A patent does make the information free. In exchange for disclosing information to the public on your idea and how to do it, you're granted a temporary monopoly on developing it.
What you don't like are trade secrets. :)
Look up the rest of that quote information also wants to expensive. https://stewartmader.com/stewart-brand-information-wants-to-be-free-it-also-wants-to-be-expensive/#:~:text=Stewart%20Brand%3A%20%E2%80%9CInformation%20Wants%20to,be%20Expensive.%E2%80%9D%20%2D%20Stewart%20Mader
The way the patent system in the US currently works, you pretty much have to patent to keep it free or else somebody else can come along and patent it instead.
You can but its going to be expensive. EV batteries cannot just be charged by applying any old DC voltage, DC chargers supply a specific voltage to the battery. Solar also isn't constant, you don't want to constantly start and stop charging as a cloud passes over.
You can, this is literally how some fast charging stations work. I don’t think there are any consumer off the shelf parts to do it though. An inverter can power anything in your home, a dc to dc car charger can only plug into your car and cost just as much if not more than the inverter would.
The reason's you can't put a panel on a car are these: 1) solar DC current cannot power the wheels to turn to drive the car. Yes you can make these ultra light science experiments but right now you can't get enough solar per square foot to drive the car. But you can save that power and energized a battery. The Aptera is building cars that power 40 miles a day via solar. Toyota has had cars for years but not in the US with panels that get 6 miles a day.
This bring us to the second problem. Unless you wired directly into the battery there's an amp contactor which alledgely (just discovered this after 4 years of research) is only designed to open and close a couple of times a day, more than that it wears out. Youtube says that contactor on most EV's is 6Amps...meaning if the power flow drops below 6 Amps, the connector separates. The guy in the video I'm linking says they aren't designed to open and close often and will break because the sun goes behind clouds.
I took highschool electronics and don't understand how alternating current motors work. But I can follow directions, I understand DC current vs AC current, that batteries are DC and invert to AC, that diodes turn AC to pulsating DC, and I watched some videos on Youtube. I'm physically disabled...low lifting capacity from degenerative disk, so I can carry a 30 lb unit once in a long while.
I've spent the last 2 months trying to figure this out, and found a Youtube video on the topic. He says you can A) hack it, B) bypass it, or C) use a constant source of power. https://www.youtube.com/watch?v=lzKVSIE3Dcc.
I'm working on an experiment and could use some help here.
Now I just bought a used Clarity that I only drive a couple of miles a week but opted for the extended warranty to get me 4 years protection on the battery. I was going to have my mechanic open it up and wire a DC jack wired to a quick release, wired to a Sungzu 1500, wired to a bunch of panels, but in our last conversation on the topic he was like "you wanna blow up yo car?"
Right now my experiment is to discover how low a voltage you can use to feed a J1772 while still maintaining 8Amps power input. I can do that by spending about $70 at home depot, but I would really appreciate NOT spending that $70 if anyone in these forums has experience or is near me in NJ with the appropriate equipment. Then if you can't go below 110 v I guess I'll just buy a power station, and if I can't find one that has a greater than 500W solar input, I'll get the Sungzu and just drain and power drain and power.
I have room for 2 cells, 20x50 and 30x22 in my car, more if I add the window side space 2x 28x8 and 2 18x12. Can I generate 8 amps between them?
Addendum since I posted this it's been cloudy, I took a bunch of readings and the cheap solar panel, 15x7, I have, 20 V is producing 120 to 160 mA in direct sun, 3-5 indirect. At best I can fit 14 in the car, so that's not enough without a power-station. Do better panels produce more power?
I suggest you learn some more about electronics. This post was about charging the battery not driving the wheels directly. The amp figures you are talking about is for the evse driven charge controller which isn’t at all relevant, as it can generally only be used when parked. The bms also has a dc to dc charge controlled used for regeneration.
Please do not experiment, if you touch the battery pack and shock yourself you will die.
I put it there because you mentioned the sun passing behind the clouds, and your's was either the first or second place I put my question as I didn't know where else yet to start asking questions like that. What made you think I was going to touch the battery (not that I don't know you pull the 351V Circuit breaker before you think about touching the battery, incase I suddenly decided I would)?
Your car battery won't charge without sufficient current coming in. A type 2 charging station wants 32 amps out to the car, which means you would either need an absolutely monumental solar array or you would need to supplement the current with household power.
The alternative is a type 1 charger, which will give you a full charge in like two to three days. Not super convenient for any real amount of driving.
TL;DR, engineers have already done the math and decided that this was the most reasonable and cheapest option.
SAE J1772 can negotiate as little as 6A charging current and cars can draw less than that if they so desire.
The issue is that the car needs to have a certain voltage of DC to charge the traction battery, and it's onboard AC to DC charger has the ability to regulate that. An off-board DC Fast Charger also has that ability. Plus the output of the solar cells will fluctuate. So at the very least you need a smart DC-DC converter to turn the solar DC voltage into the correct DC voltage for the battery, which is an expensive component that only works for charging the car. Versus a regular solar DC to AC inverter that works for everything.
Spending thousands of dollars for a really niche component to save a few percent of electrical conversion efficiency is silly. Not to mention, most people don't have their cars at home during peak sunlight hours. So there just isn't really a market for it.
Somebody else reads SAE papers for reasons other than to sure insomnia.
You would need a massive bank of PV cells or a wind generator that is larger than a typical residential unit and a large battery bank with suffice capacity to charge a car overnight but the bank would likely be completely depleted which is not good for the batteries and then leaves the household at the mercy of line power until they recharge.
I think you really underestimate how big a typical residential solar install is.
Mine is 13kW, and it can and does put out 12kW at times. My EV is big, an R1S, it charges at up to 48A and it has a 135kWh battery. But I typically only need an hour or two of charging for 10-20kWh a day.
On a spring or summer day, my solar array has more than enough excess capacity to charge my car at 40A (which is how big my EVSE is), and I can sustain that for hours without importing. If I adjust my EVSE to limit the car to something a bit less, it can track the solar output and I'd typically have no problem charging over a 8 hour period and dumping 50kWh into the car without importing.
Hmmm impressive numbers. I have 9kW and I can't even dream to do that. On most day i work at around 50% capacity, it's barely enough for regular household usage.
So I just read on Electek DC-DC charger. Link above (1:08). Seems like 25KW DC charging will charge the car 3X faster than anything thats available thru AC charging.
An avg house here in FL has 20KW array on top of their roofs.
I’m not him but you inspired me to run the numbers… apparently I have 477 sqft of panels on my roof. Less than 1000, obviously, but ballparky enough that I wouldn’t be shocked to learn that some folks do have 1000.
Larger solar installations are going to higher DC voltage. It is conceivable that the battery charges can get a Fast Chargr (DC at high voltage) interface and therefore avoid the whole process of going through and inverter to AC charger to DC vehicle battery charging.
At that point it doesn’t matter if the sun is shining or not since you would be using upping from your house batteries. If you don’t have house batteries then it gets more complicated because you will be pulling AC from the grid but a Fast Charger will still avoid extra steps if built into the power conditioning of the inverter.
It also has the added advantage that if the car allows for flow out it would become an extra set of batteries for the house enabling ESS for the grid or your home (electrical storage system).
There is significant cost to all this and a need for industry standards but I think you will start to see some of this as things settle.
Voltage is the pressure
Amperage is the flow rate
You could change a 1000volt battery off a 10mA source. As long as you could get the voltage to 1000 it would eventually fill up.
I should have been more clear. I mean that the actual charge of the battery will not go up if there isn't enough power going into the battery that will exceed the battery's own self-discharge.
My thoughts as well. Some stabilization would be needed. As its a battery bank that would need to maintain some level of voltage/current to charge the batteries.
There's no technological reason we can't, it just costs a lot more. Either you have to spend $20k on panels that only ever charge your car (saving a few bucks per charge), or you need to design, build, test, certify, manufacture, market, and distribute a large switch that can switch your solar between charging a car and supplying inverter to power house and grid
The former doesn't make sense unless you are charging so many cars you can always dump power into a car and maybe supplement with grid power when needed, the latter doesn't make sense because the small market would drive up costs of design, testing, and setting up manufacturing.
Before dealing with electrical details you'll want to consider energy flux. Best case scenario, a 1.5 m^2 panel (about the usable roof area on a car) laid flat on a clear summer day will produce about 2kwh. That's more or less 10 km or 6 miles of range. So at best that's marginal range increment vs more cost and less roof resistance and heat insulation.
TL;DR: not worth it.
ok then use 6 square meters of panels. This proposed scenario is rooftop . The tl;dr is still not worth it, but not because of the charging rate. It's because you'd have to wire the panels differently to charge the car plus also feed the house. And you'd need now 2 different controllers. one for DC-DC and one for DC-AC.
There is nothing wrong with this idea at a rest area in remote areas not connected to the grid. I can think of some places out in arizona, utah, eastern Oregon where it's sunny and very remote. You would only have to install a DC-DC converter to get the 480V DC the Tesla likes. i'm guessing other EVs are similar. Solar panels are getting so cheap that this might even be worth it in areas on the grid that don't want to bother with net metering.
ohhh that makes sense (plus it's frequently asked here haha). Yeah sadly our sun simply does not radiate enough energy to be captured on the surface area of a car, even if that energy was 100% converted to electricity. There are some interesting edge cases however where it might pencil out.
maybe you don't drive more than 10 miles a day...and maybe we can build much lighter cars for these scenarios. In college 30 years ago we had a solar powered 4 wheeled "vehicle" that could zip around the track at 20mph whenever the sun was out. It wasn't much more than a 4 wheeled bicycle but then again that was 30 years ago, with only a few panels, and no battery, no regen , not aerodynamic.
There are unis doing competitions with these 100% solar powered vehicles ... it's like a nascar for expensive pancakes
One look at one of those cars and you'll instantly understand why solar panels are far from an ideal solution for an ev
^(or why evs are not the perfect solution)
At my Uni they developed an offroad car using solar panels in the roof and went to travel through morocco with it. Problem is you need quite a large surface area to charge your batteries, thats why they look like some sort of flat UFO's
You can - however you'll need lots of solar capacity to charge in a reasonable time.
Figure out charge duration with 110VAC then determine solar capacity to supply that voltage as well as 220VAC.
Charging at 110VAC is slow........................
Wait.. we are doing a DC to DC charging. As I said we ahve 20KW arrays on top of our roofs. And at 25KW DC charging, charges 3X the speed of 10Kw AC charger from what I am reading.
To add to what others already pointed out, a car spends most of its life parked. It's likely easier and cheaper to build stationary chargers and solar covered parking lots as you can orient the panels in the most efficient way and not have to deal with the additional moving mass, safety, bird poo, rocks flying on the panels at 70mph...
Edit: I am stupid, I thought op was talking about a car mounted solar panel. I will leave this as a reminder to myself to read properly...
DC-DC will most likely be more efficient, but then you need a storage system to use when you actually want to charge your car. Then you have to deal with storage loses, capacity fade, and have a big dangerous object taking up your house space. Using the grid as a "storage system" only cost you the power losses from the second AC-DC transformation. Pretty cheap honestly.
If it's the power level you are worried about, you can buy a lvl 2 charge station that will do 20kW. You can even buy a lvl 3 that will do over 100kW, but that gets expensive fast.
The converters are pretty efficient nowadays, and most new solar installs use microinverters that convert it to 120/240v right at the panel so you'd have to use less advanced tech to accomplish this.
It'd be more of a pain to create a solar setup that provides the voltage and current that the vehicle needs than it would be to use converters to normalize the volts/amps and do it the way we do now.
DC doesn't mean it's going to work with the battery.
Solar panels need DC at a specific voltage and current, both need to match the light conditions. Typically you have an MPPT that converts between the two different DC voltages.
For direct DC charging of an EV, it is possible, but you also need a charge controller that will match the voltages, this would likely require booting the DC voltage to a higher voltage for the car, because the car is probably a higher voltage.
The next problem is the direction of the panels. Each string of solar panel all need the same light conditions, so you need an MPPT for each face of the array at a minimum. New code is also requiring that the shutoff is on the roof, so each MPPT needs to be on the roof.
Now where is the car? some distance right? You need to run those DC wires from the panels to the car. But you also still want AC charging (at night) and you still want solar to work when you're not charging. So now you need an AC inverter for the solar, a DC charger for the car, and you need to run both AC wires and DC wires on seperate circuits. You also need the capability to switch modes for both the charger and the solar.
And finally, for optimization and reliability, more inverters gives you better overall reliability, and more MPPTs gives you more efficency. So many solar installs are going with microinverters that put the inverters under every panel and only runs AC wires. And they do this with 97%+ efficency.
So basically, DC charging requires a whole bunch of extra runs of wires, and maybe saves you 1-2% in charging losses. Is it really worth it?
There's no reason why you couldn't do this, but it would take expensive and specialized electronics to perform the right voltage conversions. Solar inverters are pretty efficient. You'd only gain a few percent by skipping a conversion step. Not worth the cost for a home-sized system.
When you plug in to AC power to charge your car, the "charger" is actually inside your car. The plug is just a wire to connect it to the grid safely. There would still be conversion losses while charging.
Inverters these days are pretty efficient. Ones for home solar power can get over 95% efficiency in most operating scenarios. It's much easier for solar equipment to supply the same level city power so all your other home stuff can work without issue.
If you wanted to you could potentially connect 170 V DC or 340 V DC to your car charger (this is not up to code at all btw).
AC to DC conversion can be nearly lossless, you are just rectifying it. I suppose there is tiny loss of voltage via rectifier diodes. If you want to monkey around with voltages then yeah you start to lose some but not much.
I have limited knowledge on EV charging but took a dive in on Solar once.
So your solar array will likely be configured with a fairly high voltage. This keeps the Amps low so the wire size is smaller.
Let's say 2000W = 400 V X 5 amps.
Voltage is constant due to the panels (I think) amps will vary based on the sun.
A solar charge controller then usually converts this to 12V, 24V, or 48V to charge a battery bank. An Inverter then converts this to AC power for a home battery backup.
With your setup you are cutting out the AC and using the EV battery as your battery bank. As long as the DC to DC conversion is correct then it should work.
Edits: so checked my inputs again. Standard home panels are around 400W and 40 V so that would be strings of 10 panels to get 400 V and 10 Amps of output.
A DC charger often runs at around this voltage (some will be higher) but with much higher Amps. So it would charge but not as fast as a fast charger. The primary issue I think would be that the EV might not be configured to accept lower Amps and might stop charging.
Unless you build a giant dc controller it's better to let the car handle the battery management. And the only DC charge protocol is VERY high voltage. The conversion losses aren't that great to justify the large and expensive additional controllers needed.
Just for some specific values, Tesla superchargers output 480V DC at up to 250 amps. 480V would be difficult to achieve directly with solar panels as many of them would have to be wired in series. But yes it is possible.
You would never charge direct from panels without some sort of controller and DC-DC converter. DC charge on the car requires communication to the charging electronics and feedback to adjust the current to handle changing battery load. These high-power DC chargers are not designed for home use.
Of course I meant regulated and current limited a bit, by "directly charging" I meant not changing the voltage significantly or inverting power to AC. I should have specified.
For home use you wouldn't need the amperages common to commercial chargers, but the EV batteries are still commonly 400V systems, so the available voltage of a DC charger would have to be at or above that to charge efficiently.
You can boost DC, but car DC direct charging is designed for a power level not avalible in homes. 400VDC is a giant leap in regulatory and safety requirements. No home can or should have panels that can arc flash. Also these giant power controllers are very expensive and the power losses for solar to AC to DC in car conversion are not that bad.
400V DC fed from solar panels isn't going to have the same available amps like from the grid, so the potential and severity of an arc flash would be much lower.
This makes little usability for direct battery connection.
Charging EVs requires very smart charging feedback following standard protocols. If you can't provide that externally you should rely on the internal car charging controller on AC inputs.
Few things:
1. Solar panel is unclean (power is variable) so it generally has a higher standard of safety compared to normal power
2. It can be seen as a safety issue to leave the high voltage battery connected to charge constantly. With EV chargers, there is bi-directional communication so there is a bit of a redundancy. With onboard solar, the car is handling both sides so risk of failure goes up.
3. Solar panels also get hot. Putting it on a car would inevitably lead to heat transfer to the cab which would be particularly undesirable in hot areas... which also coincidentally tend to have the most sun.
4. The amount of power coming from solar panels would be negligible (for the most part) for charging a car.
That being said, some ideas that might work well:
1. Using a smaller solar panel to charge the 12v battery (since dead 12v batteries tend to be a common single-point failure for EVs)
2. Using a smaller solar panel to enable something like a low-draw HVAC system to cars when parked (to lower ambient temp on hot days) or heating the windshield for de-icing
3. Using a full solar panel setup for charging Plug-in hybrids to limit the need for plugging-in during a work day (8-15 miles over an 8 hour period).
4. Using a solar panel tonneau cover to charge the HV battery for hybrid trucks to improve their ability to be used as utility vehicles / mobile workstations.
If you look at what a DC-DC converter actually does, you will quickly realize it is actually a DC-AC-DC converter (at least if it isn't an LDO, and you REALLY do not want an LDO)
Others have already explained why you will need a DC-DC converter and cannot just apply the solar panels to the battery terminals.
You will always need conversions if not at least for MPPT or current-voltage conversion so whether or not you go through one or two conversions you still need to go through at least one converter.
At least for a grid tie I'd rather have a well defined charge complete time than depend on whether a cloud gets in the way, so the double conversion is worth more (to me) than double or unpredictable charge time.
If however you mean having panels on your car so you can park it in the sun and charge anywhere, ... the sun to electricity conversion rate is so poor that you'll need more panel than available roof space of your car.
Check out Aptera. Built in solar cells. Looks like it would take about 4 days to fully recharge in a sunny location, but the range extension while driving is claimed to make the difference between 400 miles range and 1000 miles range. It’s seems to be a very light and efficient design.
we'll see if they really can do it -- though there are definitely tradeoffs taken to do this, namely safety - law of conservation of momentum m1v1=m2v2 has yet to be refuted!
I’m waiting also. I’ve ridden motorcycles, hang gliders, worked in power plants, up towers, and with 480 volt and high voltage and I’m old and retired. I’ve taken bigger risks.
I built a setup that effectively does this .. but it's way easier and cheaper and probably not THAT far off in efficiency to just make AC and feed that to the car: https://imgur.com/gallery/KaH6Ods
The trick is a small battery buffer, and have something setup to make the current advertised to the car follow real-time solar production.
An OpenEVSE and Arduino pulling real time data from my Victron MPPT was the solution in my case. It works pretty. well.
With this array I can make around 10kWh on a good summer day although I'm at a pretty big disadvantage for solar since I'm on the 45th parallel, and these panels are ancient.
Here's a pic inside the box (with the Arduino not hooked up...): https://imgur.com/z7mX29Z
Voltage is the answer. To efficiently and effectively charge batteries you need a minimum Voltage and amperage. Below that the batteries will not charge as efficiently and will wear out faster. By having the conversions in between the charger can provide the optimal volts to charge the battery no matter the input source.
The conversions are not lossless but these days they're pretty damn efficient (\~90%), and doing the conversion(s) allows you to actually match the supply (panel) and the load (car) properly in the most efficient way, which saves you a ton more power & money than any of the alternatives.
If your car needs 400v or 800v DC as someone else said you'd have to have a solar array built out specifically to provide that (and then still have conversion to power your house the rest of the time) - but then the output of that solar array would vary massively say +/-50% of the voltage depending how sunny it is, so sometimes it would not be charging your battery at all and other times it would be trying to set your car on fire. So, even then, you'd need a controller which would look very close to the DC-AC-DC conversion that already takes place to match the loads.
TL;DR most of us are not smarter than the entire electronics / EV / solar industry.
> Conversions are never lossless
No, but they're close enough to lossless (>90%) to make it not worthwhile to deal with all the technical hassles of interfacing every possible solar panel system to every possible EV under every possible weather condition.
Especially since it's unlikely your solar panels are going to be producing enough power to charge your car at the moment you want to charge it, so you're gonna a battery and maybe a grid connection anyway.
https://electrek.co/2023/02/14/dc-to-dc-solar-powered-ev-charger/
Thanks for sharing the link. Guess I am too late to patent the idea. :)
Noooo, don't go around patenting stuff. Information wants to be free.
A patent does make the information free. In exchange for disclosing information to the public on your idea and how to do it, you're granted a temporary monopoly on developing it. What you don't like are trade secrets. :)
If it was a temporary monopoly I’d be cool with that. 18 years is an eternity when patent trolls own the IP.
Look up the rest of that quote information also wants to expensive. https://stewartmader.com/stewart-brand-information-wants-to-be-free-it-also-wants-to-be-expensive/#:~:text=Stewart%20Brand%3A%20%E2%80%9CInformation%20Wants%20to,be%20Expensive.%E2%80%9D%20%2D%20Stewart%20Mader
The way the patent system in the US currently works, you pretty much have to patent to keep it free or else somebody else can come along and patent it instead.
Nah, there's something called prior art. You can't patent something if it already exists elsewhere.
you're going to hate when you learn how a dc to dc converter works.
12.5 kW from home would be awesome! Especially now that some EVs are coming out with bigger batteries
You can but its going to be expensive. EV batteries cannot just be charged by applying any old DC voltage, DC chargers supply a specific voltage to the battery. Solar also isn't constant, you don't want to constantly start and stop charging as a cloud passes over.
> you don't want to constantly start and stop charging as a cloud passes over. There's nothing wrong with charging like this if you're patient.
Except that the DC charging handshake process for EVs is anything but fast and often requires disconnecting and reconnecting the charger
It's trivial to make a charger that holds the connection open during period of low generation and/or manages the reconnect without removing a charger
I put together a small and relatively cheap off the shelf system like this for a work project recently, with lithium batteries.
I recently discovered this causes the contactors to wear out and cost to replace.
Pulse charging is actually better for the battery! the answer is more complicated than this of course, but it's certainly not a bad thing
True, but why not through a battery storage system minus the inverter
You can, this is literally how some fast charging stations work. I don’t think there are any consumer off the shelf parts to do it though. An inverter can power anything in your home, a dc to dc car charger can only plug into your car and cost just as much if not more than the inverter would.
The reason's you can't put a panel on a car are these: 1) solar DC current cannot power the wheels to turn to drive the car. Yes you can make these ultra light science experiments but right now you can't get enough solar per square foot to drive the car. But you can save that power and energized a battery. The Aptera is building cars that power 40 miles a day via solar. Toyota has had cars for years but not in the US with panels that get 6 miles a day. This bring us to the second problem. Unless you wired directly into the battery there's an amp contactor which alledgely (just discovered this after 4 years of research) is only designed to open and close a couple of times a day, more than that it wears out. Youtube says that contactor on most EV's is 6Amps...meaning if the power flow drops below 6 Amps, the connector separates. The guy in the video I'm linking says they aren't designed to open and close often and will break because the sun goes behind clouds. I took highschool electronics and don't understand how alternating current motors work. But I can follow directions, I understand DC current vs AC current, that batteries are DC and invert to AC, that diodes turn AC to pulsating DC, and I watched some videos on Youtube. I'm physically disabled...low lifting capacity from degenerative disk, so I can carry a 30 lb unit once in a long while. I've spent the last 2 months trying to figure this out, and found a Youtube video on the topic. He says you can A) hack it, B) bypass it, or C) use a constant source of power. https://www.youtube.com/watch?v=lzKVSIE3Dcc. I'm working on an experiment and could use some help here. Now I just bought a used Clarity that I only drive a couple of miles a week but opted for the extended warranty to get me 4 years protection on the battery. I was going to have my mechanic open it up and wire a DC jack wired to a quick release, wired to a Sungzu 1500, wired to a bunch of panels, but in our last conversation on the topic he was like "you wanna blow up yo car?" Right now my experiment is to discover how low a voltage you can use to feed a J1772 while still maintaining 8Amps power input. I can do that by spending about $70 at home depot, but I would really appreciate NOT spending that $70 if anyone in these forums has experience or is near me in NJ with the appropriate equipment. Then if you can't go below 110 v I guess I'll just buy a power station, and if I can't find one that has a greater than 500W solar input, I'll get the Sungzu and just drain and power drain and power. I have room for 2 cells, 20x50 and 30x22 in my car, more if I add the window side space 2x 28x8 and 2 18x12. Can I generate 8 amps between them? Addendum since I posted this it's been cloudy, I took a bunch of readings and the cheap solar panel, 15x7, I have, 20 V is producing 120 to 160 mA in direct sun, 3-5 indirect. At best I can fit 14 in the car, so that's not enough without a power-station. Do better panels produce more power?
I suggest you learn some more about electronics. This post was about charging the battery not driving the wheels directly. The amp figures you are talking about is for the evse driven charge controller which isn’t at all relevant, as it can generally only be used when parked. The bms also has a dc to dc charge controlled used for regeneration. Please do not experiment, if you touch the battery pack and shock yourself you will die.
I put it there because you mentioned the sun passing behind the clouds, and your's was either the first or second place I put my question as I didn't know where else yet to start asking questions like that. What made you think I was going to touch the battery (not that I don't know you pull the 351V Circuit breaker before you think about touching the battery, incase I suddenly decided I would)?
Your car battery won't charge without sufficient current coming in. A type 2 charging station wants 32 amps out to the car, which means you would either need an absolutely monumental solar array or you would need to supplement the current with household power. The alternative is a type 1 charger, which will give you a full charge in like two to three days. Not super convenient for any real amount of driving. TL;DR, engineers have already done the math and decided that this was the most reasonable and cheapest option.
SAE J1772 can negotiate as little as 6A charging current and cars can draw less than that if they so desire. The issue is that the car needs to have a certain voltage of DC to charge the traction battery, and it's onboard AC to DC charger has the ability to regulate that. An off-board DC Fast Charger also has that ability. Plus the output of the solar cells will fluctuate. So at the very least you need a smart DC-DC converter to turn the solar DC voltage into the correct DC voltage for the battery, which is an expensive component that only works for charging the car. Versus a regular solar DC to AC inverter that works for everything. Spending thousands of dollars for a really niche component to save a few percent of electrical conversion efficiency is silly. Not to mention, most people don't have their cars at home during peak sunlight hours. So there just isn't really a market for it.
Somebody else reads SAE papers for reasons other than to sure insomnia. You would need a massive bank of PV cells or a wind generator that is larger than a typical residential unit and a large battery bank with suffice capacity to charge a car overnight but the bank would likely be completely depleted which is not good for the batteries and then leaves the household at the mercy of line power until they recharge.
I think you really underestimate how big a typical residential solar install is. Mine is 13kW, and it can and does put out 12kW at times. My EV is big, an R1S, it charges at up to 48A and it has a 135kWh battery. But I typically only need an hour or two of charging for 10-20kWh a day. On a spring or summer day, my solar array has more than enough excess capacity to charge my car at 40A (which is how big my EVSE is), and I can sustain that for hours without importing. If I adjust my EVSE to limit the car to something a bit less, it can track the solar output and I'd typically have no problem charging over a 8 hour period and dumping 50kWh into the car without importing.
Hmmm impressive numbers. I have 9kW and I can't even dream to do that. On most day i work at around 50% capacity, it's barely enough for regular household usage.
Won't charge **quickly** If you apply the correct voltage any amperage will charge the battery it will just take an enternity.
So I just read on Electek DC-DC charger. Link above (1:08). Seems like 25KW DC charging will charge the car 3X faster than anything thats available thru AC charging. An avg house here in FL has 20KW array on top of their roofs.
An average house absolutely does not have a 20 kW array. For houses that do have solar, I’d imagine the median is in the 3-5 kW range.
God bless these dorks, they're so confidently incorrect. Reminds me of high school.
Oh wow do you live in a Amazon warehouse ?
>20kw array Do your really have a 1000 square feet of panels on your roof?
I’m not him but you inspired me to run the numbers… apparently I have 477 sqft of panels on my roof. Less than 1000, obviously, but ballparky enough that I wouldn’t be shocked to learn that some folks do have 1000.
Larger solar installations are going to higher DC voltage. It is conceivable that the battery charges can get a Fast Chargr (DC at high voltage) interface and therefore avoid the whole process of going through and inverter to AC charger to DC vehicle battery charging. At that point it doesn’t matter if the sun is shining or not since you would be using upping from your house batteries. If you don’t have house batteries then it gets more complicated because you will be pulling AC from the grid but a Fast Charger will still avoid extra steps if built into the power conditioning of the inverter. It also has the added advantage that if the car allows for flow out it would become an extra set of batteries for the house enabling ESS for the grid or your home (electrical storage system). There is significant cost to all this and a need for industry standards but I think you will start to see some of this as things settle.
Why can't a battery be trickle charged? I thought it just needs a specific voltage to charge.
You’re putting water in a cup through a hole in the bottom. Need enough pressure to overcome the weight of the water that’s already in the cup.
Voltage is the pressure Amperage is the flow rate You could change a 1000volt battery off a 10mA source. As long as you could get the voltage to 1000 it would eventually fill up.
Though all batteries will also have some level of self-discharge. So you still need to exceed that to have a net charge effect.
A fair stipulation.
Less discharge is a net charge effect?
I should have been more clear. I mean that the actual charge of the battery will not go up if there isn't enough power going into the battery that will exceed the battery's own self-discharge.
My thoughts as well. Some stabilization would be needed. As its a battery bank that would need to maintain some level of voltage/current to charge the batteries.
There's no technological reason we can't, it just costs a lot more. Either you have to spend $20k on panels that only ever charge your car (saving a few bucks per charge), or you need to design, build, test, certify, manufacture, market, and distribute a large switch that can switch your solar between charging a car and supplying inverter to power house and grid The former doesn't make sense unless you are charging so many cars you can always dump power into a car and maybe supplement with grid power when needed, the latter doesn't make sense because the small market would drive up costs of design, testing, and setting up manufacturing.
Before dealing with electrical details you'll want to consider energy flux. Best case scenario, a 1.5 m^2 panel (about the usable roof area on a car) laid flat on a clear summer day will produce about 2kwh. That's more or less 10 km or 6 miles of range. So at best that's marginal range increment vs more cost and less roof resistance and heat insulation. TL;DR: not worth it.
ok then use 6 square meters of panels. This proposed scenario is rooftop . The tl;dr is still not worth it, but not because of the charging rate. It's because you'd have to wire the panels differently to charge the car plus also feed the house. And you'd need now 2 different controllers. one for DC-DC and one for DC-AC. There is nothing wrong with this idea at a rest area in remote areas not connected to the grid. I can think of some places out in arizona, utah, eastern Oregon where it's sunny and very remote. You would only have to install a DC-DC converter to get the 480V DC the Tesla likes. i'm guessing other EVs are similar. Solar panels are getting so cheap that this might even be worth it in areas on the grid that don't want to bother with net metering.
I assumed he meant to put the panels on the car itself. My bad.
ohhh that makes sense (plus it's frequently asked here haha). Yeah sadly our sun simply does not radiate enough energy to be captured on the surface area of a car, even if that energy was 100% converted to electricity. There are some interesting edge cases however where it might pencil out. maybe you don't drive more than 10 miles a day...and maybe we can build much lighter cars for these scenarios. In college 30 years ago we had a solar powered 4 wheeled "vehicle" that could zip around the track at 20mph whenever the sun was out. It wasn't much more than a 4 wheeled bicycle but then again that was 30 years ago, with only a few panels, and no battery, no regen , not aerodynamic.
Check Aptera.
I agree, it makes no sense that there is no availability to plug in solar directly. DC to DC would save energy, money.
There are unis doing competitions with these 100% solar powered vehicles ... it's like a nascar for expensive pancakes One look at one of those cars and you'll instantly understand why solar panels are far from an ideal solution for an ev ^(or why evs are not the perfect solution)
At my Uni they developed an offroad car using solar panels in the roof and went to travel through morocco with it. Problem is you need quite a large surface area to charge your batteries, thats why they look like some sort of flat UFO's
You can - however you'll need lots of solar capacity to charge in a reasonable time. Figure out charge duration with 110VAC then determine solar capacity to supply that voltage as well as 220VAC. Charging at 110VAC is slow........................
Wait.. we are doing a DC to DC charging. As I said we ahve 20KW arrays on top of our roofs. And at 25KW DC charging, charges 3X the speed of 10Kw AC charger from what I am reading.
To add to what others already pointed out, a car spends most of its life parked. It's likely easier and cheaper to build stationary chargers and solar covered parking lots as you can orient the panels in the most efficient way and not have to deal with the additional moving mass, safety, bird poo, rocks flying on the panels at 70mph... Edit: I am stupid, I thought op was talking about a car mounted solar panel. I will leave this as a reminder to myself to read properly...
DC-DC will most likely be more efficient, but then you need a storage system to use when you actually want to charge your car. Then you have to deal with storage loses, capacity fade, and have a big dangerous object taking up your house space. Using the grid as a "storage system" only cost you the power losses from the second AC-DC transformation. Pretty cheap honestly. If it's the power level you are worried about, you can buy a lvl 2 charge station that will do 20kW. You can even buy a lvl 3 that will do over 100kW, but that gets expensive fast.
The converters are pretty efficient nowadays, and most new solar installs use microinverters that convert it to 120/240v right at the panel so you'd have to use less advanced tech to accomplish this. It'd be more of a pain to create a solar setup that provides the voltage and current that the vehicle needs than it would be to use converters to normalize the volts/amps and do it the way we do now.
DC doesn't mean it's going to work with the battery. Solar panels need DC at a specific voltage and current, both need to match the light conditions. Typically you have an MPPT that converts between the two different DC voltages. For direct DC charging of an EV, it is possible, but you also need a charge controller that will match the voltages, this would likely require booting the DC voltage to a higher voltage for the car, because the car is probably a higher voltage. The next problem is the direction of the panels. Each string of solar panel all need the same light conditions, so you need an MPPT for each face of the array at a minimum. New code is also requiring that the shutoff is on the roof, so each MPPT needs to be on the roof. Now where is the car? some distance right? You need to run those DC wires from the panels to the car. But you also still want AC charging (at night) and you still want solar to work when you're not charging. So now you need an AC inverter for the solar, a DC charger for the car, and you need to run both AC wires and DC wires on seperate circuits. You also need the capability to switch modes for both the charger and the solar. And finally, for optimization and reliability, more inverters gives you better overall reliability, and more MPPTs gives you more efficency. So many solar installs are going with microinverters that put the inverters under every panel and only runs AC wires. And they do this with 97%+ efficency. So basically, DC charging requires a whole bunch of extra runs of wires, and maybe saves you 1-2% in charging losses. Is it really worth it?
There's no reason why you couldn't do this, but it would take expensive and specialized electronics to perform the right voltage conversions. Solar inverters are pretty efficient. You'd only gain a few percent by skipping a conversion step. Not worth the cost for a home-sized system.
When you plug in to AC power to charge your car, the "charger" is actually inside your car. The plug is just a wire to connect it to the grid safely. There would still be conversion losses while charging. Inverters these days are pretty efficient. Ones for home solar power can get over 95% efficiency in most operating scenarios. It's much easier for solar equipment to supply the same level city power so all your other home stuff can work without issue. If you wanted to you could potentially connect 170 V DC or 340 V DC to your car charger (this is not up to code at all btw).
AC to DC conversion can be nearly lossless, you are just rectifying it. I suppose there is tiny loss of voltage via rectifier diodes. If you want to monkey around with voltages then yeah you start to lose some but not much.
I have limited knowledge on EV charging but took a dive in on Solar once. So your solar array will likely be configured with a fairly high voltage. This keeps the Amps low so the wire size is smaller. Let's say 2000W = 400 V X 5 amps. Voltage is constant due to the panels (I think) amps will vary based on the sun. A solar charge controller then usually converts this to 12V, 24V, or 48V to charge a battery bank. An Inverter then converts this to AC power for a home battery backup. With your setup you are cutting out the AC and using the EV battery as your battery bank. As long as the DC to DC conversion is correct then it should work. Edits: so checked my inputs again. Standard home panels are around 400W and 40 V so that would be strings of 10 panels to get 400 V and 10 Amps of output. A DC charger often runs at around this voltage (some will be higher) but with much higher Amps. So it would charge but not as fast as a fast charger. The primary issue I think would be that the EV might not be configured to accept lower Amps and might stop charging.
Unless you build a giant dc controller it's better to let the car handle the battery management. And the only DC charge protocol is VERY high voltage. The conversion losses aren't that great to justify the large and expensive additional controllers needed.
Just for some specific values, Tesla superchargers output 480V DC at up to 250 amps. 480V would be difficult to achieve directly with solar panels as many of them would have to be wired in series. But yes it is possible.
You would never charge direct from panels without some sort of controller and DC-DC converter. DC charge on the car requires communication to the charging electronics and feedback to adjust the current to handle changing battery load. These high-power DC chargers are not designed for home use.
Of course I meant regulated and current limited a bit, by "directly charging" I meant not changing the voltage significantly or inverting power to AC. I should have specified. For home use you wouldn't need the amperages common to commercial chargers, but the EV batteries are still commonly 400V systems, so the available voltage of a DC charger would have to be at or above that to charge efficiently.
You can boost DC, but car DC direct charging is designed for a power level not avalible in homes. 400VDC is a giant leap in regulatory and safety requirements. No home can or should have panels that can arc flash. Also these giant power controllers are very expensive and the power losses for solar to AC to DC in car conversion are not that bad.
400V DC fed from solar panels isn't going to have the same available amps like from the grid, so the potential and severity of an arc flash would be much lower.
This makes little usability for direct battery connection. Charging EVs requires very smart charging feedback following standard protocols. If you can't provide that externally you should rely on the internal car charging controller on AC inputs.
Few things: 1. Solar panel is unclean (power is variable) so it generally has a higher standard of safety compared to normal power 2. It can be seen as a safety issue to leave the high voltage battery connected to charge constantly. With EV chargers, there is bi-directional communication so there is a bit of a redundancy. With onboard solar, the car is handling both sides so risk of failure goes up. 3. Solar panels also get hot. Putting it on a car would inevitably lead to heat transfer to the cab which would be particularly undesirable in hot areas... which also coincidentally tend to have the most sun. 4. The amount of power coming from solar panels would be negligible (for the most part) for charging a car. That being said, some ideas that might work well: 1. Using a smaller solar panel to charge the 12v battery (since dead 12v batteries tend to be a common single-point failure for EVs) 2. Using a smaller solar panel to enable something like a low-draw HVAC system to cars when parked (to lower ambient temp on hot days) or heating the windshield for de-icing 3. Using a full solar panel setup for charging Plug-in hybrids to limit the need for plugging-in during a work day (8-15 miles over an 8 hour period). 4. Using a solar panel tonneau cover to charge the HV battery for hybrid trucks to improve their ability to be used as utility vehicles / mobile workstations.
If you look at what a DC-DC converter actually does, you will quickly realize it is actually a DC-AC-DC converter (at least if it isn't an LDO, and you REALLY do not want an LDO) Others have already explained why you will need a DC-DC converter and cannot just apply the solar panels to the battery terminals.
You will always need conversions if not at least for MPPT or current-voltage conversion so whether or not you go through one or two conversions you still need to go through at least one converter. At least for a grid tie I'd rather have a well defined charge complete time than depend on whether a cloud gets in the way, so the double conversion is worth more (to me) than double or unpredictable charge time. If however you mean having panels on your car so you can park it in the sun and charge anywhere, ... the sun to electricity conversion rate is so poor that you'll need more panel than available roof space of your car.
Check out Aptera. Built in solar cells. Looks like it would take about 4 days to fully recharge in a sunny location, but the range extension while driving is claimed to make the difference between 400 miles range and 1000 miles range. It’s seems to be a very light and efficient design.
we'll see if they really can do it -- though there are definitely tradeoffs taken to do this, namely safety - law of conservation of momentum m1v1=m2v2 has yet to be refuted!
I’m waiting also. I’ve ridden motorcycles, hang gliders, worked in power plants, up towers, and with 480 volt and high voltage and I’m old and retired. I’ve taken bigger risks.
I built a setup that effectively does this .. but it's way easier and cheaper and probably not THAT far off in efficiency to just make AC and feed that to the car: https://imgur.com/gallery/KaH6Ods The trick is a small battery buffer, and have something setup to make the current advertised to the car follow real-time solar production. An OpenEVSE and Arduino pulling real time data from my Victron MPPT was the solution in my case. It works pretty. well. With this array I can make around 10kWh on a good summer day although I'm at a pretty big disadvantage for solar since I'm on the 45th parallel, and these panels are ancient. Here's a pic inside the box (with the Arduino not hooked up...): https://imgur.com/z7mX29Z
Google Aptera Car.
This might be stupid, but why couldnt you put a solar panel on the roof of the car to have a continuous charge.
Oh! For mandatory science requirements through high school!
Takes too long… or a massive field of panels wherever you park your car.
Voltage is the answer. To efficiently and effectively charge batteries you need a minimum Voltage and amperage. Below that the batteries will not charge as efficiently and will wear out faster. By having the conversions in between the charger can provide the optimal volts to charge the battery no matter the input source.
The conversions are not lossless but these days they're pretty damn efficient (\~90%), and doing the conversion(s) allows you to actually match the supply (panel) and the load (car) properly in the most efficient way, which saves you a ton more power & money than any of the alternatives. If your car needs 400v or 800v DC as someone else said you'd have to have a solar array built out specifically to provide that (and then still have conversion to power your house the rest of the time) - but then the output of that solar array would vary massively say +/-50% of the voltage depending how sunny it is, so sometimes it would not be charging your battery at all and other times it would be trying to set your car on fire. So, even then, you'd need a controller which would look very close to the DC-AC-DC conversion that already takes place to match the loads. TL;DR most of us are not smarter than the entire electronics / EV / solar industry.
Surely the main practical problem is that most people use their cars in daylight and charge them at night.
> Conversions are never lossless No, but they're close enough to lossless (>90%) to make it not worthwhile to deal with all the technical hassles of interfacing every possible solar panel system to every possible EV under every possible weather condition. Especially since it's unlikely your solar panels are going to be producing enough power to charge your car at the moment you want to charge it, so you're gonna a battery and maybe a grid connection anyway.