Solar Charger for EV?

[mrpackethead]

Hi All, On Sunday i ordered a Kia EV6, ( standard 58kwH battery ). I've got a few months before it arrives.. lol ( i'll get it early 2023, long wait list ).

- I am ongrid, however there is nearly no economic benefit for me to put solar back into the grid. I'll only get a few cents a kW, and it will never repay the cost of a grid tie and the associated installation.
- I can get cheaper power overnight, which is when i would charge the EV...
- I work from home so my car is likely to be parked at home a lot during the day.
- I can control the charge rate for the car dynamically to match the available power ( https://www.openevse.com/ )

I'm thinking this through now.. What i'm thinking is sticking around 4-6kW of pannels on the carport roof. ( nicely pointed north ), and a stand alone inverter.
I'm guessing i'll need a small battery to act as a buffer but the assumption is that most of the energy will just go into the car. and if the car is full, and the small battery is charged, we'll just turn off, If i need a bit of a boost ( winter time ), i'll have a transfer contactor ( break before make ) to swap between the solar source and the mains. The system will have some microcontroller supervision system.

Does this seem viable? ( at least in theory )

 

[time2roll]

Yes works in theory. Still might be more practical to go with grid tie. Can minimize export by charging the Kia while the solar is producing. Or running the air conditioning etc. If the car is full even a few cents from the grid will add up with no extra effort.

 

[Ampster]

Still might be more practical to go with grid tie. Can minimize export by charging the Kia while the solar is producing. Or running the air conditioning etc. If the car is full even a few cents from the grid will add up with no extra effort.

I agree. I would not waste any money on a battery until you try a GT inverter with a limiter that allows you to use the grid as a buffer. The currrent transformer and program setting prevents any backfeed so no permission from the power company is needed. Theoretically all you would need is a building permit for the additional circuit. The solar panels on the carport would not require any Rapid Shutdown like they would if on the roof of your home.

 

[mrpackethead]

I agree. I would not waste any money on a battery until you try a GT inverter with a limiter that allows you to use the grid as a buffer. The currrent transformer and program setting prevents any backfeed so no permission from the power company is needed. Theoretically all you would need is a building permit for the additional circuit. The solar panels on the carport would not require any Rapid Shutdown like they would if on the roof of your home.

Differnet rules here. Dont need building permits.. But grid tie is expensive here, not because of the equipment, but because of the compliance that you have to jump through.. Its many thousands of dollars.

I agree. I would not waste any money on a battery until you try a GT inverter with a limiter that allows you to use the grid as a buffer. The currrent transformer and program setting prevents any backfeed so no permission from the power company is needed. Theoretically all you would need is a building permit for the additional circuit. The solar panels on the carport would not require any Rapid Shutdown like they would if on the roof of your home.

2kW of panels + Grid Tie Invertor and all the related interconnects will cost me in the region of $12,000. I can't do any of it myself, its all got to be a certified installation.
2kW of panels + standalone inverter + 2kWhr battery will cost me around $2,000 all up. $10,000 is a lot of energy to save.
Sure i' might waste a bit of 'opportunity' to divert any surplus power into the house.. that might come one day later... Remember i wont' be deeply discharing this battery.. Its only there to buffer things while the charger adjusts the current to match the Solar output.. Which is likely only to be in the region of 1-2 seconds.. If theres no power being generated, there will be no charging.. ( I can bypass to grid if i need to at 10pm and get cheaper power )..

Ballpark 2kW will give me ball park of 10kW of energy for the car every.. Which on average will be enough.

 

[furkidmom]

I'm dealing with a similar situation looking at an off grid ev charging station for a Ford Lightning. But I could use some education/help figuring out if it is viable. I think there are pieces of the electrical dynamics when setting up for an EV charge that I don't fully understand. Our rooftop solar is maxed out and would be expensive to expand. We have 2.5 acres in CA and plenty of open space for panels to get maximum sun, not a long run cable run to the driveway, no pge or county permits. But, my math says we'd need a huge battery supply.. That alone would be more than $5K. Am I doing something wrong here? I see posts from people having done such systems.. do we really need that much battery? Then, the part that I really don't understand, would a 240V/100Amp Inverter power the EV charger, and what rate would it charge at? Would appreciate any advice/insight here.

Estimate of solar need​
Miles Driven/Day	35​
Range mi/kw	1.88​
Battery used KW	18.59​
add 35% for system losses	25.102​
Inverter efficiency	90%​
Amt of Elec supplied by panels to inverter and battery	22.591​
Ave. Irradiation hrs/Day	6​
Solar Panel KW needed	3.7652​
solar panels needed @ 370kw	10.176​
Battery Bank Size​
Energy needed kwh	18.594​
Depth of Discharge	80%​
Battery storage needed KWH	23.242​
Battery Voltage	24​
Amp hrs (1000xKwh/voltage)	968.42​	Yikes!

 

[furkidmom]

whoops, error in formula on the 90% efficiency. Corrected numbers below. We think that 6 hrs of sunlight is a pretty conservative number, and we upped to 8 just to see. With the range on the lightning, we can go on average close to 10 days with just our day to day driving. Even in the winter, we seldom go several days w/o sun. Also, we will normally be charging during the day. I am retired, so my commute is to the tennis courts and back. Seems like this formula assumes that you drive the car and charge the batteries during the day, and then charge the car at night. On our pond system, I know that it runs pretty much off the solar all day, and then at night on the batteries for a few hours before it switches to grid, then when the sun comes up, it is back running off grid. If we are charging during the day, do we need this much battery? Appreciate any advice.. Thanks.

KWh Demand
Miles Driven/Day	35​
Range mi/kw	1.88​
Battery used KW	18.59​
Solar System Size
add 35% for system losses	25.102​
Inverter efficiency	90%​
Amt of Elec supplied by panels to inverter and battery	27.891​
Ave. Irradiation hrs/Day	8​
Solar Panel KW needed	3.4863​
solar panels needed @ 370kw	9.4225​
Battery Bank Size
Energy needed kwh	18.594​
Depth of Discharge	80%​
Battery storage needed KWH	23.242​
Battery Voltage	24​
Amp hrs (1000xKwh/voltage)	968.42​

 

[mrpackethead]

I'd start by getting some real world weather data for your location. I'm sure it exisits for your location.. In NZ we get can get it from NIWA solar view.. Using the average '6' hour thing is a bit broken.. Your 35% system loss seems really high too. If its that big, you might need to consider why..

 

[furkidmom]

I got the 35% figure from an online solar system sizing guide. Seemed high to me too, but I'm not an electrical engineer, that's why I have to ask all these stupid questions and can't solve this myself :-(.

 

[time2roll]

Then, the part that I really don't understand, would a 240V/100Amp Inverter power the EV charger, and what rate would it charge at? Would appreciate any advice/insight here.

Yes that inverter would work but not at all necessary. Yes the Lightening extended range will charge at 19.2 Kw (80 amps 240v) and require a 100 amp supply to accomplish this. However to drive 35 miles per day this fast charge is completely unnecessary. A 16 or 20 amp charge would be fine (and require 20 or 24 amp supply). It just takes a few hours more time. Can charge as slow as 6 amps. The wall charge equipment, known as an EVSE, has a pilot signal to tell the vehicle the maximum charge rate to avoid overloading a smaller rated circuit.

 

[furkidmom]

Thanks for the information. Still looking for some education on the battery sizing issue. Do the inverter specs also affect the battery amp required

 

[time2roll]

Thanks for the information. Still looking for some education on the battery sizing issue. Do the inverter specs also affect the battery amp required

Yes the batteries will have a maximum amp output and a preferred amp output (often about half the max). This will need to meet the requirements of the inverter.

 

[400bird]

Differnet rules here. Dont need building permits.. But grid tie is expensive here, not because of the equipment, but because of the compliance that you have to jump through.. Its many thousands of dollars.

Where about is this?

Remember i wont' be deeply discharing this battery.. Its only there to buffer things while the charger adjusts the current to match the Solar output.. Which is likely only to be in the region of 1-2 seconds.. If theres no power being generated, there will be no charging.. ( I can bypass to grid if i need to at 10pm and get cheaper power )..

I have an Openevse. I love it, but I've got a couple notes for you.

The minimum current is 6 if your Kia has a J1772 plug. That is set by the J1772 standard.
Max is 40 amps depending on which kit you buy.
If you go 120 volts for the charger you can harvest more of the available power.
Otherwise, at 240 volts. You're only charging at the peak of the day when your 2kw system can put out 1440 watts (plus inverter inefficiency, so maybe 1600-1700 watts)
With 2kw of panels you might get that much for a short time each day of you angle the panels or longer if you use a tracker.

At 120 volts, your minimum wattage is more like 800.

I'd shop and wire carefully so you can charge from solar at 120 volts, but with the transfer switch, charge at max current on 240 vac when needed. I've only needed to charge at full current a couple times, normally I just charge with PV.

Edit: I just wanted to add that you will be wasting power at the beginning and end of each day. You might have difficulty finding the right charge rate.
I can envision a case where the sun comes out and fully charges the battery before the PV reaches the 720-800 watts needed to begin charging. A larger pack may help because you could build in some more logic and drain down the pack some by forcing the charger on a certain amount of time after PV begins producing.

 

[DJSmiley]

There are also chargers which allow you to use any excess PV.

Zappi eg has those, you can set it so it only charges with PV, or configure it to slowcharge from grid and ramp up the current as soon as there is PV available.

EV Charger | Low Cost Home Electric Car Charging

Get a fully installed zappi home EV charger, featuring low cost energy tariff integration and solar charging, all proudly made in Britain.

myenergi.com

edit: Not sure if they are available around the globe. Might probably work with 240V in the US as well, but i'm not familar with that. And also I'm not sure if they are available with J1772.
Here in Europe CCS has become the primary standard nowadays.

 

[mrpackethead]

Where about is this?

New Zealand
I have an Openevse. I love it, but I've got a couple notes for you.
The minimum current is 6 if your Kia has a J1772 plug. That is set by the J1772 standard.

Yeah, thats what i've found.. its not the end of the world. The ev6 (as supplied here) has an IEC 62196 (type2) connector. but the underlying charge system is the same.. its 6A min..

Max is 40 amps depending on which kit you buy.
The max i can run on single phase is 32A @ 240V ( we are 240V single phase here ) . This is a 7.1kW charge rate.

 

[OldSolarGuy]

I have a different set of circumstances; I live in north Georgia, USA, and I have been turned down by my HOA for solar on my roof. I have a Volkswagen ID.4 on order. The 120 V charger supplied with the ID.4 is approximately 1100 watts. Need some guidance, and feasibility, on a two panel (550 watts/panel) system that I can store in my garage and use on good sun days to charge the ID.4. I would also like to use it on power outages for a freezer, refrigerator, and internet. Thanks in advance!

 

[time2roll]

I have a different set of circumstances; I live in north Georgia, USA, and I have been turned down by my HOA for solar on my roof. I have a Volkswagen ID.4 on order. The 120 V charger supplied with the ID.4 is approximately 1100 watts. Need some guidance, and feasibility, on a two panel (550 watts/panel) system that I can store in my garage and use on good sun days to charge the ID.4. I would also like to use it on power outages for a freezer, refrigerator, and internet. Thanks in advance!

Condo is a jerk. Usually the HOA owns and maintains the roof and does not want anyone messing with it. Then there is the visual issue that people love to hate because you are getting something that they are not. Some states have laws that require HOA to be reasonable. Not sure it is worth the fight and end up being the bad guy.

Portable panels set out periodically may also get a citation if they are in view. Consider a battery-inverter to power the fridge. If a few panels to go out during the day when the power is off may not get as much of a bad impact. This could charge and extend the battery.

True independence may eventually need to include SFR not in an association. Best of luck and enjoy that ID.4

 

[watchdoc]

I like the cheap Will Prowse setup. MPP 6048 Inverter, EG4 rack batteries, whatever panels you want or can afford. Native split phase so you just add a 14-50 plug and you can charge at 240v and about 25amps. If you wanna spend some real money, buy a 15k Sol Ark inverter.