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> Unless stated otherwise, none of the published devices has passed regulatory certification, so use them at your own risk and responsibility

This somewhat limits the usefulness of the hardware anywhere you need to be insured, e.g. your house, boat or van.

Not that this is accepted by insurers or AHJs ("authorities having jurisdiction"), but one can use UL-certified components in an (open-source) _assembly_ that itself isn't UL certified. This at least supports the argument that the overall product is safe if thoughtfully designed and assembled. An example is the OpenEVSE level-2 car charger (which I had a really good experience with).

If you're not selling them then there isn't really any certification requirements until you start to get into the mains voltages. This all seems to be 12/24V DC stuff on the battery side and 60V DC on the solar side which comes under 'extra-low voltage' in basically every jurisdiction which is usually not really regulated because it's difficult to shock someone.

The battery stuff is more risky (bringing lithium cells into the picture) but I don't think anyone should be worried by the MPPTs.

This is for DIYers and enthusiasts, not someone looking for an off-the-shelf box.

(Also, Amazon is where most people get their solar equipment these days and you would be amazed how much of it is not UL certified either.)

DIYers and enthusiasts should still worry about their house burning down because one of these boards started a fire. An insurance company would investigate and find any excuse they can to deny payment.

Should is doing a lot of work there. The reality is most don’t. These are people who don’t understand minimum conductor size trying to DIY a solar system.

Insurance covers the insured's own gross negligence. This is a trope up there with believing the "warranty void if removed" stickers.

The real reason this should give you pause is that you don't want your house to burn down regardless of an insurance payout. That is how your incentives remain aligned with the insurance company.

> This somewhat limits the usefulness of the hardware anywhere you need to be insured, e.g. your house, boat or van.

Same goes for all the random Chinese inverters people are buying and installing in their Homes, Boats and Vans. Doesn't seem to stop them.

those are usually certified?

The cheap stuff usually have the certification labels printed on them, but a cursory look inside usually shows breaches if you know what to look for (like we have had stuff from China where the ground wire wasn't connected to anything, but even if that's right there are things like just not having enough clearance between mains and isolated DC in power supplies etc.). So they are definitely not actually certified, they just slap the labels on anyway.

Of course, there is a rising group of actually really high-quality native brands starting to come out of China - Anker were an early one of these, Xiaomi is a massive one, UGreen is really popular on Amazon etc. These kind of brands actually will be properly certified and are scary good for how cheap they are. So it's changing a lot.

Definitely not UL (if we're talking about the $300 inverters on Amazon or AliExpress from companies like Anenji)

That's basically what most software Open Sorce projects state in their licenses as well: Use at your own risk. As someone who publishes design files openly you really don't want to be liable if someone uses the hardware in a wrong way.

That being said, the Libre Solar components are also meant to be used as the basis for customization (hence, called building blocks). Some of the devices are used with minor modifications in certified commercial products.

Apart from boats/caravans, DC systems are used a lot for rural electrification in the global south. This is also where the communication features of Zephyr RTOS are very important.

How hard is it to get stuff certified by UL? I would assume expensive and time consuming but don't really know.

I don't know much about UL but I can say that FCC certification (also technically required) for electronics can range from about $3k to something like $30k depending on what you're doing.

($3k would be for "unintentional radiator" device, i.e., not supposed to be a radio, $30k would be for "intentional radiator" device, i.e., supposed to be a radio)

FCC ensures a product doesn't cause radio interference, while UL ensures the product is safe to use and won't cause fires or electric shocks. For DIY, your primary concern is UL certification.

Because of customs product import rules, that FCC stamp is often not optional. Now if it was a dodgy seller, the stamp will not match the physical devices on rare occasion. =3

I think expensive and time consuming, but not necessarily difficult, if the product is already safe.

In general, almost all insurance companies will demand UL stamped hardware, and most mortgage/lease/commercial property requires insurance.

A hobby BMS is usually a bad idea, as most kits from unknown origins prioritized cost over safety. Depending where you live, prior to roof installation there may be additional zoning and signed engineering drawing requirements.

It is not hard to find UL equipment, but expect to pay about another $600 for the BMS. Yet, it is better than a house burning down, and the insurance provider denying coverage.

Have a look at local certified installer companies, and make sure to get some real references in your town. Just like most HVAC companies... some installers are just over priced scams. Some folks claim https://www.pegasussolar.com/ was inexpensive, and might be worth a call. Best regards =3

It doesn't have to be a certified install company in many places, it just needs to be inspected which most states will do for homeowners. (if your area is different contact your representative)

UL or other certification is a very good idea. They can't automatically deny coverage for lack of certification, but it becomes a much harder fight for you to prove the non-certified equipment wasn't at fault.

Why ZephyrOS?

ZephyrOS: https://github.com/zephyrproject-rtos/zephyr

Would there be value in modeling this system with TLA+?

Why build another open product?

There are a few GitHub topics for solar electricity:

solar: https://github.com/topics/solar

photovoltaic: https://github.com/topics/photovoltaic

pv: https://github.com/topics/pv

battery-management: https://github.com/topics/battery-management

ups-management: https://github.com/topics/ups-management

inverter: https://github.com/topics/inverter

Photovoltaic system: https://en.wikipedia.org/wiki/Photovoltaic_system

> Why ZephyrOS?

They say right here: https://libre.solar/software/

This is a very nice development, but it is tackling the easy stuff. I'd love to see an open source inverter that can operate in stand-alone mode or in grid connected mode. All of these grid connected devices with closed source are a massive risk, especially given how small and cheap a WiFi or cell modem is nowadays.

They are pretty clearly targeting DIYers and enthusiasts who like tinkering with off-grid solar.

Grid-connected is an entirely different ball game. You will not see any open source projects there, or at least not any that anyone will want to use.

Let's think about why not. Anything grid-connected, you REALLY want a licensed electrician to plan and install. And competent electricians will NOT go anywhere near a piece of equipment that is not UL certified. A company producing equipment is NOT going to go through the expense of getting UL certified and then just release their design, PCB, and schematics for free.

And I want to be clear that I am a strong proponent of open source hardware, there are just certain situations where the incentives in reality just don't line up. This is one of them.

> Anything grid-connected, you REALLY want a licensed electrician to plan and install.

Have you heard of balcony solar?

It's a solar panel, a microinverter, and a standard wall plug. It doesn't need an electrician to install any more than anything else, you just plug it in. Outlets work both ways.

LibreSolar doesn't seem to be working on any inverters, but a complete open source system like this would be great.

https://en.wikipedia.org/wiki/Balcony_solar_power

If that wikipedia article is right, then balcony solar is not legal where I live (in the US). Here, we require a hard-wired, permanently installed automatic transfer switch that disconnects the solar generation from the grid when the mains power goes out. This is to protect line workers when working on downed lines.

It's probably coming soon for you, 30 states have bills announced or introduced legalizing plug-in solar and one (Utah) has already passed. They should be fairly uncontroversial.

Also, there's no need for a transfer switch in any grid-tied system, whether plug-in or hard-wired. Grid-tied inverters shut off automatically if there's no grid frequency to sync to.

Could the inverse process work? Design, then (crowdsource?) pay for UL certs? Don't know the process for certification, but in the software side, I've heard from foss projects asking for money for, e.g, security audits

Theoretically, yes. But in practice you need to bake certification requirements into the design or it will never pass.

Bollocks. I've been making grid connected hardware for decades, there is nothing magical about any of that. You just need to be careful, use proper fusing and you need to know how to read the electrical code.

Competent electricians are licensed professionals who (1) stand to make money on selling gear and (2) have customers that hire them simply because they don't want the hassle or the liability. Obviously a licensed professional is not going to install your home brew inverter, but at the same time if you can design a homebrew inverter you probably don't need a licensed professional anyway.

I've rewired lots of homes and have never had an issue with any of this and designed my first inverter when I was 17 to power my room when my betters decided I should go to sleep and cut the power.

This stuff is not magic. If someone designs a modern open source inverter I'm definitely going to build and install it. Fortunately insurance companies here are reasonable: if your homebrew device wasn't the cause of the mishap then you are still insured.

The one thing they are very strict about is gas, because there is no such thing as a 'fuse for gas'. But if you've properly designed and fused your gear then it should be no less safe than any other grid connected device, even if the magic UL or TUV mark isn't there.

The big one is EMI, that can be hard to get right and you need some gear for this, which is why it pays off to pool the money for an open source design to be certified. And once certified of course the design is 'type approved' and frozen, so you can't change any of the hardware without going through recertification. This is expensive, but if you don't do it every other week should still be well within the means of a properly set up open source project.

Why the fearmongering? It's not as if we're 12 here.

>Bollocks. I've been making grid connected hardware for decades, there is nothing magical about any of that. You just need to be careful, use proper fusing and you need to know how to read the electrical code.

I would say that rules out about 80-95% of DYI users.

This is 'hackernews', not 'consumersRus'. Though on odd days you might think differently.

And even days. And twice on Sundays.

A UPS-style grid connected inverter (with phase balancing) would be significantly more complicated by also significantly more useful. More in the critical/specialized part category, rather than near-commodity (like MPPT/BMS)

Deye/Solark famously bricked a bunch of inverters remotely not long back

I opened up all inverters here and disabled all remote access hardware physically. I'd rather not have a warranty than the risk of either seeing my critical hardware hacked or bricked by the manufacturer. And given the size of these (one is a 17KW unit) the risk of real damage to my home circuits and/or the feed is not imaginary, just rapidly turning it off and back on would already be a big problem, especially on a really sunny day. I try everything I can to not trip the breakers on the inverter around solar noon on sunny days because the amount of current is non-trivial, even on a 960V system. It will generate an absolutely spectacular arc.

My SolArk inverter came with a wifi dongle that uses Modbus over RS232 to interface with the inverter. I removed the dongle and connected a Pi to provide a Modbus-over-TCP interface that I can use from Home Assistant. I got more control (the officially-supported Modbus interface is read-only), and SolArk no longer has any access to my equipment.

That's a nice trick. I should try that.

Open source open hardware microinverter incoming (with certification for EU grid):

https://fosdem.org/2026/schedule/event/7Q9HMF-open-solar-pow...

2025 for archive:

https://archive.fosdem.org/2025/schedule/event/fosdem-2025-6...

Always a bit jarring to see a devboard stacked on an otherwise neat board. Looks promising though.

I've seen commercial products that use socketed devboards inside. If anything, it's just an indication that the hobbyist and professional spaces are slowly converging.

Glad to hear it - but cost of renewable energy isn't the software or hardware locked behind vendors. Its installers, wholesalers and permitting. Pricing is set to about where homeowners will be willing to pay and installers will make a good profit. If only it was a 5 year payback - we'd see it everywhere in NA.

Not sure cost saving is the priority.

I got solar installed by the local power company and while it's well done and was a great deal regarding the price, the inverter stats are locked behind a really terrible app. At least there isn't a subscription cost but I wouldn't be surprised if they add one someday.

Would gladly pay more for fully open and serviceable replacement.

I get that - but also solar should be cheap. If we lower the cost of power we knock off a lot of the bad externalities of power production and allow people to be more inventive with their power use.

Agreed - a lot of the inverters do some real BS moves around data management clearly a way to extract more value in a subscription mode. Its mind numbingly frustrating.

Price isn't determined by the cost of supply but by the value provided to the buyer.

The stats are the least of your problem, the bigger ones are remote updates, planned obsolescence, hacking and bricking.

Yes, and?

This project isn't being marketd to people who call up a company to white-glove the whole-home installation end-to-end. This is for DIYers who have enough knowledge to tinker with self-designed solar projects but not the EE degree required to engineer some of the more specialized equipment themselves.

I'll give a good example: I use solar to power a ham radio station for a weekend in the summer. However, nearly ALL of the equipment you can buy for the production and storage of solar power emits some degree of radio-frequency interference, which is bad when your whole goal is to power a very sensitive radio.

When it comes to charge controllers in particular, there are exactly two companies that claim to make RFI-quiet MPPT controllers. One has mixed reviews (some people say they work great, some say they are not any better than anything else), and one is very good but also very expensive for what you get. So, more open design and community feedback from people like me might get the cost of a reliable RFI-free charge controller down to where it should be.

That's especially nasty when you're doing LF or VLF because the frequencies of the switches in those things are right in the middle of the bands that you are trying to receive.

Great use case for solar shed/offgrid/cabin... I think people underestimate how much you can do with a solar shed , batteries, and the sorta reduced risk aspect of a shed catching fire vs a house. That being said its really easy to follow safety precautions. I cant wait to try this out.

My wishlist:

- dc motor conversions for air conditioners and voltage controllers that can adapt to multiple panel types to drive it. There's a lot to be gained without going all-in an inverter. What if I stayed on grid but heavily offset my heating / cooling bill by having a wall mount unit that was free to run during daylight hours on a completely separate circuit?

- conversion kit to make the wall mount unit a heater in the winter months

- a DC home system for select appliances such as lights, computers, or even refrigerators. This requires more precise voltage regulators because DC is more finicky when you add / remove loads. But you save some losses in efficiency.

- a thermal battery, so my window mount cooler can freeze a solid block of ice all day during the sun, and use it to cool me when I get home. It would be sealed of course. But condensation would still have to be managed. Maybe a hot water tank adapter that uses excess electricity and dumps it in the tank, but not so much to explode. Again, a form of offset, not a replacement for gas. Another thermal battery could be a sewage tank that aborbs heat from the AC unit before it goes down the drain. This would reduce the load of the fan.

- a wind generator that works best in storms. It could dump straight to a heating element and fan indoors. Who wouldn't love free heat during violent storms? Maybe it could have a clutch (mechanical or electric) to tune the load to the wind gusts.

- a solar cooker, maybe with a molten fluid or superheated steam. The latter can go well above 500F so plenty hot enough for cooking. But of course very dangerous so would need a professional device, if it's even possible. But this would allow e.g. restaurants in the summer to offset or replace heating for their kitchens. It pains me to think of how much energy is wasted in a hot desert city to pay for a gas grill and then pay again to pump to he excess heat outside.

A meta comment and really don't want to distract from the product but as a Spanish speaker, the word "libre" for open source projects really grids my gears. It's specially bad when used with "libre" before the subject (like LibreOffice or Libre Solar). It sounds a bit like Brad Pitt saying "bonjourno" in Inglourious Basterds.

Libre does mean free as in freedom, but it also means available and released from prison.

It's from French, not from Spanish, and besides, everybody knows what the intentions are here so I don't think you need to feel offended in any way, that's your choice.

chill, I'm not offended, just thought it was worth mentioning it sounds bad to native speakers. Wouldn't you mention it if someone was misusing a Dutch word?

Also, it comes from French and Spanish [https://www.gnu.org/philosophy/free-sw.en.html], it's the same word and same grammar, subject before adjective.

> Wouldn't you mention it if someone was misusing a Dutch word?

Not a chance. Language is a tool, not some kind of holy house. If the meaning comes across that's already more than you could hope for.

The whole idea that language is something to be condensed and frozen is relatively new, it used to be much more fluid which made it harder to have a decisive set of words (sorry, Scrabblers (tm)) but language could adapt faster to circumstances. What we consider the 'final form' of all of these languages isn't final at all, it is just what we are used to and more of a convention than anything else.

Some countries (including mine, unfortunately) have groups that will go out of their way to harass people to use the 'correct form' ignoring that what those forms are is subject to change and that not everybody grew up with the currently agreed upon preferential way to spell things, and meaning is so much more complicated than spelling.

I think the easiest way to deal with these kind of frustrations is to see them as compliments: at least someone was aware enough of your language to name something in it, that's more than you could say for many other languages, if only because the scripts are different.

I’m fine with people using „gratis“ to differentiate libre software from software that doesn’t cost anything and I’m German.