, freezer etc, but I really don’t want to use it to charge the battery.

Many thanks for your help!

 

[BentleyJ]

but I really don’t want to use it to charge the battery.

Most inverters have either/or features called Charge Block based on a 24hr clock or charging from AC can be disabled all together. Before purchasing the Inverter its worth reading through all the user set up menus to get familiar with the features and capabilities.

 

[PhilUK]

I seen on YouTube that Growatt has something similar to Charge Block. But if I can’t get the required VOC to power the charge controller, is there another solution you’d recommend I look at? Is there such a thing as an inverter that uses mains power to power the charge controller?

 

[sunshine_eggo]

Is there a different AiO that would work better with your limited array size?

 

[BentleyJ]

I seen on YouTube that Growatt has something similar to Charge Block. But if I can’t get the required VOC to power the charge controller, is there another solution you’d recommend I look at? Is there such a thing as an inverter that uses mains power to power the charge controller?

We seem to be having either a major failure of communication or a misunderstanding of terminology.
There are only 2 ways to charge batteries. (we are excluding wind and you riding a bicycle with a generator attached, etc. etc) The solar charge controller uses energy from solar panels and the AC charger uses utility or generator power to create a regulated DC output based on the battery chemistry being used. Yes, you can purchase charge controllers that have both a solar and an AC input. Internally they may even share some of the electronics. That is all irrelevant, charging batteries takes power and it either comes from the solar panel or the mains.
You just stated above that you didn't want to use utility power to charge batteries yet are still asking about charging batteries with the mains?? I suspect you are ACTUALLY asking is if there are alternative charge controllers that would work at lower voltage levels on a cloudy day. Yes, there are and you could connect one with a 3 way switch so when the built in MPPT in the inverter shut down due to low voltage you could switch over to the other charge controller that has a lower start up. You could even purchase a low cost Buck and or Boost converter from ebay, I use them all the time to charge cells. They don't have high output currents but if you need to extract every last electron from your panels on a cloudy day or at dusk, there is your answer.
Lastly, what sunshine said above.
End of Rant. I'm out.

 

[PhilUK]

Have you ever thought of a career in teaching? I have to commend you on your patience when a beginner (we are in beginner’s corner aren’t we?) asks questions which may not match your superior intellect or use the correct terminology. Bravo on your boundless encouragement of those less confident morons.

 

[Darren67-72]

Reading the owners manual is a great starting point. understandably, a bit confusing when your new; many of us have ideas of what we want for our particular needs. Sometimes you can get there many different ways.
I think, the growatt has a way, in the settings, to do what you want. The settings can be difficult for even "experienced" users. Some settings have conflicts with others, but nothing that will damage the aio (all-in-one inverter). But, they can mistafy some users.
I understand there are a lot of choices out there. Do your best research and through your money at it. Cuz that's what we all did. Haha (humor)?
Questions are welcome. AND, try to be patient with us here, some here are "new" to being helpful to others....
P.S. you might run into a unfriendly here, just like the rest of the world. Not saying anything, about any particular person. We are just different.