I would challenge the assumption that EV on-board chargers use Diode-based AC to DC conversion (rectification), along with the associated losses. Modern electronics (such as in EVs) use "Synchronous Rectification", which uses extremely efficient MOSFET transistors as the AC to DC rectifier switches. This reduces the "rectifier losses" of a typical 0.5v voltage drop of a Schottky diode - down to 0.1v drop... reducing the rectification losses by 80%. These manufacturers have marketing departments whose job is to come up with the best sales pitch, and drastically over-estimates the power losses in modern EV onboard chargers. Also, the trend today is to use micro-inverters on home solar installs, which makes them far more resistant to the effects of residential shading. However, this eliminates the possibility of using the solar array for DC-DC charging, because the solar array does not output DC... only AC. Even if the solar array is series DC connected, the external charge controller still has to perform DC Current Regulation (to prevent damage to the solar array and equipment), which is a high speed switching circuit, which has losses... just as in the onboard EV charger. Just have a think... marketing is always about stretching the truth... hoping someone who knows better doesn't burst their bubble. (yes, I am a EE, and have been designing electronic circuits since 1980, and also drive an EV... an i3 BEV)

I've been looking for DC-DC chargers forever! so happy to hear this.

At last! This is such a glaringly obvious need; I’m glad someone is working on it.

This could apply to home appliances. Most electrical devices in the home are 24 Volt DC or thereabouts. Only a few devices use 220 Volt AC. A home could be wired with two systems: a DC system for low-powered devices including lights; and an AC system for big appliances, making it more efficient to power smaller devices directly from DC solar panels, and meaning that smaller devices don’t need to be supplied with AC adapters.

Great visuals! The demonstration of the motion of the current through the diagram helped me understand what you were describing.

DC slow chargers makes perfect sense for parking lots. The cars will be parked for hours so no need for fast charging. 10 cars can get slow charged at 20kWh chargers instead of 1 car fast charging at 200kWh, and it will be cheaper too. Fast charging should only be used for long trips, not for daily charging.

A parking lot covered with a solar panel canopy, then we would get shade while we walk in from the parking lot, I call that a win-win!

I've been waiting for this tech for 6 years now. I can't believe it's taken this long for what seems like a common sense solution.

Well I've lived off grid in the mountains of Santa Barbara for a super long time and the vast majority of my house is DC and we have been doing DC solar to DC batteries to DC loads since the late 90s. This newer stuff is a bit tricky however as there are much higher DC voltages.

A good micro inverter conversion efficiency is about 97.5%. This was a relevant piece of data for your video and it was better to mention that but putting the rest of the video in context

Looked at SolarEdge marketing materials for this and the main benefit seems to be the ability to simultaneously use grid AC and solar DC for faster charging. No particular efficiency gains (other than the benefit of solar itself). FYI, AC->DC conversion has a power loss as mentioned. DC->DC conversion also has a power loss. MPPT solar charge controllers are converting higher panel voltages (20-100Vish) to previously lower battery voltages (12,24V etc.). Now, with direct to EV charging you need to take solar panel voltages to higher battery voltages (at highest 400-800V). Every conversion comes with a penalty. It's not so much that AC->DC efficiency is worse than DC->DC efficiency, but the combination of DC->AC->DC is extra losses, shorter transmission (hundreds of km/miles to a power station vs 10s of m/yards to your panels) and the fundamentally greater efficiency/cost of distributed solar over centralized thermal combustion (full system costs).

But the car battery wants a specific voltage, and it would be a rare coincidence if the PV panels happened to produce that particular voltage. So you need a DC- DC converter. And while they are getting better, they are not lossless. So the net benefit of direct pv- to vehicle is less than the 13% cited. And there is a definite advantage to being able to have the pv panels and the vehicle in different locations, with the ac grid as the intermediate.

Those 13% losses must be the absolute worst scenario, not a typical one. There's absolutely no way that they've chosen such poor electronics. And DC-to-DC transformations (which are needed, as your PV system won't run on 400 V) also have losses. I can't imagine the gains being all that huge. If this technology can reduce costs by providing a simpler solution, then great, but I don't think shaving off a few percent of losses is going to be a game changer

Brilliant explanation of complex ideas … well done

As NEM3.0 kicks into California solar, this makes more sense

Nice explainer of a rectifier circuit. It's key to remind ourselves that we could manufacture these circuits for ourselves.

I love your ability to express complex things simply. Thank you

We installed 13.2 kW Solar PV system in 2012 and two Tesla Powerwall batteries in 2018 to our all electric home with Heat pump and heat pump water heater and have been net positive in producing more energy than we use for past 12+ years, operating effectively as a microgrid for 8+ months of the year. We also charge our two EVs off our roof utilizing our solar panels to charge our cars 95% of the time and charge predominately during the peak solar period (11a.m.- 3 p.m.).

One detail that I would like to challenge is the commonly communicated mistruth regarding the idea that a DC only system is more efficient than a system that uses AC. The commonly quoted idea is that PV panels produce DC power and that batteries store DC so maintaining a full DC system is more efficient as it avoids the conversion losses from DC to AC. The detail missing from this very simplistic argument is that the PV panels produce a different and variable DC voltage which will invariably be different to the voltage of the battery. This difference in the DC voltage is accomodared by using DC to DC converters to change the DC input from one voltage and current to a different voltage and current value. So the only difference between a DC coupled and AC coupled system in this regard is that one system uses DC to DC converters and the other uses DC to AC converters. The converters in either system have associated losses. Proponents to DC only systems will claim that DC to DC converters are more efficient than DC to AC converters and will quote some really low efficiency figure for the DC to AC system that they are comparing to - but this is simply misleading marketing lies. The reality is that all DC to DC converters work by converting the input DC to AC and then converting this intermediate AC back to DC. Hence there is no theoretical difference in the possible efficiency difference between a DC to DC or DC to AC converter. The only efficiency difference comes down to simply the engineering design decisions when it comes to trading efficiency vs product cost. The main difference between a full DC system and an AC coupled system really comes back to the requirements regarding the safety protection equipment required for DC vs AC - the alternating nature of AC has an inbuilt mechanism for electrical arc interruption allowing existing electrical AC fuses and circuit breakers to be used. In contrast full DC systems require very expensive DC circuit breakers which also have a significant negative impact on the overall system efficiency.

Im just amazed people have not thought of this before, its so simple to reduce losses due to the conversion process

I made this like 2 year ago, Diy homemade car and directly hooking up the battery to my of grid solar inverter

Best episode yet. Thoroughly enjoyed it

Yes this is the thinking and stuff we need to make a better world. Thanks for great videos.

In Australia, 20 million BV parked 23hrs all day long and all night long. TRICKLE currents all day long. Like the home robotic vacuum cleaner's selfplug-in feature. Every building parking space with a $60 wall outlet.

Thanks Dave once again for positively encouraging reports that continue to exercise that part of my intellectual capacity I haven’t used since I studied physics and engineering! 🤔🤷‍♀️💫😊

Can’t wait to get my hands on one of these.

An increase of 13% efficiency is huge.

As you say, what we have now in cheap overnight rates, will change over time. This is a really interesting idea, cutting out conversion of our solar and feeding straight into the EV, makes total sense and gives more miles per kWh. Great news.

I think the best possible solution would be to charge a stationary battery in your home via PV DC. Then charge the car from that as and when. That way you get to collect sunshine watts all day regardless of where your car is and then top it up at night when you’re in the land of nod. This would also feed into options of trickle charging to reduce dendrite build up (presumably). Any excess could be converted to AC and used by the home or fed back into the grid for credit.

Love that blue jumper...😊

Nice find. Ive often wondered why we don't have a DC system wired into each home for lighting, TVs computers etc 💚

Thanks for another informative video, we definitely need this in Australia.

Since I work from home 4 days a week, this paired with a solar car port would be fantastic. (I have a slate roof, so going solar on the house would have to be a whole roof replacement/ solar tiles). I could put a car port on my driveway turnaround (two car parking area) and charge my car under the car port during the day. I still have my 48A charger in the garage for faster charging. I need to do the math on possible charge speed of a set of panels covering approx two parking spaces getting decent sun all day. Though as others point out, $2500 for the charger is steep!

Very good!! It is unstoppable progress.

Thank you, Dave, for another very interesting video!

Thank you again. Well presented.

A bit off topic…but I am still shocked that it only costs me $1.60 USD to charge my Model Y from 0 to 100% here in Burlington, Ontario, Canada - every night from 11pm to 7pm the rate is 2.8 cents (CDN) per kwhr - this along with the fact I am paying zero for maintenance is amazing

I'm off-grid. My house is single-phase and the cost of converting it to 3-phase is uneconomical. This leaves me with a maximum charge rate of 7.36kWh for my EV. Even if I had 3-phase, the AC charger in the vehicle is limited to 11kWh, but there is no such limitation on DC charging. I can't wait for it to hit the market here in Oz. Something like this DC-DC charging would enable me to get upwards of 13.5kWh.

Whatever makes lives more affordable, easier & simpler. In much of the world most people live in apartments making charging at home difficult, forcing them to rely on public chargers. Unfortunately many govs are not installing recharge points to keep with demand, delaying the transition to EVs. All this (among many other issues) while the enviro unravels before our eyes. Good luck everyone.

Thanks Dave

Years ago I knew an old timer who had a bank of those old Edison batteries and an old d.c. generator to change them. His house had d.c. wiring for lighting and few other things, and regular a.c. incoming power also, for the rest.

Here in the Netherlands some energy providers are already switching their peak and off peak hours around to be off peak when the sun is out and abundand during the day

It's interesting that you mention Australia as a place that has solar energy geographically for longer periods of time, but we actually don't have any grid connections between the Eastern and Western states. The USA, Europe or China are probably better examples of good utilisation of peak solar.

Excellent as always thanks Dave

Awesome. thanks for vid

Thanks for sharing this resource.

Great info! Thank you… will have to look into the cost, hopefully it is reasonable.

Thanks

Amazing. Hopefully people will get engaged with this new tech.

I've been designing a home solar/battery system, and this would make a great addition to my setup.

Amazing

Great educational content!

Thanks for the info on direct to direct

Great vid, thanks for sharing. 👏⚡️👍

Doah, i just upgraded my solar edge. Well I welcome the new tech, thanks Dave.

Always good content. Affordable dc home chargers are long overdue. Can't wait for the option to get one.

This is great news! Always wondered why our solar panels generate DC power that has to get converted to AC power for home appliances and then has to be converted back to DC to power our electric vehicle. And we're off-grid so this news will be a game changer.

Cant wait to get my hands on one

Pet peeve, the conventional AC wall units that connect to a vehicle are not chargers, the charger is built into the vehicle. The wall units are simply "smart" cables, they do no conversion of the AC power delivery, they just turn it on and off when signaled by the on board car charger. That's why most EV's can charge from a conventional 120VAC or 240VAC household plug.

Personally, until Bidirectional chargers are mainstream and much, much cheaper, i think that it's better to just add an extra panel or 2, to cope with the losses.

Amazing Video!

Brilliant 🎉 thanks for that

A Solar PV DC-DC EV charger with V2H/G capability & mains charging option is fantastic. 1) enables me to install more solar.* 2) don’t have to buy a home battery to use own generation at night. 3) EV gets charged (for ‘free’) without cannibalising own home PV consumption. 4) option to earn $$ selling power back to the grid. 5) back-up mains charging when needed. 6) lower system losses. This doesn’t need thinking about as it’s a win, win, win, win, win & win! * at time of installation local electricity authority limited solar PV system size to 5KW to avoid overloading local grid. Though now systems with 5KW peak export limits with over provisioned panels can be installed.

Great info, as always.

On neat, that's awesome! And thanks for the explanation of how inverters and rectifiers work, every other source just seems to assume that's a known and understood thing, and I've just let it be a black box component in my head. (I'm sure I'd have looked it up if I ever actually needed to know, it's just never come up)

Thanks Dave. With the new GaNfets efficiencies are getting so good that it really isn't a big deal, we're seeing efficiencies of over 95% on DC to pure AC inverters now. I thought about this myself and what I did was install an Emporia EVSE. It only charges my batteries when the sun is out through my paid off PV system. Works like a charm. In fact, last month, charging my car, cooling my house, hot water and all appliances we only used 40 kWh from the grid - that's about $4.00!

Lots of talk on this thread about DC systems being more efficient. What's not been made clear is that DC systems often require dc to dc conversion which is just a lossy as dc to ac. Also ac to dc, if it's using a simple bridge rectifier, is very efficient. BTW I run an off grid system with 48v battery, various 12 and 24v dc loads plus 230v ac for mains appliances including charging an EV.

Great round-up, have been looking for a DC to DC, two way charger (solar to car and car to 30kwh of LFP battery) for our 8KW solar system. Will watch these suppliers. Thanks Dave.

Sounds like a good idea.

Great video thanks

I think it premature to worry about EVs drawing all that night time power, certainly in Europe. Things might be different in Oz, NZ the US and other places with a lot of sunshine. In the UK our build out of wind power will exceed EV demand dramatically in the next 3 years. Assuming that folks grab overnight power on the windiest mights too which we are likely to be incentivised to do from 2025 the power on low wind nights is still likely meet demand from EV charging and all the other night time demands. (About 12 GW is being built at the moment)

I am currently charging my EV at home from a DIY solar power system. My system has to convert to AC and then back to DC and in the process loses that 13% you are talking about. It works pretty good and provides free car charging but a DC version would be nice if it manages through the ups and downs of cloud cover. I would want it to be pretty steady so I would think a battery would need to be involved in the design somehow??? Great video, Thanks!

Awesome!

Thanks for the new video! I don't have a car, electric or otherwise, so this one isn't really for me. But from the comments it sounds like a lot of people could really use one of these chargers.

I feel like celebrating too 😊

Cheers Dave

Good thoughts there, with a couple of caveats. The modern and more efficient micro-inverter array systems deliver AC from each panel, optimising the array efficiency. So this uses sub optimised arrays. Current 'smart' chargers and tariffs can demand shift any plugged in car to balance any grid needs, while achieving the required charge for a customer.

I'd like to see more modular solar/hydro systems for rural communities. I live off the paved road and be nice to have a way to power my well, and other things but in a Lego approach where each year I could add more panels, batteries, etc. A charger that work with solar would be a step towards that.

It doesn't quite make sense, because you still have to adjust the panel voltage to match what the battery wants - and that involves something like a buck boost converter - which involves conversion to AC, and then back again.

A house battery is needed because most people take their electric car to work and only come back in the afternoon, so most of the day the care is not there for the solar panels to charge it. Businesses on the other hand should be able to cover their parking lots or building roofs with solar panels and provide charging for their fleets of EVs and for their employees.

The DC-DC Charger is just a bolt on or extension of your solar inverter and linked management of the power storage. 100% right we have miles of roads and parking areas where we can better manage the collection of solar for electricity and heat and also add water management. When are we going to give up trying patch up the legacy AC grid and see a move to a parallel DC and HVDC grid, Big Solar Energy projects and Mega Batteries linked to it.

Sounds good to me

Great video as usual 👌

This has existed for many years and is currently built into some new houses in Scotland. 8 years ago I built a house for a client in Scotland and he engineered vehicle charging using solar panels, a wind turbine and batteries.

Totally agree with your arguments. The local airport in Illinois has been moving to cover the entire parking lot with panels to power the airport and an increasing number of EV vehicles, both private and airport support commercial units. As a side benefit, personal vehicles are shaded from the sun and snow not to mention thevoccasionsl hail. The latter opens different issues. Your example of covering Walmart and other commercial business parking lots depends on the desire to invest in the business and the general n public. The future is here and simply the mommentem is increasing.

You're doing a great job Dave, certainly a bit more optimism about renewables in the UK this week; let's hold them to their promises

Thanks Dave. I am off grid and have just purchased an ev.

Solar Edge has been making a charger built in to its inverters for a while now. It isn't DC, but it puts the AC from the inverter to the charger before it hits the production meter, so it saves customers money in cases where net metering gives home owners less-than-retail value for the kWh they produce. A friend of mine has one and avoids a 3 cent penalty from the utility, just on his EV charging.

Really useful I charge my ev during the summer just off solar PV on the eco plus plus setting so that extra 13% could be really useful as I have been down to 17milez state of charge this year because of UK bad summer

Thanks Dave, this is a reason to celebrate. In Australia, the wholesale cost of electricity is negative between 10am and 2pm in most States, except for summer. We have lots of rooftop Solar PV here (43% of residences where I live), so it makes good sense to divert as much of that generation during the Solar peak period to EV and other battery storage. Most residences are connected by single phase AC mains which limits EV charging to 7.2 kW rate. A hybrid AC + DC input / DC output charger could typically double that rate, based on most residences having 6kW ~ 10kW of Solar PV output when there’s little domestic load. There are two major issues though : 1. many vehicles are used to commute during the day, and won’t be at home during the Solar peak, 2. While efficiency is important, a DC/ DC charger needs to be economic. AC from my Solar inverter costs ~ AUD $0.06 kWh. Losing 13% charging efficiency still doesn’t increase the cost of charging an EV from Solar PV by much. The only bidirectional DC/ DC charger currently approved for V2X in Australia cost around AUD $11,000 - hopefully that will change.

DB raises a good point, that most people don't seem to be aware of, that when everybody can use off peak electricity, off peak will no longer exist, especially not as a fixed number of hours overnight. With high levels of wind and solar in the electricity mix, peak and off-peak periods are likely to move around from day to day, which is why we need a properly intelligent grid and genuinely smart smart meters that allow you to control equipment automatically in real time based on real time electricity pricing data. As far as I am aware, this is not something that current (UK) smart meters allow you to do, which is why I would suggest they are a very limited value. With regard to dcdc charging systems these are probably going to make an insignificant difference to electricity demand or cost savings. I'm not quite sure where Entelligent get their 13% higher efficiency claim from (I saw it claimed on their site but then couldn't find the screenshot again) because knowing the efficiency that you can get from chargers (which are basically switch mode DC power supplies) and inverters, even when combining them you should get well over 90% combined efficiency and when you take into account that Entelligent's chargers have a maximum efficiency of 98%, then I suspect the real world efficiency gain is probably closer to around 5%, and then only if you're charging from your PV panels or batteries. However, that wouldn't be a very good marketing ploy for a 12.5KW charger which, at $2,499, probably costs about 3 or 4 times more than it should. You can get 11KW mains chargers for well under £400 (although you can pay much more) so I don't understand why anyone would pay an extra £1,500+ to save themselves 5 to 10% on their electricity (but only when the sun shining closed bracket) and you are probably looking at about 100,000KWh (300,000+ miles) of charging before you get your money back. I would say Entelligent's marketing is basically green hype to justify an over inflated price tag, and their claim that with it being DC to DC is some great advantage, because you don't have to have AC to DC, is part of the hype. A PV system will not be producing a DC voltage at the right level for charging your EV so this charger is basically a dc dc converter, and internally a dc dc converter is basically a DC to AC to DC converter, albeit quite high efficiency one. Okay, you get rid of the AC to DC rectifier bit on the input, but at mains voltages that will probably only save about 0.5%, and the rest of the gobbins inside will be very similar. If you're charging from your PV system or batteries you also save another 5% by eliminating the mains inverter, a useful saving if you're not paying a huge price premium for it. Also, you could probably replace the basic rectifier with a synchronous switching rectifier to save a fraction of a percent, but it's probably not worth it.

Not sure it's possible, but it'd be awesome if they added the ability to couple it with batteries...without attaching it to a home electrical system. Then, it'd be super diy friendly...

Here’s a thought. When building shopping malls, put a subterranean battery storage facility in so surplus from the DC canopies can be stored and used to either DC charge EVs when there’s no sun or exported to the grid as and when permits have been obtained and the grid requires.

YEA!!! SOLUTIONS! 😊❤😃👍

Known as a Wheatstone bridge. Anyway. Dave, keep your eye open for a kit that would allow someone with solar panels to buy, say, a used Leaf with at least 10kWh of storage left and to connect it as a home battery. The price of degraded leafs is becoming quite attractive for such an application.

Cheers

I'm increasingly of the mindset, that de-centralized approaches may have to provide a good deal of solution. One can't upgrade the grid fast enough. Self consumption systems can move more rapidly. This doesn't necessarily mean being totally off-grid. One can draw power from the grid, as needed, as backup, and as capacity would allow, just as any appliance. Feeding electricity back to the grid creates a whole lot of complications for those who have to manage the lines. Plus it adds more resilience and local independence. At least more options, when the sun is shining, during parts of the day.

We are currently building a off-grid home in regional Victoria, Australia. When the home is completed, we will be purchasing an EV with a bidirectional battery - this DC-DC charging is one of the innovations I have been waiting for! Nonetheless, I am still eagerly anticipating the advent of technology that would enable an EV to directly power home storage batteries during extended periods of ‘dunkelflaute’. To me, this is the missing link which would allow people to go off-grid using the EV as the backup generator (avoiding the use of a fossil-fuel generator). PS - I am not referring to V2L/H as this is too selective and restricted.

Most people just don't understand product lifecycles. They always start off crap, have problems, slowly get better, then finally work really well and are quite efficient. I think we're up to the 'have problems/slowly get better' point in EV's. I don't think it will be long until we reach the next step.

Been watching this technology for a while now, but still no word on the cost. I don’t think it’s going to be cheap as buying a conventional 20kW DC charger is prohibitively expensive in a domestic setting. I am off-grid, charging my EVs during the day from solar and connecting V2L to my solar system for a little extra backup power sometimes at night.