Fire safety for a battery storage rack? NEC 706 questions.

[Zimm]

I'm just getting started on looking into a battery back up system to pair with generator and solar. How does one best guard against a battery fire? I see YouTubers putting battery server racks on the floor of a garage of basement. I just learned about the NEC 706, in which case the batteries have to be out of impact range of a vehicle- so that means high mount wall rack. It also stipulates 5/8" drywall required in a garage and integrated/networked smoke alarm system. Would that be enough to keep a server rack from burning down the house? I thought about outside storage or a little "battery shed" but I'm drawing a blank on how to efficiently keep it above freezing temperature being in New England.

I also see the NEC says if you have more than 20kw/hr of storage, you have to go to commercial standards? So a 5 battery SOK rack would be 25-ish, putting me into that category?

Normally I wouldn't worry too much about passing an inspection and just DIY wire it all up. But if I want to sell power back to the grid, doesn't everything have to be checked out by the power company?

 

[OzSolar]

But if I want to sell power back to the grid, doesn't everything have to be checked out by the power company?

Not everything is checked out. Around here they only inspect the equipment that directly interfaces with them and not even that closely in my experience.

Particularly they are looking to see if your equipment complies with IEE1547 and UL1741. You submit single line drawings along with your application that is signed off by a "licensed electrician or professional engineer" in this state. They review them then issue you a conditional letter or approval or reject them. You can make thier corrections and resubmit.

Once you're finished you send in a request for inspection and net meter installation. They come out, make a cursory attempt at making sure your system looks like what your submitted, has the correct placarding, close your disconnect, observe that it takes 300 seconds to interconnect, open the disconnect to make sure the house side of the disconnect dies to prove that your system will disconnect from the grid.

If all that happens they convert your meter to a net meter either physically or by reprogramming it then drive away. Takes about 10 minutes.

I'm not saying you shouldn't do everything to code, just answering the particular question.

 

[Lifepobuildandservice]

There are 2 lithium technologies to consider. Lithium nickel cobalt batteries, i.e. Tesla, do suffer from run away fires that even gyprock siding and ceiling will likely not stop. Lithium iron phosphate are generally reported to not suffer this problem. Also careful selection of brand is really important. Brands with heat sensors inside and a BMS (battery management system circuit board inside) should ALWAYS shut down the battery before there is a problem. Also good cases that are geko and rodent proof are necessary. Certainly a car crushing a battery could still short circuit everything in an unpredictable way that could lead to a fire so that is important to consider too.

 

[dielectric]

Call me paranoid but I'm building a concrete "cabinet" outside, next to garage wall. Even with LiFePo4 and the best BMS and fuses etc.
I want to be sure that my power wall is safer than Tesla's. Cinder blocks are cheap, rebar is cheap, cement is cheap. Pretty much everything is cheap compared to batteries and the rest of it. Good night sleep is priceless.

 

[Browse]

Is there any history of LIFEPO4 rack mount batteries with BMS starting a fire?

 

[dielectric]

Is there any history of LIFEPO4 rack mount batteries with BMS starting a fire?

Some rely on government regulations, some don't give a ...t, some read forums to learn...

Absence of confirmed stories doesn't make me feel confident enough. All this stuff is too new.

If there's a precaution that I can take and it means only a marginal effort and cost, I do.

 

[Danke]

Call me paranoid but I'm building a concrete "cabinet" outside, next to garage wall. Even with LiFePo4 and the best BMS and fuses etc.
I want to be sure that my power wall is safer than Tesla's. Cinder blocks are cheap, rebar is cheap, cement is cheap. Pretty much everything is cheap compared to batteries and the rest of it. Good night sleep is priceless.

I’d like to do that, but it can get -30°F here. So I’d have to figure out a way to heat the shed, economically…

 

[Zimm]

My same thoughts too about a battery shed but need heat. I see trophy batteries are heated, but I haven’t even looked into how much energy that takes. If it uses a days worth of solar to stay warm, that defeats the purpose.

 

[Quattrohead]

I’d have to figure out a way to heat the shed

More likely to cause a fire than the batteries themselves.

 

[SparkyJJO]

Lots of insulation and heat the batteries directly to keep just warm enough (maybe like 40-50 ish F). Probably won't take that much energy if the insulation is good enough around the batteries themselves. The rest of the shed could remain unheated.

 

[SilverbackMP]

I refurbished a 12x12 shed with new outside metal (had T11) and added 2 inches of spray foam on the walls and floor (added joists over the existing concrete) and 3 inches on the ceiling. And then a layer of mineral wool (fire resistant and plugged up any cavities). And then 3/4 plywood on the walls and then 5/8 type X sheetrock. I'm putting in a high SEER mini-split for cooling and emergency heating, but I think that heat will only be required on extended days below zero Fahrenheit. I will also have some light networking gear for home and office in the space too (10gbe switch, smallish servers/NAS, POE switch, etc).
Probably a bit of overkill here, but I like overkill.