Stacked Flexpower

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Stacked Flexpower

Postby bear_essentials on Thu May 24, 2018 8:38 pm

I have 2 identical systems each comprised of an FP8048A with 7320W PV and 1150AH battery banks ea. How do I stack them?
They are 75 feet of wire away from each other. Each "system" has its own Mate3, battery management, and hub. The manual indicates that I should unplug the inverters from the "slave" hub and connect them to ports on the "master" hub. This makes sense that the "master" Mate3 is bringing the inverters online as needed, and is synchronizing the sine wave of the master and slave inverters.
But what about the configuration options? Does the master Mate3 need to be programmed with the combined battery capacity, since the inverter and charger are a single unit, or does the slave Mate3 magically handle the charging of its batteries? If the former is true, then what about the fm80s and the Mate3 on the slave system? What do they do?
I guess I'm asking for a good description of exactly how each of the components works together in a stacked flexpower system? I found a rudimentary wiring diagram in my documentation but no good description and no indication of the configuration changes needed to support stacking.
Thanks,
Bear
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Re: Stacked Flexpower

Postby raysun on Fri May 25, 2018 8:34 am

If I'm not mistaken, the OB stacking architecture is based on multiple inverters/single battery. Only one Mate and FNDC are used.

You have a whopping huge amount of power production in your two systems. What are you trying to accomplish by stacking?

Did you buy a couple of new arc welders? ;)
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Re: Stacked Flexpower

Postby bear_essentials on Fri May 25, 2018 12:45 pm

It is a bit of overkill.

This particular system is off-grid. We have constructed a chapel, sacristy, vesting/resting house and a pavilion that will all be powered from these two combined systems.
These buildings are not located near utility power and we don't want the poles spoiling the view. We might eventually trench some under-ground power to the site, but not anytime soon.
The major draw will be the AC units for the vesting/resting house. The rest is just some lighting and sound equipment, and probably a bottle fridge for cold water.

When I run the numbers and assume support for 3 days without much sunlight, we will barely have enough battery capacity. The inverter capacity is overkill.
bear_essentials
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My RE system: Flexpower Radian 8048A, 1000AH battery bank, CSUN 305W x 24, Midnite Solar combiner

Re: Stacked Flexpower

Postby raysun on Fri May 25, 2018 12:59 pm

Given the physical separation, and the separate battery banks, I don't think stacking via OB design will work. However, it might be possible to cobble together some relay logic that uses the two systems sequentially - System 1 on day 1, system 2 on day 2, system 1 on day 3, etc.
raysun
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Posts: 239
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower One: FX3048T, MX80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 4Sx3P)

Re: Stacked Flexpower

Postby bear_essentials on Fri May 25, 2018 4:29 pm

Bummer.

So is there nothing out there that will take the 2 feeds and correct the phase difference to produce a single output?
bear_essentials
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Posts: 26
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Re: Stacked Flexpower

Postby raysun on Fri May 25, 2018 6:24 pm

Sure, but what's the benefit to pouring out of two buckets at the same time v.s. pouring out of one, then the other?

I bet you could finesse the built-in smarts on the OB gear to make one of the inverter/charger/battery systems be in the role of "Off Grid" and the other be in the role of "Grid". The system has a lot of logic to manage balancing Off-grid and Grid consumption. It could be made to be very smooth-functioning and automated, I'd think. No additional stuff to get, and no foreign object integration needed.
raysun
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Posts: 239
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower One: FX3048T, MX80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 4Sx3P)

Re: Stacked Flexpower

Postby hendrik krijt on Sat May 26, 2018 11:11 am

Bear

I have 2 battery banks of differrent make and charging parrameters. I have 2 outback inverters parrallel stacked with a hub and mate. Each inverter is connected to one of the banks. Using a contactor and voltage monitoring relay, I parrallel the 2 banks if the voltage is below that of the lower requirement bank, and split them when the voltage goes higher. One bank has 2 fm80's, the other has 1 fm80, each programmed individually according to the bank it is connected to. In operation, the inverter connected to the lower voltage bank draw propotionately less current, and the one connected to the higher voltage bank draws more current. As soon as the banks are parrallel(voltages equal), their currents are equal.

I have no battery monitoring system, I monitor them myself.
I think you could have one system with batteries, chargers, battery, monitoring system(no inverter) run its self, the other system running with 2 inverters parrallel. I cannot recall what the max cable run is between the inverter and the hub. The inverter with less load can then help the one with more load, also the one with more battery capacity will contribute proporionally more to the load.

I have never shyed away from experimenting to find novel solutions for novel problems, in this case as bonus found that the inverters can share the load in proportion to the battery capacity each has available.

My 2cents worth!

Lots of South African Southern Sunshine to you all!

Hendrik Krijt
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Re: Stacked Flexpower

Postby bear_essentials on Sat May 26, 2018 3:18 pm

Thanks. So is 50 amps the top end continuous output for a grid tied inverter?
If I feed the one inverter output to the grid in of the second inverter, what is the limit on the combined output of the second “grid tied” inverter? I’m not sure I’ll need it, but I was hoping to get a combined 100amps max output.
bear_essentials
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Posts: 26
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My RE system: Flexpower Radian 8048A, 1000AH battery bank, CSUN 305W x 24, Midnite Solar combiner

Re: Stacked Flexpower

Postby hendrik krijt on Sat May 26, 2018 10:39 pm

Bear.

I have no experience of connecting the output of 1 inverter to the grid input of a 2nd inverter. My system parrallels 2 inverters to syncronize their output frequency and both their outputs feed into the common load, in this case the full output of the 2 inverters added together is available to the load. In my case I have each inverter connected to its own separate battery bank. This is what may work for you, 2 inverters connected to one hub, stacked to syncronize and help each other drive the common load, your current 2 AC loads connected with appropriatly sized cables. Each battery bank monitored and charged separately by their own array of solar panels, own charge controlers, own battery monitoring system.

Lots of South African Southern Sunshine to you all!

Hendrik Krijt
hendrik krijt
Forum Whiz
 
Posts: 35
Joined: Sat Dec 31, 2016 6:33 am
Location: South Africa, KZN province
My RE system: pv=4.9Kw, 2xflexmax 80, 2x 24v-240v 50Hz outback inverters, fla's 12x Willard rt25 tubular 2v cells. rsa, kzn prov. (may change to aquion batteries)


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