Outback FM-80 CC with 1770w PV

manzanita · January 2018

I'm doing things backwards ... with the talk of tariffs on PV, I quickly bought 6 Solarworld 295w 9.45a 31.5v (about 1770w total) mono-crystalline panels.

I'd like to buy an Outback FM-80 CC. The spec sheet for the Outback FM-80 CC lists a VOC limit of 150v and recommends 1000w max input for 12v ... makes sense since that is close to the output wattage for that voltage.

I'd like to connect all 6 PV panels, to improve amps when solar conditions are less than ideal. Not sure if I should do two or three strings. Two strings looks okay, but I haven't calculated VOC for +10F degrees. (I shouldn't be mentioning a 10F low in January, should I? Sorry!)

Someone mentioned that input current should be less than 64amps. My panels would be around 57amps in parallel, but I'm already forgetting that putting panels in series would reduce the current to 20 or 30 amps (two or three strings respectively).

So as long as I don't mind the inefficiency of half of my array not doing much on a good sunny day, I should be okay to do this right?

BTW: I plan to upgrade my 12v system to a higher voltage, but it is expensive to upgrade and it may take several years. I'm buying the FM-80 now, knowing that it will be more useful later when the system voltage is higher.

Thanks,
Dave

mcgivor · January 2018

Without a plan, known loads, existing system details etcetera, it's difficult to make suggestions other than to say once the PV gets to a certain wattage, going to a higher voltage is the logical choice.

Photowhit · January 2018

It looks like you have thought it through somewhat Dave... I think the Fm80 can be over-paneled without harm, but this is from my faulty mind.

As to wiring in 2 or 3 strings, I'd try to figure out your end point voltage and shoot for 2 strings if 48 volt and 3 if 24 volt. Most MPPT type charge controller work most efficiently at 130-200% of the charging voltage (28-30 volts for 24 volt systems or 56-60 volts for 48)

You also might look at limiting your output current. While batteries will self regulate to some degree if it would be nice to know you aren't pushing more than 13-15% of the capacity of lead acid batteries into them...

Vic · January 2018

Hi manzanita.

On a 12 V system, the MidNite Classic 150 has considerably higher output current, than does the FM-80 (96 A, verses 80 A) ...

YES, system design DOES matter, but if you are wedded to a 12 V system, the Classic can work with more PV power:
https://www.solar-electric.com/mnclassic.html

FWIW, Vic

Estragon · January 2018

Assuming the voltage is in the acceptable range of the controller, I'm not sure that the string size (and resulting input current) really matters that much.

Controller current is rated on output (eg 80a) at charging voltage, say 14.5v = 1160w. Does it matter much (in terms of the controller) if that's 1160÷90v=12.8a input, or 1160÷60v=19.3a? Bucking from the higher voltage might be a bit less efficient, but if there's much distance from array to controller, the efficiency gain may not matter much.

I assume the FM80 has a setting to limit output current, which should be set to some reasonable value for yor system. That way the big array can do what it can on less than ideal days without risking too high charge rate on good days.

Do check Voc on record cold days, but I think 3 in series should be okay for 10°F and a 150v controller.

manzanita · January 2018

Photowhit said:

It looks like you have thought it through somewhat Dave... I think the Fm80 can be over-paneled without harm, but this is from my faulty mind.

As to wiring in 2 or 3 strings, I'd try to figure out your end point voltage and shoot for 2 strings if 48 volt and 3 if 24 volt. Most MPPT type charge controller work most efficiently at 130-200% of the charging voltage (28-30 volts for 24 volt systems or 56-60 volts for 48)

You also might look at limiting your output current. While batteries will self regulate to some degree if it would be nice to know you aren't pushing more than 13-15% of the capacity of lead acid batteries into them...

@ Photowhit: Yikes! I thought that the FM-80 would limit the current to the battery by default. Didn't think about setting a high current limit. Thanks for the warning. The battery has been abused, voltage may rise quickly due to poor capacity. Thanks for the string advice.

@ mcgivor: I wasn't asking for advice to re-design for a new system voltage -- at least not yet. Thanks for suggesting that you'd try to do that if I provide more info.

@ Vic: Thanks for the info. I looked at their controllers a little. The ArtDeco designs are distracting to me, but that's my problem.

Well, I was trying to avoid writing a book and I know folks won't like my system. The current status of my system is dismal. It used to be bigger, but time, multiple moves and storm damages have reduced my existing system to:

Two 75w pv panels (in parallel), a PWM controller, two 6v 225ah batteries (in series) and a 300w inverter. Plus a 7000w generator and a poorly regulated truck battery charger. I've even used my Ford Ranger to charge the batteries in an emergency. Won't be able to do that with a bigger battery bank.

I've beat the heck out of my 6v golf cart batteries with deep discharges and poorly regulated charging. If the sun is shining, I can power my laptop. At night I just run a few LED lights and a radio. Unless the genny is running, then I can use 300w ... or more if I want to power things directly from the genny.

I'm trying to improve the system, but money is tight. I'm trying to buy components that I can grow into. Right now I'm stuck with 12v.

I didn't intend to buy six 295w PV panels, but they were talking about tariffs and I panicked and bought as much I could. Now I'm just trying to use them the best way possible.

After buying the PV panels, buying a charge controller, building a rack, wiring and extras to get this working at all is going to put me in a financial hole as far as expendable funds are concerned. I wouldn't be doing this if I wasn't already wasting money running the genny. That's my problem.

Even with the new PV, my battery bank is way too small. As far as system voltage is concerned, I would prefer to go to 48v to get more power in a single string battery bank, but that won't happen soon. Batteries are next, but not soon. Then a new inverter but that won't happen soon either. Unless I go crazy with a multi-string battery bank, I'll have to buy the inverter and the batteries at the same time.

Vic · January 2018

Estragon said:

Assuming the voltage is in the acceptable range of the controller, I'm not sure that the string size (and resulting input current) really matters that much.

Controller current is rated on output (eg 80a) at charging voltage, say 14.5v = 1160w. Does it matter much (in terms of the controller) if that's 1160÷90v=12.8a input, or 1160÷60v=19.3a? Bucking from the higher voltage might be a bit less efficient, but if there's much distance from array to controller, the efficiency gain may not matter much.

I assume the FM80 has a setting to limit output current, which should be set to some reasonable value for yor system. That way the big array can do what it can on less than ideal days without risking too high charge rate on good days.

Do check Voc on record cold days, but I think 3 in series should be okay for 10°F and a 150v controller.

Regarding the OB FM CC INPUT current ratings, both the FM CCs and the Schneider SCC 150-60 (or whatever the designation happens to be this month) have INPUT current maximums speced -- this is just the NEC derating to 80% of the output current ...

From the OB FM-80 CC Manual:

" ... For NEC* compliance and the Charge Controller’s 80 amp output rating / MPPT capabilities, the largest

PV array input must not exceed a rated short-circuit current of 64 amps. "

This is almost always only an issue with parallel-connected PVs ... some say that this should be applied to all MPPT CCs, some others say, that the CCs that spec this input current limit can have relatively S L O W control loops for limiting current, and need a limited current input, in order to not risk being damaged under some fault condition ... I dunno, but always try to apply this "rule" when designing any system, regardless of what CC is being used.

FWIW, Vic

manzanita · January 2018

@ Estragon: Thanks for your input. I was hoping that no one would say my idea was crazy or dangerous to the equipment.

Of course some of my ideas are a little crazy.

manzanita · January 2018

@ mcgivor: Oh heck. I guess you were wanting more info to recommend what string arrangement would work best. I'm sorry that it took me awhile to figure that out.
Thanks

Photowhit · January 2018

manzanita said:

@ Vic: Thanks for the info. I looked at their controllers a little. The ArtDeco designs are distracting to me, but that's my problem.

If it makes you feel better, the guys who started Outback and their MPPT charge controllers sold the company and started Midnite. I think the FlexMax are a later design but I think the brothers Gudgel owned a piece of Outback at the point of their design...

manzanita said:

Even with the new PV, my battery bank is way too small. As far as system voltage is concerned, I would prefer to go to 48v to get more power in a single string battery bank, but that won't happen soon. Batteries are next, but not soon. Then a new inverter but that won't happen soon either. Unless I go crazy with a multi-string battery bank, I'll have to buy the inverter and the batteries at the same time.

Short term, you can stretch out the expenses but purchasing the batteries and running them in parallel. For a small inverter at 12 volts, you could run smaller cables and just parallel them for a while. I did this when I was building my new cabin, it wasn't as dramatic a switch as 12-48, (12-24) but they were fine. I needed to replace my 2 golf cart batts and knew I was going to switch to 24 volts to run an air conditioner in the new cabin so bought 4 golf cart batts and when I moved the system over figured they'd last a couple years. Managed to get 4 more years out of them even running them into the ground in the summer.

Estragon · January 2018

@Vic - agreed, there's a point where, NEC aside, overpanelling doesn't make sense. In this case though, even with strings of 2 using STC output, current potential is ~1770÷60v=29.5a, well under the 64a quoted above.

@manzanita - if something is dangerous, we absolutely should and will say so. As for crazy, well that's more in the eye of the beholder :-)

Vic · January 2018

Estragon said:

@Vic - agreed, there's a point where, NEC aside, overpanelling doesn't make sense. In this case though, even with strings of 2 using STC output, current potential is ~1770÷60v=29.5a, well under the 64a quoted above.

@manzanita - if something is dangerous, we absolutely should and will say so. As for crazy, well that's more in the eye of the beholder :-)

YES, and, was just trying to make the point, that there CAN be input current limits on some CCs. This almost always applies only to PVs in parallel ... that was all.

FWIW, Vic

Vic · January 2018

Photowhit,

Here is a bit of the History of the Brothers Gudgel, and Pacific Northwest companies that were involved in electronics and the Solar biz:
http://www.midnitesolar.com/pages/frontPage/nwHistory/history.php

... And there is this fairly long Thread on the MidNite Forum:
http://midniteftp.com/forum/index.php?topic=474.msg4446#msg4446

MidNite Solar has my business, as they are a very capable company, doing interesting products -- small enough (and still a Private Co.) to get things done, and large enough to get distribution of their great products, etc.

FWIW, Vic

Photowhit · January 2018

Vic said:Here is a bit of the History of the Brothers Gudgel, and Pacific Northwest companies that were involved in electronics and the Solar biz:
http://www.midnitesolar.com/pages/frontPage/nwHistory/history.php

Vic, if you drop that link into the search engine here, you will find I have used it before, I've also used different links with the similar info... I'm a fan...

I like The Evolution of the E-Panel, Midnite has it on their site, but not as a single PDF file. More a history of Robin in the industry. It comes from a slightly different angle so I'll post a link;

https://www.altestore.com/static/datafiles/Others/Evolution_of_the_E-Panel.pdf

Vic · January 2018

Photowhit said:

Vic said:Here is a bit of the History of the Brothers Gudgel, and Pacific Northwest companies that were involved in electronics and the Solar biz:
http://www.midnitesolar.com/pages/frontPage/nwHistory/history.php

Vic, if you drop that link into the search engine here, you will find I have used it before, I've also used different links with the similar info... I'm a fan...

I like The Evolution of the E-Panel, Midnite has it on their site, but not as a single PDF file. More a history of Robin in the industry. It comes from a slightly different angle so I'll post a link;

https://www.altestore.com/static/datafiles/Others/Evolution_of_the_E-Panel.pdf

Hi Photowhit,

In that earlier reference to you, was not trying to say that you were completely unaware of the History of PNW electronic/Solar manufacturers ... the links were just something that had been rattleing around here.

Had also wanted some of that history to be available to any others who might be curious, or care, etc.

Thanks for that Alt-e Link, had not seen that before.

Thanks again, Vic

littleharbor2 · January 2018

Yes, Thanks Vic and Photowhit. Made for some good reading this morning.

manzanita · January 2018

Photowhit said:

manzanita said:

@ Vic: Thanks for the info. I looked at their controllers a little. The ArtDeco designs are distracting to me, but that's my problem.

If it makes you feel better, the guys who started Outback and their MPPT charge controllers sold the company and started Midnite. I think the FlexMax are a later design but I think the brothers Gudgel owned a piece of Outback at the point of their design...

manzanita said:

Even with the new PV, my battery bank is way too small. As far as system voltage is concerned, I would prefer to go to 48v to get more power in a single string battery bank, but that won't happen soon. Batteries are next, but not soon. Then a new inverter but that won't happen soon either. Unless I go crazy with a multi-string battery bank, I'll have to buy the inverter and the batteries at the same time.

Short term, you can stretch out the expenses but purchasing the batteries and running them in parallel. For a small inverter at 12 volts, you could run smaller cables and just parallel them for a while. I did this when I was building my new cabin, it wasn't as dramatic a switch as 12-48, (12-24) but they were fine. I needed to replace my 2 golf cart batts and knew I was going to switch to 24 volts to run an air conditioner in the new cabin so bought 4 golf cart batts and when I moved the system over figured they'd last a couple years. Managed to get 4 more years out of them even running them into the ground in the summer.

Huh. The forum software kept the answer I started writing before I was interrupted the other day. I didn't know it would do that!
Sorry for the delay, I don't have Internet at home.

I didn't know the history of the Gudgel brothers. I did notice that Outback was listed as a division of a larger company nowadays. It does reinforce that Midnite products have good designers, which was your point, I believe.

I thought about multi-string battery banks. My experience with them hasn't been positive, but I was using a poorly regulated charger back then too. But I was checking the SG of batteries and re-arranging them in an effort to balance the strings.

Back on topic, I keep trying to convince myself to plan for a 48v system. That would give me four strings when used in a 12v system.

Regarding Midnight Solar controllers, I know their controllers have higher capacities and probably more features, but I'm not excited about the price. Their controller is a good idea, but I'm not certain I can convince myself to spend that much.

Thanks again for the help guys.

Photowhit · January 2018

manzanita said:
Regarding Midnight Solar controllers, I know their controllers have higher capacities and probably more features, but I'm not excited about the price. Their controller is a good idea, but I'm not certain I can convince myself to spend that much.

Not sure what the problem is? The FM-80 is $521
https://www.solar-electric.com/outback-power-flexmax-fm80-150-mppt-charge-controller.html

...and the Solar only Midnite Classic is $545, so not much difference. If you had intended to do wind as well, I usually suggest a separate charge controller for that...
https://www.solar-electric.com/midnite-solar-classic-150-sl-charge-controller.html

I actually thought it was closer to the 150 lite price. I had thought about buying one instead of just a full MNGP for my Classic Lites. I think it comes with a battery temperature sensor but without the "Whiz Bang Jr" , The FM80 says it does NOT come with a battery temperature sensor.

The cost of the FM80 might also be the start as you may need a 'mate' graphics panel, I think it is needed to make some changes, though I might well be wrong.

manzanita · January 2018

Sorry. The quoted price I saw was much higher. I was looking in the wrong places.
You're right. The prices are close enough not to be an issue. Considering that the Midnite CC includes the temp sensor, it is probably cheaper than the FM-80.

I am a bit overwhelmed by the features of the Midnite unit. I would like to be able to connect my laptop to transfer collected log data now and then, but I will never connect my CC to the Internet. (No Internet at my place, but wouldn't connect it if there was.)

I finally calculated my coldest day VOC for my SolarWorld 295watt panels.
STC VOC is listed as 40V.
TCVoc is -0.30%/̊C
My coldest day is +10F which equals -12C (It has only been down to +10F here once in my life.)
gives me a 37C difference between STC and -12C
dividing 0.30% by 100 to get rid of the % symbol = 0.003
0.003 * 40volts = 0.12
37C * 0.12 = 4.44v
40 + 4.44 = 44.44v coldest day VOC per panel

If I put three panels in a string the resulting voltage could be 133.32 volts, which is below the CC's 150 coldest VOC rating.

BB. · January 2018

Most MPPT vendors (at least in the US) do have online string/array calculators. Here is Midnite's:

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

-Bill

Dave Angelini · January 2018

If you plan to grow the system Outback has there new 100A /300 v charge controller in the store here. Mate that with one of their Inverters and you will have a simple to operate system that can grow over the years and be monitored through their Web Portal anywhere worldwide.
https://www.solar-electric.com/outback-power-fm100-300vdc-charge-controller.html

Vic · February 2018

Two cents;

The MidNite Classic SL is really intended to be in a system with at least one standard Classic -- the SL lacks the EtherNet port of the standard Classic. The EtherNet port allows monitoring, control and recording of data from the Classic, and free Remote monitoring of Classic CCs via the " My MidNite " website.

The standard Classics can easily be plugged into a Router, or Bridge (wireless Range Extender), if the Classic is located some distance from your desired monitoring/control location.

https://www.solar-electric.com/mnclassic.html

Here is a quick Comparison Chart for Standard, vs SL Classics:
http://midnitesolar.com/pdfs/Classic-Lite-SL-Chart.pdf

The OB CCs have needed to have an expensive Mate (interface gadget) connected to the CCs/system for monitoring.

The Classic has an inexpensive monitoring device (WhizBang Jr -- about $50.) that, with a Shunt for the battery, allows monitoring of approximate SOC, Remaining Ah, and Shunt Ending Amps, for Absorb termination. The OB CCs need the FNDC -- another relatively expensive thingie to provide similar functions.

On a 48 V system, the Classic CC provides considerable room for expansion of the system, at a later date.

All, just opinions, FWIW, Vic

Dave Angelini · February 2018

And when Midnite finally has an inverter all the rest of the data will be there

manzanita · February 2018

Can the midnite classic two hundred be operated without the internet?
(my keyboard just went crazy all the shift and capslock functions are messed up cannot type numbers)

i probably will try the classic two hundred but am disappointed that they do not have an inverter

Estragon · February 2018

Yes, classics work fine without internet. I have three hooked up with cat5 ethernet to a wireless router so I can monitor from my laptop and phone. Internet at the cabin isn't good enough to use the MN online monitoring.

Without networking, classics can be set up using the display, if so equipped, or DIP switches if not. Personally, I'd want at least one to have a display, but it isn't essential AFAIK.

manzanita · February 2018

@ Estragon
Thanks for the quick reply and useful info.
(Fixed the odd keyboard problem by restarting the computer. Odd!)

@ Bill
Thanks for the reminder. Their calculator gives similar results, except they warn me that 1770 watts of PV is excessive for a 12 volt system. This brings me back to asking if the MidNite 200 Charge Controller will protect itself from too much PV as long as the temperature corrected VOC is below the design voltage limit.

Raj174 · February 2018

@manzanita
VOC of 133V is well within the limits of the Classic 200, in fact it's ok for the Classic 150 also, which has a higher output potential. If power production in the form of charging amps happens to be too high for the battery bank, the charge current limit can be set to a suitable level in the Classic's setup menu.

Rick

Estragon · February 2018

With a Voc at record low temp of 133v, I would definitely go for a 150. On a 12v system, pv voltage could get as high as 162v on a 150 without damage.

IIRC, MN recommends 120% max overpanelling on classics and you're probably close enough. As Rick notes, you can limit current in setup. I think the concern might be that with massive overpanelling (eg 2-3x potential max current), you could get a sudden surge (eg sun comes out from behind a cloud in cold weather) which increases current faster than the classic can limit. If it's still a concern to you, you might want to shoot MN an email and ask about your specific config.

manzanita · February 2018

I did read about Midnite's Hyper Voltage feature. I was happy to be under the rated VOC without using the Hyper V, just in case.

Oops. I did make a mistake in looking at the Classic 200. I was reading the Classic owner's manual when I discovered that the 150 has a higher output in amps. Thanks for mentioning it also.

Oh boy ... I didn't envision conditions in which the charge controller might not limit the output enough ... even though I'd heard of the Edge of Cloud phenomena that can increase irradiation.

With a pair of badly beat up T-105 batteries (6v 225ah), I didn't envision being able to use much of the controller's output. But the batteries will stay as charged as they can. I didn't think about it, but I might have to limit the current more than recommended due to the condition of the batteries. I was hoping that the batteries would last until I can pay off what I've spent on this project in the last few months.

Thanks again for the advice and comments.

manzanita · February 2018

@ Dave A.
I keep looking at the outback equipment. But I've been won over by MidNite on this round. Thanks for your comments.

manzanita · February 2018

I just ordered the MidNite Classic 150 and other gear from NAWS, spending more than I wanted to spend

, but none of it is unnecessary.
Thanks for the comments and support.

Outback FM-80 CC with 1770w PV

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