DC solar directly to EV (no AC!)

zuzullo

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Do we always need to invert solar DC to AC in order to charge an EV?

Since EVs take DC charging, isn't there a way to wire DC directly from the solar into EVs battery?fireshot-capture-277-usa-stock-stackable-2400w-14kw-24v-120vac-charge-80a-mppt-solar-60-www-eb...jpg
 

chrisski

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I would not want to do that with the system you have pictured.

I don’t think the charger you have listed would provide the exact voltages and charge profile for the car. If you had your car hooked up and it worked, how do you feel about the car battery running the house…

I would think differently if it was eight batteries six volts each in series for 48 volts and this was an electric Polaris side by side. I would rather include a dc to dc converter to charge the Polaris off instead of a being the ,aim battery.
 

zuzullo

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I would not want to do that with the system you have pictured.

I don’t think the charger you have listed would provide the exact voltages and charge profile for the car. If you had your car hooked up and it worked, how do you feel about the car battery running the house…

I would think differently if it was eight batteries six volts each in series for 48 volts and this was an electric Polaris side by side. I would rather include a dc to dc converter to charge the Polaris off instead of a being the ,aim battery.
Ok, thanks that is it then. We need a DC to DC charger between the all-in-one device and the car. That DC to DC charger needs maybe to be specific for the charge-profile of the car.
1 - Do you know of any device like that?
2 - Is that dc-dc charger bi-directional, so that it could power the house?
 

pollenface

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If your car powers your house ... your car will be flat when you want to pick up the groceries ... henceforth I advise against bidirectional dc-dc chargers if there is such a thing...

I'm going to go out on a limb here when I say "I'm pretty sure the picture in the OP was for illustration purposes only and not intended to be listed as such" being that this is a completely hypothetical discussion
 

HRTKD

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I think the battery on my Leaf is something like 400 volts. No way I'm messing around with voltage that high. No way I'm going to bypass the charging system either. At least not while it's still under warranty. That would require some serious hacking that I'm not qualified for.
 

hardtop

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You could look at the DC charging station manuals and maybe that would provide insight. A separate controller to communicate with the car is required. At one point there was an open source controller for L2 charging, maybe there is one for DC too.
 

curiouscarbon

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Cutting out the DC->AC->DC double conversion loss would be amazing, right?

You need to be VERY careful with the High Voltage Traction Battery. I suggest you not attempt any of this unless you have long talks with either the manufacturer or people who have hacked on the vehicle you want to convert. You could easily be harmed by the high voltage potential of the traction battery, or cause the vehicle's other systems to dangerously malfunction in a way that is hard to anticipate. Not fearmongering, but seriously this is very intense engineering required for safety. HVDC plugs have big insulation requirements and even sheathing to prevent arcing.. be careful please!

I plan on experimenting with VIPV (Vehicle Integrated Photo Voltaic) in the near future, and this topic is pretty central to overall efficacy.

I plan on doing Solar PV DC -> MPPT -> LiFePO4 battery pack -> AC inverter -> vehicle AC charger -> traction battery.

It's unfortunate for now but there is not a safe alternate way for now that I am aware of.

Good luck, be safe, VIPV needs earnest engineering effort :) there are going to be some interesting vehicles in the next 10 years..
 

zuzullo

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Cutting out the DC->AC->DC double conversion loss would be amazing, right?
EXACTLY!!!!
That could be a better title for this post :)

I plan on doing Solar PV DC -> MPPT -> LiFePO4 battery pack -> AC inverter -> vehicle AC charger -> traction battery.
That is insane right?!? The amount of resources that are needed there. And in theory you would just need a DC to DC charger with MPPT. (A bit like the concept of the Renogy DC-DC chargers with MPPT, but with a selectable output profile for the different EVs)
But I understand now that there is nothing like that on the market.
 

zuzullo

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It's unfortunate for now but there is not a safe alternate way for now that I am aware of.
Well I am looking into the Setec Power and the native Nissan PCS solution but this last one is really hard to find info online.
If you guys have any more info, let me know.
(Oh and none of them include solar. But its been 8yr since this was launched. I was expecting to see a lot more on the market.)
nissan-leaf-to-home-power-station_100406461_h.jpg
 

HRTKD

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zuzillo, that looks to be a CHAdeMO charger. I could be wrong. If it is CHAdeMO, it has a higher amperage requirement than most homes can supply. That said, this article indicates it can be used to provide power back to the home.

 

zuzullo

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@HRTKD This leaf to home unit does charge at only 6kW and provides the same output to the house. It has a peak 8kW according to Nissan Denmark here:
 

curiouscarbon

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That is insane right?!? The amount of resources that are needed there. And in theory you would just need a DC to DC charger with MPPT. (A bit like the concept of the Renogy DC-DC chargers with MPPT, but with a selectable output profile for the different EVs)
But I understand now that there is nothing like that on the market.
Indeed, insane. Practically reminds me of pumped hydro efficiency.. Wish it were possible to just connect a 150-200W panel to a boost DC-DC MPPT converter direct to traction battery…… probably arriving in the next 5 years.

I certainly hope someone posts about a safe solution soon. Unfortunately, support seems pretty much necessary from the manufacturer to pull off direct traction HVDC charging safely :(
 

ChangeMachine

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Your EV's BMU needs to negotiate a power supply, so your options would be
1) Bypass a car's BMU (a stupid horrible idea)
2) Find a DIY solution to ask the nice BMU for some juice.
3) Go to a fast-charge station.
 

summit

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here is one option, hopefully more is in the work. I've suggested to mpp to build one, as i don't think it's all that difficult given their existing hybrid inverter/charger. mpp mentioned that it's in the work. The dcdel is undergoing UL approval for US market, but may be available outside

 

curiouscarbon

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i have given up hope on this idea until manufacturers support it.

ideally cars will just start to have MPPT input as a standard feature. this might upset some but it’s perfect logic.

people can carry multiple panels in trunk and connect to vehicle MPPT to directly charge HV traction pack

ok, car manufacturers, ready, go!
 

eXodus

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Cutting out the DC->AC->DC double conversion loss would be amazing, right?

You need to be VERY careful with the High Voltage Traction Battery. I suggest you not attempt any of this unless you have long talks with either the manufacturer or people who have hacked on the vehicle you want to convert. You could easily be harmed by the high voltage potential of the traction battery, or cause the vehicle's other systems to dangerously malfunction in a way that is hard to anticipate. Not fearmongering, but seriously this is very intense engineering required for safety. HVDC plugs have big insulation requirements and even sheathing to prevent arcing.. be careful please!

Good luck, be safe, VIPV needs earnest engineering effort :) there are going to be some interesting vehicles in the next 10 years..
While I agree that high voltage should be respected - 400V is nothing special. When you get closer 1000V - like 800V (Porsche Tycane) then insulation requirements go up.
We got outlets like that in Germany :p where you plugin devices, like your dryer, or saw in the garage. 400V can be easy handled.

What should be respected are all the possible AMPS from a battery. Further that when you go DC - all the intelligence is in the Charger - because a EV AC "Charger" is in reality nothing more then a fancy extension cord, with some lights on it. The AC charger is deep inside the EV.

Do we always need to invert solar DC to AC in order to charge an EV?

Since EVs take DC charging, isn't there a way to wire DC directly from the solar into EVs battery?
The trick is - many DC to DC chargers are reality are DC-AC-DC internally. When the voltage level are not perfectly matching.
So you are actually not gaining that much.

Most peoples have their cars plugged in most of the day anyhow - so that doesn't really matter for most applications. The car is full most of the day.
 

curiouscarbon

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Be careful with the Taycan, the battery voltage is higher, and incidence of complete recalls due to bad firmware too 🥺 but that’s unrelated to HV stuff, which I have no experience with anyways.

May I ask for any recommendations to read about HV insulation properties and safety practices?

Ask me to work on a 48V DC battery and I’ll be lookin fer magid gloves lol.

I want people to survive their solar adventures; please forgive my potential overblowing of risk. Hehe potential like voltage.

solar DC -> mppt -> battery DC -> inverter AC -> onboard AC charger -> HV battery DC is the path i plan on taking. there are losses, but hey, if ice vehicles are allowed to be considered cool and smart, and they shed 30% of heat unused, why can’t i, if it still means an absolute positive count of coulombs 🙂
 

RCinFLA

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Short answer is yes.

Your 'charger adaptor' at home is pretty much just an AC outlet. The actual charger and its checks and balances is in the vehicle. Bypassing the internal charger would likely void any warranty and may be dangerous unless you really know how the battery and charging system is designed for the specific vehicle.

What I mean by 'pretty much' is the adaptor tells the vehicle it can only pull a certain amount of AC current from outlet.

 
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