MidNite Solar Classic 150 , XW60 or FM80-150V MPPT Charge Controller?

[Elie]

I have 3900 watt in panels (20 x 195w) that will be connected in 4 string of 5 (Voc ~90V). Also I have a XW6048 inverter. I help to decide which charge controller to get between the MidNite Solar Classic 150 , XW60 or FM80-150V.

I was considering the Midnite solar because it can deliver 80 Amps and has a build-in ground fault detection.

Any help will be greatly appreciated
EA

[Cariboocoot]

Welcome to the forum.

The MidNite classic would be an excellent choice here. You have a potential for over 60 Amps peak charge current, and either the Classic or an Outback FM80 would work. The Xantrex unit is limited to 60 Amps and would "clip" any extra power. On the other hand it can "talk" to the XW6048; sometimes component integration is desirable.

I'm going to assume you're following the rule and having a battery bank of 600+ Amp hours.

[Elie]

my battery bank is 370 Ah. I wont have any big loads connected to the system. Also I forgot to mention that I will be grid tie

[Cariboocoot]

my battery bank is 370 Ah. I wont have any big loads connected to the system. Also I forgot to mention that I will be grid tie

370 Amp hours? That may be a problem.
First of all, the 60+ Amp capacity of the array and controller is more than that battery bank needs. Possibly more than it can take: you have a potential 16% charge rate here which could create a lot of heating of the batteries. Not good.
Second, Xantrex (and others) recommends a minimum battery bank of 100 Amp hours per kW capacity. Even though your array is "only" 3900 Watts the inverter is 6000 (another mismatch in my opinion; if you have a 6kW GT inverter why not have 6kW of array so you can make the most of it?).

Others may disagree with my POV on this.

[jeffkruse]

Welcome Elie, I am sure you will be coming back here often. These guys know their stuff.

I was recommending to Elie that he should stick with the XW60 because it would play well with the 6048.

Elie is concerned about losing potential power. I told him that IMO I think his loss would be minimal. He has 3900 watts of panels. He will be on Grid and the batteries will be floating. He has 8 6V 370AH Deka Solar batteries (They were 3 years old but not used and kept charged monthly, I sold them to him for $300)(These are beginner batteries).

My thought is that 54V *60Amps is 3240 Watts. It’s warm here in Puerto Rico and we have lots of clouds in the afternoon. Only for a few months (Dec – March) do we have a dry season. With the heat and clouds I really doubt that he could exceed 3240 Watts. If he did it would be for so little time.

How important is it for the inverter to talk to the CC?

What other solutions or Charge controllers should he consider?

Also, he does not have the system control panel. Is this an absolute must to use the inverter?

I also think he went with the 6048 because he plans on running most if not all of the house on the protected/critical load side of the inverter basically putting his whole house on a UPS while being grid tied and running his meter “backwards”.

[jeffkruse]

Can anyone else offer suggestions? I told Elie he would have a dozen suggestions in no time.

Thanks!
Jeff

[Cariboocoot]

Elie is concerned about losing potential power. I told him that IMO I think his loss would be minimal. He has 3900 watts of panels. He will be on Grid and the batteries will be floating. He has 8 6V 370AH Deka Solar batteries (They were 3 years old but not used and kept charged monthly, I sold them to him for $300)(These are beginner batteries).

He's got grid, so the panels probably won't have to do anything for the batteries most of the time. Even so, 3900 Watts is a lot for that small a battery bank and that bank is not ideal for running grid tie. In short the inverter needs the higher battery capacity to keep from switching between SELL/NO SELL rapidly; it filters the PV input and keeps the Voltage stable.

IN PR you've got nice warm temps, which neither panels nor batteries like. Both will lose capacity. So your 3900 Watts of panel isn't 3900 Watts and your 370 Amp hour batteries aren't 370 Amp hours. Unfortunately the difference won't be nicely symmetrical.

You don't really need peak charge current at the Absorb Voltage, as that is not when demand is highest. When the battery is lowest is when the current will be greatest which is why I plan as: 48 Volts * 37 Amps = 1776 Watts / 0.77 efficiency = 2306 Watt array. But the real issue here is not the array size so much as the battery bank size. Besides; the less you discharge the battery the less actual current you need to recharge it. In a GT situation you should not be seeing a 50% DOD unless there is a prolonged outage.

So in my opinion the main thing here would be to do the set up to accommodate the GT aspect. Since the inverter is capable of 6kW the array and battery bank should be sized to handle that. The back-up aspect will then take care of itself.

How important is it for the inverter to talk to the CC?

Not very. Many systems have "mismatched" inverters & controllers and work fine. Many such components don't even have any method of talking to each other and still work fine. Where this function becomes desirable is when you have a complex system with multiple controllers and/or inverters.

What other solutions or Charge controllers should he consider?

If he needs even more power, the Outback Radian inverter (8kW). The MidNite Classic controllers are the best thing going right now.

Also, he does not have the system control panel. Is this an absolute must to use the inverter?

The Xantrex inverter needs it, really. Just like the Outback needs a MATE.

I also think he went with the 6048 because he plans on running most if not all of the house on the protected/critical load side of the inverter basically putting his whole house on a UPS while being grid tied and running his meter “backwards”.

Sensible plan, especially if the utility is unreliable. Check out the grid tie accommodation very carefully.

Okay, where are all the dissenters to tell me I'm wrong?

[niel]

my thoughts aren't any different than coot's are. i think the classic is the way to go here, but the outback fm80 may also suffice.
the battery bank is below the minimum for ripple and although the current loads are low the batteries may not last quite as long due to the ripple. this begets the question of why such a big inverter for small loads then? my advice is to parallel another identical string of batteries to help with the ripple, but if the loads are too shallow this too can present a problem with battery life.

[solarix]

In general, I like the Classic as well, but because the inverter is a Xantrex XW and is planning to be grid-tied (that is use the "Sell" mode), I think you need to also use a Xantrex charge controller as they need to play together using the Xanbus. Maximum harvest of solar power on these hybrid systems is tricky as there is a conflict between keeping the batteries as charged up as possible and exporting as much power as possible. The Inverter wants to keep the batteries charged to be ready for an outage, where the charge controller will shut down when the batteries get full. Xantrex has a special mode to try to handle this, but the XW needs to be able to take command of the CC. Also, the XW software needs to be up to date. Will also need the special external control panel for the XW (can't even set it for Sell mode without it). A large battery bank is helpful to minimize the voltage swings caused by the Inverter / Charger push-pull.