Looking to expand off grid system, needing input/opinions

dbarnard67

OK, been off grid for about 3 years and wanting to expand it a little bit.  I currently have 6848xw+ with the midnite wiring center, midnite classic 150, Schneider AGS with Kohler 12RES for backup and 18 280 Watt panels wired in groups of 3 to a midnite solar combiner box coming into the schneider setup.  Here is what I am wanting to do.  I haver 18 more of those exact same panels.  Would like to add 6 or to just help out with those early morning and late evening sun positions, and will probably just do another midnite classic 150 connected to the existing.  Additionally I have my garage, small barn/workshop and wood boiler pumps running from this system.  I am wanting to set up another independent system out there that could also be a "hot backup" for the home.  What are your recommendations for affordable, but reliable ( I think that still exists, lol) inverter/charge controller units that would be able to back up the feed to the house in case of emergency.   Homes heaviest load would be about 4500 watts.  These buildings would only really pull about 3200 watts, so if I am a little light on the house if it is an emergency then I would just watch my power consumption while on the lighter system.  I already have 12 300W panels that are new that could be used for it and a solid FLA bank that is 430ah at 48v or 24V I could double that, not sure if I should do 48v or 24v open to thoughts on that.  Hopefully I have given everyone enough background to at least start a dialog on it.  Thanks.

BB.

I don't know what a "67848xw+" is... I guess an XWpro 6848 Schneider Conext hybrid inverter?

The battery bank for that inverter is 430AH @ 48 VDC or 860 @ 24 VDC battery bank (if rewired)?

18 * 280 Watt = 5,040 Watt array?

Somewhere in the Chicago IL area?
http://www.solarelectricityhandbook.com/solar-irradiance.html

Chicago
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 48° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
2.80	3.42	4.13	4.57	4.87	5.18
Jul	Aug	Sep	Oct	Nov	Dec
5.36	5.06	4.98	4.23	2.90	2.60

For a flooded cell Lead Acid battery bank with a 6.8 kWatt AC inverter--Suggest something like a 680 AH @ 48 volt battery bank as a good starting point to use the full capability of the inverter (starting surge/running max continuous power).

You are full time off grid with this system now?

What is your daily Watt*Hour consumption... How deep do you cycle your battery bank (75% SoC typically overnight? What happens on dark overcast/stormy days--How deep of cycling)?

What are you looking for from they system? Seperate battery bank+inverter+panels+etc. for truly redundant power?

Does the system meet your needs today? If not, what is it that you want (have to use the genset during winter to bulk up battery bank? Want more energy for more loads--Computers, family, more water pumping for irrigation, etc.)?

I am not a huge fan of separate systems for a common need (powering one home/shop area with two (or more) separate systems)... 2x more hardware to support (hardware has a ~10+ year life). Separate battery banks to monitor/maintain (depending on batteries--Typically 5-10 year life--Unless something "goes wrong" and kills a bank).

And you have two systems--Either both need to be oversized (for reduced active load management)--Or one system may have "excess capacity" while the second system does not--Shuttling power/AC connections between systems to "balance" load vs supply).

Which would be better? 2x solar power systems or 1x solar power system and (possibly) a second backup genset/larger fuel supply/etc.?

Depending on where the price of fuel goes--The cost of solar ($$/kWH) vs the cost of genset operation ($$/kWH of fuel burn)... It may not be that much of savings when you add initial solar hardware costs/new hardware every 10+ years, new battery banks every 5-10 years, etc.) vs a "cheap" genset and fuel (that is only burned when needed for backup/bad weather)...

Perhaps look at your present solar power system and add battery bank to bring up to "capabilities" of the 6.8 kWatt hybrid inverter... Possibly a bit more battery bank AH for a day more of bad weather?

Solar panels are relatively "cheap" these days... Adding more panels to your system is usually pretty nice (save on genset runtime) and can make your battery bank "happier" (less deep discharges, faster recharging after bad weather/heavy load days). Look at panels facing south east/south west to give you more "hours on charge" (lead acid banks really like time on charge--Facing some panels SE and others SW, give you a "virtual tracking array" and more hours in morning and late afternoons.

Ideas....

-Bill

mike95490

If I was in your shoes, I'd
a)  get a 48V, MPPT 60A 150V controller and wire it to existing batteries
 b) panel it with __ strings of 3 facing east and ___ strings of 3 facing west

That would boost your morning and afternoon charging quite a bit.  Add strings of 3  in the directions that it makes sense, if mornings are cloudy, focus on a boost in the afternoons

dbarnard67

Umm, ok, might need clarify here.  Current system is fine, I am wanting to add a separate system that will run my out buildings and serve as a hot standby

BB.

It comes down to the typical load questions... Peak Watts (you said), how many watt*hours per day, physical location (free of shading?), any seasonal variations in load (winter/summer), backup genset (share home backup with outbuildings), conditioned space (sub freezing space will temporarily cause lead acid batteries to have less AH capacity--Lithium Ion batteries--Cannot run in freezing conditions), do you want auto-start genset e

And is cost an issue (it always is--But the question between FLA and Lion is becoming are big question mark for many)?

All in one systems (inverter-chargers, to inverter-charger-solar chargers) vs "piece part" back box systems (inverter, solar charge controller, AC to DC charger for genset, etc... Sort of nice to have separate black boxes to make repairs and bypasses easier (vs one failure taking out entire system).

Although, the "all-in-one" systems seem to offer a level of integration & automation that is almost impossible with stand alone hardware. And wiring/configuration becomes much easier.

And the issue--Many all-in-one systems are imports... Will you have/need local support vs the "non-support" from some/many of the off-shore firms?

More or less--I suggest that 10+ years is a "good life" for power electronics. "Simple" black boxes are probably easier to replace when needed years down the road. Integrated systems after 5-10 years pretty much lose any support (live support, parts, repairs) after that period... And you are left with the same decisions again in a decade or so (what hardware, replace all or try to keep piece part systems going a piece at a time).

With lithium ion batteries, we are at that point where BMS systems are becoming a "product" in themselves... Questions about integration with charge controllers, what happens when "protection" is required/protection systems "kick in" and cut battery power to your house on a cold winter night...

Obviously--You have a lot of experience and knowledge right now (your own home running well on an off grid solar system)--What is it that you are looking for from us to try and help/discuss?

-Bill

dbarnard67

Thank B.B. and not trying to be difficult.  Whole idea here was this, my home is up and running.  I have a barn/workshop and an a separate one car garage that is 20x30.  Having stated what I have in my home with the Schneider equipment, I was just looking for anyone's thoughts/comments on suggestions for a separate system for these out buildings.  Like I said above, those loads would be 3500 or less more like the 1200 to 1500 watt range continuous with only the 3500 being a spike for a few seconds.  When I am looking to build this I think it would be good to have it spec fairly close to that 3500 peak output because it would be a good "hot" backup for the house in case of emergency.  I have the panels, and the FLA from my home as I have kept them cycled "just in case".  So you started hitting on it, should I spend more and go a Schneider 4048, and midnite classic or the all in ones.  I have very little experience with the all in ones.  Not worried about support as I am usually left to my own to figure it out.  Thanks again.

Dave Angelini

We do this alot for people who want redundancy offgrid. The issue of having 2 split-phase masters on the same xanbus has been solved with Gateway facility.  You really are missing many of the advantages by mixing different makes of equipment. You just lose too much solar data that makes this easy on a smart phone. The Soc and all the remote config really makes it easier for a significant other who may not want to learn all of the details.

Typically the system below each has it's own battery for complete redundancy offgrid. Each can be shown on a screen but typically we leave one system off for protection reasons.

 Agree with Bill on the all in one approach. Just wrong for offgrid unless you have the spare all in one! Alot of the all in ones also spec watts in peak and not RMS like XW. None I have seen are as rugged and proven over 17 years now. Nice to be off the grid these days!
Good Luck !

dbarnard67

Thanks for the input Dave, always good to hear your point of view on these.  Would it be a mistake to do a 4048, for cost savings (or should I not mix that with the 6848).  Since this is for the outer buildings the draw would not be as great and if it is for emergency backup I would just have to watch how much I load up.  Or should I just hold off a little bit until I can get a little more in the fund for this project and do the 6848?

Dave Angelini

I think the CSW is a great spare to XW. It gets you the ability to charge with a 120 or 240vac genset. The downside is it is like all of the 4KW inverters, it can get unbalanced in split phase applications in a home!  Drop me an email below.