ESS (energy storage system) sizing in residential garage

[Watts Happening]

I've been poking around each aspect of my install to ensure I'm not going to upset an inspector in the near future and when it comes to ESS, I'm confused.

Per this well written article, which sums up the codes relating to ESS, I'm trying to define what the "20kWh max each" means:

Fire Codes and NFPA 855 for Energy Storage Systems — Mayfield Renewables

Fire codes and standards inform energy storage system design and installation and serve as a backstop to protect homes, families, commercial facilities, and personnel, including our solar-plus-storage businesses. It is crucial to understand which codes and standards apply to any given project...

www.mayfield.energy

Is this a single battery with a max of 20kWh, or a stack of server rack batteries totaling 20kWh? IE, if it was a max in one location such as a server rack, we couldn't have more than (3) standard server rack batteries in one location without going over the 20kWh mark (we'd barely be over, but that .3kWh will matter to someone I'm sure).

So again, is it a single battery, or combination of batteries in one location without spacing? I'll be fine with the 80kWh total in the garage, but I want to ensure I'm not stacking six server rack batteries right next to each other and creating a violation right out of the gate.

 

[Rednecktek]

It appears that any combination of batteries, whether 1 big battery or 10 little ones, counts towards the limit.

It's a real pain in the ass...

 

[Watts Happening]

It appears that any combination of batteries, whether 1 big battery or 10 little ones, counts towards the limit.

It's a real pain in the ass...

Very annoying.

So, if that is the case, would it be fair to say that any/all EG4 server racks with six of their batteries is "illegal" or maybe I should say, "not code compliant"?

I'm not picking on EG4 by any means, they're just a well known battery/rack for the purposes of this discussion. I assume the same would be true for the SOK rack with five batteries or any other similar brand/rack setup.

That sure does seem dumb, and also would seem to nullify the entire point of one of those racks. They're super handy yet, apparently "not allowed"??

Or, is the fact that they have different listings such as UL1973/UL9540/UL9540A a determining factor of some sort. IE the EG4 LL batteries have a fire suppression system inside, maybe that somehow excludes them from said 20kWh max?

Dumb that I can park my 75kWh car anywhere and nobody bats an eye but if I set four batteries next to each other I'm a rebel..

 

[Oldphile]

I've also been poking around trying to understand this. How would HomeGrid be allowed to have a stack of more than 20 KWH?

 

[zanydroid]

I believe those diagrams show the standard rules but there are exemptions if the listing cert indicates that it is tested for closer spacing.

 

[Watts Happening]

I've also been poking around trying to understand this. How would HomeGrid be allowed to have a stack of more than 20 KWH?

My guess is simply that if you go above the 20kWh in one location, or max per area (say 80kWh in a garage) then this line is what becomes relevant:

• The maximum energy rating per ESS unit is 20 kWh. The maximum kWh capacity per location is also specified—80 kWh when located in garages, accessory structures, and outdoors and 40 kWh in utility closets or storage spaces. For storage capacities that exceed these limits, non-residential requirements come into play (NFPA 855 Chapters 4-9).

I've not read or reviewed anything relating to NFPA 855, so I can't intelligently comment (I'll look at it now). Maybe those requirements are met by the products we're talking about. IE maybe they need to be in a rack that can't easily be accessed by children, or they must have a fire suppression system or whatever is required. Being that most of the article I linked talked about fire, I imagine the requirements are biased towards that.

Maybe a server rack full of batteries is totally code compliant. I just want to make sure I handle it all correctly, I'm not looking to have an insurance claim later denied.

 

[DIYrich]

So, if that is the case, would it be fair to say that any/all EG4 server racks with six of their batteries is "illegal" or maybe I should say, "not code compliant"?

Correct. You can put 3 in a rack, and have a 2nd rack 3 feet apart. You can also add one more battery 3 feet from that.

I'm guessing they designed the racks prior to UL 9540. What's dumb is that NEC didn't set the limit at 21k, so you can put four 5.1kWh batteries in a rack.

 

[DIYrich]

So again, is it a single battery, or combination of batteries in one location without spacing? I'll be fine with the 80kWh total in the garage, but I want to ensure I'm not stacking six server rack batteries right next to each other and creating a violation right out of the gate.

No, it is 40kWh in the Garage. The combined Garage, Accessory Structure, and Outdoors cannot excess 80kWh.
In addition, you get 40kWh in Utility Closets and Storage Spaces (inside the house).
Total of 120kWh per house.

 

[DIYrich]

I've also been poking around trying to understand this. How would HomeGrid be allowed to have a stack of more than 20 KWH?

They are capable of being stacked to 38.4 kWh per stack.

UL 9540 itself limits the stack to 20kWh.

 

[Watts Happening]

No, it is 40kWh in the Garage. The combined Garage, Accessory Structure, and Outdoors cannot excess 80kWh.
In addition, you get 40kWh in Utility Closets and Storage Spaces (inside the house).
Total of 120kWh per house.

I'm certainly not here to say you are wrong, as I don't know the rules well enough to determine, but based on that article and the image I posted from said article, it's stating 80kWh in the garage.

 

[timselectric]

Seems pretty simple.
1. 3 batteries per rack.
2. Pass inspection.
3. Add 3 more batteries per rack.
Problem solved.

And just for me.
4. Get 3 more racks. lol

 

[Watts Happening]

Seems pretty simple.
1. 3 batteries per rack.
2. Pass inspection.
3. Add 3 more batteries per rack.
Problem solved.

And just for me.
4. Get 3 more racks. lol

I'm all for that, I just don't want to have an unrelated fire or something down the road and have my batteries become a point of contention for an insurance payout.

Also, any reason the batteries "need" to be in a rack? I've got mine on top of a gun safe, it's a convenient location, keeps my child from being able to reach them and efficient use of space. Not sure that would make any difference?

 

[zanydroid]

Presumably the UL9540/1973 destructive testing was done with a particular configuration for the equipment.

Also, code says you need to follow the installation instructions.

 

[timselectric]

I'm all for that, I just don't want to have an unrelated fire or something down the road and have my batteries become a point of contention for an insurance payout.

Also, any reason the batteries "need" to be in a rack? I've got mine on top of a gun safe, it's a convenient location, keeps my child from being able to reach them and efficient use of space. Not sure that would make any difference?

That would depend on what your inspector wants.
I would think that if everything is covered and protected from contact, it should be fine. But, it's really up to your inspector.

 

[Watts Happening]

That would depend on what your inspector wants.
I would think that if everything is covered and protected from contact, it should be fine. But, it's really up to your inspector.

It pays to have a nice inspector haha!

Now, for someone like you that has 76.8kwh of DIY batteries, are you just "not code compliant" in their eyes?

God I get tired of the rules!

 

[timselectric]

It pays to have a nice inspector haha!

Now, for someone like you that has 76.8kwh of DIY batteries, are you just "not code compliant" in their eyes?

God I get tired of the rules!

I'm definitely not code compliant. lol

 

[DIYrich]

I'm certainly not here to say you are wrong, as I don't know the rules well enough to determine, but based on that article and the image I posted from said article, it's stating 80kWh in the garage.

Must have changed since I learned about it. I can find a 2020 edition that has the 40 + 80 you mentioned, plus 80 on exterior wall, and another 80 "outside".

 

[Watts Happening]

Must have changed since I learned about it. I can find a 2020 edition that has the 40 + 80 you mentioned, plus 80 on exterior wall, and another 80 "outside".

Gotcha. I’m still bummed about how this is written. I’ve got PLENTY of room on top of my gun safe for 7-8 batteries, yet now I’m restricted to 3. Certainly not convenient.

 

[Oldphile]

My state NH has not adopted NFPA 855, so I'm not going to limit myself to 20 KWH per ESS. Hopefully that doesn't change before I have batteries installed. Last code adoption was July 2022.

Edit: oops, just found an amendment to NH adoption of NFPA 1 to include NFPA 855.

 

[Danke]

Seems pretty simple.
1. 3 batteries per rack.
2. Pass inspection.
3. Add 3 more batteries per rack.
Problem solved.

And just for me.
4. Get 3 more racks. lol

Quiet You!

So where is the best place (via USA) to order Grade A 320/302/280ah EVE/CATL batteries from?

Looking to build a few sets of 16 cells 48v setups for home. Are there any sellers in US that sell brand new.. reputable, and you dont end up with bloated or lied about batteries? Is it worth the price taking the risk on Alibaba or Amazon?

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