Inverter recommendations for 48V off-grid installation

[jsocolof]

Looking for recommendations for off-grid inverters for a system with these characteristics:

• 48V
• un-inspected: off-grid, no building or electrical inspections required
• ~6 KW solar panels expanding to 12-18 KW over time
• PV array would probably settle in at around 400 V, 19 A initially, expanding to multiple arrays
• battery storage (looking at the EG4 batteries at the moment)
• 9100 ft elevation
• many days below freezing, with many also below zero
• ~5-6 KW of inverter capacity initially, expanding if required
• 240 V required
• The cabin will be uninhabited 3-5 days/week
• generator backup, and I have a Honda EU700is generator, currently without autostart

If you have an inverter brand/model recommendation based on your experience, please indicate why you recommend, and pros/cons. I've seen a lot of discussion of issues with certain brands on this forum, but not anything collecting it into one place for my scenario.

Research so far:

• Sol-Ark 12K: Perhaps not the best for off-grid use. Seems to include features that benefit grid-tie systems that I would not want to pay for. Seems touchy, as a lot of folks have struggled with it shutting down with slight imbalances on the AC legs. Needs an additional autotransformer to overcome this. Pricey.
• Victron Quattro 5000 KVA: Seems straightforward. You buy two to get 240 V. Not UL listed, which does not matter for me. Less pricey than Sol-Ark for two. Reputable brand.
• Growatt 5000W 48V: Price seems too good to be true. Needs an autotransformer to produce 240 V. Relatively high idle watt usage. Reputation of the brand? Reliability? Longevitiy?

Would appreciate any advice you guys can provide as I embark on my design.

 

[robby]

Research so far:

• Sol-Ark 12K: Perhaps not the best for off-grid use. Seems to include features that benefit grid-tie systems that I would not want to pay for. Seems touchy, as a lot of folks have struggled with it shutting down with slight imbalances on the AC legs. Needs an additional autotransformer to overcome this. Pricey.

Your research is probably based on listening to David Poz who knows nothing about electronics and very little about Solar equipment.
Sol-Ark 12K or the Sol-Ark 15K makes for a great off grid Inverter and so long as you update the firmware (which POZ did not do) and you balance your loads properly (which all installer do) you will be fine.

• Victron Quattro 5000 KVA: Seems straightforward. You buy two to get 240 V. Not UL listed, which does not matter for me. Less pricey than Sol-Ark for two. Reputable brand.
• Growatt 5000W 48V: Price seems too good to be true. Needs an autotransformer to produce 240 V. Relatively high idle watt usage. Reputation of the brand? Reliability? Longevitiy?

Would appreciate any advice you guys can provide as I embark on my design

If price is your driving factor then I assume Sol-Ark is out of the mix. Other brands like Outback and Schneider are not going to be any cost savings over Sol-Ark, so your really limited to Growatt with all of it's issues going Split phase or you could try the MPP LVX6048.

 

[jsocolof]

Price is not my primary concern. Actually the primary concern is reliable power without the inverter tripping for when we are away from the cabin. I can certainly balance the loads, but I would rather have an inverter that can compensate for reasonable imbalances. I do not want to be trying to instruct the family where they are allowed to plug in a heater or a blow dryer, so at least a 1500 W permitted imbalance between 120 V legs would be appreciated. For while we are away, I can pretty precisely control the minimal loads to be in balance (refrigerator, freezer, some minimal resistance heating).

I had not seen the MPP one, and on initial review it looks interesting. Is there much experience out there with the Victron Quattro? I have installed several Victron MPPT charge controllers and battery monitors on RVs, but never used an inverter of theirs. I am impressed with the quality in the products I've used.

Back to price: If I can get reliable power for $2k or $4K rather than spend the $7k for the Sol-Ark, I would need to be sold on the advantages to spend the extra money - and I am willing to be sold if the case is made.

One thing I forgot to mention in my parameters: remote monitoring over the internet is a BIG plus, and it looks like the MPP at least advertises that.

 

[offgriddave]

Going off grid, the biggest let down to me was the idle power on different brands. Victron and Giandel have the best performance. My Victron Phoenix 375VA uses 13 watts idle. In contrast, the Growatt 3000 (forgot model) measured 70 watts! MPP LV 5048, a split phase 240, measured 60 watts. There's one growatt, I forget which model, that uses 130 watts idle! That's 130 watts * 24 = 3120 or 3 KW wasted of battery, solar panels, connectors, etc for absolutely NOTHING of value. Once you go off grid and realize how much of a waste that is... it is very upsetting. With my Phoenix 375VA, having 13 watts idle is only wasting 312 watts per day. And I plan on putting a bus bar in and hooking up my MPP LV 5048 for 5000w loads. On Victron, I can use my phone's bluetooth to turn it on and off in bed, saving 8 hours of usage.

I am not sure about Outback, Schneider, Sol-Ark idle power consumption.

If you are an off grid inverter company the idle power consumption should be the #1 advertised feature, put up at the top, or in the model number itself.

The Victron Quattro 5000 KVA is suppose to have low watt usage. I seem to remember it is the same as the Phoenix 375VA but I'd look it up.
I would go for that if you already picked it out. Look for a thread for idle power consumption usage here and see if somebody reported it.

 

[Zwy]

Going off grid, the biggest let down to me was the idle power on different brands. Victron and Giandel have the best performance. My Victron Phoenix 375VA uses 13 watts idle. In contrast, the Growatt 3000 (forgot model) measured 70 watts! MPP LV 5048, a split phase 240, measured 60 watts. There's one growatt, I forget which model, that uses 130 watts idle! That's 130 watts * 24 = 3120 or 3 KW wasted of battery, solar panels, connectors, etc for absolutely NOTHING of value. Once you go off grid and realize how much of a waste that is... it is very upsetting.

Any low frequency inverter will draw around that, doesn't matter which manufacturer. If someone is buying a low frequency inverter, they are purchasing it for a reason, high amperage starting loads.

You're comparing apples to oranges. If you want to post statements like that, you should differentiate what type of inverter instead of posting what you have.

 

[Zwy]

As you plan on expanding down the road, I'd opt for something that is stackable. $2 to $4K will get you two LV6548's which will give 240V split phase, no autotransformer needed. Second choice would be LV6048, the advantage there is you only need one to get started with 240V split phase.

 

[Wellbuilt]

I use a flex power one outback system 3600/48
It uses 35 watts for every thing , inverter , charge controller , fndc , mate .
Works good ?

 

[BMcL]

This is a good one to consider IMHO. It also comes in a 18kw unit, which is what I'm using
It's a heavy low frequency type that handles a lot of surge current.

For internet monitoring, I'm using two Midnite Solar CC's

 

[Hedges]

Price is not my primary concern. Actually the primary concern is reliable power without the inverter tripping for when we are away from the cabin.

One thing I forgot to mention in my parameters: remote monitoring over the internet is a BIG plus, and it looks like the MPP at least advertises that.

https://files.sma.de/downloads/SI6048US-DS-en-28.pdf

SMA will even monitor it for you and send a message if something goes wrong.

 

[Wellbuilt]

My out back uses only 6 watts on standby
It will run nite lights ( blinking ) and when the frig or freezer turns on the inverter starts to power it .
I use 10% of my battery over nite or 8% on standby .

 

[Mr-Sandman]

https://files.sma.de/downloads/SI6048US-DS-en-28.pdf

SMA will even monitor it for you and send a message if something goes wrong.

That's true. I was impressed when they sent me an automated email warning of a sensor failure detected in one of my Sunny Boys. A ticket was created and replacement inverter shipped all the same time. It was still working, so I didn't even notice the alarm light, pro-active support.

 

[Mr-Sandman]

Put Schneider XW Pro 6848 with MPPT 100a 600v SCC, and an insight gateway on your shopping list.

That will get you started and I think it meets your design requirements. It's expandable to more Solar by adding additional MPPT controller or if 6800 watts continuous output with surges up to 12000 isn't enough power, you can add another inverter. Completely Scalable.
It is customizable as far as charge and battery parameters and I run my with the EG4's now.
It has a "search mode" for off grid no low power savings. This maybe useful in your setup, if you have periods of no load.
It's massive LF design that weights 140lbs and built to last and handle large motor loads, etc. No autotransformer needed with this inverter!
If you have Internet access, you will have complete monitoring and control of your system remotely thru insight cloud.

Cost wise, it's middle of the road, more than the cheap Chinese import inverters, but less than a Solar-Ark. I think they are a good value for the quality of the equipment.

You mention freezing temps. Those EG4's should NOT get below freezing. You ned to keep them above freezing or they will not be happy.

 

[MurphyGuy]

If reliability is your biggest concern, the SMA Sunny Island is what you want.. after that, an Outback Radian would be my next choice.

I own both. The Sunny Island's are the best, by far, not even a close second place. Remote monitoring is not available however.

 

[BMcL]

If reliability is your biggest concern, the SMA Sunny Island is what you want.. after that, an Outback Radian would be my next choice.

I own both. The Sunny Island's are the best, by far, not even a close second place. Remote monitoring is not available however.

Murph,
Don't the Sunny Islands require a separate PV controller ?
So couldn't he monitor it remotely with something like a Midnite Solar Classic ?

 

[Hedges]

The Sunny Island's are the best, by far, not even a close second place. Remote monitoring is not available however.

I think it is, by several generations of datacom equipment.

I presently have Sunny Web Box connected, which can see and adjust both Sunny Island and Sunny Boy.
Not advisable for internet connection because they gave it a hardwired admin password.
I also have the earlier Sunny Data Control.

Other interfaces are currently marketed by SMA.

Discover Monitoring & Control SMA Products | SMA America

SMA products for system monitoring offer the widest range of possibilities ► Wireless or internet based ► Compact or complex ► Concise or elaborate.

www.sma-america.com

Murph,
Don't the Sunny Islands require a separate PV controller ?
So couldn't he monitor it remotely with something like a Midnite Solar Classic ?

You can use DC coupled SCC, but better is AC coupled, e.g. Sunny Boy GT PV.

 

[Rednecktek]

• battery storage (looking at the EG4 batteries at the moment)
• 9100 ft elevation
• many days below freezing, with many also below zero

Anyone else think that might be a problem? ?

 

[MurphyGuy]

Murph,
Don't the Sunny Islands require a separate PV controller ?
So couldn't he monitor it remotely with something like a Midnite Solar Classic ?

Like Hedges said, you can DC Couple them like most other off grid inverter systems, but they are capable of AC coupling, which is a better way of going off grid in my opinion.. Not a lot better, but I think AC Coupling has advantages, especially if you're driving loads during the daytime hours.

The problem with the Sunny Islands is that they lack features.. They're designed to do a job and they do it exceptionally well, but they lack all the bells and whistles if you're into that.

Its a $5000 inverter and they equipped it with a 2 line dot matrix display that's 2.5 inches wide and 5/8 inch tall.. LOL

 

[jsocolof]

Anyone else think that might be a problem?

Current plan for battery location is in a sub-basement or root cellar that will keep the batteries above freezing. The BMS on the EG4s also will shut down charging < 32 F. Is there more I should be considering?

 

[Hedges]

Current plan for battery location is in a sub-basement or root cellar that will keep the batteries above freezing. The BMS on the EG4s also will shut down charging < 32 F. Is there more I should be considering?

Charge rate allowed is something like 0.5C at temperature of 25 degrees C, taper down to maybe 0.1C at 10 degrees C, taper further to freezing.
My suggestion is determinate max charge rate available and set temperature of charge disconnect in BMS accordingly, something higher than freezing.

A heater may help. I could imagine a root cellar having warm dirt but cold air. Insulation may help, or further earth sheltering.

Some systems (All-in-ones, Victron, AC coupled systems) should be able to regulate max battery charge current while allowing higher wattage from PV if there are loads consuming it. (Only beneficial for some systems with large PV, small battery.)

 

[jsocolof]

Put Schneider XW Pro 6848 with MPPT 100a 600v SCC, and an insight gateway on your shopping list.

Looking at the specs for the Schneider/Conext XW Pro 6848, surge capacity is 2X capacity for 60 seconds, which is a lot. Also, the weight of the inverter is 122 lb. (comparatively more than other similar capacity inverters). I've understood that both of these are indicators that the inverter is low frequency. Can someone confirm? Also, it outputs 120/240 VAC without an external autotransformer. At ~$3600, it seems like a pretty good deal for a LF inverter with good specifications and features. One thing that is not clear in the literature for this inverter is what kind of charge controller is included, if any. It is called an inverter/charger, but looks like it may only come with a PFC charge controller, which is not great.

What's the experience of the group with this inverter?