diy solar

diy solar

NEC 2020 Compliant Batteries/Energy Storage Systems

Jojohoho

New Member
Joined
Jun 10, 2021
Messages
7
Tried posting this in the beginners' corner, but I am guessing that perhaps wasn't the right place for it. Apologies if this comes across as spam.

After reading an earlier thread about NEC 2020 and DIY installs, I'm completely rethinking my storage plans. Definitely not going to be building my own LFP battery packs. (If I could and still meet code, I absolutely would. And I plan to have a detached shed specifically for batteries + inverter anyways for safety.) I have started to engage my local electrical inspector, who still needs to read up on the new rules. But I'm wondering what others are doing for NEC 2020-compliant batteries/"energy storage systems". I really want to stick with LFP if I can, but I also don't want batteries to break the bank. There do not seem to be very many options.

Looks like SimpliPhi got UL9540 certification this year for a couple of their storage solutions (link), but their batteries are only UL 1973 certified (spec sheet)

Also appears that Fortress eFlex 5.4 is UL 9540 certified (spec sheet)

The California Go Database (mentioned in another thread) has also been helpful in tracking down UL certified ESSs, but few of them look promising.
 
Last edited:
Have you verified that that even applies to you? Many states aren't even using the 2020 code yet.. and plus with a detached shed where they will be stored you'd have even less to worry about. The code also appears to be lumping all ESS into one bucket even though LiFePO4 is safer than Lithium Nickel Manganese Cobalt Oxide (and other lithium based cells) which a Tesla Powerwall uses. Even that SimpiPhi article you linked to states "affirming the inherent safety advantages of using cobalt-free, non-toxic lithium ferro phosphate (LFP) battery chemistry".

I think the general problem is you have end users installing sometimes questionable BMSs and/or don't know what they are doing which increaes risk of having problems. Having a plug and play ESS alleviates an inspector having to make a call if a system is safe but you can still have a safe DIY ESS.
 
Have you verified that that even applies to you? Many states aren't even using the 2020 code yet.. and plus with a detached shed where they will be stored you'd have even less to worry about. The code also appears to be lumping all ESS into one bucket even though LiFePO4 is safer than Lithium Nickel Manganese Cobalt Oxide (and other lithium based cells) which a Tesla Powerwall uses. Even that SimpiPhi article you linked to states "affirming the inherent safety advantages of using cobalt-free, non-toxic lithium ferro phosphate (LFP) battery chemistry".

I think the general problem is you have end users installing sometimes questionable BMSs and/or don't know what they are doing which increaes risk of having problems. Having a plug and play ESS alleviates an inspector having to make a call if a system is safe but you can still have a safe DIY ESS.
I have verified that nec 2020 has been adopted in Maine, where I will be building.

And I completely agree regarding safety. Lfp is quite safe AND I will be taking extra precautions. And I feel much more comfortable building and maintaining a system than I do plugging it in and praying that it works as intended.

As pointed out in tbe previous thread, though, even if an inspector signs off, it's potentially a big risk if the insurance company can use it as grounds to deny a claim.
 
Best to comply with future code, especially if not inspected and approved when you put it in.
Having battery in a remote bunker protects house from fire, and I think that's the future code for repurposed EV batteries (lead-acid not subject to this restriction.)

UL approved lithium batteries have been recalled after several house fires.
 
The cost difference is substantial. A SimpliPhi battery costs about $36/Ah ($2700/75Ah). A DIY LFP battery is around $9.5/Ah ($1700 for 16 280Ah cells + generous $1000 for BMS, time, etc).
 
The cost difference is substantial. A SimpliPhi battery costs about $36/Ah ($2700/75Ah). A DIY LFP battery is around $9.5/Ah ($1700 for 16 280Ah cells + generous $1000 for BMS, time, etc).
Completely agree. It's a huge difference as we will be off grid and want 20-40 kWh of storage.
 
Best to comply with future code, especially if not inspected and approved when you put it in.
Having battery in a remote bunker protects house from fire, and I think that's the future code for repurposed EV batteries (lead-acid not subject to this restriction.)

UL approved lithium batteries have been recalled after several house fires.
Agreed. Unfortunately NEC 2020 seems to make it hard to comply with the code without restricting purchases to a very very small set of products and suppliers, all of which are quite expensive.

I still don't understand how this will impact solar installers, as they'll also have to meet code.
 
The only thing I saw coming with new NEC was ESS Energy Storage System had to be listed (if not lead-acid), but a provision to allow repurposed EV batteries if kept > 5' from the house. What else?

I thought rapid shutdown etc. already in older code was all that affected typical grid-tie systems. Change just for battery. Most would buy a listed ESS so it is legal (even if not 100% safe.)

Where I'm playing, I have AGM (primarily due to cost and number of anticipated cycles) and my PV is grandfathered prior to UL-1741SA.
I noted my Sunny Island were on the approved list before, no longer since "SA". I'm sure SMA could do a firmware update for that but more likely will only have that in new model when that comes. Seems to me SI is still UL listed, OK as a UPS, just can't be used with DC coupled PV for net metering in a new installation.
 
The only thing I saw coming with new NEC was ESS Energy Storage System had to be listed (if not lead-acid), but a provision to allow repurposed EV batteries if kept > 5' from the house. What else?

I thought rapid shutdown etc. already in older code was all that affected typical grid-tie systems. Change just for battery. Most would buy a listed ESS so it is legal (even if not 100% safe.)

Where I'm playing, I have AGM (primarily due to cost and number of anticipated cycles) and my PV is grandfathered prior to UL-1741SA.
I noted my Sunny Island were on the approved list before, no longer since "SA". I'm sure SMA could do a firmware update for that but more likely will only have that in new model when that comes. Seems to me SI is still UL listed, OK as a UPS, just can't be used with DC coupled PV for net metering in a new installation.
Regarding repurposed EV batteries, do you happen to have a link? I know that 2018 IRC has a 5' detached shed clause for repurposed EV batteries (referenced on page 27 of this slide deck). I am not aware of any similar clause in NEC 2020.

I believe you're right about rapid shutdown.

And my biggest concern is around batteries. I would like to have batteries as opposed to "storage systems" as I don't want to be out $10k+ if something fails. (And it seems the warranties at best only apply to licensed installers.) I could go the LA route, but that would be a bummer in terms of cost, maintenance, and longevity.
 
You're right. I read that regarding IRC not NEC


I think you can get yourself approved to install some batteries like LG so warranty is good.
I'm using lead-acid because only backup during rare grid failures. Either AGM or commercial lithium was same cost per kWh of life cycle, and even AGM should have more cycles than I need in a decade. Only cheap commercial (e.g. made with recycled) or DIY is cost-competitive with utility rates.
My approach is store as little as possible in battery, just enough to get through the night. Oversize PV array, use it or lose it when not on grid; cost is a fraction of utility rates. Some day I'll automate enabling loads based on SoC. For now I just have load shed of entire house at 70% DoD.

Rapid shutdown is something I would need if I moved panels to the roof. AFCI also (built in to some inverters but not others.) I've picked up a couple AFCI units, should be able to monitor multiple strings on roof. Would wire to RSD. I previously saw some 4-panel RSD units but not lately. Those seem more cost effective - four strings of 3 series 12V PV panels on one RSD unit, two RSD units per 24 panel string.
 
You're right. I read that regarding IRC not NEC


I think you can get yourself approved to install some batteries like LG so warranty is good.
I'm using lead-acid because only backup during rare grid failures. Either AGM or commercial lithium was same cost per kWh of life cycle, and even AGM should have more cycles than I need in a decade. Only cheap commercial (e.g. made with recycled) or DIY is cost-competitive with utility rates.
My approach is store as little as possible in battery, just enough to get through the night. Oversize PV array, use it or lose it when not on grid; cost is a fraction of utility rates. Some day I'll automate enabling loads based on SoC. For now I just have load shed of entire house at 70% DoD.

Rapid shutdown is something I would need if I moved panels to the roof. AFCI also (built in to some inverters but not others.) I've picked up a couple AFCI units, should be able to monitor multiple strings on roof. Would wire to RSD. I previously saw some 4-panel RSD units but not lately. Those seem more cost effective - four strings of 3 series 12V PV panels on one RSD unit, two RSD units per 24 panel string.

Regarding LG warranties, that's good to know. I'll look into that more.

We'll be doing entirely off grid because it would be ~$50k to run power to the site, so it's an either or proposition for us.

Since we'll be ground mounting (for other reasons) definitely planning to oversize the array. Still will want 3-5 days of autonomy so we can avoid regular generator use.

Thanks for the helpful feedback.
 
We'll be doing entirely off grid because it would be ~$50k to run power to the site, so it's an either or proposition for us.

Since we'll be ground mounting (for other reasons) definitely planning to oversize the array. Still will want 3-5 days of autonomy so we can avoid regular generator use.

Consider a DC Solar trailer. They come with my favorite, Sunny Island.

I don't know what they went for at the original auctions, but I've seen postings between $8k and $10k for one without generator. More with diesel generator, which might be good in your case.
If the batteries are healthy (some were dried out), you get two Sunny Island MSRP $5k MSRP each, two GNB forklift batteries $5k MSRP each, one Midnight charge controller and 2400W of panels, and Homeline breaker panel. On a trailer.
Add up to 24kW of Sunny Boy, overpaneled with up to 40kW of PV panels if you put them in multiple orientations.

Those batteries should give you several days autonomy, last maybe 10 more years or 15 from original manufacture date. Although some people report even longer life (like 25 years) from quality lead-acid. I think these are individual cells so besides hygrometer you could charge individually rather than equalizing a series set of cells.
 
Best to comply with future code, especially if not inspected and approved when you put it in.
Having battery in a remote bunker protects house from fire, and I think that's the future code for repurposed EV batteries (lead-acid not subject to this restriction.)

UL approved lithium batteries have been recalled after several house fires.
Yes - lots of listed and Code compliant equipment has started fires. No shortage there. New equipment = new code and best practices for safer implementations.
 
Back
Top