Author Topic: How much excess panel output can the Classic 150 take reliably?  (Read 324 times)

WillEert

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A period of time ago I decided to split my existing 4.4 Kw array into two arrays and add 1 Kw to them  both. This meant I had to buy additional racking to accommodate the new panels. My wife however, after I bought the required racking bits and 6 new 330W panels, suggested that I leave our existing 4.4 KW array alone and instead build a whole new array that maximized the new Classic 150 that I bought for the new split 3.3 Kw array. Yay!!!! I thought and then quickly installed a new 4.9 Kw array. 

The panel racking has been weighting on my mind however and the other day I thought - why not just add 6 X 185w (1.11 Kw) panels to the old 4.4 Kw array which would be an inexpensive and easy thing to do, since I already have the racking and I have room in the combiner box, etc. I don't want to lose reliability or stress my equipment. My wife said - go for it.

So the question is how much overpaneling can the Midnite Classic 150 take? The increased array size would be 5.5 Kw. I presently limit the arrays to 75 A input and would continue to do so. The Classic would have to be able to adjust the now 5.5 Kw of panels that in good insolation conditions would be inputting more than the 75A. I know it can do this but is it within normal operating parameters.

Thanks for any replies.

Will
24 ET 185 mono, Classic 150,8x Surrette 6CS25p, 3x Magnum 4448, homecooked diversion system
+ 15 Heliene 330 mono, Classic 150

Vic

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Re: How much excess panel output can the Classic 150 take reliably?
« Reply #1 on: April 11, 2018, 11:53:57 AM »
Hello Will,

The String Vmp of the array/s would have some effect on the ability of a Classic to handle that much PV power,   but,   just my guess that 5.5 kW STC would really be overloading a Classic 150.

Suggest that you plug-in the details of the proposed array,   to the Classic String Sizer:
http://www.midnitesolar.com/sizingTool/displaySizing.php

And then FOLLOW the advice that results.

Had a similar design,  with an STC String Vmp of about 93 V STC,   and decided that it was obviously an overload on a Cl 150 with STC PV power at 5.88 kW  --  went with a pair of Cl 150s,   and they just loaf along.

Over PVing  almost always raised the Vin that the CC sees.   This can raise the operating temperature of most MPPT CCs.   This heating is not a great thing.

All,  IMO.   FWIW,   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

WillEert

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Re: How much excess panel output can the Classic 150 take reliably?
« Reply #2 on: April 13, 2018, 10:54:40 AM »
Hi Vic,

Thanks for your reply. I think I am going to move on from this concept. I was hoping to gain an inexpensive incremental power supply increase in order to help charge the car more and also do more heating in the winter time. We will look at an AC coupled system on our shop building instead I think. The newer generation of string inverters will reduce output based on voltage level and should work well for an offgrid system, I think. More learning to be done....

Cheers

Will
24 ET 185 mono, Classic 150,8x Surrette 6CS25p, 3x Magnum 4448, homecooked diversion system
+ 15 Heliene 330 mono, Classic 150

Vic

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Re: How much excess panel output can the Classic 150 take reliably?
« Reply #3 on: April 13, 2018, 03:05:39 PM »
Hi Will,

Sounds like the new approach will be a fun project.

Please let us know how this works out for you.

Thanks,   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

welmore

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Re: How much excess panel output can the Classic 150 take reliably?
« Reply #4 on: April 22, 2018, 12:35:05 PM »
The charge controller will only draw the amount of current it needs.  Excess panel wattage is wasted. But, in reduced light conditions, the over sized array will provide more usable watts.  This extends the charge time into earlier in the morning and later at evening.

welmore

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Re: How much excess panel output can the Classic 150 take reliably?
« Reply #5 on: April 22, 2018, 10:38:27 PM »
Next addition I am working on will have the PI send email system alerts.

It will monitor commercial power.  My system is not grid tied to sell power to the utility.  The Magnasine inverters will draw off commercial and charge my batteries only if the battery voltage drops too low.  Normal operation, I am running on solar or battery power.  In a recent arear power outage, I had no indication the power was out, until my neighbor asked me how log the power was out.  If I know the commercial power is out, I can reduce my battery load to extend the back up time.

It will monitor invertor output.  Invertor output loss would mean a dark house.  BAD.  The PI and interface circuits are on separate 12 VDC battery, charged off the invertor output.

It will monitor over temperature of the batteries and chargers.

It can monitor other events such as brown out alerts.  More alerts will likely be added.

Work is proceeding on the powered vent covers for the battery box.  I am working on the mechanical build.  The plan is to have the vents open when there is current going to the battery bank  (charging) and close when there is a draw on the battery bank (night time).  I will add a delay to insure full venting and to prevent rapid open / close action during transition periods.