Home system for solar EV recharging

I don't know a lot about electric vehicles, but I'm curious. Does anyone recharge their EV from their home solar electric system? Or does anyone know enough about EVs to tell me something about what it would take to size and make a system to recharge them?

Leigh Tate wrote:I don't know a lot about electric vehicles, but I'm curious. Does anyone recharge their EV from their home solar electric system? Or does anyone know enough about EVs to tell me something about what it would take to size and make a system to recharge them?

First it depends on which EV you are going to get. Once you know which one you getting then looking at the spec the charging system can be designed.

Jeff Bosch wrote:First it depends on which EV you are going to get. Once you know which one you getting then looking at the spec the charging system can be designed.

Okay, so give me an example. Any make and model will do. I'm just trying to get a ballpark idea of what it would take.

Leigh Tate wrote:I don't know a lot about electric vehicles, but I'm curious. Does anyone recharge their EV from their home solar electric system? Or does anyone know enough about EVs to tell me something about what it would take to size and make a system to recharge them?

I'm trying to figure out how to do this with an electric bike I may purchase.

Leigh,

Do you have an EV now or are you planning on getting one in the future?

The reason I ask is that charging an EV is no trivial deal.  I don’t have any battery numbers off the top of my head, but charging at 240 volts took a matter of a couple of hours where charging at 120 volts required something like 10-12 hours or much more than double the time at 240 volts.

I am certainly not saying that you can’t do it, but at some point it may become cost prohibitive.  But if you can get me some more specifics, I would love to take a crack at this problem.

Eric

I've been wondering about this, too. To consider is the fact that you'll probably be charging at night, once you get home from work. And what happens when you don't get any sun for two weeks in the winter?

At some point in the future it might turn out that the $30,000+ to get hooked up to the grid is worth it to us.

Let's look at a few numbers:

The 2023 Nissan leaf has a 40kWh battery (149 mile range) (Nissan USA)

An average pV installation for UK is 4KW (costing £5-10k). ( solar installer website) This would need to store energy at full power for 5 hours to half charge the car battery. That would leave nothing for the rest of the house needs, and as has been pointed out, the charging ability will be reduced in overcast conditions or non optimum angle sun.

However, the car could also be used as an additonal battery bank for the house, at least while it is plugged in, which I think could at some point in the future be a useful attribute.

Nancy, that’s a good starting point for this thought experiment.  It also assumes a 100% efficient charge controller and inverter (actually these might get to 90% so we are still in the ballpark).

Still, I think you illustrated the difficulty of charging an EV battery using only solar panels.  It can be done, but it is not a cheap task.  The only free part is the sunlight.  Don’t get me wrong, I love the idea, I just know from dipping my toes into solar what kind of limitations Solar can have.

Eric

2022 Tesla Model 3

Lithium Ion Traction Battery w/11.5 kW Onboard Charger, 10 Hrs Charge Time @ 220/240V and 82 kWh Capacity

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So you will need at least a 13-15kW inverter to power the charger and if you are charging at night you will need a 75-100kWh battery bank to store the power until the EV is charged.

Eric Hanson wrote:Do you have an EV now or are you planning on getting one in the future?

Eric, no, and probably not. For our lifestyle, we need a pick-up truck capable of hauling livestock or a couple of round bales of hay. I just can't imagine as EV like that ever being affordable on our small income.

Add to that the cost of recharging, whether by plugging it into our household grid, or making our own, then the true cost seems very steep. Especially as the cost of energy goes up (because it never comes down! LOL). But with predictions that combustion engine vehicles will be prohibited in the future, I can't help but wonder what the realistic options are.

. . .charging an EV is no trivial deal.  I don’t have any battery numbers off the top of my head, but charging at 240 volts took a matter of a couple of hours where charging at 120 volts required something like 10-12 hours or much more than double the time at 240 volts.

Good point!

Jan White wrote:I've been wondering about this, too. To consider is the fact that you'll probably be charging at night, once you get home from work. And what happens when you don't get any sun for two weeks in the winter?

Jan, exactly! Currently, I have my freezer and an auxiliary fridge on solar, but when the weather is dark and cloudy for too long, I have to plug them back into the grid.

Trace, I hope you'll keep us updated on that!

Check out the YouTube channel DIY Solar Power with Will Prose. This young man is a master at solar power knowledge.

Leigh Tate wrote:I don't know a lot about electric vehicles, but I'm curious. Does anyone recharge their EV from their home solar electric system? Or does anyone know enough about EVs to tell me something about what it would take to size and make a system to recharge them?

One of the first things I would want to know is what you consider a home system. If you are grid connected you can charge any car you want. If you are off grid it gets a lot trickier. Most manufactured cat come equiped with an on board charger that plugs into a standard outlet. It will charge at roughly 1200 to 1500 watts hr per hour. Here is a good chart I found listing various vehicles and hour to charge.  
It's someplace to start.

David Baillie wrote:One of the first things I would want to know is what you consider a home system.

David, what I'm thinking of is being able to recharge an EV at home without having to rely on the grid. (I do have another question about how an EV increases one's electric bill, but that's another topic, I suppose.)

Most manufactured cat come equipped with an on board charger that plugs into a standard outlet. It will charge at roughly 1200 to 1500 watts hr per hour. Here is a good chart I found listing various vehicles and hour to charge. It's someplace to start.

Good information and interesting chart. If I'm understanding it correctly, the more expensive chargers recharge faster (and the cheaper ones slower, which makes sense). So, it seems a home solar system would have to include an inverter to plug in to.

Full-size EV charging can take place at three standard levels.  If your system can meet that standard, then yes, it will work.  You just need the appropriate electronics wired with the appropriate connections.  Here are the numbers....

Tier 1: 120VAC, 12A, 1440W total
Tier 2: 240VAC, 20-50A, 4800W-12,000W  (I've been told that a Telsa can be scaled down to 10A which would be 2,400W)
Tier 3: 480V either DC or AC (Commercial charging only.  There are no consumer electronics you can buy to plug into a system for home charging)

So, your system just needs to be scaled to either tier 1 or 2.

My system, with 5500W of solar online as of today, could easily meet tier 1 charging from about 7:30AM till about 4:30PM, also supplying power to all other loads.  At 240V (I have a XW+6848 split-phase inverter), I could manage 10A charging at 240VAC from about 9AM to 3PM.

A big advantage I have is that my solar arrays are placed on rotating mounts, so they could be rotated East in the morning, and West in the afternoon, so that's why I can start tier 1 charging at 7:30AM.  With a fixed array, I'd guestimate you could reach that level with 3000-4000W of panels from about 9:00-9:30AM till 2:30-3:00PM, or roughly 1/2 what my system can do.

Now, for the actual driving?  I looked into a Ford EV truck with a 30kWh battery.  Assuming you depleted it halfway, it would take tier 1 charging about 10-11 hours to fill it back up.  So, let's say you drove into town on Monday morning, spent the day buying supplies, and then drove back Monday afternoon.  Most likely you will get back after optimal charging is over, so even if you plugged the vehicle in, you don't get any charging till Tuesday morning.  I would NEVER use my house battery to charge an EV.  If I drained the house battery, and the refrigerator shut off, that would be really, really bad.

So, assuming you can start charging on Tuesday morning, you most likely will reach full charge by Tuesday afternoon at ~4:30.  You'll have to disconnect anyway, because the system can not longer keep up with even tier 1 charging and would severely drain the house battery.  With a system half the size of what I described above, assume that one full day becomes 2 full days.