Batteries and 3 FX80 controllers

BilljustBill

With the temps outside currently in the low 20's, I'm using the time to plan for my solar project. In spite of all the "health events" and "Fundraiser events" causing time and dollar detours along the way, it's been almost 3 years in the making and I'm finished collecting panels, wiring, and equipment.

My off grid system will have three arrays totaling about 5,000 watts. It's built around two of Outback's GVFX-3524 inverters, three of the FX80 solar controllers, and three 4-battery strings of U.S. Battery L16HC XC's. Each is rated 420amp hr. at a 20hr rating.

With three strings of four 6v batteries forming a 24v system, I'll have three of the FM80 controllers to hook into the battery bank. How would you connect all three controllers to the battery bank?

Thanks for your insight and help,
Bill

stephendv

Re: Batteries and 3 FX80 controllers

Why 24V? With such a big system there are only advantages in going to 48V. At 48V you'd only need 2 x 80A outback controllers and you'll need fewer strings of battery in parallel, i.e. 2 instead of 3.
Thinner wire, more efficient system.

Cariboocoot

Re: Batteries and 3 FX80 controllers

BilljustBill wrote: »

With the temps outside currently in the low 20's, I'm using the time to plan for my solar project. In spite of all the "health events" and "Fundraiser events" causing time and dollar detours along the way, it's been almost 3 years in the making and I'm finished collecting panels, wiring, and equipment.

My off grid system will have three arrays totaling about 5,000 watts. It's built around two of Outback's GVFX-3524 inverters, three of the FX80 solar controllers, and three 4-battery strings of U.S. Battery L16HC XC's. Each is rated 420amp hr. at a 20hr rating.

With three strings of four 6v batteries forming a 24v system, I'll have three of the FM80 controllers to hook into the battery bank. How would you connect all three controllers to the battery bank?

Thanks for your insight and help,
Bill

#1 I agree with Stephen that you're in "48 Volt territory" with that size of a system
#2 If you go with those three parallel battery strings you should use bus bars for positive and negative and connect the inverters and charge controllers to the bus bars. Don't forget the fuses/breakers. A MidNite E-panel might be a darn good idea for this.
#3 If you don't have a MATE and a HUB 10 you will regret it mightily. That would allow co-ordination between the inverters and charge controllers. If you went to 48 Volts you'd only need two FM80's and a HUB 4.

BilljustBill

Re: Batteries and 3 FX80 controllers

I started collecting 12v panels for a "smaller" system, but found a closeout sale from "Real Goods" and I bought 20 new Kaneka 60w, 48v panels for a delivered price of $40 each. Several months later I bought 10 more from an Ebay auction. For those 30 panels and a beginning rating of 1800 possible watts, the 10'x32' ground array framework will be out of 3"x3" vertical tubing posts on 6' centers, and 2"x2" steel tubing for the remainder of the framework.

With help from this forum, I learned that the 24v system was about the best voltage I could expect with that array's panels on its own MPPT controller.

With the help of finding a 3-1/2" wide by 1/4" thick, 5' long piece of copper bought from a local scrapyard as a takeout from a large electrical box, I'll have enough to saw it into long buss bars. So, if I understand you, hooking each controller to a buss bar would be the best way?

Not knowing how MPPT controllers work, I didn't know if the three controllers output to the 12 batteries all at one time and from one point would cause a misreading interference in how each one was reading battery voltage while the other two trying to put power into the battery bank. I thought that placing the controller input lugs on each 24v battery string might help...

Cariboocoot

Re: Batteries and 3 FX80 controllers

BilljustBill wrote: »

With the help of finding a 3-1/2" wide by 1/4" thick, 5' long piece of copper bought from a local scrapyard as a takeout from a large electrical box, I'll have enough to saw it into long buss bars. So, if I understand you, hooking each controller to a buss bar would be the best way?

With all the connections you need to make (three controllers, two inverters, three battery strings) it's the only way to do it and hope to have even flow between the various devices.

Not knowing how MPPT controllers work, I didn't know if the three controllers output to the 12 batteries all at one time and from one point would cause a misreading interference in how each one was reading battery voltage while the other two trying to put power into the battery bank. I thought that placing the controller input lugs on each 24v battery string might help...

They'll work together fine, as each will see Voltage on its output and function accordingly. In theory they will all see the same Voltage at the bus bars and be programmed the same so they'll be in the same mode at all stages. In practice there will always be a slight difference causing some variation in Voltage readings and stages. This will be better with the HUB connection between them, but won't be as good as MidNite's "follow me" system where other controllers are slaved to the master one.

You want to treat the battery strings as one big battery as far as the charge controllers and inverters are concerned. Oh and it would be a good idea to have separate fuses on each battery string (in addition to the protection for each controller and each inverter).

BilljustBill

Re: Batteries and 3 FX80 controllers

Cariboocoot wrote: »

With all the connections you need to make (three controllers, two inverters, three battery strings) it's the only way to do it and hope to have even flow between the various devices.



They'll work together fine, as each will see Voltage on its output and function accordingly. In theory they will all see the same Voltage at the bus bars and be programmed the same so they'll be in the same mode at all stages. In practice there will always be a slight difference causing some variation in Voltage readings and stages. This will be better with the HUB connection between them, but won't be as good as MidNite's "follow me" system where other controllers are slaved to the master one.

You want to treat the battery strings as one big battery as far as the charge controllers and inverters are concerned. Oh and it would be a good idea to have separate fuses on each battery string (in addition to the protection for each controller and each inverter).

With the "Separate fuses on each battery string", I take it that the Buss Bars are used in connecting the four batteries in each string. Then, 4/0 cable with a fuse on each of the three positive cables that are bolted to a Main set of buss bars where the inverters are connected. Any pictures or drawings I could see what we are talking about?

With the 440 amp hour battery strings, what's the best type of fuse or breaker brand and size to use? What fuse brand and size would you use on each controller ouput and input to the inverters? With three different electrical utility company's just behind the property line, I want to not only be safe, but also be NEC compliant if ever I use the grid tie abilities of both inverters.

Thanks for the help

Cariboocoot

Re: Batteries and 3 FX80 controllers

BilljustBill wrote: »

With the "Separate fuses on each battery string", I take it that the Buss Bars are used in connecting the four batteries in each string. Then, 4/0 cable with a fuse on each of the three positive cables that are bolted to a Main set of buss bars where the inverters are connected. Any pictures or drawings I could see what we are talking about?

With the 440 amp hour battery strings, what's the best type of fuse or breaker brand and size to use? What fuse brand and size would you use on each controller and inverter? With three different electrical utility company's just behind the property line, I want to not only be safe, but also be NEC compliant if ever I use the grid tie abilities of both inverters.

Thanks for the help

You need to think about the system as a group of separate but interacting circuits.
Fuses on battery posts protects circuits to bus bars.
Fuses from bus bars to charge controllers protect those circuits.
Fuses from bus bars to inverters protect those circuits.

As such the wire sizes on each of these circuits is in accordance with the expected maximum continuous current, and the fuses sized to protect that wire.

So the current from the batteries to the bus bars will be the same as to the inverters; the heaviest current = heaviest wire. Battery fuses need to protect that.

Each 3524 inverter can pull 150 Amps continuous (program 24 Volt shut down) so you're looking at that much current from the bus bars to the inverters. But you are looking at 300 Amps from the batteries to the bus bars. If there is a lot of distance involved the wire size may need to be even larger. Hopefully that will not be an issue, so you could use 4/0 from each battery string to the bus bars and a 300-350 Amp fuse on each battery string. Some will say divide up the current by three, and make it 100 Amp service from batteries to bus bar. If you do that and one fails the other two will take the full load and may fail in turn as well. Much depends on how close to full power you run it. With two inverters planned I would expect you probably need the power? Or are you stacking them for 240 VAC?

The charge controllers are fairly simple: 6 AWG to handle the current (80 Amps max), and fuse accordingly (100 Amp).

Note that if you decide to grid-tie this you may have quite a few issues with the inspection, such as housing wiring in conduit, etc. Also note that 'breaker' may be used in place of 'fuse' for some of the description above.

BilljustBill

Re: Batteries and 3 FX80 controllers

Cariboocoot wrote: »

#1 I agree with Stephen that you're in "48 Volt territory" with that size of a system
#2 If you go with those three parallel battery strings you should use bus bars for positive and negative and connect the inverters and charge controllers to the bus bars. Don't forget the fuses/breakers. A MidNite E-panel might be a darn good idea for this.
#3 If you don't have a MATE and a HUB 10 you will regret it mightily. That would allow co-ordination between the inverters and charge controllers. If you went to 48 Volts you'd only need two FM80's and a HUB 4.

Thanks for your insight, too. Although I still need the third of three FM80 controllers and the third string of L-16's, I have gathered the heavy wiring, breaker and combiner boxes, the hub, the Mate II, and a Trimetric to get two of the arrays up and going by late Spring/early Summer. I'll look into the E-panel. But if the economy holds together until the last of March, a good home garage sale "fundraiser" should cover the cost of the remaining needs and rent a good ditch digger for the underground wiring conduit runs.

There was one webpage I ran across that let you put in what's been spent and the total wattage of the system and get what a KWH would actually cost. By doing the work myself, and finding solar panels on clearance or on sale, it said my system would provide electricity for .07 cents a KWH...

It's taken longer than expected, in view of "Life" getting in the way of plans. Not only is there a good feeling of buying solar bargains from the profits of selling garage sale collectibles and precious metals before they took their tumble, I've found and kept much of the Sterling jewelry, some 10kt,14kt, and 18kt gold jewelry, and a lot of antique woodworking tools I would never have owned if it wasn't for being out and gathering funds for this solar project.

Thanks again for your help.

Cariboocoot

Re: Batteries and 3 FX80 controllers

Okay note on the Trimetric battery monitor:

If you're going to include one of those it makes the configuration of the negative side a bit different, as you will have to join all three battery strings together on one side of the Trimetric's shunt and connect all the negative wiring for controllers and inverters to the other side. You may need two separate negative bus bars, one for batteries and one for controllers & inverters, with the shunt in between them.

Sorry about the 'no diagrams' but each system tends to be different and their aren't off-the-shelf schematics for every configuration. I could work full time drawing wiring diagrams, but since no one is paying me to do so ... I'm not going to.

vtmaps

Re: Batteries and 3 FX80 controllers

Cariboocoot wrote: »

You may need two separate negative bus bars, one for batteries and one for controllers & inverters, with the shunt in between them.

Sorry about the 'no diagrams' but each system tends to be different and their aren't off-the-shelf schematics for every configuration.

Take a look at the wiring diagrams for Midnite's ePanel... they pack quite a few bus bars in those boxes. You will be hard pressed to put together a more cost effective solution. If you don't want an ePanel, look at their wiring diagrams anyway... it may give you some ideas.

The ePanels formerly had a DC GFP device in them. After Midnite started selling their own charge controller (which has a built in GFP) they have stopped routinely putting a GFP in the ePanel. The Outback controllers do NOT have built in GFP. If you need a GFP, you will want to look at Midnite's older wiring diagrams. (they still sell an ePanel with GFP for use with Outback controllers).

--vtMaps

BilljustBill

Re: Batteries and 3 FX80 controllers

Cariboocoot wrote: »

Okay note on the Trimetric battery monitor:

If you're going to include one of those it makes the configuration of the negative side a bit different, as you will have to join all three battery strings together on one side of the Trimetric's shunt and connect all the negative wiring for controllers and inverters to the other side. You may need two separate negative bus bars, one for batteries and one for controllers & inverters, with the shunt in between them.

Sorry about the 'no diagrams' but each system tends to be different and their aren't off-the-shelf schematics for every configuration. I could work full time drawing wiring diagrams, but since no one is paying me to do so ... I'm not going to.

Wiring the trimetric shunt is something I hadn't thought through, but I may need to go copper buss bar hunting again. I have several sheets of the 9-ply Baltic plywood, but is seems there should be something better for mounting buss bars and the Outback equipment. Any ideas there?

I fully understand about the wiring pics and schematics being unique to each system. Time is money and one can only be so chartable on a public forum such as this. If you and other members have seen diagrams and/or pics of wiring and fusing a multi array and battery system like mine, posting will be surely appreciated.

Bill

Cariboocoot

Re: Batteries and 3 FX80 controllers

You're up against the situation where your choices for insulative mounting material are wood and plastic, both of which are unfortunately combustable.

Have you looked at MidNite's E-panels? http://www.solar-electric.com/misoe.html
As-is may not be exactly what you want, but if you talk to them they may be able to accommodate you with a connection box that has just what you need for tying it all together.