diy solar

diy solar

Electric cars

I charge two(2) EV's from my Solar. I'm playing with extending my afternoon output with west facing panels, but for me my charge window is 1030-1630. I charge with a cheapo Adjustable 10-40A 120/240 charger at 24A on 240, so about 5600kw. The mean load at my house is between 4 and 5 kw, and my panels kick up to around 10kw at 1000, and falls to 9kw around 1630, the peak is around 12-13. This enables me to have at least 80% charge on my 30kw solar batteries, by the time my solar output falls below my house mean to take it past 2000/TOU. The inverters claim 99% efficiency PV->AC, so the idea is to maximize effiency PV->AC->EV, and avoid BAT->AC->EV. 110v charging is pretty abysmal, but for home you really don't need a 60A charger unless you just drive hundred's of milies a day. if you have (for example) an electric hot water heater in the garage, there is a box you can buy that splits it, giving you 30A (24@80%) for your EV whenever the HWH is not running. This is a really inexpensive way to add a L2 charger, and generally 24A will charge a car with a 65KWH pack from zero to full in about 12-14 hours. To that end with a 6 hour solar window, I can generally get from 50% to 95% on Friday, and top up on Monday in mine, the Lady gets to plug in Saturday and Sunday, she generally doesn't drive as far during the week, and we generally take my car around on the weekend, so it kind of works out.

The biggest problem is being at work when I need to be charging. I'm actually considering a 3rd EV to keep plugged in during the week to absorb my excess solar. That way I always have a fully charged vehicle I can use.
 
400bird said:
Level 3 charging isn't a thing, it just goes to DC charging. Typically, faster, hence DC Fast Charge.
But, that's not applicable here.
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probably true but also somewhat possible? i don't know the current state of DIY DC charging but the first question would be what is the lowest amps the car will accept? typical DC charging is 480 VDC and 100 amps. if 100 amps is the minimum then you would need a 50 kw solar array. the amps would need to drop down to 20 before it would even be realistic for most people. i think 10 kw solar is the max many states/cities allow individuals to have have.
 
as a data point. my 2017 leaf uses 225-250 wh per mile. i have 2.8 kw array on the house but since it faces west with a large hill it is really 2.1 kw. my house is 100% electric and i only drive electric but i produce more power than i use each year. i drive around 4000-5000 miles per year and don't use public charging very often. i estimate the car is 1/4 to 1/3 of my total energy use.
 
rustythorn said:
probably true but also somewhat possible? i don't know the current state of DIY DC charging but the first question would be what is the lowest amps the car will accept? typical DC charging is 480 VDC and 100 amps. if 100 amps is the minimum then you would need a 50 kw solar array. the amps would need to drop down to 20 before it would even be realistic for most people. i think 10 kw solar is the max many states/cities allow individuals to have have.
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There is not really a minimum for DC charging. I've seen it drop to 2-3KW at the end of a session, and I actually had a fast charger that would only give me 5KW. There just aren't any non-commercial DC charging solutions you can buy. The problem is you have to bump your DC voltage up above whatever the vehicle requires, so unless you are pumping out 500v or so now you need a DC-DC up conversion, at which point you may as well just use 240vac. When I was researching this, I found most of the DC-FC's were fed with 480 3-phase, which makes it easier to produce higher DC voltages by splitting and stacking. 480 AC peak is around 670v, flipping it to DC with a big filter cap, you could 'easily' stack the three phases into 1500vdc, then switch it down to whatever you need. Somewhat more difficult with PV in a string starting at 350 odd volts or something. I did run across some 100W panels with an 85 VOC, like 60 operating, but once you string a dozen of them there are no MPPT's that will handle 1000voc (yet?).

With claimed PV->AC above 98% and the AC->DC in the car being similar, I don't think the engineering effort is really worth it, especially if at the practical level you have to end up running an up-conversion on voltage, and your never really going to pump 100KW at your car from home. I actually have been expecting to see larger onboard chargers. J1772 is actually rated to 100 or 120A, and as a practical matter, your not really going to have a need to charge over 20KWH at home anyway. With the adoption of the Tesla charging port by more and more companies, and tesla already having onboard charging above 10KW and battery pack voltages moving up to 800v, trying to wrangle DC-DC at a non-commercial level gets a bit obtuse.
 
MichaelK said:
There are three standard charging levels here in the US, Level 1, Level 2, and Level 3. Their specifications are.....

Level 1: 12A at 120VAC (1440W, or 1.44kW)
Level 2: 10-50A at 240VAC (2400W-12,000W, or 2.4kw-12kw)
Level 3: XA at 480VDC (commercial charging stations only)

Saying you have "plenty of solar panels" is a bit overoptimistic I think. Do you have enough panels to put out 1440W from 7am till 5pm? That would give you about 10 hours of charging, only at level one. That means maybe 2-3 days to fully charge the EV battery.

I myself have 4500W of panels on rotating mounts, and I think I could match level 1 charging from about 7:30 in the morning till about 4:30 in the afternoon. That's only about 13kWh total of power. I might do 10A at 240VAC from maybe 8:30am till 3:30pm, call that 17kWh.

Could the EV owners here please chime in as to what their day to day kWh values are from routine day to day driving.
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This is an excellent post that gives you an idea of what it's going to take.

I have a 4.3kw panel setup running thru 2-EG4's at 240v. Also have 10 Lifepower batteries.

When I go to just 10amps of charging on my 240v line, it taxes the system...or more importantly whatever power I have in the batteries. My system isn't yet robust enough to fully charge the car. Charging the car takes a tremendous amount of electricity. It's basically a system dump if I left it on.

What I do is build up some excess power in the batteries, then put about 10kw of power in the car. Which is the equivalent of 35 miles of range. Then I have to wait for more solar excess. My system currently produces about 22kwh per day, but I use about 17 of those for the house items. Right now, its a trade off.

I still have six more panels to put up, then that will be a game changer for me. I should be close to 32kw per day with some nice excess.
 
Redflyer said:
When I go to just 10amps of charging on my 240v line, it taxes the system...or more importantly whatever power I have in the batteries. My system isn't yet robust enough to fully charge the car. Charging the car takes a tremendous amount of electricity. It's basically a system dump if I left it on.
Click to expand...

If you want to charge a car from PV you are going to want to have at least half again as much actual solar available while charging as you need. You do not want to charge a battery and then dump battery to battery via AC back to the car. This may occur from time to time if you catch a cloud or something anyway, but for efficiency sake you want it to dump straight in. As your PV production/charge rate goes lower you will likely want more overhead. Unlike even an HVAC charging your EV is a never ending flat line draw until it's done or you stop it. When I charge my cars I'm pulling down well over 100kwh/day. When I'm not, it's around 75. For me, more batteries, then more panels. I'd love to get charging to 30A during the solar window.
 
Ampster said:
Sorry to be such a cynic, but there are more Chinese EVs than the rest of the world combined and they have not developed such a product to date. Most motorbikes in major cities in China have to be electric and outside every aparment there are charging stands for charging those. Also some cities have mandated EV taxis and many of the busses are electric.
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I think they are more interested in fire suppression systems for the chinese ev's in china right now :)

 
Crowz said:
I think they are more interested in fire suppression systems for the chinese ev's in china right now
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i have followed Serpenza {author of the above YT video) for years going back to when he lived in China. He left because he says he was about to be arrested for being negative about the government, It is hard to tell how big a problem EV explosions really are.
 
Ampster said:
i have followed Serpenza {author of the above YT video) for years going back to when he lived in China. He left because he says he was about to be arrested for being negative about the government, It is hard to tell how big a problem EV explosions really are.
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With the way they clamp down on news there never will be a way to really know how bad or not it is :)
 
Crowz said:
With the way they clamp down on news there never will be a way to really know how bad or not it is
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But the US statistics about vehicle fires per miles driven are fairly acurate as far as I know. EVs are far less likely to have a fire, but when they do, it is on the front page. ICE vehicle fires do not get the same publicity.
There is also some FUD, the sources of which are unknown. A friend recently sent me a video, supposedly showing two EVs which had collided. I did a reverse lookup and that video was actually from a 2016 accident involving a truck in Russia carrying propane bottles. From a distance the exploding bottles of propane were spectacular and the flames covered up any sign of what kind of vehicle it was that was burning.
 
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MichaelK said:
Saying you have "plenty of solar panels" is a bit overoptimistic I think.
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This thought crossed my mind as well. I will have 22kw of bifacial panels mounted by this spring... off grid. I am happy for all those with EV's. However, for many reasons, unless things change, I don't think I would ever buy an EV. The numbers just don't work for me.
 
ksmithaz1 said:
If you want to charge a car from PV you are going to want to have at least half again as much actual solar available while charging as you need. You do not want to charge a battery and then dump battery to battery via AC back to the car. This may occur from time to time if you catch a cloud or something anyway, but for efficiency sake you want it to dump straight in. As your PV production/charge rate goes lower you will likely want more overhead. Unlike even an HVAC charging your EV is a never ending flat line draw until it's done or you stop it. When I charge my cars I'm pulling down well over 100kwh/day. When I'm not, it's around 75. For me, more batteries, then more panels. I'd love to get charging to 30A during the solar window.
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Agreed.

I need the extra panels. I have close to the same amount of battery kwh as the car has. So I do charge the car in the sunlight, but it's still pulling something from the batteries because I'm low on PV panels. Even at 4.8 (Twelve 400's). My extra panels will help even things out during the day.
 
TOU47 said:
This thought crossed my mind as well. I will have 22kw of bifacial panels mounted by this spring... off grid. I am happy for all those with EV's. However, for many reasons, unless things change, I don't think I would ever buy an EV. The numbers just don't work for me.
Click to expand...
My 15+KW of panels produce more than I can use and store during the day, I could hit just under 100KWH., I picked up 16 fairly old used 250's they peak about 2300kw (Not 4000), but technically I have just under 20kw. Saturday, I managed to hit ~115KWH. 30 of it hit the batteries, and another 30 in the car. I made it to midnight.

I have to schedule it, but it's not really a problem charging the two cars between 1000-1600, but I flip back to the grid around 2200-0100 every night anyway because I don't have enough battery. The 30KWH rack is generally around 90% if I charge at 24A/<6KW. When I get the extra battery I should be able to get thru the night whenever I'm not charging a car. At that point I will probably replace the 250 panels with some newer 450+.

To your point, I think to get 100% Offgrid I would like to have around 30KW of panels, and another 60KWH of batteries. This is what I wanted to know when I started the project. I also note I only have a 1500sqft house, albeit poorly insulated brick, with old windows, and it gets really warm here in the Summer.
 
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