Different Panels on a FM 80 controller?

BilljustBill · October 2013

It's been 2-1/2 years of collecting solar equipment and materials, but I getting ready to start my project. Paid for along the way ...

I'm doing it in three phases while keeping the KW rating end-total in mind. It is a 4KW, OFF Grid system; no grid feedback unless Hell Freezes Over (private joke in view of experience with a local Electric Co-Op)

Panels are to be wired for 48v strings to a Outback FM 80 controller (I have two if needed) to a 24v with an eight L16 battery box.

Phase I: 30 new Kaneka 48v, 60w, panels (Fifteen strings of 2 panels wired in parallel) on a 10'x34' ground array equals 1800 watts.

Phase II: 12 new Kyocera 135w, 12v on 48v strings on a 12'x12' C-band satellite actuator w/Redroc tracker equals 1620 watts on single axis Tracker

Phase III: 16 panel combination of assorted makers/wattages in four 48 volt strings equaling 1560 watts. (Four used 80w, 2 new 90w + 2 new 100w, Four new 100w, two used 120w + two new 140w) Roof Mount of Storage Shed.

I believe I need to understand how a MPPT like the FM 80 works. Should I use one FM 80 for the 30 Kaneka panels for the MPPT to do what it does, or could I use the same FM 80 to also control the Phase II 48v strings of Kyocera panels?

OVERVIEW of Materials and Equipment:

Have two GVFX3524 Outback Inverters. two FM 80 controllers, an Outback Hub, Outback Mate II, Trimetric meter,

All the strand copper wire needed in #10, #6 , #2/0, #4/0, and flexible and/or straight metal conduit, and PVC conduit. 5/8" ground rods

Breakers and combiner boxes, 100amp disconnect box, 200amp AC/DC breaker/disconnect. 3/16" thick by 1-1/8" wide copper bar materials for L16, 6v U.S. Batteries' connection.

2"x2" & 3"x3" tubing for panels' ground array and 2"x2" for roof array, tripod of three sections of 6" pipe filled with concrete for Tracker.

Home info:

Home has split utilities: LP gas for HVAC gas furnace and hot water heater. Home will be wired so that Grid provides all 220v requirements of deep water well, cook stove, clothes dryer, Central A/C system compressor unit, and workshop power.
Solar to power all 120v circuits until GVFX2524 inverter(s) trip over to Grid after battery level drops (or manual switch over)

If you had the same materials, how would you wire it or use the two inverters and two controllers? Your insights and opinions are appreciated.

Cariboocoot · October 2013

Re: Different Panels on a FM 80 controller?

Whether or not you can mix different panels on a controller depends on the Vmp and Imp of those panels. No controller can make up for the losses if the Voltage and current specs are out of whack.

"48V" is a nominal rating, and not the specific numbers you need to work with. If the Vmp of the Kaneka panels actually matches (within reason) the Vmp of the string of Kyoceras they can be used in parallel. The one potential problem is that the reverse Voltage may be different, and under rare circumstances the Kaneka's may "back feed" the Kyoceras if the latter are shaded, costing power.

Now a note about the controller: on 24 Volts an 80 Amp controller can handle about 2500 Watts of panel. Right there is a problem as you're proposing to put 1800 Watts of Kaneka and 1620 Watts of Kyocera or 3420 Watts total on one controller. That's a no-go. Likewise combining the other proposed string of 1560 Watts with either of the others would exceed the maximum.

vtmaps · October 2013

Re: Different Panels on a FM 80 controller?

BilljustBill wrote: »

It is a 4KW, OFF Grid system; no grid feedback unless Hell Freezes Over
<snip>
Home will be wired so that Grid provides all 220v requirements of deep water well, cook stove, clothes dryer, Central A/C system compressor unit, and workshop power.
Solar to power all 120v circuits until GVFX2524 inverter(s) trip over to Grid after battery level drops (or manual switch over)

You have grid. What do you have against grid tied system? Your proposed array is larger than your batteries can effectively use. You will be using grid power for your air conditioner while your panels sit there producing 30 watts to float your batteries.

One of us is missing something here

--vtMaps

Vic · October 2013

Re: Different Panels on a FM 80 controller?

Hi Bill,

Looking at some of the specs online for the Kaneka PVs, seems that strings of two will have far too high voltage for the FM CC.

As I read it, the Nominal V (this is probably Vmp) is 74 V each initially and 67 V after time in the sun, and Voc is 96/92 volts, this is a killer in any configuration of strings with more than ONE PV with the FM CCs.

EDIT: Perhaps you are using a different "Kaneka 60 W" PV, but those are the specs found in a quick search on the net.

These seemingly inexpensive PVs really do cost a lot to mount and wire.

More later, Vic

BilljustBill · October 2013

Re: Different Panels on a FM 80 controller?

vtmaps wrote: »

You have grid. What do you have against grid tied system? Your proposed array is larger than your batteries can effectively use. You will be using grid power for your air conditioner while your panels sit there producing 30 watts to float your batteries.

One of us is missing something here

--vtMaps

What is missing is the 'rest of the story' of dealing with a questionable electric Co-op's action toward electrical damages caused them. There is NO TRUST.

In 1980 I put up an 120v, Enertech 1800 grid tie wind gen. I bought the 120v meter and the buy-back meter from the coop. I also had to provide a half-million dollar liability policy. The original meter seals were broken, to "take out the coop's name", then resealed....yet, the coop had outside decal stickers that were left. Meter readings were always low....and of the $64 of buy back power the meter showed, I NEVER received a penny in cash or credit. To have the meters checked, each one would have to go through the same coop; much like 'the fox watching the hen house;....
The same fellow is still there that certified the win-gen, and ever since it went down (Enertech design failure), they have been trying to get both meters back as if something is wrong with them... About 3 years ago, I managed to get a 440 amp meter box from them (they normally charge $100+) as I planned to do away with one of their wireless Smart meters (and $15 a month account charge), but copper jumped so high, the 340' distance between the workshop and the house made that project halt.

In 2011, the same coop put in new poles and power lines. When the day came to switch over to the new lines, coop reps came to the door and said turn off TV's and computers.... When the new lines came on, ANYTHING that was plugged in and on 'standby and didn't have individual surge protectors, like emergency lighting, DLP 60" TV, remote control 220v workshop's dust collector's blower controllers all were damaged. When I called, the coop came out and wrote up a slanted review of the incident, leaving out the workshop's damage because it's wiring was the newest and also certified by them when they sat their 2nd meter in 1994, even though it is off the same pole transformer and on a 2nd meter. The total damage was almost $1,200. NEVER RECEIVED A PENNY!

The coop's 'grid tie' rule book is a nightmare. I'd be happy to forward the email file they sent me several years ago and is still current. So, for now, I'll stay off grid and may buy an additional battery set of L16's once I see what production the three arrays actually do.

Have you any other insights and suggestions?

BilljustBill · October 2013

Re: Different Panels on a FM 80 controller?

Cariboocoot wrote: »

Whether or not you can mix different panels on a controller depends on the Vmp and Imp of those panels. No controller can make up for the losses if the Voltage and current specs are out of whack.

"48V" is a nominal rating, and not the specific numbers you need to work with. If the Vmp of the Kaneka panels actually matches (within reason) the Vmp of the string of Kyoceras they can be used in parallel. The one potential problem is that the reverse Voltage may be different, and under rare circumstances the Kaneka's may "back feed" the Kyoceras if the latter are shaded, costing power.

Now a note about the controller: on 24 Volts an 80 Amp controller can handle about 2500 Watts of panel. Right there is a problem as you're proposing to put 1800 Watts of Kaneka and 1620 Watts of Kyocera or 3420 Watts total on one controller. That's a no-go. Likewise combining the other proposed string of 1560 Watts with either of the others would exceed the maximum.

Thank you for that insight. Although the panels and equipment are purchased, and with my original plan of needing a controller for each phase, it's information like you've written that underscores the data I know I need to fully understand as the solar project begins to take shape. I appreciate the insight!

BilljustBill · October 2013

Re: Different Panels on a FM 80 controller?

Vic wrote: »

Hi Bill,

Looking at some of the specs online for the Kaneka PVs, seems that strings of two will have far too high voltage for the FM CC.

As I read it, the Nominal V (this is probably Vmp) is 74 V each initially and 67 V after time in the sun, and Voc is 96/92 volts, this is a killer in any configuration of strings with more than ONE PV with the FM CCs.

EDIT: Perhaps you are using a different "Kaneka 60 W" PV, but those are the specs found in a quick search on the net.

These seemingly inexpensive PVs really do cost a lot to mount and wire.

More later, Vic

I bought the Kaneka panels from two different sources. The cost of the FM 80 controller and the 30 new panels (including shipping) came to $2,500. At the time, that total cost was well under the cost of the twelve 130 watt Kyocera panels I bought along the way.

Here is a page showing the 30 Kaneka panels I have:
http://www.wholesalesolar.com/kaneka-solar-panels.html

I have a friend that has used two in parallel on an older Outback MPPT controller, running them in parallel, and hasn't had a voltage issue like you are describing.

The metal tubing has cost about $300 and the wire to the combiner boxes and large 2/0 and 4/0 wire I found at garage sales and estate sales. An example is last year I bought 93' of 2/0 and 91' of 4/0 for $45 apiece. So racks and wire aren't an issue.

Can you go into your thinking a bit more?
Thanks.

Cariboocoot · October 2013

Re: Different Panels on a FM 80 controller?

The Voltage issue is with the Voc @ 96/92 Volts: put two in series and you're feeding 180+ Volts to the charge controller. Most controller's input limit is ~150. In the case of a Classic 150 on a 12 Volt system the HyperVoc function keeps it safe only up to 162 Volts. There is a real possibility of controller damage here.

Two in parallel on a controller would not be a problem.

BilljustBill · October 2013

Re: Different Panels on a FM 80 controller?

What's your insight on an Outback FM 80 on a 48v to 24v battery system. If the Kaneka's become over voltage due to a cloud effect or new efficiency that declines, how do you think the controller will handle the panels' increased voltage?

Thanks

Cariboocoot · October 2013

Re: Different Panels on a FM 80 controller?

BilljustBill wrote: »

What's your insight on an Outback FM 80 on a 48v to 24v battery system. If the Kaneka's become over voltage due to a cloud effect or new efficiency that declines, how do you think the controller will handle the panels' increased voltage?

Thanks

The input Voltage to a controller is in most respects independent to the system Voltage. Minimum Voltage must be met to affect charging and maximum Voltage must not be exceeded to avoid damage to the controller.

The Kaneka panels will go down a bit in Voltage over time, but not up. Edge-of-cloud events will focus light on to panels and increase insolation, thereby raising the array current but won't have a significant effect on Voltage.

I use an Outback MX60 (predecessor to the FM series) with a nominal 48 Volt array on a 24 Volt system. My panels are "true 24 Volt" units with a Vmp of 35 and Voc of 44 so the array is Vmp 70 Voc 88. With the extreme cold temps here the Voc can hit 115 at most, well under the 150 (141 really) input limit.

The Kaneka panels' Vmp is 74 to start with, shifting down to 67. That would be minimal for a 48 Volt system but would work fine for a 24 or 12. Without sufficient Vmp proper charging Voltage may not be achieved after V-drop through the system.

Vic · October 2013

Re: Different Panels on a FM 80 controller?

Bill,

As has been explained, you should be fine with "strings" of one of those Kaneka PVs that you have, especially on a 24 V system (as it seems that you will have, given your OB 3524s). It would probably be fine on a 48 V system as well, you might not be able to EQ FLA batteries on a warm/hot day outside, with cool batteries.

These amorphous PVs just need a lot of area to make not so much power output. It is this, plus the strings of one that work against one when doing off-grid systems, in particular. The large area per watt output increases the wire lengths, number of connections, and the combiners can get busy, although believe that one CAN parallel a number of PVs that can then feed a single breaker/fuse in the combiner (given the Max fuse size rating of 7 A), as I interpret it.

Just to beat the point to death, a common Mono PV available now gives about 2.6 times the power output per square area, compared to the Kaneka 60 W PVs (this is just at STC ratings of each). This may be a bit different at NOCT or PTC ratings, and realize that you appear to have bought the Kanekas some time ago, and so on ...
Opinions, YMMV, Vic

BilljustBill · October 2013

Re: Different Panels on a FM 80 controller?

I've been on a long learning curve in acquiring the panels and equipment as the fundraiser budget allowed and new information sinking in..

Can you teach me an easy way how to remember all those panel terms like Voc,etc., and what they mean?

Thanks for all the input so far,
Bill

Cariboocoot · October 2013

Re: Different Panels on a FM 80 controller?

Easy way to remember it? I've no idea.

But we do have a glossary of terms: http://forum.solar-electric.com/showthread.php?6136-Glossary

Includes things like Voc and Vmp and Imp and Isc and lots of other things pertaining to solar.

BilljustBill · October 2013

Re: Different Panels on a FM 80 controller?

"....you should be fine with "strings" of one of those Kaneka PVs...."

To help clarify this phrase, my plan is to have 2 Kaneka 60w/48v panels in Parallel to keep the voltage down and the amps up. Would you help me understand if there is a problem with having 15 runs from the thirty panels?

Thanks

Cariboocoot · October 2013

Re: Different Panels on a FM 80 controller?

Fifteen "runs" from 30 panels to where? Most people combine the panels at the array and make one "run" from there to the charge controller. If this is any significant distance, then the combined current of fifteen strings of two panels each could be quite a challenge with Voltage drop before reaching the controller.

This is the main advantage of an MPPT controller; greater flexibility in array design. You could, for example, put three panels in series and have only ten parallel connections; higher Voltage, lower current, same array power.

More about configurations: http://forum.solar-electric.com/showthread.php?16241-Different-Panel-Configurations-on-an-MPPT-Controller

BilljustBill · October 2013

Re: Different Panels on a FM 80 controller?

Cariboocoot wrote: »

Fifteen "runs" from 30 panels to where? Most people combine the panels at the array and make one "run" from there to the charge controller. If this is any significant distance, then the combined current of fifteen strings of two panels each could be quite a challenge with Voltage drop before reaching the controller.

This is the main advantage of an MPPT controller; greater flexibility in array design. You could, for example, put three panels in series and have only ten parallel connections; higher Voltage, lower current, same array power.

More about configurations: http://forum.solar-electric.com/showthread.php?16241-Different-Panel-Configurations-on-an-MPPT-Controller

Coot,

I'm trying to keep the terminology straight. I thought I read that "strings" are panels in a series and that panels in parallel are called something different... just so we're talking "Apples to Apples".

But, with the 48v panels, plus over voltages that could occur, I'm using a "T-branch" connector in parallel of two panels to make the connections short(http://www.ebay.com/itm/One-Pair-T-Branch-Connectors-Solar-Panel-Cable-MC4-Splitter-Coupler-Combiner-CE-/251348693636?pt=LH_DefaultDomain_0&hash=item3a858cb284). Is there a possible over-voltage if the Kaneka 48v panels were wired in pairs and in series?

The 15 pair of parallel panels will run to a single combiner box that has fifteen 65v DC breakers I've already purchased. Getting this array's 48 volt power to the FM 80 MPPT controller using the bargain 2/0 or 4/0 copper strand wire, used in runs of under 90', should allow for as little line loss as is possible. The 4/0 size short leads of 5 feet each, from the disconnect switch to the solar controller and to the battery bank should be easy to keep.

So, do you see a problem with how this ground array of these 30 panels wired in parallel pairs would be a problem for the FM 80 and GVFX 3524?

Cariboocoot · October 2013

Re: Different Panels on a FM 80 controller?

BilljustBill wrote: »

Coot,

I'm trying to keep the terminology straight. I thought I read that "strings" are panels in a series and that panels in parallel are called something different... just so we're talking "Apples to Apples".

Panels connected in series are a string. However you can have a string of one.
All the panels together connected to one controller is an array.

But, with the 48v panels, plus over voltages that could occur, I'm using a "T-branch" connector in parallel of two panels to make the connections short(http://www.ebay.com/itm/One-Pair-T-Branch-Connectors-Solar-Panel-Cable-MC4-Splitter-Coupler-Combiner-CE-/251348693636?pt=LH_DefaultDomain_0&hash=item3a858cb284). Is there a possible over-voltage if the Kaneka 48v panels were wired in pairs and in series?

Voltage increases only with series connections. Where you usually get into trouble with too much Voltage for the controller is Voc & cold temperatures; that's what will 'hit' the controller first thing in the morning.
The 'Y' branch connectors are fine for two parallel connections, but beyond that you can run up against a couple of problems. The first being will the wire 'beyond' the final connection point be large enough to handle all the current of the panels it is connected to? The second is that you now have the potential for one failed panel to receive the combined current of the others and possibly ignite. The latter is solved with fuses or breakers on each and every panel, the former is solved by going up in wire size. Both are made simpler by the use of a combiner box.

The 15 pair of parallel panels will run to a single combiner box that has fifteen 65v DC breakers I've already purchased. Getting this array's 48 volt power to the FM 80 MPPT controller using the bargain 2/0 or 4/0 copper strand wire, used in runs of under 90', should allow for as little line loss as is possible. The 4/0 size short leads of 5 feet each, from the disconnect switch to the solar controller and to the battery bank should be easy to keep.

This 48 Volts, is that nominal, Vmp, or Voc? I ask because two 'normal' 24 Volt panels in series is 48 nominal, but the Vmp will be 70 and the Voc around 88. As such breakers rated for 65 Volts would not actually be suitable. This is why MidNite makes the 150 Volt breakers.

So, do you see a problem with how this ground array of these 30 panels wired in parallel pairs would be a problem for the FM 80 and GVFX 3524?

Well the inverter simply isn't going to care as it gets its power from the batteries. The FM80 will only have a fit if the Voc can exceed its input maximum (150, but it probably quits working around 141). Otherwise it can accommodate a 2500 Watt array on 24 Volts.

BilljustBill · October 2013

Re: Different Panels on a FM 80 controller?

Cariboohoot,

Thank you for your help and giving your time to help a "Beginner". I started my quest when I bought two used 120w panels at a local flea market, then added more as "bargains" were found. Doing this on a 'shoestring' has been as much an adventure as the 'fundraising' part. I've put a lot of money into the project and I've put almost 3 years in time used to generate the funds and pay as go to get it to this point.

It will be a celebration of reward and of both sharing and getting help from you, SawMill, and the different forums on this website when each array begins production of power.

Most sincerely,
Bill

Vic · October 2013

Re: Different Panels on a FM 80 controller?

Hi Bill,

Did not mean to confuse things by referring to "strings" of one. That was the reason for the quotes. They are really not strings, but, calling it a "string" seemed simpler than any other thing that came to mind.

Good luck with the new project, and seems like you are making great progress. Have Fun, Vic

BilljustBill · October 2013

Re: Different Panels on a FM 80 controller?

I'll take any help and will be grateful for the time spent giving it.

Of the thirty panels, 2/3's of the Kaneka panels were on a closeout from a company that realigned it's market focus, called 'RealGoods', and including the shipping, they cost $39.95 each. In view of the current economic times, coming Winter, and getting things qualified as 'Operational' for a solar tax credit this year, I'm getting antsy to get the ground array started and 1/3 of the project producing.... ;>)

Thanks,
Bill

BB. · October 2013

Re: Different Panels on a FM 80 controller?

One thing to be aware of--Won't make a big difference for your array--Kaneka and DuPont thin film panels are one of the few that have different rules possible for parallel connections of panels...

For example the 60 Watt Kaneka panels have an Isc of ~1.2 amps and a fuse requirements of 7 amps... So you can put upwards of five strings in parallel before you need to use individual fuse/breaker per panel string.

-Bill

BilljustBill · October 2013

Re: Different Panels on a FM 80 controller?

BB. wrote: »

One thing to be aware of--Won't make a big difference for your array--Kaneka and DuPont thin film panels are one of the few that have different rules possible for parallel connections of panels...

For example the 60 Watt Kaneka panels have an Isc of ~1.2 amps and a fuse requirements of 7 amps... So you can put upwards of five strings in parallel before you need to use individual fuse/breaker per panel string.

-Bill

Thank you Bill, I guess that's why I posted here in the 'training-wheels' Beginner Forum because what you just said went over my head... ;>)

Do you mean that if up to 5 panels are wired in parallel, because of Kaneka's design, I'd need only one breaker?

It is so odd or coincidental, but I ran across an unused weatherproof, rubber gasket sealed door & locking electrical box several years ago. The breakers I bought mount on a DIN rail and all 15 of them, and an insulated collector bars for both a positive and negative will easily mount inside what will become my single combiner box. In running the wire to the combiner box from parallel pairs of 48v panels, I've not only 'collected' solid and flexible conduit for each of the runs, but I also found #6 strand copper awhile back. The black run is made of that insulation and copper wire coating that resists the positive side of a DC circuit from turning into that infamous 'black powder'.....

As for grounding all 30 panels with a single run of bare solid #6 copper wire, how would you do them? Those individual ground clamps are expensive and 30 of them on this array does run the cost up....is there a NEC approved, but 'cheap' way to do it? Because this array goes to the controller and inverter to my home, would I just ground the panels to my array's own grounding rod, or run the panel ground and ground rod wire to the grounding bar of my combiner box? This way in keeping the negative white wire isolated back to my disconnect switch? I have my 7' heavier 5/8"diameter copper clad grounding rod and a way to get it set that deep.

My plan is to weld the 10 x 34' array using 2" and 3" tubing on site. Then deck the array framework with 1/2" thick by 4x8' sheets of standard roof decking panels, 30# tar paper, and some 30 year Owen/Corning asphalt shingles. This way, with a 4" thick slab poured under the array, and using some natural color paint and lattice work panels, I'll have a dry place to store my firewood..... Two birds with one stone sort of approach.... Primarily built for solar panels, the decking and shingles are considered 'free' and not added in the array's cost, plus because it's classified as a 'solar improvement', the rest of the actual cost qualifies for Uncle Sam's tax credit, and in Texas, the local taxing entity can't tax 'Solar' as an "Improvement"....

Bill

BB. · October 2013

Re: Different Panels on a FM 80 controller?

Don't worry about the off the wall issue of fusing--It only matters if you have a small array of 5 or fewer panels (and you don't need the fuse per string--unlike most solar arrays which do not need the extra fuse for just two parallel strings).

Regarding using your existing 60 watt panels.. You are starting to see why larger systems are going to 250 Watt (or even larger) panels... That is 1/4 the number of panels, 1/4 the number of mounting hardware+grounding clips, 1/4 the wiring connections, etc.... (probably 4x more reliable array too).

-Bill

Cariboocoot · October 2013

Re: Different Panels on a FM 80 controller?

What Bill is talking about with the "seven panels": every panel has a maximum current it can carry, based on the materials it's made of. In the case of these panels the current they can output is much lower than the materials are capable of handling. This is usually not the case.

It as with a wire: normally 14 AWG wire is meant for 15 Amps continuous. But it can actually handle 20 Amps. Normally a panel puts out, say, 7 Amps but as a conductor can handle 10 Amps before things start to melt. So you should see a "series fuse rating" on the panel which indicates the most current it can handle as a conductors.

In the case of these Kaneka's they only put out <2 Amps, but the conductive material can handle much more than that because it's pretty much the same stuff as a higher output panel. Since the safety issue is having a shorted panel back-fed more current from others in parallel with it than its can safely conduct you have this phenomenon of the series fuse rating being much higher than the short circuit current rating.

For the most part it's not something to worry about either way.

Different Panels on a FM 80 controller?

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