construction of a 5.4 kw solar aray ground mounted system

[cmxterra]

So if I am understanding this correctly. If I break the panels up to smaller groups and then run those to the charge controller I can get away with using something like the Flex 80.

Although looking at the specs for the Flex 80 seems that the largest wattage they are rated for is 2500 and not the 2580 that the 12 panels could produce. Am I reading that correctly?

[fasteddie]

I will have to look for you but its mardi gras in st louis the next couple of days so I probably won't be back online untill Sunday, T G has one so she likely knows off the top of her head. I don't think that is the case though. I will get back with you guys later.

[TexasGirl]

So if I am understanding this correctly. If I break the panels up to smaller groups and then run those to the charge controller I can get away with using something like the Flex 80.

Although looking at the specs for the Flex 80 seems that the largest wattage they are rated for is 2500 and not the 2580 that the 12 panels could produce. Am I reading that correctly?

Yes, you can break the panels down into several strings.  If everything is on one long string and one panel has a failure, everything stops.  Multiple strings are more reliable, just make sure the panels have internal diodes (usually in the connection box) so they can't backfeed.

Most charge controllers are limited (rated) by amperage, amperage of the OUTPUT which in your case is 24 VDC.   That would be 1920 watts @ 24 v, before the 80% factor (by code) is applied.   So a FlexMax 80 on a 24 volt nominal system will control 1536 watts of panel.  Doesn't matter if a controller will handle a gazillion volts, the wattage is limited by the output amperage.   

But then how can I throw 12 panels on one FM80?  My system voltage is 48, a FM80 will handle 3072 watts on a 48 volt system.   Conversely, an 80 amp controller will only handle 768 watts on a 12 volt system.  That's why things have moved away from 12 volt systems.

Using two controllers also eliminates a single point of failure.  But the two controllers must be synchronized to work together.  That's the beauty of the Outback modular system, the controllers and inverters will work as one.

~TG

[cmxterra]

Yes, you can break the panels down into several strings.  If everything is on one long string and one panel has a failure, everything stops.  Multiple strings are more reliable, just make sure the panels have internal diodes (usually in the connection box) so they can't backfeed.

Most charge controllers are limited (rated) by amperage, amperage of the OUTPUT which in your case is 24 VDC.   That would be 1920 watts @ 24 v, before the 80% factor (by code) is applied.   So a FlexMax 80 on a 24 volt nominal system will control 1536 watts of panel.  Doesn't matter if a controller will handle a gazillion volts, the wattage is limited by the output amperage.   

But then how can I throw 12 panels on one FM80?  My system voltage is 48, a FM80 will handle 3072 watts on a 48 volt system.   Conversely, an 80 amp controller will only handle 768 watts on a 12 volt system.  That's why things have moved away from 12 volt systems.

Using two controllers also eliminates a single point of failure.  But the two controllers must be synchronized to work together.  That's the beauty of the Outback modular system, the controllers and inverters will work as one.

~TG

I thought it could handle 2500+ watts.. did I mess up there or would I need two charge controllers for the 12 panel array? I am not sure that two charge controllers into one battery bank would work out too well.

[TexasGirl]

Hi,

I'm planning a similar setup using a pre-configured OutBack Power FLEXpower TWO (for ease of installation and electrical inspector approval) with 2x3648 and 2xFM80 (for future expansion) and the X240 Transformer,

Which BP panels are you using?

I was thinking of a pole mounted tracker or building a similar ground based setup, in the back of the property so it could not be seen from the surrounding area or from the road. I have to replace the leech field and want to do the underground wiring while I have have the area excavated and open.

What battery bank configuration would you suggest?

Any help would be appreciated. This is a complete gut rehab of the property so I will be installing new electrical panels/wiring/etc and it will be grid tied to take advantage of the state and power company incentives. (Although I am not sure that the batteries will be part of the power companies incentives) My total allowable system size is 5kw without having to go with additional inspections or approvals.

Hi Al, welcome to the forum!

Great system choice, too.

I picked up a pallet of BP 220's, but also have a few BP 230's laying around.  A friend will be using half that pallet for another project.

Run the $ numbers on a tracker, yes it will provide more efficiency through increased solar hours, but with the cheap prices of panels, it may be easier to simply add more fixed panels instead.  Mechanical things require additional maintenance, eventually break down, and scream "solar" like a billboard.  But in some locations, they are still the better way.  It depends on your circumstances.

Batteries.  Most DIY installations use AGM gel batteries because they are less hazardous to work with.  They are generally considered "5 yr" batteries but can last longer with good care and proper sizing.  My favorites here are size L16h, and Rolls Surette as a manufacturer.

Most preppers are lured to the wet cell batteries because they see the 7 or 10 year life, or to forklift batteries with a 20 year life.  I plan on using wet cells. 

*CAUTION* Wet cells outgas hydrogen.  They must go in a well ventilated explosion hazard rated environment.  The best way I can explain this...  If you would be unconfortable leaving an open natural gas jet spewing gas 24/7 in the location the batteries will sit, then the location is wrong for wet cells.  Hydrogen gas is more explosive than natural gas.

Down south we can use ventilated enclosures outside, up north there are temperature factors to deal with.  Where are you located?

Normally the power company gives incentives for grid tie systems only, no batteries.  Grid tie systems are designed to shut down when the grid drops out for safety of the utility company workers.  While the GVFX inverters will grid tie, they will also run stand alone, but not at the same time.  Each mode is set up and wired differently.  Some folks install the system grid tie without batteries, collect the rebates, then convert them to grid fed stand alone.  Because you are rewiring the house, this would work well.  The how-to is TMI for posting here, though.

Sounds like you need a knowledgeable local electrician to hold your hand.

~TG

 

[TexasGirl]

I thought it could handle 2500+ watts.. did I mess up there or would I need two charge controllers for the 12 panel array? I am not sure that two charge controllers into one battery bank would work out too well.

Unless the controller is rated greater than 130 amps, you would need two running tandem.  This is not the same as running independently parallel, "tandem" implies the ability to coordinate.  Many charge controllers do not have the networking function to run tandem.  That's why I said:

"But the two controllers must be synchronized to work together.  That's the beauty of the Outback modular system, the controllers and inverters will work as one."

 My system (and Big Al's) uses two FM80's running in tandem.  One controller takes the lead and the other follows.  The Outback controllers go through five different stages of charge control on each charge cycle, each stage determined by the circumstances.

A good charge controller is worth it's salt, and not the place to skimp.  Battery strings are quite an investment to care for!

~TG

[BigAl]

Hi Al, welcome to the forum!

Great system choice, too.

I picked up a pallet of BP 220's, but also have a few BP 230's laying around.  A friend will be using half that pallet for another project.

Run the $ numbers on a tracker, yes it will provide more efficiency through increased solar hours, but with the cheap prices of panels, it may be easier to simply add more fixed panels instead.  Mechanical things require additional maintenance, eventually break down, and scream "solar" like a billboard.  But in some locations, they are still the better way.  It depends on your circumstances.

Batteries.  Most DIY installations use AGM gel batteries because they are less hazardous to work with.  They are generally considered "5 yr" batteries but can last longer with good care and proper sizing.  My favorites here are size L16h, and Rolls Surette as a manufacturer.

Most preppers are lured to the wet cell batteries because they see the 7 or 10 year life, or to forklift batteries with a 20 year life.  I plan on using wet cells. 

*CAUTION* Wet cells outgas hydrogen.  They must go in a well ventilated explosion hazard rated environment.  The best way I can explain this...  If you would be unconfortable leaving an open natural gas jet spewing gas 24/7 in the location the batteries will sit, then the location is wrong for wet cells.  Hydrogen gas is more explosive than natural gas.

Down south we can use ventilated enclosures outside, up north there are temperature factors to deal with.  Where are you located?

Normally the power company gives incentives for grid tie systems only, no batteries.  Grid tie systems are designed to shut down when the grid drops out for safety of the utility company workers.  While the GVFX inverters will grid tie, they will also run stand alone, but not at the same time.  Each mode is set up and wired differently.  Some folks install the system grid tie without batteries, collect the rebates, then convert them to grid fed stand alone.  Because you are rewiring the house, this would work well.  The how-to is TMI for posting here, though.

Sounds like you need a knowledgeable local electrician to hold your hand.

~TG

Thanks for the info, I was looking at wet cell Trojan T-105, I have quite a bit of experience with maintenance routines, My plan was to use the charging relay switch on the FM80 to operate an exhaust fan run to the outside and keep the batteries in a couple of oversized marine ice coolers I came across, Easy to pipe together and fairly air tight and non-corrosive.

The tracker I'm looking at is in the next state so I could pickup and has a automated "snow removal" function (automatically tilts to drop off snow, I'm in the upper North of the Country) and the pricing is comparable to a multi-pier install with attachment brackets.

What panels/brands would be a good choice, There is a distributor's warehouse not far from where family lives and was looking to pick that up on a trip down there to save on the shipping. I was also looking at the UniSolar Flexible solar panels to mount as a secondary set of panels, I will be redoing the roof with metal and since they integrate with the metal panels they would not be obvious from far away, any thoughts?

Thanks for all the help.

[TexasGirl]

Sounds like the tracker would work well where you are.

Keep in mind that the fan will be operating in the hazardous environment and should be rated for such (brushless, if DC).  Also, the batteries can outgas during discharge as well.

Panels are a personal decision.  Mine are all domestically made with warranties.  But I may order a pallet of cheap ones for grins.  Just be aware that most full sized panels are engineered for 240 watts, but graded and sorted according to performance.   So a 205 watt panel has enough defects to only make 205 watts.  While I don't have any documentation to support the theory, I can't help but think there would be less chance of future problems (is: hot spots, burn outs, impedance mismatching) with panels that hit closer to the engineered goal.  YMMV

I look for "UL listed" and grade "A", not seconds.

~TG

[cmxterra]

So.. Texas Girl.

Knowing that I have 6kw worth of panels and need the charge controller and considering the Outback 80. If I break it up into two arrays of 2kw each I can get by with only one Outback Flex 80 per array, correct?

And if I keep it at two arrays of 3kw each I will need two Flex 80's per string (total of four), Right?

Trying to figure out which way would work the best. If I do the 2kw arrays that would leave me with extra unused panels that I could either save as replacement panels in case of damage or to use in smaller areas to run little things.

[TexasGirl]

Hi cmxterra,

Charge controllers are rated by output amperage, the FlexMax 80 will handle 80 amps.  Since you are working with 24 volt inverters, the wattage will be divided by 24, not 48 like Eddie's. 

Looking at the math from the capacity side...

80 amps x 80% (this is the same 125% Eddie used figuring from the load side) = 64 A, times the system voltage of 24 = 1536 Watts per controller.  (Running 48 volt inverters would allow 3072 watts per controller, that's where 48 volt systems shine.)

1536 divided by 215 watts per panel = 7.1 panels, which is an odd number.  7 is too many to put in series, you would need to run 6; either two strings of 3, or three strings of two.  The choice depends on the lowest temperature they will be running at.  (Where are you living?)  I can apply the 125% margin on temperature gain like Eddie was using, so three panels in series tops out at about 140 volts on the coldest day.  If you are in an area where winter can bring a 15 degree or less day, it's safer to stick with two in series.  The FM 80 will shut down if input voltage exceeds 155, but will start up again when it drops back below.

Either way, with 6 panels per controller you will need 4 FlexMax 80's to use all 24 panels.  Eddie and I are running 48 volt systems so we get 12 panels per FM 80.

I hope that helps clarify things.

~TG

[cmxterra]

Looking at the Flex's spec sheet it talks about being able to convert higher panel voltages down to lower battery voltages.

That being so could you series the 24v panels to make them 48v panels and still use the 24v battery and inverters?

[TexasGirl]

Looking at the Flex's spec sheet it talks about being able to convert higher panel voltages down to lower battery voltages.

Correct.  Two of your panels in series is about 48 nominal volts, three in series is about 72 nominal volts.  But with 24 volt inverters, you will need a 24 volt battery bank, and the output of the charge controller will need to be set on "24 volts".

The advantage of running a MPPT controller like the FlexMax is efficiency.   Any input voltage over the needed charge voltage (in your case the charge voltage might be around 26-27 volts) will be converted into useable power.  The older PWM style chargers could not use excess voltage, it was just lost as waste.  So, with two panels in series you might have 60 or more volts total (30 volts each) on a moderately sunny spring day, but on a dark cloudy summer day the panels might only make 20 volts each.  But in series that's 40 volts, enough to still charge batteries.   

On an "old school" system where panels were strung together at their nominal voltage, no charging would be happening on a dark day, because that 20 volts wasn't enough.  A charge controller needs input voltage above the battery charge voltage. 

And who thought throwing a couple panels and some gadgety inverters together would be anything but simple?

~TG

[cmxterra]

Well am going to do 24v batteries and I do have 24v inverters. So if I series the panels together to get the higher voltage should I be able to put more panels onto one charge controller and end up using fewer controllers?

[TexasGirl]

Well am going to do 24v batteries and I do have 24v inverters. So if I series the panels together to get the higher voltage should I be able to put more panels onto one charge controller and end up using fewer controllers?

No.  (Sorry to say the magic calculator dust won't apply this time.)

The limitation is the charge controllers output amperage, which will be 80 amps at 24 volts.  Doesn't matter how the panels are strung together, this is a physical current limitation between the charge controller and the batteries.   

The advantage of having more panels in a series string is: cloudy day voltage, and less copper wire between the panels and controller.

If you have a 55 gallon drum, it will have a capacity of 55 gallons.  No matter if you fill it fast with a fire hose or slow with garden hose, it still only has a capacity of 55 gallons.  So is the charge controller capacity.  It's rated at 80 amps, doesn't matter if the feeding voltage is high or low, it only has an 80 amp output capacity.  At 24 volts, that translates to 1920 watts, but per code, the calculated continuous load is limited to 80% (1536 watts).  So no matter how you string the panels, there is a limit on this specific application to 1536 watts per charge controller.     

Using 80 amp controllers on a 24 volt system, you will need four to run all 24 panels.

~TG

[cmxterra]

So am I reading this right that I can do a string of 10 panels for one controller (5 parallel 2 series)

http://outbackpower.com/resources/string_sizing_tool/
using the Evergreen Es-e-215-FC3 panels

[TexasGirl]

So am I reading this right that I can do a string of 10 panels for one controller (5 parallel 2 series)

http://outbackpower.com/resources/string_sizing_tool/
using the Evergreen Es-e-215-FC3 panels

I am unable to access the sizing tool from my apple device.   

Check to make sure the calculations are based upon a 24 volt charging system and not a 48 volt system.  Ten panels at 24 volts sounds a bit high, my calculator says that's 90 amps at 24 volts, 45 amps at 48 volts.

~TG

[fasteddie]

I got my new electric bill today it was$2.68 for last month, I can't complain also I got my second rebate check from ameren electric and it was $6800.00 yesterday and I ordered an outside wood boiler furnace today it should be installed in a couple of weeks. The wood boiler is $9250.00 for the one that will heat my house.

[Truik]

I got my new electric bill today it was$2.68 for last month, I can't complain also I got my second rebate check from ameren electric and it was $6800.00 yesterday and I ordered an outside wood boiler furnace today it should be installed in a couple of weeks. The wood boiler is $9250.00 for the one that will heat my house.

I think I may have said this before but, in case I haven't...that solar system you built is freakin' awesome!

[Nicodemus]

I got my new electric bill today it was$2.68 for last month, I can't complain also I got my second rebate check from ameren electric and it was $6800.00 yesterday and I ordered an outside wood boiler furnace today it should be installed in a couple of weeks. The wood boiler is $9250.00 for the one that will heat my house.

That is really awesome, fasteddie!

[cmxterra]

So who would you suggest I get the Flex 80's from? Any suggestions?

[TexasGirl]

So who would you suggest I get the Flex 80's from? Any suggestions?

Other than checking Outback dealers, I would hit eBay.  You might PM Maverick, too.

~TG

[fasteddie]

in the paperwork process of adding apx 4 kw  of evergreen solar panels to our allready existing 5.88 kw also adding another small off grid pole mounted system soon.

[TexasGirl]

Wow Eddie,

That grid-tie will be powering the whole neighborhood before long.

Awesomely cool!

~TG

[fasteddie]

I hope so texas girl, i finally got my approval from ameren ue. now i can start construction of my 3.9 kw addition to this 5.88 kw system that is already producing most of the power i need. the only problem is the weather is bad so it might be a couple months before i get started. I originally was going to add almost 6 kw to the current system but ameren said 10kw total was the biggest residential system they would allow. anything larger than 10 kw then i had to be considered a commercial entity and had to install a commercial meter etc so i stayed under 10 kw. I will use 20 evergreen solar ese195 195 watt modules on this expansion. I will have 11 of these modules left that i plan on building another off grid system next. Fast Eddie

[mike77]

T. G. sorry it took me so long to answer your question, The answer is no. In my advanced class at school we built a 2kw solar array with gvfx 3648 outback inverters and a flex 80 charge controller and 8 l 16 batteries.

What class and school was this? Thanks.

[fasteddie]

mike, i went to the evergreen institute located in Gerald mo. with author instructor Dr. Dan Chiras, it was a 4 day class you stay on the campus farm or nearby in a town but you really have to go to beginner and intermediate classes first and they are both 2 day weekend classes.

[mike77]

Thanks fasteddie. That's only about an hour from me, so I'll definitely look into it!

[fasteddie]

mike, it is a life changeing experience to learn this stuff so if your that close it is a no brainer. you have no idea how lucky we are to have dan and this school in our area. trust me make the time to go. everything you can think of will try to stop you but do it anyway and i promise you that you will be really glad you did. ps i am apx 3 hours away all backroads and i make it happen even though i have to take off work and hire people to run my business while i am at school. and everything goes wrong while i am gone.... its like i am being punished for trying to better myself. i am just saying make it happen no matter what. you will be glad you did.

[cmxterra]

learn all you can

[oktheniknow]

Looks like an awesome system.
I have considered putting up unisolar thin film panels up seeing as how I will have a metal roof at my new place. Could also put on our RV. The local solar guy was poo pooing them because they have no warranty (are bankrupt). Well, if shtf that will not be important now will it! He said they are 16" wide and that a standing seam is needed for them. Has anyone tried these peel and stick panels? They are black, so would stand out on a roof. I'm tempted to buy while they are still available.