Mixing Charge Controller with Sol-Ark 15K?

[Danke]

I will have too many panels for the Sol-Ark 15K, but instead of the expense of adding another 15K, what are the thoughts about a MPPT charge controller?

So the 15K plus the MPPT charge controller on the same busbar to charge the batteries in a open loop system.

Sol-Ark representative that I talked with today said it should be OK. They have windmills that operate this way. Just make sure amps are limited to batteries capabilities.

But in a past when I asked Sol-Ark, I got the impression it could lead to problems and faults.

Pros and Cons?

 

[timselectric]

Not a problem at all.
Pros - more solar production.
Cons - none

 

[timselectric]

Actually the only con would be that the Sol-Ark wouldn't report the extra production.

 

[Danke]

Thanks for the response. I was concerned that if, for instance, one put out a different voltage (higher) that maybe the Sol-Ark or charge controller would think the batteries are full and stop charging.

 

[timselectric]

Thanks for the response. I was concerned that if, for instance, one put out a different voltage (higher) that maybe the Sol-Ark or charge controller would think the batteries are full and stop charging.

They will balance their output based on the voltage of the battery bank.

 

[GregTR]

Have you considered just adding a cheap grid-tie string inverter to the generator/smart load input of the Sol-Ark 15K as AC coupled PV? Then that would have the ability to be used to power your loads as well as charge the battery as needed. It would also be measured by the Sol-Ark.

Pros: see all that above
Cons: losing the generator input/smart load capability and possibly lost efficiency when it comes to battery charging.

 

[Danke]

Have you considered just adding a cheap grid-tie string inverter to the generator/smart load input of the Sol-Ark 15K as AC coupled PV? Then that would have the ability to be used to power your loads as well as charge the battery as needed. It would also be measured by the Sol-Ark.

Pros: see all that above
Cons: losing the generator input/smart load capability and possibly lost efficiency when it comes to battery charging.

Yeah, the problem is I won’t be selling back to the grid. No way to limit with AC couple on the Sol-Ark. If what is AC coupled not used by the load (or battery), it has to go to the grid. Otherwise, I’d put micro inverters on some of the panels. Unless what you’re saying, I can use an inverter and AC couple it, that would work differently.

 

[timselectric]

I think that the Sol-Ark can handle AC coupling with zero export, if you never let the battery get full. So that it has somewhere to dump the excess until it can get it under control.

 

[Danke]

I think that the Sol-Ark can handle AC coupling with zero export, if you never let the battery get full. So that it has somewhere to dump the excess until it can get it under control.

Key: “if you never let the battery get full”

Guess I’ll have to buy a few Teslas…

 

[OzSolar]

I will have too many panels for the Sol-Ark 15K, but instead of the expense of adding another 15K, what are the thoughts about a MPPT charge controller?

Plenty of great answers already.

I'm curious how many more panels you are talking about? I wanted to offer that it might be simpler to clip for a few hours here and there then go to much extra trouble. Generally speaking systems that are 150% over paneled or even a bit more on fixed arrays (no tracking, no seasonal tilt adjustment) only clip a few hours a year.

 

[Danke]

Plenty of great answers already.

I'm curious how many more panels you are talking about? I wanted to offer that it might be simpler to clip for a few hours here and there then go to much extra trouble. Generally speaking systems that are 150% over paneled or even a bit more on fixed arrays (no tracking, no seasonal tilt adjustment) only clip a few hours a year.

Yes, I have thought about that, but I am getting bifacials and want to maximize power to charge batteries during the winter on cold short days.

 

[OzSolar]

Yes, I have thought about that, but I am getting bifacials and want to maximize power to charge batteries during the winter on cold short days.

No argument from me, I'm just trying to help. How many of kW are you installing? Ground or Roof mount? What angle?

 

[Danke]

No argument from me, I'm just trying to help. How many of kW are you installing? Ground or Roof mount? What angle?

Well, that’s a big question.

460W bifacials.

I have no idea yet what the city will approve. I have a flat roof where theoretically I could fit around 60 panels (~50 might be more realistic), in addition, I would like to build a large awning/pergola.

Plan for roof panels facing 180°, tilt 15° and for the awning/pergola facing 210°, tilt 25°

 

[OzSolar]

Well, that’s a big question.

460W bifacials.

I have no idea yet what the city will approve. I have a flat roof where theoretically I could fit around 60 panels, in addition, I would like to build a large awning/pergola.

Plan for roof panels facing 180°, tilt 15° and for the awning/pergola facing 210°, tilt 25°

60 x ~450 watts? ~27 kW? Definitely worth figuring when you need it and how to optimize how to get as much as you can when you need it. I still would offer that if you're trying to optimize for winter kWh's on that flat of an array you aren't going to see much clipping.

Open loop? What batteries are you planning on?

 

[Danke]

60 x ~450 watts? ~27 kW? Definitely worth figuring when you need it and how to optimize how to get as much as you can when you need it. I still would offer that if you're trying to optimize for winter kWh's on that flat of an array you aren't going to see much clipping.

Open loop? What batteries are you planning on?

I bought the batteries from a local installer who had the best price at the time. Supposedly he will be working with Sol-Ark to get them to communicate. He said they’re like the SOK Battery’s BMS (identical?).

Where I live, they don’t have to be UL listed. But I am concerned that might change before I get everything permitted.

 

[Danke]

I still would offer that if you're trying to optimize for winter kWh's on that flat of an array you aren't going to see much clipping.

True. I’m at 45 north. So optimum angle is probably around 55-60° in December.

Is there a calculator for the decrease in output as a percentage, for being off of the optimum angle? In my case, 40° from optimum angle?

 

[Ampster]

Is there a calculator for the decrease in output as a percentage, for being off of the optimum angle? In my case, 40° from optimum angle?

Yes, PVWatts can do some simulations. Just by changing the tilt you can see the difference in output for the same size system.

 

[Danke]

Yes, PVWatts can do some simulations. Just by changing the tilt you can see the difference in output for the same size system.

Yes, I’ve done that. Just wondering if there is a calculator specifically for angle difference percentage calculation, but I can do the math… I think. Thanks.

When I did it before it looked like about 30% less for the month of December. (15° vs. 55° tilt)

 

[Ampster]

Just wondering if there is a calculator specifically for angle difference calculation

There probably are plenty behind paywalls and with subcription plans. Aurora is one that a solar installer I know uses. How much do you want to pay to avoid having to do a few interations on PV Watts? It sounds like you have the answer you needed from PVWatts?

 

[GregTR]

Yeah, the problem is I won’t be selling back to the grid. No way to limit with AC couple on the Sol-Ark. If what is AC coupled not used by the load (or battery), it has to go to the grid. Otherwise, I’d put micro inverters on some of the panels. Unless what you’re saying, I can use an inverter and AC couple it, that would work differently.

I think there is a way to do that. As long as you have more DC coupled PV than AC coupled PV Sol-Ark should be able to shut down the AC coupled PV if the DC coupled PV provides enough power.

Remember, Sol-Ark has to work in a grid down situation in island mode, and it absolutely does even with AC coupled PV.

The only thing that is problematic for the Sol-Ark is to adjust/modulate the AC coupled power, but in reality it doesn't have to do much with it other than turn it on/off as long as your DC coupled PV is more. As for the battery, you can absolutely have your batteries hover between 25-95% at all times, it needs that buffer to have a place to dump the AC coupled PV power if there is a sudden change on the load side.

You can contact Sol-Ark to get a better answer. I think the only caveat is that they simply can't guarantee that you will never export to the grid ever in this setup as there might be tiny instances where some current would leak to the grid if the Sol-Ark can't shut the AC coupled PV down quick enough.