Off grid system advice

[jsmitman82]

What I'm aiming to get settled soonest is my battery bank, as I'm looking to buy from the current batch that Amy Luyuan has ordered. My plan is to create a 48v battery bank with 48x Eve LF280K 3.2V 280AH cells arranged as 16S3P. I am also considering 4 strings instead of 3, which would be 64 cells instead of 48 - but kinda thinking that might be more than I need and would likely die of old age long before reaching max cycles (6000). I'd estimate about 12-15 KWH normal daily usage, and they'd be stored in a basement due to more ideal year round temperature. I am looking for BMS recommendations - Amy sells JBD, Daly, Chargery, and JK. Also interested in urls of similar builds, happy to learn from others experiences.

I'm thinking 16 KWH in solar panels and 12 KWH inverter capacity, ideally with a high 30sec burst capacity somewhere in the ballpark of 20 KWH. I've always liked the Schneider Conext inverters from past years of research, but as I've been trying to catch up on more modern info I've found them to not be as favorable as they once were? I think I read that they don't yet support charging lifepo4 batteries? I have no idea what solar panels I want, I intend to ground mount them, not roof mount.

I am happy to receive advice on or field any questions for any component of this build, I have a lot to decide and to learn still, but I need to get it done this year for an off grid home I'm building. My first purchase is the battery system components, as I'd like to get that going since the lead time is so long from china currently, and then I need some time to learn/tinker with building out packs and balancing them. I'll be spending the winter researching, no doubt.

Thanks

 

[alcook62]

I think I read that they don't yet support charging lifepo4 batteries?

Wow, I'm impressed with the system you are planning! Much more elaborate than my 24v off-grid setup.

I'm currently, and for the foreseeable future, using a Schneider CSW4024 inverter/charger with my puny 280ah lifepo4 battery. If you go into the "advanced" menu, select the "custom" setting, you can plug in the parameters you desire.

Thus far I've had a good experience with mine.

 

[jsmitman82]

I do recall reading that you could get the Schneider Conext to function with lifepo4 batteries, but as I'm learning about all the fancy communications protocols between smart BMS and inverters, I'm leaning towards a solution where the inverter and BMS can interact. Although, I am still undecided on the inverter since I have more to learn here.

The quantity of BMS info on this forum is overwhelming (which is where my studies are currently directed), but I'm leaning towards paying a bit more for a more full featured and robust solution, which is currently looking like Batrium K9's.
This thread is a wealth of information that I'm still going through, video's included:

Batrium K9/Core BMS for 16s2p Basen eve/lichen 32 cell review

Batrium is great for 16s+, 32 cell+ systems. For our large property high voltage gets you further distances with less voltage drop. 48v was my goal from day one for our ground mount system. We are fully off grid which meant we needed a lot of kwh. But how do you manage 32 cells, or even more in...

diysolarforum.com

I am aware that people are doing amazing things with less expensive BMS solutions, but expertise level for these amazing projects is more than I'm looking to take on at the moment. I'll also be fully off grid, so I'm also trying to avoid components with a higher failure rate.

 

[MichaelK]

A few details about units and scale. You might be using 16 kWh of power per day, but you don't need a 16kW inverter to power it. Most likely you'll be just fine with the 4000W Conext 4024. You don't buy KWH of solar panels, you buy xxxW panels and wire them in series and parallel to get the number of kW of power you want. You then multiply the kW of panels X the number of SunHours (sh) you get per day to determine your output.

Let's say you want to make 16 kWh of power. Don't type KWH, that's not the correct designation. Let's say your location gets 3sunhours of sunlight in winter, and 5 sh in the summer. You scale your system for the worst day, not the best. So, for 16 kWh that's 16000/3 sh = 5333W of panels.

Actually, 16 kWh is a lot, and most likely you'll use far less when you really start to conserve. I'm using 6-7 kWh of power in summer, and that's including an air-conditioner, besides just the lights, refrigerator, and TV. It's my well-pump that's the real power hog. On irrigation days, I'm consuming 20+ kWh of power. Let's do the math again with 5 kWh as your target. 5000W/3 sh = 1666W of panels, just a bit smaller than the 24V system I've got for my workshop. I was just panel shopping on Craigslist yesterday and saw 290W panels for 110$ each. Six of those would be 1740W, just a bit more than calculated above.

Since you want to use a ground mount, I can show you a pic of a dual-row single-pole mount that I designed/built. It could hold those 6 panels. Wire them 3S2P and they will about 30A into your battery bank at noon. { (290W X 6 panels)/50V charging} X 85%fudgefactor = 29.6A.

If you decide you want more, you can add a second array and more panels later. If you find you need far more inverter output, both the Conext series and XW 6848 series can be paralleled to get more power.

 

[jsmitman82]

Ah right, I did incorrectly phrase it as "kwh", what I meant was just 16 "kw" of total panel output rating, and was not referring to my daily usage. My primary concern is lessening generator usage in the cloudy winter months in the pacific northwest, so that's why I'm aiming for more solar panel capacity than I would need in the summer. I'm also considering the bifacial cells to get a bit more from snow reflection on the back side. I have evaluated my energy usage and have had a 8.58kw grid tied system in a previous home in the past (8.58kw in solar panel rating, that is), and based on my research and experience I doubt I'd be satisfied with much less than 16kw of solar panel capacity.

I understand that my normal inverter usage would be quite small (I've reviewed the hourly energy usage in my current dwelling that our power company provides), but I want to be able to easily support surge loads that come with things like a well pump. I understand you can find 'soft start' options for many such products, well pumps included (ie grunfos), but my research typically indicates that you often pay more and/or get less lifetime out of such products.

Do you have a document for that ground mount build? Materials list and/or assembly instructions? I'm not sure I'm up for doing any fabricating at this point in my life, I need to get all this functional before I learn to weld. Cutting angle iron, drilling holes, torqueing bolts - would be fine of course.

 

[BMcL]

What I'm aiming to get settled soonest is my battery bank, as I'm looking to buy from the current batch that Amy Luyuan has ordered. My plan is to create a 48v battery bank with 48x Eve LF280K 3.2V 280AH cells arranged as 16S3P. I am also considering 4 strings instead of 3, which would be 64 cells instead of 48 - but kinda thinking that might be more than I need and would likely die of old age long before reaching max cycles (6000).

I'm thinking 16 KWH in solar panels and 12 KWH inverter capacity, ideally with a high 30sec burst capacity somewhere in the ballpark of 20 KWH. I've always liked the Schneider Conext inverters from past years of research, but as I've been trying to catch up on more modern info I've found them to not be as favorable as they once were? I think I read that they don't yet support charging lifepo4 batteries? I have no idea what solar panels I want, I intend to ground mount them, not roof mount.

The system I'm building is close to the one you're doing.
I have a 1575 sq ft well-insulated house near Nashville.
I plan on running a 2.5 ton central air unit, a fridge and freezer and a heat pump water heater on my off-grid system.
I also have a huge air compressor, an Ingersoll Rand 80 gallon 7.5 hp model.
The ac and compressor will cause a big surge in current, so my inverter is an 18kw SunGold Power
that can handle 3X the surge current (54kw for 20 seconds).

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I have 3 sets of 16s batteries and will add a 4th. Not sure if that will be enough. I know others who tell me I will need more.
I'm starting out with 24 Solarever 440 watt panels. Plan on adding at least 6 more.
I'm using two Midnite Classic 150 charge controllers but may add a 600V controller a friend told me about.

 

[jsmitman82]

Yes, I also intend to run central A/C, large air compressor, and eventually a welder. Planning for surge loads is a must for me, way too much trouble trying to design around high surge loads. That's one reason I like the low frequency inverters with high surge capacity (usually ~2x their continuous rating).

I had not come across that inverter brand yet, what are all the reasons you selected it? The 3x surge it provides is quite impressive. I will read up on it.

4x banks of 48v 16s EVE LF280K should come out to 56.7kwh of capacity, which means it should handle that max 54kw surge just fine at ~1C. Short 1C surges are no problem for these batteries from what I understand. And the 18kw continuous rating of that inverter would be around ~0.33C which is perfectly fine for long life continuous draw. 4x is probably the minimum number of these 16s 48v batteries you'd want if you intend to run loads this high, though. Tbh I've been talking myself into 4x banks instead of 3x the past couple days any way... Hurts the wallet...

Which way are you leaning for a BMS? The Batrium is still the way I'm leaning (likely K9, maybe Blockmon). It seems prudent to go with an expandable BMS system when you have multiple banks in parallel, and I haven't found a 48v one that appears to be better than the Batrium yet, infact I haven't found anything other than the Batrium one yet... but I may be overlooking options from reputable brands like Orion/REC that I failed to locate. With 4+ banks in parallel, the cost difference between Batrium and others starts to shrink considerably, if your plan is 16s1p so that you can monitor each cell individually.

 

[BMcL]

Yes, I also intend to run central A/C, large air compressor, and eventually a welder. Planning for surge loads is a must for me, way too much trouble trying to design around high surge loads. That's one reason I like the low frequency inverters with high surge capacity (usually ~2x their continuous rating).

I had not come across that inverter brand yet, what are all the reasons you selected it? The 3x surge it provides is quite impressive. I will read up on it.

4x banks of 48v 16s EVE LF280K should come out to 56.7kwh of capacity, which means it should handle that max 54kw surge just fine at ~1C. Short 1C surges are no problem for these batteries from what I understand. And the 18kw continuous rating of that inverter would be around ~0.33C which is perfectly fine for long life continuous draw. 4x is probably the minimum number of these 16s 48v batteries you'd want if you intend to run loads this high, though. Tbh I've been talking myself into 4x banks instead of 3x the past couple days any way... Hurts the wallet...

Which way are you leaning for a BMS? The Batrium is still the way I'm leaning (likely K9, maybe Blockmon). It seems prudent to go with an expandable BMS system when you have multiple banks in parallel, and I haven't found a 48v one that appears to be better than the Batrium yet, infact I haven't found anything other than the Batrium one yet... but I may be overlooking options from reputable brands like Orion/REC that I failed to locate. With 4+ banks in parallel, the cost difference between Batrium and others starts to shrink considerably, if your plan is 16s1p so that you can monitor each cell individually.

There was a nice review of the smaller 12kw SunGold inverter here. The 18kw model weighs 220 lbs !
The only reason I looked at SunGold Power was a friend who is an electrical contractor has been using an 18kw for the last 5 years.

I haven't settled on a BMS, although I do have one 100 amp Overkill Solar BMS.
The batteries aren't for surges in current. It takes a lot to get through the night time and during cloudy periods.

 

[jsmitman82]

270 watt idle power draw is a bit rough.

 

[MichaelK]

My primary concern is lessening generator usage in the cloudy winter months in the pacific northwest, so that's why I'm aiming for more solar panel capacity than I would need in the summer. I'm also considering the bifacial cells to get a bit more from snow reflection on the back side.

Yes, I can understand that. What I'm seeing with my own system is that I get about 10% production in cloudy/rainy weather, and right now with about 5500W of panels online for the cabin, I'm making about 2.5kWh in the rain per day. That works out to be ~ 0.5sh per day.

Yes, I also intend to run central A/C, large air compressor, and eventually a welder. Planning for surge loads is a must for me, way too much trouble trying to design around high surge loads. That's one reason I like the low frequency inverters with high surge capacity (usually ~2x their continuous rating).

OK, you are talking BIG! Really big! I'm running my cabin on a single Schneider XW+6848 with a 568Ah Rolls battery. I routinely run my 240V well-pump off the Schneider. I also routinely run a 8000BTU wall-mount air conditioner off it two. I have on occasion run my 120V MIG welder, but I really am scared doing that. I'd rather run the welder off my generator. With the kinds of loads though you are talking about I'd say you'd need two or maybe even three XWs in parallel for the level of capacity you need. And that would be with a 1000Ah battery.

Do you have a document for that ground mount build? Materials list and/or assembly instructions? I'm not sure I'm up for doing any fabricating at this point in my life, I need to get all this functional before I learn to weld. Cutting angle iron, drilling holes, torqueing bolts - would be fine of course.

The ground mount is my own design, which you should feel free to copy, but there are no documents. It's made out of schedule 40 pipe and 10' unistruts, welded together.

Basically, I measured the screw to screw mounting holes, and custom built my frames to fit my panels. I bought the welder at HomeDepot and taught myself to weld on the garage floor. The first welds were of such poor quality that the frame broke when I dropped it into place. After multiple design changes, you can now see my V4.0 design in the pic.

BTW, the XWs draw about 27W per hour as compared to 270W. And, all of Schneider's inverters are UL listed.

 

[BMcL]

If he uses 3 Schneider XW pro's in parallel, I doubt the idle power would be much of a difference with the SunGold Power 18kw.
I paid $3660 for the 18kw but the $300 off sale ends today.
The cost would be $6000 less with Sungold ; also wiring and complexity costs would be higher with Schneider.
If the Sungold unit isn't as reliable, that would be a solid reason to avoid it but it's extremely heavy-duty and I know about one that's 5 yrs old.

 

[jsmitman82]

Missing a sale is unfortunate, but I'm not yet ready for the inverter purchase. I will certainly keep the sungoldpower in mind while I'm researching inverters. I'm currently trying to complete an order with Jenny Wu of Docan for 68x EVE LF280K cells, with upgraded busbars (braided instead of solid).

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Note: Given my largest concern is winter power consumption and minimizing fuel consumption from generator usage, 270w idle is of concern to me given that is an extra 6.48kwh used per day just doing nothing. 3x of the Schneider KW pro's would actually be less at 27w x 3 = 81 watts. This will be something I factor in during my inverter search, as that extra diesel burned over a couple decades does add up - but more importantly, I like the idea of being able to go as long as possible without needing a fuel fill up. Ideally I'd not need a backup power solution at all, but that isn't really realistic no matter how big my battery bank or solar panel array is, in the pacific north west.

 

[BMcL]

Missing a sale is unfortunate, but I'm not yet ready for the inverter purchase. I will certainly keep the sungoldpower in mind while I'm researching inverters. I'm currently trying to complete an order with Jenny Wu of Docan for 68x EVE LF280K cells, with upgraded busbars (braided instead of solid).

I just got another set of 16 LF280K cells from Jenny; only took 5 days !
I would like to order some flexible busbars but I want to drill the holes myself to get more contact area.
I can't find any way to email Weber Power Tech ?
Since I have a buddy who's been running a 18kw Sungold, maybe he can tell us what the idle power is.

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[jsmitman82]

An update:
- I got my order in for 68x of the EVE LF280K cells via Jenny Wu at Docan (building 4x 16cell 48volt packs, with 4 spares incase some cells have problems, and ultimately building a 12v aux pack if I end up with 4 spare cells when I'm done).
- I ended up scrapping both 'Expandable BMS' and 'Relay BMS' ideas. The Batrium BMS is nice, but if I wanted to treat each battery bank as a separate standalone thing (so that a fault doesn't shut down all banks) I'd need a 'core' module for each one, which is pricey and defeats the purpose. All of the built-in relay BMS's I investigated were a bit sketchy (JBD, QUCC, Heltec). I ended up going with the JK BMS that "Off-Grid Garage" recommended. Mosfet BMS's worry me due to their charge/discharge limits, among other things; but I think a good relay BMS would probably end up costing a ridiculous amount of money (~$500-$600 or more). The JK BMS's 200amp continuous / 350 amp surge is an acceptable compromise for the 48v 280AH batteries I'm building, and it is really well made. And actually, the JK BMS does offer a 600a version that requires buying separate relays, 'on sale' at the moment for $534.06, and then you have to buy 2x relays (good ones are $100+ each !). I don't want to spend ~$800 per BMS...

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[jsmitman82]

I'm on to researching inverters now. I loved what I read about the Schneider XW+ 6848 years ago, and after a lot of catching up the Schneider XW Pro 6848 is at the top of my list. I tried to like the Sol-Ark, but it isn't doing it for me. The Victron Quattro is tempting. All the tier 1's are pricey of course.... the less expensive models like Sungoldpower are tempting... I can't get past the high 270w idle though (and I also like high efficiency in general, less conversion losses). Infact my biggest turnoff of the Victron Quattro (other than price) is the mere 60w idle of the 10k va model. If I were to go victron it would be 2x of the 10k va (8kw) models, because their 15k va model is 110w idle - and I could get 20k va from 2x 10k's for a similar idle power. I'm leaning towards starting out with 2x Schneider XW Pro 6848's atm (56w idle in total, for 13.6kw continuous and 24kw surge).

 

[MichaelK]

I'm on to researching inverters now. I loved what I read about the Schneider XW+ 6848 years ago, and after a lot of catching up the Schneider XW Pro 6848 is at the top of my list. I tried to like the Sol-Ark, but it isn't doing it for me.

One of the reasons I'm annoyed with Sol-Ark is they basically made their comparision to the XW by comparing to the XW with two of Schneider's already expensive MPPT controllers to show that THEIR system was actually cheaper than the XW system. They don't mention though that you don't have to mate Schneider's inverter with Schneider's controller. I mated my XW to a Midnight controller, using one of Midnight's power centers and put it together for thousands less. It's handled 4500W of solar for years now.

 

[jsmitman82]

I saw that comparison, I think it was actually 3x of the schneider mppt charge controllers in their quote, and they used MSRP price to compare - which you can easily get schneider units for much less than msrp whereas sol-ark has price fixing with dealers and a NDA for them to not reveal their cost. Sol-Ark does a lot of shady shit imo, so I'm with ya...

I hadn't considered using midnite charge controllers, are they as good as the schneider ones?

 

[BMcL]

Do any of the really heavy low frequency models that can handle high surge loads idle at really low wattages ?
Something tells me that 100+lb transformer costs you some idle power ; but to me it's worth it.
A 54kw surge rating is pretty impressive. And at what cost ? One extra solar panel maybe ?
------------
jsmitman82: I hadn't considered using midnite charge controllers, are they as good as the schneider ones?

From people on this forum, I've heard the Midnite Classics have the best software and hardware is as good as you can get.

 

[MichaelK]

Do any of the really heavy low frequency models that can handle high surge loads idle at really low wattages ?
Something tells me that 100+lb transformer costs you some idle power ; but to me it's worth it.
A 54kw surge rating is pretty impressive. And at what cost ? One extra solar panel maybe ?

Well, I tried starting my well pump at 9:00pm with the XW after it was totally dark, so I'd call that a high surge load. It worked just fine. The XW seems to have about the lowest idle consumption around. I don't know why everybody keeps talking about it?

 

[BMcL]

Well, I tried starting my well pump at 9:00pm with the XW after it was totally dark, so I'd call that a high surge load. It worked just fine. The XW seems to have about the lowest idle consumption around. I don't know why everybody keeps talking about it?

I know the Outback, Schneider and Sol-ark are good units. I just didn't want to tie 3 of them together to run my house.
The Sol-Ark may have been marginal with one unit. But I don't think 12kw was enough.