Battery selection for large off grid system

[AzRoute66]

OK Sensij,

Although I am done with the tilt thing until it moves, I will DISCUSS with you this very relevant portion of your thoughtful reply as it is back on track to assisting Mr. Silver with his pallets of panels. I know that consumption is king, but I still maintain there are other ways to skin this cat, and call it Devil's Advocacy, or since that sounds antagonistic, call it 'throwing a stick on the fire to see if it burns' I will continue with a heinous supply side discussion.

[perhaps Morningstar would say...] Mr. Silver - do you have a specific site in mind? In other words, could someone do a preliminary site survey to determine IF you can deploy all of those panels in a meaningful way? Perhaps you, you probably have a notion of that probability. If the site is already fixed, and won't support full deployment it will tailor the rest of the conversation without knowing anything of your preferred anticipated load envelope.

[perhaps Morningstar would say...] Mr. Silver - would you be amenable to adding more panels in order to balance multi-MPPT input configurations? If so, to what extent? This would also tailor the conversation without knowing anything of your preferred anticipated load envelope.

[perhaps Morningstar would say...] Mr. Silver - Under the assumption that we would deploy the panels provided only, our minimum suggested equipment list to maximize yield would be $_______. This would include everything up to and including AC service panels. It does not provide for split AC, lightning suppression, or any generator. Would that be a deal breaker?

IF Morningstar was to say/ask these things, and a few more I could think of, without knowing anything about consumption or load, would you call them 'irresponsible' or 'brash'?

EDIT: The above two posts came in while I was typing this. Glad to see we're back on track. Thanx.

[Joe Silver]

Thanks guys, I appreciate all the dialogue. Assuming this thread has not blown up, over the weekend I will give an estimation of my loads. As the novice, it is not may place to suggest to those of you that are more experienced that I don't want to supply this information.
There is much that has been mentioned that I understand, but don't really grasp. I need to think more deeply about this.
Yesterday I quickly reread some of Sunkings sticky threads, I need to go over them again. Also, probably more than a year ago I read COlsens thread on generator support. Seems to me that has some good info., so I will go over that again.
I know very little about Lithium batteries. I like what karrak has said, but will balance that with Sunkings disagreement.
My panels are sitting in a container now, and if my memory serves me correctly, the engineer/design guy at Wholesale Solar has the 54 panels split into 3 groups of 18. Each group consists of 6 strings of 3 in series. The panels are a Chaori-crm280S (VMP=36 volt & IMP=7.77 amp).

I have a neighbor that has lived exclusively on his 2000watt Honda generator for the last year, and gets by fine. He is a happy man, other than the nearest golf course is an hour away. My thought is still anything beyond a frig, freezer, some lights and a little extra electric is a bonus. I want as much of a bonus as possible (I think AzRoute66 identifies with me on this, and appreciate his comments), but will accept whatever battery technology will give me in 2018. I hope to learn enough to make a reasonable decision. A decision balancing current costs with future technology. Balancing lead acid maintenance issues with care free lithium---LOL, and maybe generator support. We probably have too many cooks in the kitchen to reach a concensus, but it is forcing me to learn so I appreciate that. Thanks for your help!

[Sunking]

The OP has 3 Midnight Solar Classic 150's. Those will put out a maximum of around 80 A on a 48 V battery.

86 amps to be accurate with a maximum wattage of 5000 applied. Point taken.

Which would be a poor choice IMHO. A wiser plan is to use 600 volt 100 amp controllers. Eliminates a lot of expensive combiners, fuses and a whole lot less expensive wire. 12 panels in series vs 3 panels in series.

The whole plan is senseless. way beyond 48 volt battery capability. This screams 100+ volts. More like 300 to 400 volts.

[sensij]

The whole plan is senseless. way beyond 48 volt battery capability. This screams 100+ volts. More like 300 to 400 volts.

Ok, so Morningstar's response is probably "sell the Classics on ebay, and buy four or five of our 600 V mppt controllers with 60 A output". That helps on the PV side, but the battery side is still a mess.

[Joe Silver]

Thanks guys, I appreciate all the dialogue. Assuming this thread has not blown up, over the weekend I will give an estimation of my loads. As the novice, it is not may place to suggest to those of you that are more experienced that I don't want to supply this information.

One of my neighbors has lived exclusively off his 2000watt Honda generator for the last year, and gets by fine. He is a happy man, other than the nearest golf course is an hour away. His Honda runs 18 hours a day, cost about $5 US in gas, and powers all of his needs.

In many ways, I am looking at this from a viewpoint similar to my neighbor. My perspective is after the frig, freezer, and a few lights are running, anything above that is a bonus. I want as much of a bonus as possible, but still won't be terribly disappointed when the batteries tell me enough is enough.

My thought is "almost" everything installed in the house will be the same (regardless of what loads you tell me I can handle). Maybe I can only run one ceiling fan at a time, but I am still going to have five installed. If the sun has been shining, then maybe all five will be spinning. If it is rainy and cloudy, maybe none will be spinning. So if the ceiling fans are using 75 watts/hour, how much will they run. 5 fans x 75 watts as 24 hours= 9000 watts? Maybe only run 4 fans--then I am at 7200 watts. Maybe 3 fans at 12 hours a day, then I am at 2700 watts. Too me, this is so much variance, it seems that the supply side should be taken into consideration. So my entire thought process was I was just hesitant to supply load guesstimates for worst case (high usage) scenario, mainly because it is not likely that I can handle worst case scenario.

When I say "almost", the one item that will vary depending on what I learn from this is if I attempt to install a couple mini-split high seer a/c units. Maybe I can use one or two during the day? I haven't purchased those yet, but that is something I hope to learn.

I have learned already from what I have seen posted. I appreciate that.

If memory serves me correctly, the 54 Chaori Solor panels( CRM280s) have a VMP=36 volts and an IMP of 7.77 amps. I believe the designer/engineer at Wholesale Solar has them in 3 groups of 18 panels, each group consisting of 6 strings of 3 panels.

Thanks again!

[Sunking]

Ok, so Morningstar's response is probably "sell the Classics on ebay, and buy four or five of our 600 V mppt controllers with 60 A output". That helps on the PV side, but the battery side is still a mess.

Who said anything about Morningstar? They do not make 100 amp 600 volt controllers.

[Sunking]

One of my neighbors has lived exclusively off his 2000watt Honda generator for the last year, and gets by fine. He is a happy man, other than the nearest golf course is an hour away. His Honda runs 18 hours a day, cost about $5 US in gas, and powers all of his needs.

You will be paying a lot more than $5/day in battery cost. In theory he can generate 36 Kwh/day, more than you can.

If you use the minimum battery capacity for your 15,160 wat panels of 2400 AH, and good 5 year battery will cost you roughly $23,000 plus a whole lot of Employment Prevention Agency fees for permits and inspection for all that toxic material and Spill Containment required. You will have to have the local FD inspect your site yearly with all kinds of EPA signs and Red Tape to put up with. Basically if you have a fire, the FD will just sit back and watch it burn from a distance.

That $23,000 battery will supply you with $2 to $3 worth of electricity per day (22 Kwh) if you bout it from the power company. Well if you do a little math there are roughly 1830 days in 5 years when it comes time to replace those batteries at even a higher cost if you give them TLC everyday and spend lots of time taking care of them You will be paying some $12 to $13 per day on battery cost alone, or roughly 4 to 6 times more than buying it.

$5/day for you would be a bargain. I gotta a great big surprise for you that you will just love and have so much fun with. Ready?

What size generator do you plan on buying? You do know a off-grid system requires a generator right? Without one your batteries will not last a year. Based on a 48 volt 2400 AH battery will require at least a 15 Kw generator and a honking big 300 amp 48 volt rectifier. Is that in your budget and space requirements. No gasoline generator will work. You wil be using diesel and need at least 100 gallons on site.

Told you would love it.

[sensij]

Who said anything about Morningstar? They do not make 100 amp 600 volt controllers.

That was in reference to AzRoute66 's comments. I agree that a 15 kW off-grid PV system should be getting more specialized equipment and more professional design help than what will be provided here. Still fun to kick around though and see what knocks loose.

[Sunking]

That was in reference to AzRoute66 's comments. I agree that a 15 kW off-grid PV system should be getting more specialized equipment and more professional design help than what will be provided here. Still fun to kick around though and see what knocks loose.

I agree. LOL

[Mike90250]

Karraks 300A into 500ah of battery is a dangerous suggestion, only mitigated by the controllers inability to actually produce that much, so karrack - you barely got a pass on this. Stop suggesting plans that fail in catastrophe.....

Morningstar makes a 600V MPPT controller, but it's only 60A output https://www.morningstarcorp.com/prod...tar-mppt-600v/

Magnum PT-100 only has 200Voc inut

Battery watering. Either you do it, or you buy new batteries. I add about 6-7 gallons every other week (NiFe bank) lead acid is about half that. After 6 months, you willl learn your systems
requirements, maybe go 3 weeks. Batteries on float, you might push out to 4 weeks, but that's a risk you take on your own. As to my watering, I've split my bank into about 3 sections, and only about 1/3 of the batteries get watered at any time. That cuts down on my fatigue from pouring 20 gallons at once, every 6 weeks. I do only about a third of the bank, cells have about 1/2 gallon from E-F so there is room for a little bit of adjustment there if I am a 2 or 3 early/late.

Generator Support. I learned a lot from Chris and I am confident I have my system working well with a 3Kw generator and XW gear. I've watched it cut back charging and then switch to assisting the generator when the blowdryer comes on, and it's really slick (when all the setpoints are right, sadly Schneider glosses over how to properly set things up)

But your battery requirements are unworldly. You might be able to eek by with a honda EU2000, well configured XW gear, and batteries, but you will have a generator running when the sun is not shining.

Assuming you think that you will manually run around switching gear off and back on, doing manual load application and shedding, It will work for a couple weeks, then you will tire of it, or be on vacation or something , and the replacement person will not have your motivation, and .....

[sensij]

We probably have too many cooks in the kitchen to reach a concensus, but it is forcing me to learn so I appreciate that. Thanks for your help!

I'm glad you are able to accept this forum for what it is.

[karrak]

Karraks 300A into 500ah of battery is a dangerous suggestion, only mitigated by the controllers inability to actually produce that much, so karrack - you barely got a pass on this. Stop suggesting plans that fail in catastrophe..

You really have it in for me, doesn't matter if I take the time to study the previous posts to extract all the relevant information to make an informed comment, also doesn't seem to matter if I can and do back my posts up with evidence. Give me one instance where I have suggested a plan "that fail in catastrophe".

Where is the evidence to back up your assertion that it is dangerous to charge a 500Ah LFP battery with 300A?

Both CALB and WINSTON spec a maximum charge rate of 1C or in this case 500A. Most cycle life testing I have seen for Chinese prismatic LFP batteries has been at charge and discharge rates of C/2.

Two systems on the Energy matters forum that I know of that are working well have enough solar panels to charge their LFP batteries at ~0.4C. I am not going to bother going through all the posts on the boating cruisersforum but if my memory serves me correctly there are several people who charge their LFP batteries at rates greater than C/2 when charging from their engines.

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

[max2k]

You really have it in for me, doesn't matter if I take the time to study the previous posts to extract all the relevant information to make an informed comment, also doesn't seem to matter if I can and do back my posts up with evidence. Give me one instance where I have suggested a plan "that fail in catastrophe".

Where is the evidence to back up your assertion that it is dangerous to charge a 500Ah LFP battery with 300A?

Both CALB and WINSTON spec a maximum charge rate of 1C or in this case 500A. Most cycle life testing I have seen for Chinese prismatic LFP batteries has been at charge and discharge rates of C/2.

Two systems on the Energy matters forum that I know of that are working well have enough solar panels to charge their LFP batteries at ~0.4C. I am not going to bother going through all the posts on the boating cruisersforum but if my memory serves me correctly there are several people who charge their LFP batteries at rates greater than C/2 when charging from their engines.

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

500A? Must be some wires/batteries - any remotely bad contact ... BTW, do you have any data how many cycles those batteries charged at >= 0.4C already went through and what is their remaining capacity? Just curious as it sounds unusually high for me.

[Mike90250]

You really have it in for me, doesn't matter if I take the time to study the previous posts to extract all the relevant information to make an informed comment, also doesn't seem to matter if I can and do back my posts up with evidence. Give me one instance where I have suggested a plan "that fail in catastrophe".

Where is the evidence to back up your assertion that it is dangerous to charge a 500Ah LFP battery with 300A?

Both CALB and WINSTON spec a maximum charge rate of 1C or in this case 500A. Most cycle life testing I have seen for Chinese prismatic LFP batteries has been at charge and discharge rates of C/2.

Two systems on the Energy matters forum that I know of that are working well have enough solar panels to charge their LFP batteries at ~0.4C. I am not going to bother going through all the posts on the boating cruisersforum but if my memory serves me correctly there are several people who charge their LFP batteries at rates greater than C/2 when charging from their engines.

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

You betcha. I will come down hard on dangerous suggestions from anyone. 300A charging current is really tough for neophytes (and we need to discuss things at neophyte level, because 9%% of first time visitors ARE neophytes, and use hammer crimp tool on > 4/O cable ) and many can't even properly connect an amp-meter.
Just because C1 is allowed, doesn't mean it's preferred or required. And what BMS / Vampire board is going to be able to manage that as cells fill up ?

[karrak]

500A? Must be some wires/batteries - any remotely bad contact ... BTW, do you have any data how many cycles those batteries charged at >= 0.4C already went through and what is their remaining capacity? Just curious as it sounds unusually high for me.

Yes, bad contacts at any power level can lead to a disaster. Have to make sure you have the appropriate cable and cable terminations.

Here is a graph from Winston
WinstonCycleData.jpg
For some real life data I know of two off-grid systems in Australia that have enough solar to charge at a maximum rate of ~0.4C. One system is about the same age as my system and the other is slightly younger. Both these systems have done over 1000 cycles and are still like new except for the failure of one cell in one of the systems.

As far as I can see the main determinants of battery life for LFP batteries are temperature, total amount of energy cycled through them and storage at high SOC.

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