Requesting opinions/feeback on this 6.12KW Off-Grid System

**extrafu** · 11-03-2016, 07:12 PM

I guess you meant:

1 x Inverter Conext XW 6848
3 x Xantrex MPPT-60

?

**cgofish** · 11-03-2016, 07:18 PM

Originally posted by extrafu

I guess you meant:

1 x Inverter Conext XW 6848
3 x Xantrex MPPT-60

?

Thanks for catching that! I updated the quantities in the original post.

**Mike90250** · 11-03-2016, 10:38 PM

You are designing an awfully large system for some apperently light loads. Without air conditiong, I'm not sure how you plan to use all that power.

Additionally, unless you like beta testing expensive new gear, avoid the Li battery and use lead acid at least for the first year, and have a better idea of what your usage is.
I have 5KW of PV and in summer, run a large irrigation pump, and still have 300 min of Float every day, 2 fridges and a freezer help use the power too, along with a washer and gas dryer.

**cgofish** · 11-04-2016, 07:51 AM

mike90250, Thanks for your comments. I do have some extra capacity built into the system but that is by design. We have two adults and one young adult that work from home, not necessarily with heavy load equipment but we do pull some marathon shifts of 2-3 days with little sleep and lots of work and would prefer not to have to run the generator a lot during those periods especially we we pull all nighters.

Makes sense on what your saying on the batteries and I'll definitely look at options on some cheaper solutions. I was originally thinking along those lines as I figured I could get some good but reasonable batteries to start and then years down the road purchase something more substantial as I'm assuming like most of the other solar equipment the prices will keep dropping down a bit.

From what I've been reading it seems like the Schneider gear and the panels are of good quality and I don't see many folks complaining about them. My last part of the puzzle I'm still trying to figure out is the generators. Originally I was thinking along the lines of one of the small Honda EU2000's with the second companion unit or the equivalent Generacs that are out now and I can just drag them out and hook them up as needed. That would also allow me to use them around the property for other maintenance tasks. Any opinion on that or is it typically standard to have a dedicated generator with the auto start connected to the system?

**Mike90250** · 11-04-2016, 08:34 AM

do you have any need for 240VAC, water pump, welder, big shop vac, long distance power run? The XW inverter can be configured from the native 240V to 120V.
Whatever it's output voltage is jumpered for (there are software and hardware changes needed to switch) is the only generator voltage it can accept charge from.
You CAN use a 120V generator via a 120-240 step-up transformer, to charge batteries via the XW inverter. That's how I charge off the little inverter genset, or I switch cables and charge off a 240V genset.
What are your "heavy loads" when you pull an all nighter ?

The only thing totally missing from your data, is loads. Lights ? Fridges? Band saws? Air compressors? Toaster ovens ? CRAY computers ? 1 USB phone charger?
Without Load information, everything is a guess, and 95% of the time, loads are underestimated. +6Kw of solar and 10Kw of battery is quite un-balanced.

**cgofish** · 11-04-2016, 09:12 AM

mike90250, Now that I'm getting this feedback from you I'm wondering if they designed this prior to me dropping the mini-split air conditioners from my wish list. Although I do want a system that I can expand on if I do add those.

I may need a small pressure pump when we run water from the cisterns but normal every day water usage will be from the city and we have enough pressure to run without a pump.

As far as a long distance run I do have a need to run a few small electronics to support our internet access and gate about 500-600ft away. I was thinking about using a small system to support it stand alone as I'm not sure if I can run power that far. I posted about this here: https://www.solarpaneltalk.com/forum...et-electronics

Our all nighter equipment isn't anything major but we will have 2-3 laptops running, an external LCD monitor and the girls will be cranking out good using multiple sewing machines and an embroidery machine, none of which is commercial level equipment.

Can you explain your comment on "+6Kw of solar and 10Kw of battery is quite un-balanced". Not disagreeing with you I'd just like to understand more of what you mean by it being unbalanced.

I thought I had a better list of load requirements with the actual load info per device. I'll have to work on that but here's the generic list. Note that I've also researched a bit more to find more efficient refrigerator and freezers. I've also had the electrician wire most of the wall outlets in the kitchen and areas that support the office and consumer electronics with switches so that I can disconnect them to reduce phantom loads.

Load list:
Refrigerator: Summit FFBF181SSBIIM Energy Usage/Year: 441.0kWh/year
Freezer: GE FCM11PHWW 218 kWh/yr

Occasional Use
Microwave: Summit SCM853
Ninja Mega Kitchen System (BL771)
Toaster

Sewing Work
Iron: Panasonic NI-L70SR Cordless Iron
Steamer: Homedics PS-251 Perfect Steam Deluxe Garment Steamer
Singer Serger Brother Lock 1034D
Singer Patchwork 7285Q

Office
2 Laptops
25In LCD Monitor
Firewall Router
2 Wireless Access points POE
HP 6700 MultiFunction Printer

Entertainment:
48In LED TV
Dish Network tuner
Sonos Play 5
Sonos Play 3
Sonos Play 1

Bath:
Hair Dryer
Curling Iron

All House lighting will be LED.

3 USB phone charges

Large Ceiling Fan in Living room
3 Small Fans in Bedrooms Haiku L series.

3 Unit/Zone AC for bedrooms (open for recommendations on models) All rooms are small. ***Removed from system load ***

Washer/Dryer - Have not picked it out, will be new and dryer on propane.

Thank you again for helping educate me on all of this!

**karrak** · 11-04-2016, 09:25 AM

I had a look at the Ex-Energy website and couldn't find any more information than what you have provided which I don't think is enough to make a decision to use these batteries. You need to know what exactly the BMS does. The two main functions of a BMS are to keep a battery balanced and to warn and/or disconnect the load or charger in the event that any of the individual cells go out of the normal voltage range. What functions does the Ex-Energy BMS provide?

The maximum charge/discharge current of only 80A is also puzzling. A 240Ah LiFePO4 (LFP) batteries should be able to easily sustain a charge/discharge current of 240A.

As Mike has said this seems a very large system for the small amount of use that it will be getting. Our system has only ~1.2kW of solar panels and ~10kwH (180Ah@48V) of battery storage and provides on average ~3kWh/day in winter and ~5kWh/day in summer. We use the power for all our cooking in summer and boiling water and limited cooking in winter as well as lighting, computers etc. We haven't needed a generator in the three and a half years we have had the system. Another LFP system that is worth looking at is the one that steveg has put together. His system average daily use is around 12kWh, his battery size is ~15kWh and his solar array size is 4kW.

It might also be worth looking at the new Tesla Powerwall 2. If it is suitable for off-grid power and will be available in the time frame that you need it will be hard to beat at US$5,500 for a 14kW battery with BMS, charge controller and a 5kW inverter thrown in.

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

**cgofish** · 11-04-2016, 09:33 AM

Thanks karrak. I'll see if I can get better details from them on the battery. Agree I couldn't find much information either on their site. I'll also research the Powerwall 2. The folks that I'm using for the install are "certified" for the Teslas. From what I understood about the current model Powerwall is that its not really suited well for off-grid but that may have changed in the Powerwall 2.

**extrafu** · 11-04-2016, 11:46 AM

Originally posted by karrak

It might also be worth looking at the new Tesla Powerwall 2. If it is suitable for off-grid power and will be available in the time frame that you need it will be hard to beat at US$5,500 for a 14kW battery with BMS, charge controller and a 5kW inverter thrown in.

Out of curiosity, where have you read it includes a charge controller?

**Mike90250** · 11-04-2016, 05:13 PM

OK, sewing machines, steamers, irons..... now the gear list is adding up. Maybe even a mini-split too !

Since some of these are heating loads, there is going to be some "spiky" draws. First thing to remember, don't power it all up at the same time, Switch it on in "waves" so it has a chance to shed some of the loads as the thermostats start to regulate.

Now as to un-balanced. 6Kw of pv can produce 100A @ 58V (charging voltage) A 200ah bank is too small to safely absorb that amount of power. When the battery is full, you will have a lot of idle solar PV capacity. Wasted capitol $ in the summer, but in winter/cloudy weather, it will help reduce generator run time.

Inverter: Conventional planning requires 100ah of lead acid battery per 1Kw output, to prevent 60hz ripple from damaging the battery bank, Li cells are lower resistance than lead acid, and will be more resistant to this effect. But it's not magic, Li won't run large overnight loads any longer than Lead acid would. 200ah is 200ah

Generator. For this, I'd suggest leave the inverter at 240V, wire the place conventionally like any other split-phase NA building, Most generators over 4Kw should have 240VAC output. Any generator with decent regulation (RPM & Voltage) will make the XW6048 happy, and it will charge from it. It's happy with my antique 6/1 generator.

**karrak** · 11-05-2016, 08:55 AM

Originally posted by extrafu

Out of curiosity, where have you read it includes a charge controller?

It is an educated guess. The Powerwall 1 uses one single high voltage DC power connection (350-450 volts) to charge the battery and send power to the inverter and regulates the power flow via commands sent over the CAN or Modbus to/from the inverter. I am assuming that the Powerwall 2 they would be still using the high voltage DC power connection connected directly to PV panels and a separate AC connector from the output of the inbuilt inverter as well as other communication interfaces.

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

**karrak** · 11-05-2016, 09:23 AM

Originally posted by Mike90250

Now as to un-balanced. 6Kw of pv can produce 100A @ 58V (charging voltage) A 200ah bank is too small to safely absorb that amount of power. When the battery is full, you will have a lot of idle solar PV capacity. Wasted capitol $ in the summer, but in winter/cloudy weather, it will help reduce generator run time.

This is true for lead acid batteries not lithium ion batteries, a 200Ah lithium Ion battery will happily charge at 100A

Inverter: Conventional planning requires 100ah of lead acid battery per 1Kw output, to prevent 60hz ripple from damaging the battery bank, Li cells are lower resistance than lead acid, and will be more resistant to this effect. But it's not magic, Li won't run large overnight loads any longer than Lead acid would. 200ah is 200ah

For lithium ion batteries 100Ah (@48V) will give you around 5Kw output. If you are only going to run the large overnight loads for long time periods on an irregular basis it probably makes sense to run a generator rather than having extra storage for the few times that you will use it.

For lithium batteries a small generator like a EU2000 is probably sufficient as long as the output from the generator will cover the average load with some to spare to charge the battery. The only constraint on charging lithium batteries is the maximum charge rate. Remember that you do not have to fully charge a Lithium ion battery but just put enough energy in it to get through the night.

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

**Mike90250** · 11-05-2016, 02:34 PM

The only constraint on charging lithium batteries is the maximum charge rate.

Boy, are you going to be in for an expensive surprise some day.

**karrak** · 11-05-2016, 06:09 PM

Originally posted by Mike90250

Boy, are you going to be in for an expensive surprise some day.

And what is that comment supposed to mean?

Requesting opinions/feeback on this 6.12KW Off-Grid System

Requesting opinions/feeback on this 6.12KW Off-Grid System

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