Schneider Conext XW+ (NO Solar, Grid powered ONLY) Backup power for IT Room critical loads

Radi8Solar

I have completed an install for a (qty: 3) Conext XW+ system. 
(1) single, large battery bank --> (qty: 12) 12V 220Ah Gel Battery (Victron)
I have installed the system, including the 3phase breaker kit
No MPPT connected, only inverter chargers and battery bank!

This is for an industrial client that wanted backup power for the IT & Quality Control room. It is a 3phase setup with no solar attached, no generator, ONLY grid powered. 

I plan on designating each inverter charger as their own Master, no slave units. Master 1, Master 2, Master 3.
Question: Should each Master be split phase or single phase?

I am trying to configure the settings for this and I am having to walk into this blind, as my solar installers have never done a 3phase Schneider install before.

Below I have described my suggested basic settings and would greatly appreciate some guidance on this!

XW+ Basic Settings

Battery Type:                      Gel

Battery Capacity:               2640 Ah

Charger Enabled:                YES

MAX Charge Rate:            100% 

Charge Cycle:                     2-stage

Recharge Battery Temp:   Warm 

Recharge Volts:                  48 V

Inverter Enabled:                YES

AC Input Priority:               AC1 

AC1 Breaker:                     60 A 

AC2 Breaker:                     0 A

Low Battery Cutout:           44 V

High Battery Cutout:          65 V

XW+ Advanced Settings 

DC Config                     All HouseBatteryBank1

AC Out                          All ACLoad1

AC1 Connection           ALL Grid1 

Bulk Voltage                  56.8 V

Absorb Voltage             56.8 V

Float Voltage                 55.2 V

Vic

Hello Radi..,  Welcome to the Forum.

Just a quick comment.   Your battery bank is not as large as you think.  The total battery Capacity is 3 X 220 Ah.   

When batteries are connected is series,  the voltage increases,  but the Ah Capacity remains the same as a single battery.

Generally,  multiple strings of batteries are not a good way to try to reach a Capacity goal.   Rather,  it is often a better idea,  to choose batteries that have the necessary capacity with a single string of 2 V,  or perhaps 4 V cells,  at least when specifying Lead Acid batteries.

FWIW,  Vic

Radi8Solar

So, having 12 (12V220Ah) batteries in 3 row of 4 batteries wired to the 3 battery breakers is incorrect?

Vic

Like many things,  there are many shades of grey in our battery systems.

Parallel battery strings can cause problems with charge and discharge current sharing.   Over a period of time,  batteries and strings of batteries  drift apart.   And,  with sealed batteries,  it can be difficult to determine how well each battery string is being charges.

Having one string of batteries,  where each battery has sufficient Capacity for the job that needs to be done eliminates  current sharing worries,  and using 2 V LA batteries,  allows for terminal voltages of each cell to be measured.   And,  if needed,  if a cell becomes lazy/bad,  then that single cell can be replaced,  so you might not be discarding potentially,  five good cells of a 12 V battery,  that has one bad cell,   and so on.

It is not clear exactly what is the nature of your battery bank.   Weather each inverter was planned to have its own 220 Ah battery string,  of if all inverters share a single battery bank.

BUT,  in any case,  each inverter/charger needs about 100 Ah of battery for every kW of power that it needs to provide (this is an old rule-of-thumb),  but not a bad place to start in system desigh.

Others here know much more about Schneider products,  than I.  Just wanted to mention the way Ah Capacity of series strings of batteries is determined.

Good Luck,   Vic

Radi8Solar

The battery bank is one large bank for the 3 inverter/chargers which each function as 1 phase of the 3 phase system. They all communicate via the SCP and the Conext Gateway. I was going to set each leg to have a battery capacity of 880Ah, however the total Ah would be 2640, correct?

mike95490

is your 3 phase grid feed, coming from a transformer ?

I foresee an issue if one phase drops and the inverter kicks in, and is not synced to the other phases.

Also, your batteries are GEL, so therefor can only be recharged SLOWLY. There should be a MAX recharge rating, around 10 amps, you don't want the inverters to recharge and cook the batteries on day one.  Use the charge voltage for FLOAT service.  Your absorb time should be set pretty low, half an hour maybe - you don;t want to cook the batteries too long in absorb

Vic

Well dang,   just lost another post  ...

Radi8Solar

Hopefully this will offer some understanding, as I am extremely lost in figuring out how to configure the correct specs with Conext Gateway. 

Vic

Radi8Solar said:

The battery bank is one large bank for the 3 inverter/chargers which each function as 1 phase of the 3 phase system. They all communicate via the SCP and the Conext Gateway. I was going to set each leg to have a battery capacity of 880Ah, however the total Ah would be 2640, correct?

Will try again ...

NO,   The Ah Capacity of a single string of batteries is 220 Ah @ 48 V.   Total for the battery is 660 Ah @ 48 V.

The power that the battery can deliver IS multiplied by the number of batteries in series and times the number of battery strins.

This is a relatively tiny battery  verses the amount of power that the XW inverters are capable of delivering.

AND,   Mike,   seems that if there is a way of telling this three phase stack of inverters that they are in a three phase config,  then there must be a way that the system will detect a loss of any phases,   IMO.   FWIW,   Vic

Radi8Solar

When programming each of 3 leg/phase:
Each phase separate --> 220Ah @ 48V 
Each phase the exact same --> 660Ah @48V

I am trying to program the Gateway and my Schnider rep told me each inverter charge needs to be Ph1 Master, Ph2 Master, Ph3 Master. However, the option are single phase master, phase two master, phase 3 master? Ideas

Vic

Hi again Raid8..,

Two things;   Would suggest that you get some help on this system.

AND,  it is important to size the battery bank  based upon the loads that it must supply,  and for some specific period of time.

Especially with NO other charge source than the Grid,   this can be quite important.

FWIW Good Luck,    Vic

Dave Angelini

As you have been told this is an extremely small bank for this application. Just backing this up, no matter if this is split phase or 3 phase.
It will not work correctly because of the battery size. Sorry !

Radi8Solar

The battery bank was sized based on the critical loads needed for a MAX 6 hour period. It is only to supply power in the event the grid is down for a short period of time. It is a commercial client implementing a corporate, global  "Green" initiative, instead of purchasing a generator. They are in the Oil & Gas industry. Generators would give them a negative global footprint, in their eyes. It was sized for future expansion, in the even they want it. There is bit of "luxury" to this setup that is not common in installation.

I own my own company called Radi8 Solar Solutions, LLC and I have been very successful in solar installations. However, I am not too proud to admit this is my first 3phase battery backup / grid tied system, which is a rare endeavor using Schneider products. 

I specialize in Solar Brokerage and procurement. The installers I source throughout Texas have not done a 3phase instal, which you can probably see when you try and source any Field Services via Schneider. They are all up North or international. I am trying to complete this project by figuring out a solution, passed the naysayers. I am committed to find a resolution for said client. If anyone knows someone I can PAY that is in the South Texas area I would be more than happy to give them a call!

mike95490

Regarding the battery size, what is the load the inverters will be powering ?
500w   1kw    2kw      If the load is small, the batteries will hold up for a while, but if all inverters are pushing 4kw out, the batteries are going to crash quickly and the inverters will shut down

Dave Angelini

Mike is right but I doubt the OP would buy (3) XW+ with over 25.5 kw of power for an hour to run small loads. And then why buy 3?
The OP can contact me if he want a consult but I probably have burned my bridge. 

The bank sizing is more than just doing the math. The inverter has to stay regulated over its specified voltage range. It is too small of a battery to do this, and certainly if it works, it won't very long. Without knowing peak power and the amount for 6 hours, it is a moot point. Each charger has 140adc of charge and this alone will kill this battery if not properly configured.

Radi8Solar

Each Inverter/Charger XW+ is 6800 watts

Total for both rooms:

           40A x 120V = 4,800 watts

(MAX) 50A x 120V = 6,000 watts 

Reference: 

• Amps and Voltage of the IT & Quality Control room panel. 

• 40amp 3phase 208v for both

• Max draw / critical load, including and HVAC or Electric Heating?

• 50amp 3phase 208v 

Radi8Solar

Biggest issue is grid down for 30 min to 2 hours. The 6 hour option is to only run a few computers. 

BB.

Just out of curiosity, why use an XWpro for non-solar emergency backup power?

Why not a standard industrial UPS?

Don't know specifically about the XW family, but many Grid/Off Grid/Hybrid Inverter systems may not really guarantee a fast/glitch free switch over.

A continuous conversion UPS with failover of some sort (the old issue of how do you know your "backup" or two are still working weeks/months/years down the road) would generally give a much "cleaner" transfer event.

Years made systems that use a mainstream rack mounted UPS system driving rack mounted PCs. And even though I tried any sort of power interruption, brown outs, 1/2+ cycle interrupts... The UPS would switch over cleanly.

HOWEVER, in realize power failures, it appeared that about 1 in 10 mains failures would reboot the rack-mounted PCs (which I never could reproduce in the office).

https://www.falconups.com/ups-comparison-online-standby-line-interactive.htm

Also, what is the battery type/testing/replacement plan? With gensets, starting and running 1-4x a month was not unusual, plus the bigger installations (such as modern hospital gensets) were able to feed power back into the utility mains (at least the fuel was generating useful power vs just dumping into a load bank).

-Bill

Dave Angelini

Bill, I think he is using XW+ and with a similar 8 msec switch time. XW+ is used for this kind of application. Yep they are 6.8kw continuous, 8.5kw for an hour and 12kw for 5 minutes. These power levels need a battery that can hold voltage or the Inverter will start putting out warnings, then faults, and after a few more seconds, out go the lights. He is using the grid for charge also. 

Anytime I have ever used XW in large systems the minimum requirement is 400 amp hour (20 hour rate) minimum battery per inverter. This goes back a long time now and it may not be made as clear in the new manuals. For 3 phase there is an excellent manual at Schneider.

Radi8Solar

These are XW+ 6848! The UPS system they had onsite was depleting within 30 minutes max. 

This system is grid powered, backup only. It is only to be used when the grid goes down for a short period of time to ensure the IT & quality control equipment is still online and transmitting data. Possibly run a single HVAC or Heating. 

The batteries are 12V/220Ah Victron deep-cycle Gel, there is a 2-year warranty. There is an O&M contract where we will replace any warranty claim or replacement product. The LFP option was presented, but the client chose to go with Gel instead. 

These batteries will be used as many times as we can mention power outages, which is rare. If there is a period of time that the grid is down due to lets say, as Hurricane, they will deploy a generator or shut the site down completely. There is a 108kW Solar Carport on the site, but the client insisted to not designate any portion of the Solar to the battery bank. They didnt want to waste a portion of the solar production when the usage of the battery bank would few and far between. 

I really need to find someone who has programmed Schnieder XW+ inverter chargers on a 3phase setup!!! 

Radi8Solar

Dave, 

Is my battery bank not sufficient? This question has not come been presented to me, as the Master Electrician provided the design for this. I am interested in knowing if this is part of my problem?

Dave Angelini

I have given my general advice and there is alot more, that takes my time. I do this to help out but this is not my job. I wish you luck and I am out there by e-mail, text, and voice.

Vic

Radi8.., said,   ...   "Battery Capacity:               2640 Ah   ...  "

Seems to imply,   that  someone thought that that nominal battery size was appropriate  for  this application   ...   just sayin'

Wish you all the best!    Vic

Radi8Solar

I appreciate the help. 

My calculations for a 4 series, 3 parallel setup is:

12 x 220 = 2640

2640 / 4 series = 660Ah @ 48V

BB.

I think it goes:

• 4 series * 3 parallel strings (made from 12 volt @ 220 AH batteries) or 12 total batteries
• 4 batteries * 12 volt  (at 220 AH) batteries in series = 48 volts @ 220 AH per string
• 3 strings connected in parallel  * 220 AH (@48 volts) = 660 AH @ 48 volts

So, voltage add in series strings. Current (capacity) adds in parallel connections.

For a general flooded cell battery, suggest around 1,000 Watts of AC inverter (or solar array) per 100 AH of battery capacity @ 48 volts.

GEL batteries have low self discharge and can be good for float service. However, at least with USA brands (it seems), typically have a maximum charging rate of C/20 or 5% recommended rate of charge. Flooded Cell and AGM can take C/8 or even higher charging rates (12.5% or ~13% rate of charge). Higher rates of charge should really have a remote battery temperature sensor (Lead Acid batteries; their charging voltage falls with increasing bank temperature). >~13% rate of charge (20-25% for genset charging is done) can cause batteries to overheat, falling charging voltage, charger dumps more current into hot batteries and cause damage or actual meltdown.

With GEL batteries, they can create gas pockets in the GEL next to the plates (high charging current/high charging voltage), which causes a permanent loss of capacity.

GEL are very common for UPS systems (lots of standby, short/high current discharge). Even to C/1 or faster (discharge from 100% to 0% in one hour). AGMs also can support high discharge currents.

Flooded Cell Lead Acid batteries tend to be best at C/8 or possibly C/5 discharge (deep cycle storage batteries)--And can support a few seconds or so of C/2.5 discharge rates.

If this was a flooded cell battery bank, the 1,000 Watts of AC inverter per 100 AH @ 48 volts would be the rough suggested continuous draw from the FLA battery bank (C/5 is 5 hour discharge rate). And FLA batteries are rated at various discharge rates (C/5 is less "apparent AH capacity" than C/10 or C/20 rate--"We" solar homes/cabins tend to use the C/20 discharge rate... For example 5 hours discharge in the evening, for 2 days, and leaves 50% battery capacity at end of two days--For better battery life).

UPS batteries are designed for sever discharging--But the frequently last a a handful of discharge/charge cycles before they need to be replaced (and replace every ~2 years or so for optimum UPS operation).

I think this is the PDF for your GEL batteries (two types, deep cycle and long life.

https://www.victronenergy.com/upload/documents/Datasheet-GEL-and-AGM-Batteries-EN.pdf

Victron gives a chart of discharge rate (C/20, C/10, all the way down to 5 seconds). And as you can see, the apparent capacity falls with higher discharge rates (1 hour rate, ~61-63% of "rated" capacity at C/20 or C/10 rate).

The Victron batteries seem to be very capable, and should last longer than a "typical" UPS battery--But even these batteries have much shorter lives when taken to 20% state of charge (80% discharge).

And these batteries support a 0.2C (C/5) rate of charge (for GEL batteries too?).

Note that batteries can be warranted/replaced for a 20% loss of capacity (vendors can have very different warranty requirements). So that loss of capacity (20%, 30%, or whatever you need) should be factored in too.

Are you using the one battery bank connected to the 3x inverters in parallel (i.e., 48 volts @ 660 AH)?

Or does each inverter get 1x string (48 volts @ 220 AH for each inverter)?

Or do you have 3 sets of battery banks (48 volts @ 660 AH x 3) with each inverter running from its own bank?

On the 3 phase power? The facility gets 3 phase power? Is it 3 phase Delta @ 480 volts, or 3 phase Delta @ 240 VAC (with one phase of split phase 120/240 VAC), or 3 phase Wye (Y or Star) at 208/120 VAC?

Are the loads for the computer room/facility all 120/204/240 VAC single phase? Or do you have some three phase loads too (208/204 VAC)?

There can be some safety issues with 3 phase (I am getting in very deep water--Not my field)--Basically what happens if you lose 1 or 2 phases... Should the entire system switch over, or only the loss phase (only possible with single phase loads). "Single Phasing" operation of any facility is usually not a good idea.

-Bill