This off grid project, what have I gotten myself into?

[Stormsoul]

I don't know where to start this, so I will just start with this. I have spent money and now need help installing/wiring/configuring. I got a few quotes for some parts of the heavy lifting and wire running and that's coming in at 12-14k depending on the quote. It is like I pulled the trigger, after watching videos and looking at my monthly usage and I think I am in the ballpark but installing it is overwhelming now. Below I will just list some generic info with side thought. I can provide specifics if needed.

Location-Tucson AZ
large back patio rolled shingle (new) mounting location for 24 400w panels. These are Talesuns 9.89 amp and 49.1 voc.
Inverters-LVX 6048 (yellow) inverters x2. We use a lot of power for family of 4 (19 and 21 yo use a lot).
Mounting hardware was ordered to match the panels from Santan and is K2/Everest racking. Planning surface mount on patio w/ no elevation. I will wash more often.
Batteries- 32 280ah cells from Amy. I actually received those a tad early from China so that was good. These came well packaged and have hardware. (depending on how I build these I will probably need additional l longer bus bar hardware. I don't know what my wiring diagram will be but I was thinking of 2x16 cell to bus bar managed by BMS from Overkill solar.
Installer will provide combiner boxes, disconnects, wire runs from back to front for AC and DC, sub panel. I will program inverters and build battery and tie into inverter.
I have the rolls of wire for the panels. I know there are some various wires missing. I would have to attach pictures but the run from back patio to garage is probably 150 feet. That leads to the beginning of my questions. garage mount of inverters and battery setup either on a rack like Will did or a Craftsman tool box like solar engineer did.. but then wiring diagram and BMS choice I dont know, will be very very hot in the summer. So that plan with local installer was and I agree was under back patio on outside of back bedroom wall. Again, large covered patio, that is safe from rain or direct sun. In the garage everything will be nice and close together but will need to be nice and tight against the wall as I still park cars in it. It is just the heat I worry about. The inverters will probably overtemp, Batteries would be ok and they wont freeze in the winter. They wont freeze on the back patio as if it even gets that close (very rare) I can point a small space heater in the area and be fine for the one or two nights a year we may get that cold.

I know this is just rambling right now as I have spent a lot and now need to pay my way out of this project and will end up not saving much more than just paying someone to do it all from start to finish..well I do get to pick the panels I guess but I digress. The long run of DC and AC from back patio to main panel at the garage and then from there into a sub panel and back to inverters is where I think cost is adding up. The features being listed by installer will be that the grid can assist the inverters powering sub panel load if panels and battery get to low. I like the idea and everything but kitchen and laundry would be moved to sub..

Ok thats enough for now. Right now feel like I need a couple solar buddies to learn from and maybe help me install all of this. I have read a lot and want to use some of these tools I bought, I just need someone looking over my shoulder and stop me before I incorrectly do something. Thanks in advance for any help.

 

[FilterGuy]

I have spent money and now need help installing/wiring/configuring.

My first bit of advice is to stop spending till you have a full design. There is a real danger of spending money on the wrong things.

We use a lot of power for family of 4 (19 and 21 yo use a lot).

Have you done an energy audit/survey to determine the needs and system size?

I highly recommend you go through the effort. It will give you a much better understanding of the usage and what the system size needs to be to meet your expectations. The other thing it will do is help you understand the true energy hogs and perhaps find places energy usage can be reduced. I use this tool.

System Energy Audit and Sizing Spread Sheet

To get the spreadsheet, click on the orange button at the top of this page. This sheet is intended to help you plan your system. Fill it out down to the last decimal place, look at the results..... and then make your best guess;) Notes...

diysolarforum.com

24 400w panels. These are Talesuns 9.89 amp and 49.1 voc.

Array size is 24x400 = 9.6K watts. Assuming you get 85% of the rated value, that is 9.6K x .85 = 8160W
Phoenix is fairly sunny so let's use an insolation number of 5.5. That means you will get ~ 8160W * 5.5H = 44.88KWh/day.

Inverters-LVX 6048 (yellow) inverters x2

That is 12KW of power if they are running at full load.
Assuming 95% efficiency, that means the battery is going to need to deliver as much as (12,000W/.95)/48V = 263A. That is a lot of current!!
You defiantly want to keep the batteries and inverters next to each other.

Batteries- 32 280ah cells from Amy. I actually received those a tad early from China so that was good. These came well packaged and have hardware. (depending on how I build these I will probably need additional l longer bus bar hardware. I don't know what my wiring diagram will be but I was thinking of 2x16 cell to bus bar managed by BMS from Overkill solar.

A couple of points.
* For the size of the inverters, this seems like a small storage capacity. To put it in perspective, if you are running the inverters at 100%, the batteries would go from full to empty in just over 2 hours. Granted, you would probably never run the inverters at 100% for an hour, but I suspect that if you need that much wattage, the storage may be too little. (Hence the need for an energy audit)

* The overkill BMS tops out at 100A. If you made 2 batteries (16 cells each) with the overkill BMS, you would only have 200A available but the inverters need 263A.

That leads to the beginning of my questions. garage mount of inverters and battery setup either on a rack like Will did or a Craftsman tool box like solar engineer did.. but then wiring diagram and BMS choice I dont know, will be very very hot in the summer. So that plan with local installer was and I agree was under back patio on outside of back bedroom wall. Again, large covered patio, that is safe from rain or direct sun. In the garage everything will be nice and close together but will need to be nice and tight against the wall as I still park cars in it. It is just the heat I worry about. The inverters will probably overtemp, Batteries would be ok and they wont freeze in the winter. They wont freeze on the back patio as if it even gets that close (very rare) I can point a small space heater in the area and be fine for the one or two nights a year we may get that cold.

Unless the inverters are rated for outside, I would not recommend putting them outside even if they are protected from rain. There are other factors like Dust, Humidity/condensation that comes into play. The inverters you have can have fairly high voltage PV input, so it should not be too hard to wire the PV for the long 150 ft run.

I just need someone looking over my shoulder and stop me before I incorrectly do something.

Do a detailed schematic of what you plan and post it here.

 

[boondox]

Read @FilterGuy 's post for comprehension and follow his advice.

 

[Stormsoul]

Thank you FilterGuy, I know the inverters are over doing it, I wanted to pad there. I will put together a schematic of what I am planning, I do plan on another 32 cells. and at all times the battery packs will be close to the inverters. Good point on maybe not leaving them under the patio. I just need to consider summer heat in the garage. I can utilize a small window ac to keep it in range but that's more watts out the window. Ok thanks again all. FilterGuy can you elaborate on needing 263A over what would be on the bus from the batteries (200). I will add more batteries later.

 

[FilterGuy]

FilterGuy can you elaborate on needing 263A over what would be on the bus from the batteries (200). I will add more batteries later.

The current is determined by load, not by the battery. The larger the load, the larger the current needed to supply that load.
If you are driving a single LED, the batteries will only need to provide a few milliamps. If you are driving 12KW of inverters at full load, the batteries will need to provide 263A.

Consequently, when designing the battery(s), there are 3 things that must be considered.
1) What is the total current needed - We calculated 263A

2) What can the cells handle: For your 2 battery example each battery would need to provide 263/2 = 132.5A. Therefore the cells will be providing 132.5A. This is 132.5/280 = 0.47C That is reasonable.

3) What can the BMS handle. As in step 2 above, each battery needs to provide 132.5A. However, the Overkill BMS tops out at 100A. When you do the extra 32 cells and arrange them into a total of 4 batteries, then each battery will need to provide 263/4=65.75A. In this case, the Overkill BMS would work fine.

 

[FilterGuy]

These are Talesuns 9.89 amp and 49.1 voc.

Are those the Bifacial Talesons?

Planning surface mount on patio w/ no elevation.

Bifacial panels are designed to be off the surface so they get reflected light onto the bottom of the panel.

They will still work without the reflected light, but it won't be anywhere near 400W. I don't have enough experience with bifacial to give an estimate.

 

[FilterGuy]

 

[MrM1]

@FilterGuy a possible FYI, the URE panels we bought sold as 370w had a 5-10% increase for the Bifacial

 

[FilterGuy]

@FilterGuy a possible FYI, the URE panels we bought sold as 370w had a 5-10% increase for the Bifacial

View attachment 80860

Thanks. That is good to know.

Does that mean the URE bifacial panels are rated without the backside gain? In other words, they are rated for 365W and anything you get from the back-side is over and above the rating. (I can guarantee the marketing guys would want to label them as 402W ?)

I wonder if the Talesons are rated that way as well?

 

[MrM1]

Thanks. That is good to know.

Does that mean the URE bifacial panels are rated without the backside gain? In other words, they are rated for 365W and anything you get from the back-side is over and above the rating. (I can guarantee the marketing guys would want to label them as 402W ?)

I wonder if the Talesons are rated that way as well?

That's the way I read it and that's what I was told (seller) . But I do not know, I submitted that for your evaluation.

 

[Zwy]

I don't know where to start this, so I will just start with this. I have spent money and now need help installing/wiring/configuring. I got a few quotes for some parts of the heavy lifting and wire running and that's coming in at 12-14k depending on the quote. It is like I pulled the trigger, after watching videos and looking at my monthly usage and I think I am in the ballpark but installing it is overwhelming now. Below I will just list some generic info with side thought. I can provide specifics if needed.

Location-Tucson AZ
large back patio rolled shingle (new) mounting location for 24 400w panels. These are Talesuns 9.89 amp and 49.1 voc.

8S on PV with 3 strings? 9S will get you over the 450V max PV input on cold mornings. You might be able to squeak by with 8S with 2 strings on one LVX6048, max PV amps is 20A. However that will put you over the 6000 watt PV input rating. 16x400=6400w

I don't recommend going over the rated PV input wattage per unit. I think you would be better served with another SCC on one string.

Inverters-LVX 6048 (yellow) inverters x2. We use a lot of power for family of 4 (19 and 21 yo use a lot).

You really need an idea of how much power your household uses in a day. I use a Eyedro from Amazon to monitor our usage. https://eyedro.com/

Mounting hardware was ordered to match the panels from Santan and is K2/Everest racking. Planning surface mount on patio w/ no elevation. I will wash more often.
Batteries- 32 280ah cells from Amy. I actually received those a tad early from China so that was good. These came well packaged and have hardware. (depending on how I build these I will probably need additional l longer bus bar hardware. I don't know what my wiring diagram will be but I was thinking of 2x16 cell to bus bar managed by BMS from Overkill solar.

2 things, one, you may not have enough battery reserve if your household usage is high, the low freq inverter you have chosen will have about 120w idle usage per unit and those watts need to be sourced from somewhere. During the day, PV covers it but at night you can use 240w x 10 to 12 hours which comes to 2.4Kw to 2.9Kw Second, the Overkill is a great BMS, but you are limited to 100a thru it. You might look into a BMS that can handle much higher amperage. Batrium and others are better choices for larger inverters. You have a low freq inverter with high surge ability but those watts come from your batteries thru the BMS.

Installer will provide combiner boxes, disconnects, wire runs from back to front for AC and DC, sub panel. I will program inverters and build battery and tie into inverter.
I have the rolls of wire for the panels. I know there are some various wires missing. I would have to attach pictures but the run from back patio to garage is probably 150 feet. That leads to the beginning of my questions. garage mount of inverters and battery setup either on a rack like Will did or a Craftsman tool box like solar engineer did.. but then wiring diagram and BMS choice I dont know, will be very very hot in the summer. So that plan with local installer was and I agree was under back patio on outside of back bedroom wall. Again, large covered patio, that is safe from rain or direct sun. In the garage everything will be nice and close together but will need to be nice and tight against the wall as I still park cars in it. It is just the heat I worry about. The inverters will probably overtemp, Batteries would be ok and they wont freeze in the winter. They wont freeze on the back patio as if it even gets that close (very rare) I can point a small space heater in the area and be fine for the one or two nights a year we may get that cold.

I know this is just rambling right now as I have spent a lot and now need to pay my way out of this project and will end up not saving much more than just paying someone to do it all from start to finish..well I do get to pick the panels I guess but I digress. The long run of DC and AC from back patio to main panel at the garage and then from there into a sub panel and back to inverters is where I think cost is adding up. The features being listed by installer will be that the grid can assist the inverters powering sub panel load if panels and battery get to low. I like the idea and everything but kitchen and laundry would be moved to sub..

Ok thats enough for now. Right now feel like I need a couple solar buddies to learn from and maybe help me install all of this. I have read a lot and want to use some of these tools I bought, I just need someone looking over my shoulder and stop me before I incorrectly do something. Thanks in advance for any help.

 

[MrM1]

Heltec 48v 200amp bms.

Long read, but everything you ever wanted to know

Heltec (JK) 200A Smart BMS with 2A Active Balance

I am starting a thread specific to he Heltec 200A Smart BMS with 2A Active Balance. 200A max charge. 350A max discharge I have 4 of them and I bought them from the Alibaba Heltec store here - https://www.alibaba.com/product-detail/14-24S-200A-Smart-BMS-with_62544207027.html edit: I forgot to...

diysolarforum.com

 

[FilterGuy]

8S on PV with 3 strings? 9S will get you over the 450V max PV input on cold mornings. You might be able to squeak by with 8S with 2 strings on one LVX6048, max PV amps is 20A. However that will put you over the 6000 watt PV input rating. 16x400=6400w

I just assumed he would do 2 strings of 6 on each of the two inverters. That is well under the 6000W per inverter and keeps the Voc low to cover for low temps. (without the specific specs on the panels I can't say how cold it can get, but it is a 19% margin on the Voc and that is usually good enough for extreme cold with most panels)

 

[Stormsoul]

I was planning 6s2p to stay under limits in cold snaps. I would then run into combiner box then to inverters. I was aware of the inverter idle usage, and I knew with current battery I would not make it overnight. I intended to grid assist but eventually after I know my audit is correct and I can support load overnight that I would pull the assist part off. those talesun's are not bifacial. I originally wanted bi but at the time they were out of stock. thanks for information on Heltec. I will have to do some reading. You guys are so helpful and suportave. I have been reading for long time then made an account and still didn't post. much, I was nervous about being told I can't do math. which this seems to be all math actually.

 

[MurphyGuy]

All complicated things are just a bunch of simple things put together.

Break your system down into the simple things and take them one at a time. Doesn't matter if you're in the planning stage or building stage, don't try to do it all at once, just take one component step at a time.

 

[FilterGuy]

I have been reading for long time then made an account and still didn't post. much, I was nervous about being told I can't do math. which this seems to be all math actually.

I always try to show my math in my answers, but if any of it does not make sense to you .... feel free to ask.

 

[Zwy]

I just assumed he would do 2 strings of 6 on each of the two inverters. That is well under the 6000W per inverter and keeps the Voc low to cover for low temps. (without the specific specs on the panels I can't say how cold it can get, but it is a 19% margin on the Voc and that is usually good enough for extreme cold with most panels)

Never gave 6S2P a thought, skipped right by me. I thought maybe he was purchasing the LV6048's for the 450V PV voltage rating and intended to maximize it. Staying under 250V PV, for the same money you can purchase several different units dependent upon needs. I looked at the LV6048 and even emailed Ian about it compared to the LV6548 and he suggested to stick with the LV6548. More PV input with multiple inputs per unit, more charging capacity and a few other things.

The low freq inverter idle draw for the LV6048 is what made the decision for me. I won't be running anything in the house where a low freq inverter would be beneficial.

 

[Zwy]

Heltec 48v 200amp bms.

Long read, but everything you ever wanted to know

Heltec (JK) 200A Smart BMS with 2A Active Balance

I am starting a thread specific to he Heltec 200A Smart BMS with 2A Active Balance. 200A max charge. 350A max discharge I have 4 of them and I bought them from the Alibaba Heltec store here - https://www.alibaba.com/product-detail/14-24S-200A-Smart-BMS-with_62544207027.html edit: I forgot to...

diysolarforum.com

There are plenty of choices, a Seplos would work too but all are FET based on the lower end of the price market. For larger systems, I prefer something more like the Batrium. I went thru all of this when choosing a BMS for my house system and the choice was Batrium CORE with K9's for me. I can add K9 expansion boards if I want more battery storage. I wanted a central remote monitoring capability with individual cell monitoring and the unit really fit in with my system.

 

[Stormsoul]

so I got the wrong inverters.. I thought with a decent near high or constant usage it would be a better bet.. I don't have well pumps or things like a band saw. They are unopened. I did talk to Ian and he thought I was on the right track with what I was planning.. We did not go into extreme details.

 

[MrM1]

so I got the wrong inverters.

Why do you say you got the wrong inverters?