Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

yrtrnc · September 2012

Hi guys

Im all new here, so hello to everyone. Just want to let you know I appreciate all the help you guys give in advance.

So we have a newly built warehouse in North Cyprus which we tried to get grid connected, we were asked to pay unacceptable sums so we installed a 10 KW solar system instead.

We purchased from China and were happy with it for about 2 months until the charge controller burnt out.

It was a 200 A charge controller but obviously could not take the heat, working environment was around 40 C.

So now we bought 3 pcs Outback Flexmax 80's and I need some advice setting up.

Our solar array consists of 36 pcs 285 W mono panels, total at 10260 W.
Our battery bank is 24 pcs 2V/1500 AH setup at 48 V.

With the old controller the solar array was split into two 18 + 18 as the charge controller had two separate inputs.

So how can I connect the panels with the charge controllers, now that I have 3?

A friend advised I should connect 2 in series and 6 in parallel? Is this correct? How would I go about connecting this way?

Also, how will I connect them with the batteries?

Your help will be much appreciated.

Yener

Attachment not found.
Attachment not found.

This is a picture of the junction boxes, there are two like this. The system was designed to be on grid also, if need be in the future. This can be disabled however as we will not have a need for on grid system for many years to come.

(sorry about the pictures, the junction box was taken in two parts, both pictures are the same junction box, top and bottom. )

vtmaps · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

yrtrnc wrote: »

So now we bought 3 pcs Outback Flexmax 80's and I need some advice setting up.

Our solar array consists of 36 pcs 285 W mono panels, total at 10260 W.
Our battery bank is 24 pcs 2V/1500 AH setup at 48 V.

With the old controller the solar array was split into two 18 + 18 as the charge controller had two separate inputs.

So how can I connect the panels with the charge controllers, now that I have 3?

A friend advised I should connect 2 in series and 6 in parallel? Is this correct? How would I go about connecting this way?

Welcome to the forum. To answer your question about the array configuration we need to know the Vmp, Voc and Imp of your panels. We also need to know how far they are from the controllers and what gauge cable you have between the panels and the controller. With that information it will be easy to answer your question.

--vtMaps

yrtrnc · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

vtmaps wrote: »

Welcome to the forum. To answer your question about the array configuration we need to know the Vmp, Voc and Imp of your panels. We also need to know how far they are from the controllers and what gauge cable you have between the panels and the controller. With that information it will be easy to answer your question.

--vtMaps

Hello and thank you for your reply.

Can you pls help me understand what Vmp, Voc and Imp is and help me with how I can find these values out?

Panels are on the roof, and the controllers are on the second floor, so about 10 M away from the farthest panel and about 4 M away from the closest.
Cable are 4mm from each panel to the junction boxes and 10mm from the junction boxes to the controllers.

Thanks
Yener

stephendv · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

Vmp, Voc and Imp are the electrical details for the panel. They should be printed on the back of each panel, or if you could tell us the exact make and model number of the panels we can look it up online.

BB. · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

Solar panels are a little like batteries... They have an open voltage (Voc=Voltage open circuit), and a voltage under load (Vmp=Voltage maximum power) and currents (Isc=Current short circuit; Imp=Current maximum power).

You need to then match the panels Vmp*Imp (=Pmp==Power maximum power) to the charge controller's input specifications.

Nominally, the FM80 has a maximum input voltage of ~140-150 VDC and a maximum (sustained) output current. Depending on how hot and cold it gets at your place, you probably will need to connect the panels in series for Vmp~70 volts to 100 volts (nominal).

Then you will connect several of those strings in parallel for the Imp current into the controller. Note, if you connect three or more strings in parallel to one controller, each string should have its own fuse/circuit breaker in series which each strings (prevents a short circuit in one string from being fed power by the other two strings--reduces risk of fire).

The maximum "cost effective" wattage of array into each controller would be:

80 amps * 59 volts battery bank charging * 1/0.77 panel+controller deratings = 6,130 watt max cost effective (estimated)

So, you probably have the option of connecting just two of the controllers and keeping a spare. Or using all three controllers and running them a little bit less power and cooler (always helpful for a long life).

Outback has a string sizing tool to help you define the optimum array configuration (series for voltage, then connect in parallel for current).

Just as an aside, your 1,500 AH @ 48 volt battery bank should be charged at 5-13% rate of charge from your solar array (and backup genset):

1,500 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 5,747 watt array minimum
1,500 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 11,494 watt array "nominal"
1,500 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 14,942 watt array "max cost effective"

Of course, you need to know your daily loads and the amount of sun (hours of sun per day) to ensure that you get the bank full charged (>~90% State of Charge) at least several times a week. And you have a backup genset for stretches of bad weather.

-Bill

westbranch · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

BB. wrote: »

Solar panels are a little like batteries... They have an open voltage (Voc=Voltage open circuit), and a voltage under load (Vmp=Voltage maximum power) and currents (Isc=Current short circuit; Imp=Current maximum power).

You need to then match the panels Vmp*Imp (=Pmp==Power maximum power) to the charge controller's input specifications.

Nominally, the FM80 has a maximum input voltage of ~140-150 VDC and a maximum (sustained) output current. Depending on how hot and cold it gets at your place, you probably will need to connect the panels in series for Vmp~70 volts to 100 volts (nominal).

-Bill

So in order to fill out the calculations and to match PV input to the Charge Controller the installations location is also needed along with the historic maximum and minimum temperatures as these affect the PV Voltage output. the colder it gets from 25* C the more voltage conversely for temps above 25C.

hth

yrtrnc · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

Hi

Sorry for the late reply! And thank you for clarifying. Here's the info I found:

Optimum operating voltage VM = 35.95V
Optimum operating current lm = 7.79A
Open circuit voltage Voc = 44.31V
Short circuit current Isc = 8.26A

Hi BB.

Thanks for the input, only I had to read your post a few times to understand it as my technical knowledge seems to be lacking when it comes to solar. I am grateful for the input as I look forward to learn more about this technology. Also thank you for the link to the string sizing tool. Only, I am able to partially grasp it at the moment. Im baffled about Vtmp, Vtoc, Vmp and Imp. The only values I found were the ones I mentioned above.

Our climate here is similar to lower California. Around 15 c avg in the winter and 35 c avg in the summer. Although this summer was quite hot. We saw 45 c in august.

Then you will connect several of those strings in parallel for the Imp current into the controller. Note, if you connect three or more strings in parallel to one controller, each string should have its own fuse/circuit breaker in series which each strings (prevents a short circuit in one string from being fed power by the other two strings--reduces risk of fire).

When you say string, what do you mean exactly?

So, you probably have the option of connecting just two of the controllers and keeping a spare. Or using all three controllers and running them a little bit less power and cooler (always helpful for a long life).

I think its better opting for the longer life by using 3.

Thank you in advance.

Yener

stephendv · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

yrtrnc wrote: »

Optimum operating voltage VM = 35.95V
Optimum operating current lm = 7.79A
Open circuit voltage Voc = 44.31V
Short circuit current Isc = 8.26A

Ok, with the temperatures the important thing is the coldest it ever gets in winter - the average temp isn't that important.
With a Voc of 44.31V at 25 degrees, if it ever gets down to -5 degrees in winter then the Voc would be about 48V. The outback controller has a limit of 150V before it blows up, so if you had 3 panels in series then it would be dangerously close to this limit, if it ever got down to -5 degrees.

The safer option is 2 panels in series for a Vmp of around 72V which is high enough to perform an EQ in summer and low enough not to fry the controller. A "string" is a group of panels connecting in series, in your case 2 panels in each series string. So with 36 panels and 3 controllers, you'd divide them up into groups of 12 panels to 1 controller. Those 12 panels will be connected in 6 parallel strings of 2 in series.

yrtrnc · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

Thanks

Lowest recorded temp was -6 C so you have an excellent point. Although I doubt we will ever see that again with rising temps. But you never know.

What is an "EQ in summer"?

A "string" is a group of panels connecting in series, in your case 2 panels in each series string. So with 36 panels and 3 controllers, you'd divide them up into groups of 12 panels to 1 controller. Those 12 panels will be connected in 6 parallel strings of 2 in series.

Ok so we connect 3 groups, 2 in series x 6 parallel = 36 right?

How would I go about :

Then you will connect several of those strings in parallel for the Imp current into the controller. Note, if you connect three or more strings in parallel to one controller, each string should have its own fuse/circuit breaker in series which each strings (prevents a short circuit in one string from being fed power by the other two strings--reduces risk of fire).

I would have to use a circuit breaker right? for each string? So 6 + 6 + 6 circuit breakers? How does that work? What kind of circuit braker?

Would I have to get rid of the junction boxes I have showed in the pictures? How would I connect the panels to the charge controller? Just wire them as you said and thats that?

stephendv · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

yrtrnc wrote: »

What is an "EQ in summer"?

An "EQ" is an Equalisation charge which is a high voltage charge typically performed once every few months to ecualise the cells in the battery. It's usually done at around 2.65V per cell, so about 64V on a 48V battery, which means that the controller must be able to deliver 64V... so the PVs must be able to deliver just a bit more than 64V. The same temperature effect which increases Voc in winter also decreases Vmp during summer. The temp co-efficient is about -0.37% for every degree higher than 25 degrees. So at a panel temp of 60 degrees, that's a 12% V drop. And with a Vmp of 72V at 25 degrees, you'll see about 63V at 70 degrees. So you may have problems reaching the EQ voltage at the height of summer.
Unfortunately those panels are at an odd voltage for a 48V battery, so between blowing up the controller with 3 panels in series vs. not being able to EQ at the exact right voltage during summer with 2 panels in series, I would choose the latter

The ideal would be if you could return the outback FM's, then you could install Midnite Classic charge controllers which can handle higher Voc voltages which would let you put more panels in series and get a higher voltage to the battery during summer. It would also mean fewer parallell strings and thinner cabling.
But in my opinion, it's not too serious if you have to wait till autumn to do a proper EQ charge on the batteries.

yrtrnc wrote: »

Ok so we connect 3 groups, 2 in series x 6 parallel = 36 right?
I would have to use a circuit breaker right? for each string? So 6 + 6 + 6 circuit breakers? How does that work? What kind of circuit braker?

Yep, 3 groups of 2 in series x 6 in parallel. And yes you'd need 18 circuit breakers or fuses, they should be rated for the DC Voc voltage of the string (88V) and 20% higher than the Imp current for the string so a 10A DC breaker or fuse would be fine.
E.g: http://prismsolar.co.uk/shop/index.php?_a=product&product_id=33
or
http://prismsolar.co.uk/shop/index.php?_a=product&product_id=231 + fuse holder.

yrtrnc wrote: »

Would I have to get rid of the junction boxes I have showed in the pictures? How would I connect the panels to the charge controller? Just wire them as you said and thats that?

As long as your wire sizes are ok for the current then you can keep the junction box, the DC breakers or fuse holders are also din rail mounted, so if there's space you could put them in the same junction box.

yrtrnc · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

The ideal would be if you could return the outback FM's, then you could install Midnite Classic charge controllers which can handle higher Voc voltages which would let you put more panels in series and get a higher voltage to the battery during summer. It would also mean fewer parallell strings and thinner cabling.
But in my opinion, it's not too serious if you have to wait till autumn to do a proper EQ charge on the batteries.

Yes, Im afraid they were a bit of a hurried buy, as we have been out of electricity for almost a month now. We cannot get the equipment in our country as it is not readily available you see. So we had to ship it from the US. It took a while to get here.

As long as your wire sizes are ok for the current then you can keep the junction box, the DC breakers or fuse holders are also din rail mounted, so if there's space you could put them in the same junction box.

So I just discard the junk in the junction boxes and fit 18 fuse holders?

Thank you very much for all your help, very much appreciated.

yrtrnc · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

An "EQ" is an Equalisation charge which is a high voltage charge typically performed once every few months to ecualise the cells in the battery. It's usually done at around 2.65V per cell, so about 64V on a 48V battery, which means that the controller must be able to deliver 64V... so the PVs must be able to deliver just a bit more than 64V. The same temperature effect which increases Voc in winter also decreases Vmp during summer. The temp co-efficient is about -0.37% for every degree higher than 25 degrees. So at a panel temp of 60 degrees, that's a 12% V drop. And with a Vmp of 72V at 25 degrees, you'll see about 63V at 70 degrees. So you may have problems reaching the EQ voltage at the height of summer.

What if we cooled them down with water

stephendv · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

yrtrnc wrote: »

So I just discard the junk in the junction boxes and fit 18 fuse holders?

I'm not really sure what all that stuff in the junction box is... looks like 6 solid state relays on the top row, but why you would need them for a solar array is beyond me. Perhaps it's an invention of the chinese company you bought it from and works specifically with their charge controller. Was there more than 2 wires from the junction box to the old charge controller?

yrtrnc · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

stephendv wrote: »

I'm not really sure what all that stuff in the junction box is... looks like 6 solid state relays on the top row, but why you would need them for a solar array is beyond me. Perhaps it's an invention of the chinese company you bought it from and works specifically with their charge controller. Was there more than 2 wires from the junction box to the old charge controller?

I think they may have had something to do with the on grid inverter, for when we switched over maybe.

No there was not any more wires, just the plus and minus..

Thanks
Yener

stephendv · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

Some of that wiring in the junction box may still be useful.

The end result of the wiring should be something like this:
Working in groups of 12 panels, for each series string the positive goes to its own breaker and from the breaker to a bus bar (a solid piece of conductor where you can connect multiple wires). The negative from the series string goes to a negative bus bar. Then connect the two bus bars to the two inputs on the controller.
The diagrams on page 6 of this manual should give you an idea: http://www.midnitesolar.com/pdfs/MNPV3_6_InstructionsRevD.pdf

It looks like each junction box has 2 units that do the same thing as bus bars (i.e. they tie a bunch of wires together to end in 1 thick wire), so you can re-use these to combine the negative cables from the panels. For the positive bus bar you could use the normal bus bar for AC distribution boxes that looks like a comb, to tie all the breakers/fuses together on the positive side. It looks like this: http://xinchi.en.alibaba.com/productshowimg/306832185-212388608/Distribution_box_copper_bus_bar.html just check that the spacing of the bus bar pins is the same as the spacing on the DC breakers/fuses that you choose.

BB. · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

Equalization is important--But for your needs, two panels in series should work OK. Just slightly less voltage/current for Hot Array and Cool Battery bank (solar panels output voltage falls as panel temperatures increase, and battery charging voltage rises as their temperature falls).

Also, 60-64 volt equalization is not the end of the world.

Keep an eye on the temperature of your battery bank--In theory 25C (77F) is the design/optimum temperature for your bank. For every 10C (18F) increase in battery bank temperature, the life drops by 1/2 (45F, 1/2 battery life, 65F, 1/4 battery life--Conversely, cool batteries will have a longer battery life).

Read about how to take care of your battery bank--Batteries can be very unforgiving if you don't.

Deep Cycle Battery FAQ
www.batteryfaq.org
Trojan Battery 12 page Maintenance FAQ (PDF).
Trojan Battery Maintenance FAQ in español (PDF).
Trojan Videos on Battery Maintenance

Link to more battery information
Historical Battery Mfg/Maintenance Information (1922 automotive/farm batteries)

Some tools you should have:

DC Current Clamp Meter is very handy. You can "clip" on an individual cable (solar panel or battery string) and ensure that current is properly flowing without having to insert a large current meter into the wiring. Sears (US) sells a "good enough" DC current clamp meter (really Digital Multi-Meter or DMM) for ~$60 (not a good source for you).

You should have a good quality hydrometer (glass tube+rubber squeeze bulb and float) to measure the specific gravity in your battery bank. There are now "refractometers" that can take a drip of electrolyte to measure the Specific Gravity too. This devices are difficult to work with and can introduce contamination into your battery if not kept clean. The "gold standard" for measuring battery health.

Brady Temperature Compensated Precision Hydrometer
How to take Specific Gravity Readings

I recommend some sort of Battery Monitor (Victron is a very good European brand) for quick/easy monitoring of battery bank. Very easy to use with non-technical folks too. They are not perfect (can drift from calibration if the battery bank is not fully recharged once or twice a week), but when combined with a hydrometer--Highly recommended (people kill their battery bank pretty often because of insufficient charging or taking a battery bank to "dead"). I would suggest they are almost mandatory if you have a sealed (AGM, sealed, etc.) battery bank.

Some folks do pretty well with just a good quality digital volt/panel meter--But you really need to pay attention to what is happening with your battery bank (battery voltages depend on current flow, charging/discharging/resting state, battery temperature, state of charge, age, etc.). Can be done if you are diligent about monitoring your bank--Frequently not so good if others (employees, spouse, kids, guests) are doing the monitoring too.

Link to battery voltage state of charge vs various charging/discharging/resting states

-Bill

yrtrnc · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

Ok thank you for all your input!

We have decided the easy way. because we have been without electric for some time and need to get things back online.

We will use two charge controllers with the existing wiring, and order another junction box and after we receive it we will wire in the third controller.

Thank you for all your help. Just one more thing, would I connect the charge controllers both to the same points on the batteries?

Also looking for a 20 KW 3 phase inverter can you recommend one pls?

BB. · September 2012

Re: Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

Assuming your batteries are wired correctly--Then just connect the controllers (and the inverters/loads) all to the same bus bar point.

-Bill

Chinese controller gone bust so bought 3 Outback Flexmax 80's ( now how to install )

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