Solar to electric vehicle-direct

[Doggydogworld]

Ok. Thanks. Seems a little odd that direct from controller to car isn’t an option. I thought DC-DC was easier/simpler.

It is odd, at least from and engineering perspective. MPPT controllers can take >500V DC and directly charge a 48V LFP battery, why can't one directly charge a 400V LFP battery in a car? Obviously an engineer could build an MPPT that does, but no one has. Well, a couple hobbyists have, but nothing you can buy off the shelf.

Even weirder, almost every EV (except Tesla in the US) supports HVDC charging standards. Just add a CCS1 plug and protocols in Europe, CCS2 in the US and GB/T or whatever it's called in China and you can directly charge ~15m EVs today plus another ~10m that'll be sold in the next 12 months. Seems like a huge market, right?

I think the problem is few people want to buy a bunch of solar panels and use them only to charge an EV. So the typical system will have an inverter to power appliances and such. And if you have an inverter anyway, just plug your EV into a 120V or 240V AC outlet. Sure, it's less efficient. But it's easy and cheap.

 

[billt1827]

FWIW there is a fairly simple solution if you have an AC system, either grid tied or battery.

There are controllable EVSE A.C. chargers which can be linked to PV systems. I use an OpenEVSE charger ttps://www.openevse.com/ and https://shop.openenergymonitor.com/emonevse-wifi-connected-ev-charging-station-type-2/. There are other proprietary EVSE controllers available in the UK so I would have thought that you could get them in the US too.

The charge rate can be set in an app over your local network or it can be automated. On my system it gets sent mqtt messages from a comparator in EmonCMS when the available PV power exceeds the power being used elsewhere. It's primarily meant for grid tied systems but I use it with my off-grid system. It put 18kWh into the car today.

Minimum charge rate is 6A and there is some delay in changing the rate in order to reduce stress on the car charger so the energy supplied to the car can sometimes come from the grid or battery if you get rapid sun light changes.

 

[RayofSunshine]

Check out the Enteligent Hybrid DC Bi-Directional Fast EV Charger here. I'd ask to talk to Ed Rosenberry.

 

[dcg9381]

The way we are doing it PV -> Hybrid inverter -> Batteries

We use the output of the batteries/inverters to power a level 2 charger 240V @ 50A.

Is this the most efficient way? No. Is it the easiest and perhaps the cheapest way (that I know of) - yes.

There are various ways to "control" things so that you only use PV power, but PV is somewhat "unstable" (IE, you get clouds) I believe it's best to "buffer" with a battery or grid power.

The "cheapest" way is to grid tie if you have net metering. Just make sure your array exceeds your EV power needs and you're golden in terms of paying for that power.

 

[sunshine_eggo]

Check out the Enteligent Hybrid DC Bi-Directional Fast EV Charger here. I'd ask to talk to Ed Rosenberry.

Interesting. Any pricing info? Nothing on the site.

 

[dcg9381]

Interesting. Any pricing info? Nothing on the site.

It's not out, but I expect "expensive" as it's DC to DC and it also implies that you need an EV that is capable of bi-directional (perhaps you can do it without). It's indicating 3x faster than level 2, so that's potentially 30KW - that's a LOT of DC power.

 

[SamDeleted]

It is odd, at least from and engineering perspective. MPPT controllers can take >500V DC and directly charge a 48V LFP battery, why can't one directly charge a 400V LFP battery in a car

I think one problem is , think I'm right in saying every EV runs at different voltage so guess they'd have to make a model for each car ?

 

[dcg9381]

I think one problem is , think I'm right in saying every EV runs at different voltage so guess they'd have to make a model for each car ?

No, they'll match a charge standard. EVs are very good about having a standard for EVSEs (chargers) where the car communicates with the charger. They'll simple step it up or step it down. If they depend on batteries, then they'll invert from batteries as the buffer or stable side and just use PV to charge batteries... But I'm guessing here.

 

[SamDeleted]

No, they'll match a charge standard. EVs are very good about having a standard for EVSEs (chargers) where the car communicates with the charger. They'll simple step it up or step it down. If they depend on batteries, then they'll invert from batteries as the buffer or stable side and just use PV to charge batteries... But I'm guessing here.

Yes of course sorry , you're right there


I forgot they can charge from DC input

 

[RayofSunshine]

Interesting. Any pricing info? Nothing on the site.

I spoke with Ed Rosenberry of Enteligent last summer when I was starting to finalize plans (contacting various manufacturers with questions) to interview installers. That was before further health issues severely curtailed those efforts. After my latest medical procedure this coming Thursday, I hope to be back at that same point, so I’ll have to give ol’ Ed a shout to see what is shaking with them. He was willing to work with me on pricing for their DC optimizer/RSD devices, which seemed pretty kick-ass. At the time it looked like the beta of their EV charger was going to be Q3 ’22 or Q1 ’23. I don’t remember any exact numbers on pricing, but remember getting the impression that it wasn’t outrageous – given its capabilities. They were “working closely with a number of inverter manufacturers” (one of which was Sol-Ark) on integration of both their optimizer/RSD and EV charger. If I remember correctly, the aim of the charger integration was to be able to mix any and all of DC PV, AC (coupled) PV (from microinverters, etc.), battery ESS, generator, and grid to charge the EV (without having first to convert the DC PV or DC batteries to AC, as other “integrated” EV chargers do (e.g., SolarEdge)). Ad do so at a significantly higher rate than Level 2 EV chargers. Since I plan to have a (DC coupled) battery ESS to serve both time shift and backup functions, I am loathe to lose efficiency by first microinverting at the panel to AC, then back to DC to charge the ESS (or EV), then invert back to AC from batteries to house load, then back to DC (for most devices in my house). And I definitely want a LiFePO4 ESS, and prefer (well, require) the inverter to be battery chemistry/manufacturer agnostic, which makes the Sol-Ark a solid contender for my grid-tied situation. So Enteligent’s “close work” with Sol-Ark was of great interest. I suggest you call them and ask for Ed Rosenberry. Who knows: you might even be able to work out some kind of a beta test deal with them.

 

[RayofSunshine]

It's not out, but I expect "expensive" as it's DC to DC and it also implies that you need an EV that is capable of bi-directional (perhaps you can do it without). It's indicating 3x faster than level 2, so that's potentially 30KW - that's a LOT of DC power.

I think (but am not positive) that you only needed a Bi-directional capable EV to take advantage of using the EV as part of your battery ESS. I seem to remember that otherwise it just needed to be J1772 compatible (or Tesla, with a Tesla converter) in order to do the DC->DC (and "Level 2+") charging. But call them for the latest info. I just looked back at their Web site, and they have a Version 2.1 of their datasheet for the EV charger (at the same link I gave above). It gives a lot of info (like up to ~16kW of DC (PV solar &/or ESS batteries) + ~9.6 kW AC (240V @ 40A) for ~ 25kW charging rate).

 

[HarryN]

Another way to look at the decision is - "what if a tornado comes through and tears up your place?"

If you are heavily dependent on solar - that can be a big problem.

If you have solar for some things, but also one of those hybrid pick up trucks with a substantial built-in inverter and a real engine - you will still have electricity for the house and the ability to drive.

Keep an extra 25 - 50 gallons of fuel around and you have a lot of flexibility.

Just another variation on the theme "don't put all of your eggs in one basket".

 

[chrisski]

I don’t think level 3 DC charging is doable dollar wise through solar. Level 1 or 2 is. I have done Level 1 from my RV to charge the Tesla after a 25 mile drive:

Level 1Charging a Tesla Model 3 off grid

I did level 1 charging with my Tesla model 3 with my solar setup, and these are the results: 4.33 miles / hour charged 322 wh/mile from the ac inverter 367 wh/mile from the Batteries to cover AC losses AC draw from inverter while charging 1400 watts +/-2watts. AC Draw from inverter before...

diysolarforum.com

I found the way that the software calculates the watt hours per mile, a bit off, and not the real numbers you need for solar charging size.

I Level 1 charged my vehicle off grid, and I found my model 3, although the software says it gets 200 watt hours per mile at times, I had to charge it took 320 watt hours per mile to recharge the battery.

I like to know how much power I need to put into the battery to get it to drive a mile, not how much that comes out. That’s like saying my diesel gets 75 miles to the gallon because 1/5 th of the combustion is turned into energy that gets the 15 MPG, so I multiply that by 5 to get real MPG. Not real math.

 

[pollenface]

Least expensive way I believe is to help charge the EVs 12v battery.

A lot of stuff runs from the 12v system so just helping that helps take some load off the HV battery.

 

[chrisski]

Least expensive way I believe is to help charge the EVs 12v battery.

A lot of stuff runs from the 12v system so just helping that helps take some load off the HV battery.

The newer Teslas have done away with the 12 volt batteries. Just had the high voltage batteries. Must use the converters for the 12 volt and 24 volt side.

 

[400bird]

I think one problem is , think I'm right in saying every EV runs at different voltage so guess they'd have to make a model for each car ?

While there is no specified DC voltage on an EV, most run 96s lithium (3.7v cells, so about 355 nominal)
The CCS standard covers charging from something like 50v to 800+
Commercial DC chargers vary their output voltage to match the car. There is no onboard converter for the DC input on most cars. There are a few exceptions for cars at the 800v range.

 

[dcg9381]

Keep an extra 25 - 50 gallons of fuel around and you have a lot of flexibility.

Just another variation on the theme "don't put all of your eggs in one basket".

Keeping 25-50 gallons of gasoline around is problematic. Even if you choose non-ethanol (and can get it) it's not ideal. 100LL (airplane fuel) is probably better for longer storage, but cannot be used in anything EFI that isn't a simple engine.

I solved for this by buying 100lb propane tanks. That fuel keeps forever but has it's own "storage risks". Best bet is a large underground propane tank and a dual-fuel or propane generator.

 

[dcg9381]

The newer Teslas have done away with the 12 volt batteries. Just had the high voltage batteries. Must use the converters for the 12 volt and 24 volt side.

Interesting, I didn't know that. We've had EVs "brick" their 12-volt battery which creates some interesting problems.

 

[dcg9381]

Low end DC fast chargers are 480v at 100 amps, or 48kW. In comparison, a house is 240v, 200 amps. Strings of solar are in the same voltage range, just lower amps.

Note: some fast chargers are up to 1,000 volts. For home use, 480v would work.

If you have 500v strings of solar, you could direct charge at DC High Voltage (480v). With 10kW of panels, that would be 20 amps. There should be a way to figure that out for cars. You could use ten 5kWh batteries (48v, 100 amps, total of 50kWh) in series to store the power, and delivery it later to the car. At home, you don't need 15 minute charging. 2 hour charging of 50kWh (one hour if you want to discharge batteries at 1c) would be great.

Again, I don't see how this is possible without a "battery buffer". PV is simply too unstable due to cloud coverage.
I see lots of people running 48V batteries in parallel, as that's what inverters expect, but that that low voltage you end up with some really fat copper to get to 240V of DC power.

Any reason why you can't put 48V batteries in series, assuming a charger would do much higher voltages... It'd be easiest to DC to DC charge if you can get the voltages closer.

 

[chrisski]

batteries in series, assuming a charger would do much higher voltages... It'd be easiest to DC to DC charge if you can get the voltages closer.

If you did this, the level 3 would need to communicate with the car. These batteries are in excess of 300 volts, and Tesla has at least two standards at around 310 and 340, depending on battery type.

It’s not that these Level 3 chargers aren’t available, it’s more that they are $13k + when I’ve seen them.

Hugh voltage DC with arcing or voltages in excess of 48 volts is no joke.