Drawing Critique of 16kW Solar Array, 13kW (6.5kW AiO split phase), 48V Battery (51.2V, 4480Ah) setup

[Hatorri]

Hello All,

With some reading and some direct help from people from this forum, I believe I finally got my system planned layout to the point of execution. But before I do, I wanted to have some other eyes reviewing if I may have missed anything. I live in the USA and I suspect I will need to get a permit to do everything I plan to do. I will setting this up in the concrete basement of my home. I have 2 of the 6.5kW All in Ones (Rich Solar H6548) that I will set up as split phase so that I can mainly charge my Tesla and to power most of my electrical needs from my home. That will definitely take a licensed electrician to rewire from my home breaker to the off-grid breaker. I will also be expanding the battery bank (3.2 280Ah cells already purchased) from 1 to 4 as I get 3 more active balancer BMS's. I have 32kW of solar panels (Hyperion bifacial 400W) but will be using 16kW for now. I will be buying the rest of the components next year (busbars, pv cables, battery cables, disconnects, circuit breakers, t-fuses, combiner box, load centers with main breaker).

I do need more understanding on which T-fuses to buy and the bus bar to get in preparation for 4 battery banks. Sorry in advance for my simplistic drawing.

 

[rodrick]

Looks like you have been doing your homework the one thing I would add is a good quality shunt it will be far more accurate than anything else
also math correction 4 280Ah 16s batteries will be 1120Ah

 

[Hatorri]

Thank you for the compliment on how I've been doing my homework. It has been 2 years spent on planning and purchasing of the system components. I've managed to get the bulk of the expenses purchased (batteries and panels). I believe that to make the 48V LiFePo4 batteries, it would take 16 of the 3.2V cells in series to make them. That would be 16 x 280 Ah = 4480 Ah. If I only use 4 cells, I'd only be able to make a 12V, 1120Ah battery bank which wouldn't be able to be used in my 48V All in one setup.

I'll have a JK B2A20S20P attached to it but I now read why a shunt might be good to have in case the BMS isn't as accurate or for peace of mind. Will's video shows how the Victron Energy 500A smart shunt would be useful. Question now is whether I would need one per each battery bank in the future or will one be enough. I'm currently assuming the placement of this shunt would be from my negative busbar to the 1 48V battery bank in the drawing. I would put it before the busbar but with 2 All in Ones in parallel, I'm not sure it would work right.

 

[rodrick]

Cells in series only increases voltage

 

[rodrick]

1 shunt will do you just need to pass everything on the negative side thru it, so batteries to a negative bus bar bus to shunt then shunt to 2nd bus bar where you will make all of your connections on the negative side

 

[Hatorri]

I badly miscalculated my total Ah's since I did forget that current in series are not additive. Thanks for the catch. This means I will need to have all 4 ready by the time I commission the system. It also means that I am way below what I would need to be completely off-grid since the Energy Audit I did using the recommended link from here indicated I need to have 4456.3 Ah for 3 days of storage in case of no/little sun.

Based on new numbers, it looks like I will only be able to charge my tesla for work with 1 day of backup storage in case of rainy/cloudy days. I hate having to use up an average of 25kW a day just for the round trip daily commute.

I'll need to buy another 192 3.2V, 280Ah cells to make 12 more banks. Getting off-grid is getting a bit harder to accomplish.

 

[rodrick]

I badly miscalculated my total Ah's since I did forget that current in series are not additive. Thanks for the catch. This means I will need to have all 4 ready by the time I commission the system. It also means that I am way below what I would need to be completely off-grid since the Energy Audit I did using the recommended link from here indicated I need to have 4456.3 Ah for 3 days of storage in case of no/little sun.

Based on new numbers, it looks like I will only be able to charge my tesla for work with 1 day of backup storage in case of rainy/cloudy days. I hate having to use up an average of 25kW a day just for the round trip daily commute.

I'll need to buy another 192 3.2V, 280Ah cells to make 12 more banks. Getting off-grid is getting a bit harder to accomplish.

Welcome to the battery race

 

[Hatorri]

The new sectional drawing based on your info is as below. Do you have any feedback as which T-fuse calculation is correct since I am using 2 6500W All in One's in split phase mode? I take it the busbar needs to be rated for more than the T-fuse value or it will melt the bar, right?

 

[rodrick]

Your fuses are for protection of the wire so size the wire according to the bms capabilities ( oversized is good ) then size you fuse at wire rating x1.25% to come up with fuse amp rating

your bus bar must be able to handle your max amperage of your system plus some wiggle room I would add at least 25%

 

[OffGridForGood]

Based on new numbers, it looks like I will only be able to charge my tesla for work with 1 day of backup storage in case of rainy/cloudy days. I hate having to use up an average of 25kW a day just for the round trip daily commute.

I'll need to buy another 192 3.2V, 280Ah cells to make 12 more banks. Getting off-grid is getting a bit harder to accomplish.

I hope you live in a very sunny location.

 

[OffGridForGood]

13,000 / 48v = 270A
13,000 x 1.25 /48v = 340A
I would use 350A class T-fuse and 4/0 cable.

 

[Hatorri]

I'm in the Southeast portion of the US but it isn't as sunny as Florida gets. That's why I plan to set up to 32kW of solar panels. With the current 16kW set at 30 degrees, the PV Watts website shows I'll get about 22,497kW per year.

Month	Solar Radiation ( kWh / m2 / day )	AC Energy ( kWh )
January	3.88	1,473
February	4.61	1,554
March	5.24	1,898
April	5.85	2,010
May	6.21	2,141
June	6.14	2,010
July	6.25	2,098
August	5.96	2,001
September	5.86	1,918
October	5.36	1,899
November	5.28	1,879
December	4.25	1,617
Annual	5.41	22,498

My current battery storage (57,344) is below the maximum power generation I get in a day on any given month (Jan = 62.08kW, July = 100kW) . I'll need to up my battery bank to fully utilize what I'm capable of generating or end of wasting it. Maybe I should reduce the number of solar panels (12.8kW) so that I am not generating more than I can store for now? Or maybe I can redirect some of that wattage somewhere else on my farm like providing power to the chicken coup areas and lighting for the barn.

I can't tie the system to the grid since it is an off-grid inverter. If I did have a 12kW system (wont let any 12kW+ setups be on their grid) setup that was grid tied, I'd be selling electricity back February to December and getting between 0.08 to 0.92 cents a day. They pay 4 cents per kW and sell it back to me at 12 cents per kW. My house is all electric so I think I use almost 2000kW a month.

 

[OffGridForGood]

In my set up, like you, I have excess during the summer. I use this to charge an EV for trips to the nearest city to us. In my area, those excess kWh are worth nearly zero if fed to the grid, but worth 70-centsCDN (53cents USD) each to off-set gasoline. For my area this is the biggest "win" and best place to put excess kWh when I have them.
We also pump water from our deep well into an elevated water tank - this runs via gravity for animals and the garden with mechanically controlled valves, and in the work shop, I have a HWT that comes on as a dump load when we have exess. There are other options, like compressed air or A/C for a workroom as diversion loads.
I don't think of excess solar as "wasted" I just look at if the batteries are full each day that we are doing well. The more solar panels you have, the more loads you will find for that 'free' power.

 

[zanydroid]

If I did have a 12kW system (wont let any 12kW+ setups be on their grid) setup that was grid tied, I'd be selling electricity back February to December and getting between 0.08 to 0.92 cents a day.

Are you allowed to do 12kW-DC on grid (as defined as paralleled), and the other 20kW off grid?

 

[eXodus]

In my set up, like you, I have excess during the summer. I use this to charge an EV for trips to the nearest city to us. In my area, those excess kWh are worth nearly zero if fed to the grid, but worth 70-centsCDN (53cents USD) each to off-set gasoline. For my area this is the biggest "win" and best place to put excess kWh when I have them.
We also pump water from our deep well into an elevated water tank - this runs via gravity for animals and the garden with mechanically controlled valves, and in the work shop, I have a HWT that comes on as a dump load when we have exess. There are other options, like compressed air or A/C for a workroom as diversion loads.
I don't think of excess solar as "wasted" I just look at if the batteries are full each day that we are doing well. The more solar panels you have, the more loads you will find for that 'free' power.

those are excellent ideas to store power - outside of batteries - which are expensive.
Do you have a thread somewhere about your system?

 

[Hatorri]

My coworker mentioned about the elevated water tank that can be released to run through a turbine of sort to generate energy if needed via kinetic motion of downward flowing water. I also was alerted that I could use the excess energy to use a motor that would pull up a rocks to a higher elevation via a pully system and use gravity to turn a motor that would generate electricity as well. Another suggestion is using a flywheel mechanism. I saw Will's videos on using DC converters (24V to 12V) directly on the solar panels to power 12V devices. I know if I do that, I would have to step down the 180VDC to something more usable. If I do, will this converter cause problems in parallel with the All in ones? Or should I take the electricity after the All in one has converted it to DC?

I saw your system in your signature. I am aiming to make a system similar to your setup with the 3 LV6048's.