# midnite solar MPPT charge controller 150

Shawn-H
Solar Expert Posts:

**107**✭✭
I was looking at them today and I realized something. They say that they can handle 150 volts at 94 amps on a 12 volt system. But then when you go to reading there manual it clearly states that it can only handle 2600 watts. Can somebody please explain to me how this works?

last time I checked Watts = volts × amps

last time I checked Watts = volts × amps

100% Off-grid in the White Mountains of Arizona. 36 Kyocera 265w mounted on four DPW 9 module pole top mounts, midnite solar combiners, breakers, & lightning arresters, 1 midnight solar classic 150, & 3 classic 150 lights, 3 x 1574 AH GB Industries forklift batteries total of 4722 AH @24v. Feeding a Outback power systems FW500 with 2 x VFX 3624, with the x240. 2 Honda EU3000is gensets with the 240 combiner and control box running LP, and 1 Honda EU2000is Gas.

System #2 is a off grid water system @ 1590w (6 Kyocera 265's) on a 6 module DPW top of pole mount. Feeding a Granfas deep well pump and pump controller at 580 feet. 2 x 2800 gallon above ground poly storage tanks, and 1 x 1200 gallon underground cistern and a Granfas 24v booster pump feeding a 90 gallon carbon fiber pressure tank.

Vag woodstove for heat.

Follow our journey at

https://www.facebook.com/ShawnpHarvey

System #2 is a off grid water system @ 1590w (6 Kyocera 265's) on a 6 module DPW top of pole mount. Feeding a Granfas deep well pump and pump controller at 580 feet. 2 x 2800 gallon above ground poly storage tanks, and 1 x 1200 gallon underground cistern and a Granfas 24v booster pump feeding a 90 gallon carbon fiber pressure tank.

Vag woodstove for heat.

Follow our journey at

https://www.facebook.com/ShawnpHarvey

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## Comments

17,615✭✭The 150 Volts has nothing to do with the maximum power: it is the maximum input Voltage.

94 Amps * 12 Volts = 1128 Watts, well below the 2600 Watt rated maximum.

Why? Because 1128 Watts of panel doesn't produce 1128 Watts.

2600 Watts of panel will produce about 2002 Watts on average, still more than is needed for 94 Amps @ 12 Volts or even 94 Amps at 14.8 Absorb charging Volts (1391 Watts).

So there really is not problem in its being able to handle more PV than is required to meet maximum output, is there? The 'extra' power of the superfluous PV is lost of course.

140✭✭Though I'm still in the novice stage of learning about off-grid PV systems, I can't help but wonder why you're thinking about a 12V system that needs anything near a 94-Amp charging current. I'd sooner water a flower garden with a fire hose than attempt to charge a 12V battery bank with 94 Amps; at least the flower garden's idea of "catastrophic failure" doesn't involve rapid release of corrosive liquids....

107✭✭I'm sorry but I believe you're misunderstanding me.

in the literature it says: "The Classic offers some unique opportunities if you are faced with longer than normal wire runs between

the DC source and the Classic. The Classic comes in 3 input voltage ranges letting you design a DC

source at a higher voltage if it is beneficial. For example let’s say you have a 300 ft run from a PV array to

the Classic you could wire for an open circuit voltage close to 250vdc accounting for the coldest

temperature you will encounter. This will allow you to run a smaller gauge wire than with a lower voltage

charge controller. The efficiency of a high voltage Classic is less than the lower voltage versions, so you

need to weigh the benefit. If this sounds too complicated use this rule of thumb in selecting the proper

Classic. PV runs up to 100 feet, use the Classic 150. Runs up to 180 feet, use the Classic 200. Above 180

feet use the Classic 250."

PV voltags not battery voltages. so if I had a PV

for example 4 strings of 4 panels @ 255w with a vmax of 37.4 and an Imax of 8.63 this would be a 149.6v and 34.52 amp array =5,164.192 watts. this greatly exceeds its wattage rating:

System #2 is a off grid water system @ 1590w (6 Kyocera 265's) on a 6 module DPW top of pole mount. Feeding a Granfas deep well pump and pump controller at 580 feet. 2 x 2800 gallon above ground poly storage tanks, and 1 x 1200 gallon underground cistern and a Granfas 24v booster pump feeding a 90 gallon carbon fiber pressure tank.

Vag woodstove for heat.

Follow our journey at

https://www.facebook.com/ShawnpHarvey

107✭✭I am NOT thinking about a 12 volt system never said that I was this is not my system was merely noticing something in literature that I was reading about solar I have a 24 volt system.

System #2 is a off grid water system @ 1590w (6 Kyocera 265's) on a 6 module DPW top of pole mount. Feeding a Granfas deep well pump and pump controller at 580 feet. 2 x 2800 gallon above ground poly storage tanks, and 1 x 1200 gallon underground cistern and a Granfas 24v booster pump feeding a 90 gallon carbon fiber pressure tank.

Vag woodstove for heat.

Follow our journey at

https://www.facebook.com/ShawnpHarvey

494✭✭✭Yes that setup would be too much for 12 0r 24 volts.

One thing though.... Use the Voc when calculating the maximum voltage. Use Voc with cold temperature adjustment to be precise. Better yet use the Midnite string calculator tool.

http://www.midnitesolar.com/sizingTool/index.php

You can play with it with different combinations. You can probably learn more from doing that than I can explain in 1000 words.

17,615✭✭No, you are misunderstanding. You've got Vmp and Voc mixed.

The maximum input Voltage is based on Voc, not Vmp.

Four strings of four 255 Watt panels in series is sixteen panels, a total of 4080 Watts not 5164 Watts. A 255 Watt panel with a Imp of 8.63 would have a Vmp of 29.5 and four in series would be 118 Volts. Four such strings in parallel would 118 Vmp * 34.52 = 4073.36 Watts.

If the panel specs

were37.4 Vmp and 8.63 Imp its Wattage rating would be 323 Watts, not 255.The 4073 Watt array would peak out at about 65 Amps on a 48 Volt system and would exceed the controller's ability for 24 or 12 Volts.

107✭✭thank you that is really really cool I will play around with it for hours.

but this still does not explain why they say 2600 Watts is the maximum you can handle when clearly the calculator says otherwise.in fact the calculator says that I can handle a 5100 watt load? I'm kind of lost here.

System #2 is a off grid water system @ 1590w (6 Kyocera 265's) on a 6 module DPW top of pole mount. Feeding a Granfas deep well pump and pump controller at 580 feet. 2 x 2800 gallon above ground poly storage tanks, and 1 x 1200 gallon underground cistern and a Granfas 24v booster pump feeding a 90 gallon carbon fiber pressure tank.

Vag woodstove for heat.

Follow our journey at

https://www.facebook.com/ShawnpHarvey

17,615✭✭Base calculations for output:

94 Amps * 12 Volts = 1128 Watts.

80 Amps * 48 Volts = 3840 Watts.

The maximum current ability goes down for the higher system Voltages but the total Watts on input still goes up. Those are "post derating" Watts too: to get 3840 Watts average the array's rated size would be approximately 4987 Watts. And you could go 20% over that, or even more. But at those levels the power would

notbe transferred through to the batteries.107✭✭normally I try not to argue with you but in this case that's the rating off the back of one of my 255 watt panels that I used to run the pump in my aquaponics. and I mean is 4 strings of series 5. but none of this is relevant it still comes down to the fact but they say you can run 100 and 50 volts into the charge controller at 94 amps on a 24v sys...... I'm not trying to cause a fight or anything. I'm just curious why they would say in the literature that it has a 2600 watt max!?!?!?!?!?!?!?! when later on in their literature which I copied and pasted it says clearly that you can run much higher voltages and amperage then there wat limit would allow

Vag woodstove for heat.

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17,615✭✭If your 255 Watt panel says it has a Vmp of 37.4 and Imp of 8.63 it is labeled wrong. Watts is Vmp * Imp: Voltage at maximum power times current at maximum power.

Technically the Classic 150 will operate at a Vmp up to 150, but it is dicey there as the Voc which is what first hits the controller in the morning will be above that and cause it to shut down. For this reason you will never actually get one to work with a calculated Vmp of 150. Their HyperVoc function prevents damage and allows a Voc of 150 + nominal system Voltage, or 162 on a 12 Volt system, 174 on a 24 Volt system, and 198 on a 48 Volt system.

On an MPPT controller output and input are directly related as a matter of Watts, not Voltage and current. The current ratings for the controllers are output at battery Voltage and have nothing to do with the maximum input Voltage.

For the 150 the maximum output current on a 12 Volt system is 96 Amps, for 24 Volts it is 94 Amps, and for 48 Volts it is 83 Amps. These numbers are lower on the 200 and 250 because they accept higher input Voltage (trade-off against current handling).

That equates to 1152 Watts on 12 Volts, 2256 Watts on 24 Volts, and 3984 Watts on 48 Volts.

The controller does not care what the array configuration is on the input so long as:

1). Vmp is at or above minimum needed for system charging.

2). Voc does not exceed maximum operating Voltage (max Vmp rating + HyperVoc allowance).

A 12 Volt system then could have 1496 Watts on it and it might be Vmp 17.5 * Imp 85.5 or Vmp 35 * Imp 42.7 or Vmp 70 * Imp 21 or even Vmp 140 * Imp 10.6 but as I said when the Vmp gets that high you would have problems with the Voc because it is generally about 25% higher and cold temps would raise it even more.

2,976✭✭✭✭Shawn--H,

Might help to look at these Graphs:

http://www.midnitesolar.com/images/classicFrontPage/graphs.php

The string Vmp does have an effect on the output capability of the Classis CCs, due primarily to the reduced efficiency when using higher string Vmps.

FWIW, Vic

107✭✭Thank you vic that helped a lot for some reason it didn't make sense when I saw it the first time

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2,976✭✭✭✭Of course the MidNite blurb does NOT really say this. The 150 V rating for the Classic matches the string Voc more closely than it does the Vmp, especially on a 12 V system, and also to a 24 volt system.

With ANY input voltage above 150 V, the Classic will cease operation, and wait for the input voltage to decrease below 150 V. And while the Classic is waiting for this voltage decrease, it is producing NO power.

Very high input voltages does reduce the efficiency of any MPPT CC, and this reduction in efficiency means that the Classic will limit its maximum output current to protect itself from excessive heat.

FWIW, Vic

967✭✭✭✭Remember that "typically", Vmp is about 80% of the Voc. So if the Voc is just at 150 Volts, allowing

the Classic to start up, then the Vmp will be at most, 120V but a lot of times, a bit less than this.

80% of Voc is the typical high Vmp. Sometimes as low as 75% of Voc.

Or as Vic said, Voc is about 25% higher than Vmp. Same thing but I like to error on the high side.

When you hear that a CC can "handle" a high amount of power, maybe it means it can work with

it but will still current limit. If you were to hook up, say, a 10 kW PV array to a Classic 150 running

into a 12V battery, what would happen is that it would limit the output current to 90 some amps

by raising the input voltage above the 10 kW maximum power point voltage (Vmp) to reduce

the output power. The Classic would still be at a high output current and a high input voltage though,

narrowing the gap between Voc and Vmp and the CC would run much hotter than normal.

Then it would thermal limit and the output power would go down from the maximum limit.

This characteristic of lower output power with higher Vmp is kind of visible in those power

graphs by using different Vmp values.

Turns out that a wiring the array for a compromise between Voc rating of the CC and a Vmp that is just

above the particular battery voltage is best for efficiency and partial shading degradation....The PV voltage must be

at least higher than the battery voltage to charge the battery.

boB

107✭✭thank you sir I do believe you finally answered my question. I did not realize that they were referring to output not input. I wish that they're advertising didn't try to make it sound as if that was input voltage

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5,025✭✭✭✭I think they do a very good job of explaining this! Perhaps if you go back and read with an understanding of how MPPT charge controllers work you will see how and what they are referring to in the explanation.

8,471✭✭✭✭✭There is a comma , or 3 missing in your statement from the Classic data.

The 150V is the MAX INPUT voltage from solar panels.

The 94A is the MAX OUTPUT for a 12V system (drops to 58A on a 48V system)

They have a nice wattage curve chart on page 28 of the PDF here http://www.midnitesolar.com/pdfs/Classic1.pdf

Hope this helps

PS That 58A @ 48V carry's to the chart for the classic 200 too

|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||

|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

solar: http://tinyurl.com/LMR-Solar

gen: http://tinyurl.com/LMR-Lister ,