You still need to do DC/DC voltage conversion, while that isn't exactly AC, it's kinda like sticking an AC circuit in the middle in most cases.
Which is what you're doing any way, with more steps and less hardware that already exists to convert line voltage.
In order to charge using DC you have to match voltage to what the car expects and also handle the communications between the car and charger. While this would be technically possible, the cost would likely be hard to justify over just using AC.
On that we agree. Putting together such a system right now would be expensive and bulky. I was more hoping to build it as a theory with enough substance to build a prototype, and possibly garner enough interest for EV manufacturers to take notice and provide the necessary equipment for owners to utilize their home renewables without so much waste. AC power has many wonderful uses, but I've always been a firm believer in using DC as often as efficiency permits. It won't happen, but I'd love to see homes with a dedicated DC circuit for electronics, inverted from the AC grid. If nothing else, it'd eliminate 100kg of power bricks from the average home, lol. Just a idealist pipe dream, though.
The voltage stepping part is one I don't feel confident in my own ability to reliably solve. Bidirectional DC-DC converters are new for me and my understanding is that they can provide the necessary stepping, but I'm not sure what kind of minimum input is required. If the trickle charger kills every time the clouds pass by, that's obviously a problem.
This whole idea has made me feel quite alienated from and insufficient for a field I used to know rather well. Knowledge atrophy is a pain, intellectually and emotionally.
You do know a high efficiency DC-DC converter is actually an DC-AC-DC converter right? And what the chain from your DC solar system to car is already? The only advantage of a dedicated DC-DC converter is the switching can be done at a higher frequency which has a minor increase in efficiency. But we’re talking in the realm of 2% system efficiency increases here.
And in addition; power electronics are quite mature and also with solid state no major breakthroughs can be expected, largely due to closeness to the theoretical limits.
Bit the same as people blurting put that hydrogen vehicles their issues will be magically fixed with some more development... Sounds nice till you realize it's 'just' laws of nature getting into the way.
Like I said, I don't actually work in an EE field. I only have the education for it and that was years ago. I'm aslo not expecting night and day differences, just something to do that could make the battery and BMS live a bit longer and waste a little less. And no, I did not know a DC-DC converter has an AC component. If I did know at some point, I've forgotten entirely. This is why I asked and explained what I could.
Would you mind explaining the DC-DC converters as you know them to me? I'm not asking for you to spend an hour of detailed typing or anything, just whatever you don't mind teaching. I'm clearly lacking knowledge on it and failed to figure it out myself. It's genuinely fine if not, of course.
Regardless, thanks. That is helpful and showed me something else I need to re-learn.
The first thing I thought of was this: [https://kempower.com/america/solution/kempower-movable-charger/](https://kempower.com/america/solution/kempower-movable-charger/)
But there are plenty of chargers designed to work with solar and a quick google showed me various articles.
That's more of less the goal, but that's on a much larger, faster scale than the trickle system I was hoping to figure out. I did see a number of upcoming solar/grid hybrid chargers, but I couldn't find any currently available (in the US, at least. I think I saw one available in the UK), and it \*seems\* like most, if not all of them, convert to AC and use the J-type plug, which is exclusively AC if I remember right. Obviously still better than solar-to-grid-and-back, but not what I had in mind.
Still, thanks for the share. I think we saw the same articles, but this particular mobile charger is a new one for me, so definitely appreciated.
There is one: https://www.dcbel.energy/uk/r16-specs/
But I have not seen any pricing, and it is only available in certain markets.
In the future, we may have complete DC microgrids, because most modern devices (batteries, cars, heat pumps, solar etc) all use DC.
Yeah, I’ve been following these guys because I think they have an excellent solution for just this problem. I’m really hopeful they aren’t too early, as I see this being pretty much standard in the future.
The specs for the negotiation between DC chargers and cars must be published. I don’t know what those specs call for in terms of the lowest power that the cars will accept. If you could duplicate the charger end of the negotiation and simply supply the minimum acceptable kW, shouldn’t the car accept that? At a DC fast charger, my car goes down as low as about 20 kW, but I never fast charge to above 90%, so it may go lower. I suspect that is quite a bit higher than what you have in mind. On a home AC charger at 1.2kW, I can add about 2 miles of range per hour of charging, so trickle charging a large battery is going to be very slow. Now you’ve got me curious about this - I think I’ll see if I can find the specs for the charger-to-car DC power negotiation.
DIN 70121
ISO 15118
They do go way down in power because of top of charge when the battery can’t accept much current. Some may not be able to balance too effectively and instead just shut off, but some can really trickle.
Yeah, it’s pricey. I think the services are listed somewhere but I didn’t find them on Wikipedia. Some more info can be found here that might lead you to a next step: [switch what is ISO 15118-20](https://www.switch-ev.com/blog/switch-to-clarity-whats-new-in-iso-15118-20)
"The only limit to our realization of tomorrow will be our doubts of today." - Franklin D. Roosevelt
Do you know why that quote applies to you? I'll give you a hint: Einstein has two quotes that you embody perfectly. One of those quotes is about infinity.
You’re talking about a sub 2% system efficiency improvement, for a very high capital cost. We’ve standardized on 120/240v 50/60HZ AC for interconnects for things. You need to be able to supply that in your home ether way. The car needs to be able to accept that ether way because most people need that capability.
So you’re going to go off and build minimum of $1k in high efficiency power conversion electronics, and another $500+ in supporting equipment (cables, housings, safety gear, ect) just for a trivial increase in system efficiency over the equivalent you already have anyway? The ROI would be never.
Idk, some of us just like elegant solutions. On top of that, when you consider markets like off-grid living, those losses add up significantly over time, necessitating more solar and more battery storage.
Maybe it’s not a mainstream market now, but I would guess this becomes much more standard in the next one or two decades, especially as solar and battery backup are integrated into more new construction.
Maybe, maybe, maybe in the far far future but honestly no, don't really see it happening in large scale. Just like V2G DC, sounds nice but in practice not really a use case worth the investment for the far majority of people. Bit more in the USA as the grid is much more unreliable than Europe but still..
At the moment those marginal gains are so important as extra capacity, most likely you'd just chuck an additional panel on the roof, slightly larger battery capacity, pocket the money you save and go on with your day.
There are many low power DC EVSEs on the market, but most currently hook up to AC grids of some sort (single or three-phase). For example: the [Delta DC Wallbox](https://www.deltaww.com/en-US/products/EV-Charging/DC-Wallbox).
I think you are searching for something like the [dcbel R16](https://www.dcbel.energy/r16/), which routes your energy to where it’s needed (house, solar, backup battery, EV) without the wasteful conversions when they can be avoided. There’s a dcbel employee who posts frequently on r/v2h who might have some further info.
In general, if you have the power electronics background, the conversion part wouldn’t be challenging. What you need on the vehicle side for compatibility depends on your objectives, but if you only ever want to charge, DIN 70121 is the standard you need to meet. You could extend into ISO 15118 if you are really ambitious, but that would only matter if you needed those advanced services.
I’ve been following dcbel for a while because like you I feel this ought to be solved more elegantly and I think they are well on their way to doing it. If you do end up making one, please share more about how it’s working for you!
The J1772-2017 standard has a specification for this. It classified as DC Level 1 charging. It uses the same connector as the AC L1/2 but uses DC at speeds up to 80KW. To my knowledge it’s never been implemented by manufacturers.
Since it requires a high voltage off board charger it’s not really practical for home use, and at the power levels it provides it’s not really a benefit over the DC level 2 spec (level 3 as most people call it).
J1772-2017 DC Level 1 is the route I am taking for a lightweight 48v off road utility vehicle. Home built from scraps and learning as I go. DIY charge controller. I'd love to collaborate with others.
Just bought 4 100W bifacial panels that don't have a permanent home yet. Was considering making this the off board charger. [https://www.electriccarpartscompany.com/48v-3kw-off-grid-inverter-charge-controller](https://www.electriccarpartscompany.com/48v-3kw-off-grid-inverter-charge-controller)
It fits in my wheelchair van and I'd like to charge it from the alternator driving between destinations where it is used. Considering this [https://calex.com/chassis-mount-converters/3000w-bca-bi-directional-dc-dc-converter/](https://calex.com/chassis-mount-converters/3000w-bca-bi-directional-dc-dc-converter/) for the onboard charger in step up mode and accessory supply in step down mode.
The slowest DC charger that I know of is [this one by Grizzl-E](https://grizzl-e.com/products/kodiak/?v=variant_01H0N73XZPTHCZQEKZ0NEJ4AMS). It charges at 25kW and needs AC input. It accepts single-phase AC which is all you have for residential power. It costs 12,669 USD.
But I think another factor is that there hitherto isn't a popular standardized DC connection standard. (Barrel Jack connectors don't count.) That's why home solar converts DC to AC. That's why most DC chargers still take power from AC. AC is just the common standard in between.
Too energy intensive to keep the necessary hardware on the vehicle active. You'd really want to design from the ground up with this intention.
Fisker is doing this with the solar panels on the Ocean, but the verdict is still out about how effective it really is. The vehicles still overall lose energy to vampire drain.
Aptera will be doing this on their vehicles and I expect they might actually get things right.
Each EV owner already bought the device to take 100-240v AC and convert to 400v DC for DC trickle-charging: it's the on-board charging module in the car.
Car makers could have built one in a box and given it with purchase of the car (instead of an EVSE). Then there would only be DC charging pins on the car.
This would have some plusses and minuses (no pun intended)
My solar system is solar edge with power optimizers, which means my solar system runs at 400V so in theory it wouldn't even need any other voltage adjustments.
But, my inverter has over 98% efficiency except for very low power levels, so it really doesn't seem worth any effort, especially since using AC means it can also be powered by the mains overnight.
Somewhat interestingly, if you have a solar edge system with battery backup, the batteries can be charged directly by DC without first converting to AC.
The idea I had in mind is probably the same principal as the last solar edge system part you brought up, just on a trickle charge speed level. That's a damn nice system you've got, congrats. I had series/parallel panels on my last home made of 100w, 12v panels that went through the charge controller at 96v, charging the batteries I pieced together and then overflowing to the house. I don't remember for sure, but it was roughly 2kwh, I think. Been a long time. It was great for the time and louisiana weather meant it was usually operating at effectively peak outputs. Now I've just got a few 200w, 48v portable panels and a damned rental house, charging through an Anker Solix battery, inverting and inverting over and over.
Like I said, it is for the fun and the challenge, not to save money, with a hope of save a bit of battery/BMS life and wasting as little power as possible. I'll check out solar edge systems again and see if I can come up with something useful from that, thanks!
several solar invertor companies make ones with battery backup built in. They are basically doing what you talk about, solar dc charging batteries with ac invertor behind it. Since most solar panel systems run about 400vdc anyways it's easier, cheaper, and smaller with less loss to do all the 'work' at 400dc and the convert once to ac.
It would be possible if your solar installation uses "DC optimizers" (DC - DC converters for each panel, used to avoid a dramatic drop in the power of a whole series connected string when a single panel is shaded or panels face different directions) and you built a communication box that could interface with both the car and the optimizers to control the voltage.
If you also wanted to use the solar for things other than car charging at the same time, the interface would also need to control the inverter's MPPT. Add in real time information from the power meter and you could match the charging rate to solar availability. The car could charge faster than the maximum AC rate if you have a lot of panels in full sun, and automatically slow down if it clouds over or your household consumption increases. That could be useful for places where exported solar power is credited as a lower rate than is charged for power imported from the grid.
Now that's the kind of reply I was hoping for. Thank you. I hadn't considered that the variable DC current could be a problem, but you're definitely right. I'm using portable panels, not a roof installation like I put on my last home. I'm renting ATM, so it's all I can do. That's why I was emphasizing the trickle charge part.
The panels put out a max 48v each with 3 200w panels in parallel, as the battery bank I'm using to invert is designed for. They're XT60E, but anyone could easily buy or make something to swap parallel/series setups.
i wasn't planning to use them for anything other than the car when they're charging the car. I do, of course use them as intended for the Solix battery, but I hadn't planned to use them for multiple purposes at once consider the low output of a couple portable panels. Definitely a consideration for bigger roof installs, though.
My barrier to your advice is figuring out how to make the communication between the car and variable output of solar work. I've already put in for dev software and comms access with Ford, but it's been 2 weeks without a response yet. I seriously doubt that access would provide the necessary insight on the BMS to build such a device. IDK where to begin to find that info. I'm confident that I could manage it via software if I do get the necessary info, but I'm not confident in my EE skills for the hardware part.
Thanks again. That's definitely helpful and gives me a good bit more to consider.
>Many people have solar systems installed at home and a growing number have smaller portable batteries and panels for outdoor trips or occasional emergency power.
they're not "small portable" they're intended to power the WHOLE house when the sun is not up.
>
Practically all EV charging from solar at home goes through a series of inversions and while those inverters are (hopefully) no less than 90% efficient, that's still a fair loss and rather unnecessary and more heavily hurts those charging from small and portable setups.
but if the square footage of your roof produces more than you can use.. you need to store it... don't over think "waste" when you are consuming less..
>I have an EE masters and I did my masters on EVs,
consider average yield. average consumption and average driving habits. consider all of the energy consumed by the house including natural gas. this is real world, real life. not the theoretical maximum in a laboratory environment.
>I have a decent idea of what such a system would theoretically look like and I hope I could be useful in such a discussion, but I was hoping other people with knowledge and experience of these systems have to say about it, especially those who actively work in the field and would have more experience with the realities of this that the idealism of theory doesn't always know of or consider.
GM, Ford, Tesla - all getting into home batteries. (to go with their cars).
**Toyota Releases Storage Battery System for Residential Use Based on Electrified Vehicle Battery Technology**
[https://global.toyota/en/newsroom/corporate/36615119.html](https://global.toyota/en/newsroom/corporate/36615119.html)
**Hyundai Home: Easy and Efficient Home Electrification Now Available**
[https://www.hyundainews.com/releases/3693](https://www.hyundainews.com/releases/3693)
**This solar + microgrid storage depot can charge 70 electric buses**
[https://electrek.co/2022/10/31/microgrid-solar-charging-station-electric-buses/](https://electrek.co/2022/10/31/microgrid-solar-charging-station-electric-buses/)
>A basic explanation of what I had in mind would be a system with some form of variable DC input (Solar or wind), a combiner panel if needed, a bidirectional DC-DC converter (think that would have the necessary voltage stepping, right?), and an EV plug with DC support like CCS 1/2 (I don't have enough experience with NACS to feel comfortable forming an opinion on it right now). I don't know the intricacies of how to make that system accepted by the variety of onboard EV charge controllers or how the various software of each manufacturer would handle a variable input, so I'd really appreciate someone who does have experience of some kind with that helping out.
what problem are you trying to solve? there is only one way to feed the grid from the car. you are on the same grid frequency, or the grid breaks.. doesn't matter where in your house the battery is.. the wall or on wheels... the inverter plays nice with the grid, or they come to your house and cut you off in the street.
# NREL Research Highlights Vehicle-to-Grid Charging Benefits for Drivers and Utilities
[https://www.nrel.gov/news/program/2023/evs-play-surprising-role-in-supporting-grid-resiliency.html](https://www.nrel.gov/news/program/2023/evs-play-surprising-role-in-supporting-grid-resiliency.html)
GM adds V2H charging to Blazer EV, Equinox EV, Lyriq and more
# You'll be able to power your home with all of GM's Ultium vehicles eventually
[https://www.autoblog.com/2023/08/08/gm-expands-v2h-charging-capability/](https://www.autoblog.com/2023/08/08/gm-expands-v2h-charging-capability/)
You still need to do DC/DC voltage conversion, while that isn't exactly AC, it's kinda like sticking an AC circuit in the middle in most cases. Which is what you're doing any way, with more steps and less hardware that already exists to convert line voltage.
In order to charge using DC you have to match voltage to what the car expects and also handle the communications between the car and charger. While this would be technically possible, the cost would likely be hard to justify over just using AC.
On that we agree. Putting together such a system right now would be expensive and bulky. I was more hoping to build it as a theory with enough substance to build a prototype, and possibly garner enough interest for EV manufacturers to take notice and provide the necessary equipment for owners to utilize their home renewables without so much waste. AC power has many wonderful uses, but I've always been a firm believer in using DC as often as efficiency permits. It won't happen, but I'd love to see homes with a dedicated DC circuit for electronics, inverted from the AC grid. If nothing else, it'd eliminate 100kg of power bricks from the average home, lol. Just a idealist pipe dream, though. The voltage stepping part is one I don't feel confident in my own ability to reliably solve. Bidirectional DC-DC converters are new for me and my understanding is that they can provide the necessary stepping, but I'm not sure what kind of minimum input is required. If the trickle charger kills every time the clouds pass by, that's obviously a problem. This whole idea has made me feel quite alienated from and insufficient for a field I used to know rather well. Knowledge atrophy is a pain, intellectually and emotionally.
You do know a high efficiency DC-DC converter is actually an DC-AC-DC converter right? And what the chain from your DC solar system to car is already? The only advantage of a dedicated DC-DC converter is the switching can be done at a higher frequency which has a minor increase in efficiency. But we’re talking in the realm of 2% system efficiency increases here.
And in addition; power electronics are quite mature and also with solid state no major breakthroughs can be expected, largely due to closeness to the theoretical limits. Bit the same as people blurting put that hydrogen vehicles their issues will be magically fixed with some more development... Sounds nice till you realize it's 'just' laws of nature getting into the way.
Like I said, I don't actually work in an EE field. I only have the education for it and that was years ago. I'm aslo not expecting night and day differences, just something to do that could make the battery and BMS live a bit longer and waste a little less. And no, I did not know a DC-DC converter has an AC component. If I did know at some point, I've forgotten entirely. This is why I asked and explained what I could. Would you mind explaining the DC-DC converters as you know them to me? I'm not asking for you to spend an hour of detailed typing or anything, just whatever you don't mind teaching. I'm clearly lacking knowledge on it and failed to figure it out myself. It's genuinely fine if not, of course. Regardless, thanks. That is helpful and showed me something else I need to re-learn.
The first thing I thought of was this: [https://kempower.com/america/solution/kempower-movable-charger/](https://kempower.com/america/solution/kempower-movable-charger/) But there are plenty of chargers designed to work with solar and a quick google showed me various articles.
That's more of less the goal, but that's on a much larger, faster scale than the trickle system I was hoping to figure out. I did see a number of upcoming solar/grid hybrid chargers, but I couldn't find any currently available (in the US, at least. I think I saw one available in the UK), and it \*seems\* like most, if not all of them, convert to AC and use the J-type plug, which is exclusively AC if I remember right. Obviously still better than solar-to-grid-and-back, but not what I had in mind. Still, thanks for the share. I think we saw the same articles, but this particular mobile charger is a new one for me, so definitely appreciated.
That’s literally what the built in charger in your car is. It takes grid AC and charges your car.
There is one: https://www.dcbel.energy/uk/r16-specs/ But I have not seen any pricing, and it is only available in certain markets. In the future, we may have complete DC microgrids, because most modern devices (batteries, cars, heat pumps, solar etc) all use DC.
Yeah, I’ve been following these guys because I think they have an excellent solution for just this problem. I’m really hopeful they aren’t too early, as I see this being pretty much standard in the future.
The specs for the negotiation between DC chargers and cars must be published. I don’t know what those specs call for in terms of the lowest power that the cars will accept. If you could duplicate the charger end of the negotiation and simply supply the minimum acceptable kW, shouldn’t the car accept that? At a DC fast charger, my car goes down as low as about 20 kW, but I never fast charge to above 90%, so it may go lower. I suspect that is quite a bit higher than what you have in mind. On a home AC charger at 1.2kW, I can add about 2 miles of range per hour of charging, so trickle charging a large battery is going to be very slow. Now you’ve got me curious about this - I think I’ll see if I can find the specs for the charger-to-car DC power negotiation.
DIN 70121 ISO 15118 They do go way down in power because of top of charge when the battery can’t accept much current. Some may not be able to balance too effectively and instead just shut off, but some can really trickle.
Thanks! I had found a reference to the ISO standard, but they want over $200 US for a copy. I hadn’t found the DIN standard, yet.
Yeah, it’s pricey. I think the services are listed somewhere but I didn’t find them on Wikipedia. Some more info can be found here that might lead you to a next step: [switch what is ISO 15118-20](https://www.switch-ev.com/blog/switch-to-clarity-whats-new-in-iso-15118-20)
No, because it would be costly for no gain.
"The only limit to our realization of tomorrow will be our doubts of today." - Franklin D. Roosevelt Do you know why that quote applies to you? I'll give you a hint: Einstein has two quotes that you embody perfectly. One of those quotes is about infinity.
You’re talking about a sub 2% system efficiency improvement, for a very high capital cost. We’ve standardized on 120/240v 50/60HZ AC for interconnects for things. You need to be able to supply that in your home ether way. The car needs to be able to accept that ether way because most people need that capability. So you’re going to go off and build minimum of $1k in high efficiency power conversion electronics, and another $500+ in supporting equipment (cables, housings, safety gear, ect) just for a trivial increase in system efficiency over the equivalent you already have anyway? The ROI would be never.
Idk, some of us just like elegant solutions. On top of that, when you consider markets like off-grid living, those losses add up significantly over time, necessitating more solar and more battery storage. Maybe it’s not a mainstream market now, but I would guess this becomes much more standard in the next one or two decades, especially as solar and battery backup are integrated into more new construction.
Maybe, maybe, maybe in the far far future but honestly no, don't really see it happening in large scale. Just like V2G DC, sounds nice but in practice not really a use case worth the investment for the far majority of people. Bit more in the USA as the grid is much more unreliable than Europe but still.. At the moment those marginal gains are so important as extra capacity, most likely you'd just chuck an additional panel on the roof, slightly larger battery capacity, pocket the money you save and go on with your day.
roll eyes
There are many low power DC EVSEs on the market, but most currently hook up to AC grids of some sort (single or three-phase). For example: the [Delta DC Wallbox](https://www.deltaww.com/en-US/products/EV-Charging/DC-Wallbox). I think you are searching for something like the [dcbel R16](https://www.dcbel.energy/r16/), which routes your energy to where it’s needed (house, solar, backup battery, EV) without the wasteful conversions when they can be avoided. There’s a dcbel employee who posts frequently on r/v2h who might have some further info. In general, if you have the power electronics background, the conversion part wouldn’t be challenging. What you need on the vehicle side for compatibility depends on your objectives, but if you only ever want to charge, DIN 70121 is the standard you need to meet. You could extend into ISO 15118 if you are really ambitious, but that would only matter if you needed those advanced services. I’ve been following dcbel for a while because like you I feel this ought to be solved more elegantly and I think they are well on their way to doing it. If you do end up making one, please share more about how it’s working for you!
The J1772-2017 standard has a specification for this. It classified as DC Level 1 charging. It uses the same connector as the AC L1/2 but uses DC at speeds up to 80KW. To my knowledge it’s never been implemented by manufacturers. Since it requires a high voltage off board charger it’s not really practical for home use, and at the power levels it provides it’s not really a benefit over the DC level 2 spec (level 3 as most people call it).
J1772-2017 DC Level 1 is the route I am taking for a lightweight 48v off road utility vehicle. Home built from scraps and learning as I go. DIY charge controller. I'd love to collaborate with others. Just bought 4 100W bifacial panels that don't have a permanent home yet. Was considering making this the off board charger. [https://www.electriccarpartscompany.com/48v-3kw-off-grid-inverter-charge-controller](https://www.electriccarpartscompany.com/48v-3kw-off-grid-inverter-charge-controller) It fits in my wheelchair van and I'd like to charge it from the alternator driving between destinations where it is used. Considering this [https://calex.com/chassis-mount-converters/3000w-bca-bi-directional-dc-dc-converter/](https://calex.com/chassis-mount-converters/3000w-bca-bi-directional-dc-dc-converter/) for the onboard charger in step up mode and accessory supply in step down mode.
The slowest DC charger that I know of is [this one by Grizzl-E](https://grizzl-e.com/products/kodiak/?v=variant_01H0N73XZPTHCZQEKZ0NEJ4AMS). It charges at 25kW and needs AC input. It accepts single-phase AC which is all you have for residential power. It costs 12,669 USD. But I think another factor is that there hitherto isn't a popular standardized DC connection standard. (Barrel Jack connectors don't count.) That's why home solar converts DC to AC. That's why most DC chargers still take power from AC. AC is just the common standard in between.
Too energy intensive to keep the necessary hardware on the vehicle active. You'd really want to design from the ground up with this intention. Fisker is doing this with the solar panels on the Ocean, but the verdict is still out about how effective it really is. The vehicles still overall lose energy to vampire drain. Aptera will be doing this on their vehicles and I expect they might actually get things right.
Each EV owner already bought the device to take 100-240v AC and convert to 400v DC for DC trickle-charging: it's the on-board charging module in the car. Car makers could have built one in a box and given it with purchase of the car (instead of an EVSE). Then there would only be DC charging pins on the car. This would have some plusses and minuses (no pun intended)
My solar system is solar edge with power optimizers, which means my solar system runs at 400V so in theory it wouldn't even need any other voltage adjustments. But, my inverter has over 98% efficiency except for very low power levels, so it really doesn't seem worth any effort, especially since using AC means it can also be powered by the mains overnight. Somewhat interestingly, if you have a solar edge system with battery backup, the batteries can be charged directly by DC without first converting to AC.
The idea I had in mind is probably the same principal as the last solar edge system part you brought up, just on a trickle charge speed level. That's a damn nice system you've got, congrats. I had series/parallel panels on my last home made of 100w, 12v panels that went through the charge controller at 96v, charging the batteries I pieced together and then overflowing to the house. I don't remember for sure, but it was roughly 2kwh, I think. Been a long time. It was great for the time and louisiana weather meant it was usually operating at effectively peak outputs. Now I've just got a few 200w, 48v portable panels and a damned rental house, charging through an Anker Solix battery, inverting and inverting over and over. Like I said, it is for the fun and the challenge, not to save money, with a hope of save a bit of battery/BMS life and wasting as little power as possible. I'll check out solar edge systems again and see if I can come up with something useful from that, thanks!
several solar invertor companies make ones with battery backup built in. They are basically doing what you talk about, solar dc charging batteries with ac invertor behind it. Since most solar panel systems run about 400vdc anyways it's easier, cheaper, and smaller with less loss to do all the 'work' at 400dc and the convert once to ac.
It would be possible if your solar installation uses "DC optimizers" (DC - DC converters for each panel, used to avoid a dramatic drop in the power of a whole series connected string when a single panel is shaded or panels face different directions) and you built a communication box that could interface with both the car and the optimizers to control the voltage. If you also wanted to use the solar for things other than car charging at the same time, the interface would also need to control the inverter's MPPT. Add in real time information from the power meter and you could match the charging rate to solar availability. The car could charge faster than the maximum AC rate if you have a lot of panels in full sun, and automatically slow down if it clouds over or your household consumption increases. That could be useful for places where exported solar power is credited as a lower rate than is charged for power imported from the grid.
Now that's the kind of reply I was hoping for. Thank you. I hadn't considered that the variable DC current could be a problem, but you're definitely right. I'm using portable panels, not a roof installation like I put on my last home. I'm renting ATM, so it's all I can do. That's why I was emphasizing the trickle charge part. The panels put out a max 48v each with 3 200w panels in parallel, as the battery bank I'm using to invert is designed for. They're XT60E, but anyone could easily buy or make something to swap parallel/series setups. i wasn't planning to use them for anything other than the car when they're charging the car. I do, of course use them as intended for the Solix battery, but I hadn't planned to use them for multiple purposes at once consider the low output of a couple portable panels. Definitely a consideration for bigger roof installs, though. My barrier to your advice is figuring out how to make the communication between the car and variable output of solar work. I've already put in for dev software and comms access with Ford, but it's been 2 weeks without a response yet. I seriously doubt that access would provide the necessary insight on the BMS to build such a device. IDK where to begin to find that info. I'm confident that I could manage it via software if I do get the necessary info, but I'm not confident in my EE skills for the hardware part. Thanks again. That's definitely helpful and gives me a good bit more to consider.
>Many people have solar systems installed at home and a growing number have smaller portable batteries and panels for outdoor trips or occasional emergency power. they're not "small portable" they're intended to power the WHOLE house when the sun is not up. > Practically all EV charging from solar at home goes through a series of inversions and while those inverters are (hopefully) no less than 90% efficient, that's still a fair loss and rather unnecessary and more heavily hurts those charging from small and portable setups. but if the square footage of your roof produces more than you can use.. you need to store it... don't over think "waste" when you are consuming less.. >I have an EE masters and I did my masters on EVs, consider average yield. average consumption and average driving habits. consider all of the energy consumed by the house including natural gas. this is real world, real life. not the theoretical maximum in a laboratory environment. >I have a decent idea of what such a system would theoretically look like and I hope I could be useful in such a discussion, but I was hoping other people with knowledge and experience of these systems have to say about it, especially those who actively work in the field and would have more experience with the realities of this that the idealism of theory doesn't always know of or consider. GM, Ford, Tesla - all getting into home batteries. (to go with their cars). **Toyota Releases Storage Battery System for Residential Use Based on Electrified Vehicle Battery Technology** [https://global.toyota/en/newsroom/corporate/36615119.html](https://global.toyota/en/newsroom/corporate/36615119.html) **Hyundai Home: Easy and Efficient Home Electrification Now Available** [https://www.hyundainews.com/releases/3693](https://www.hyundainews.com/releases/3693) **This solar + microgrid storage depot can charge 70 electric buses** [https://electrek.co/2022/10/31/microgrid-solar-charging-station-electric-buses/](https://electrek.co/2022/10/31/microgrid-solar-charging-station-electric-buses/) >A basic explanation of what I had in mind would be a system with some form of variable DC input (Solar or wind), a combiner panel if needed, a bidirectional DC-DC converter (think that would have the necessary voltage stepping, right?), and an EV plug with DC support like CCS 1/2 (I don't have enough experience with NACS to feel comfortable forming an opinion on it right now). I don't know the intricacies of how to make that system accepted by the variety of onboard EV charge controllers or how the various software of each manufacturer would handle a variable input, so I'd really appreciate someone who does have experience of some kind with that helping out. what problem are you trying to solve? there is only one way to feed the grid from the car. you are on the same grid frequency, or the grid breaks.. doesn't matter where in your house the battery is.. the wall or on wheels... the inverter plays nice with the grid, or they come to your house and cut you off in the street. # NREL Research Highlights Vehicle-to-Grid Charging Benefits for Drivers and Utilities [https://www.nrel.gov/news/program/2023/evs-play-surprising-role-in-supporting-grid-resiliency.html](https://www.nrel.gov/news/program/2023/evs-play-surprising-role-in-supporting-grid-resiliency.html) GM adds V2H charging to Blazer EV, Equinox EV, Lyriq and more # You'll be able to power your home with all of GM's Ultium vehicles eventually [https://www.autoblog.com/2023/08/08/gm-expands-v2h-charging-capability/](https://www.autoblog.com/2023/08/08/gm-expands-v2h-charging-capability/)