I have a BASIC solar system ( say - it could output 1000w during daytime) - and live in 220v-land
I will (eventually) get an EV that can charge from a 220v home-circuit - I think those normally draw 2000w or so - more than my system will supply
Here is my basic Q:
Is there a way or setting to “force” an EV’s system to not suck up energy at a rate of 2000w (which would trigger an “overload” disconnect), but at a rate that I can deliver (e.g. setting: charge at a rate of xyz-watts)?
Any way to make my scenario work? … (time is not of relevance, I wouldn’t mind if it takes 2 or 3 days to fill the EV’s “tank”)
Yes, absolutely. Either your car or your EVSE (“Charger”) will allow you to set how much energy it draws. It’s meant, amongst other reasons, to make it easier to use with your existing wiring . For example, I have a welder in my garage, running on a 30a circuit. I have my EVSE plugged into it, set to draw a maximum of (off the top of my head) 24 amps. Quickly googling the specs for mine, it appears it can go as low as 6amps, which would be, on a 240v system, 1440 watts. I assume other L2 chargers can go even lower, that’s just what mine does.
You should also look into L1 (120v) chargers. They’ll be capped at 12 amps or 1440v and you won’t need additional wiring out to the parking spot, assuming you already have a regular 120v outlet nearby. I’ve never looked, but I wouldn’t be surprised if you can find L1 chargers that can be set lower as well.
L2 (240v) can draw considerably more than 2kw. Mine, even with it’s lower settings, draws 5200w, but if turned it all the way up to 40a, would draw 9600 watts, and looking at Amazon, I see plenty that go up to 50a/12000w.
TLDR, yes, what you want to do is not only possible, but common. Just make sure either the car or the EVSE can be set low enough for your needs. IMO, it’s more important to make sure the EVSE can do it since not all cars can. Even if the first one can, your next one may not be able to and you’d find yourself having to replace the charger. Also, you don’t to blow a fuse if the setting in the car gets changed or someone else uses it.
Is there a reason you’re trying to precisely match up your EV charging with your home solar like this?
I ask because most home solar installs are grid-tied, so the EV shouldn’t “overload” your solar as long as it can get power from the grid. Is this an off-grid situation (like a cabin of some sort)?
Or if it’s to maximize payback, if you’re on a time-of-use plan, you might get better returns by limiting the charging to a specific time of day rather than a specific charging speed (power).
Many places do not have net metering. Any production that isn’t self-consumed is completely wasted. In that case it makes sense to figure out a way to consume 100% of your solar production, without going over and pulling from the grid.
Your charger can’t draw more power than your system can provide, so you should be good on that front.
That being said 1000w is not very much power for an EV. Unless you are not driving very much, and you plug it in the moment you get home, you will not have much charge.
It is somewhat of an edge-case (partly “intellectual exercise”) …
I have a small (legacy) solar system - OFF-GRID … that I could put to good use - of course there is always the 220v-grid fallback … but the solar is here and paid for, so it makes sense to harvest all that be harvested…
Also I am working from home and don’t use the car very intensive - so its more of an “opportunity-charging-question”, if you get my drift.
if the charger draws, all the system provides, it will push it pretty soon into “overload/undervoltage” condition.
I could visualize a scenario (which I am testing here as hypothesis) - where - If I can fine-tune the charge the EV “summons”, I could get 8-10 hours of charging out of the system (surfing slighly below the PV-system’s capacity), as opposed to tripping my system into undervoltage condition every 30 min or so … by demanding twice the systems capacity.
I could of course upgrade/beef up the system, but my first impulse is to make do with what I have, especially since its a low usage situation (maybe driving 20 miles every other day)
AND - the idea that I can fuel my (currently non-existing) car “for free” is emotionally relevant to me…
Interesting. What is the solar currently connected to?
If it’s going solar → inverters → appliances (no battery or anything), what happens if there’s a moment of cloudiness or such? Or even just what happens as the charging curve goes downward later in the day?
Ideally you’d peg the EV charging rate to 80% (or whatever) of the actual instantaneous production, not just the theoretical max under ideal noon conditions… hmm. I don’t know if any EVs can do that out of the box (modulate its own charging according to some external real-time signal). There are a bunch of solar-ready inverters that can supposedly do this, but I don’t know if any of them can be easily retrofitted onto an older off-grid system.
Your EV might also have a minimum amperage to charge from, and I don’t know what would happen if the solar blipped out for a few seconds and caused the charging to pause… would it simply restart a few seconds later?
If the car is set to automatically start charging when it’s plugged in, I’d assume it would just start right back up.
My car just finished charging little while ago, otherwise I’d go flip the breaker off for a few seconds and find out. At least WRT how my car and my EVSE would react.
My Tesla can be adjusted to level 1 or 2 charge anywhere from 5 amps to 48 amps. That is location specific, too, so if I set to 12 amps at the AirBnB where I’m using a regular outlet, it will still be at 48 amps when I get home.
That sets the maximum charge rate, and additionally the car won’t try to take more than the EVSE says it can provide. If I flip a switch on my charger it will go down to 40 amps, and the car will know and only ask for that much.
Voltage can go up and down, and that doesn’t matter. If I turn on the oven the voltage the car sees might drop from 230 to 228. The car doesn’t demand more power, it just charges a bit slower.
The power drop can be much more dramatic at public level 2 chargers. For example, many dual level 2 chargers are on a single 30 amp circuit. Charging a single car will get you 24 amps at 208 volts, but if another car starts charging it will drop to 12 amps (each) at 208 volts. The car handles this fine.
I’m really not sure how exactly it will behave with 1000W of solar, that is really putting out a variable rate of 100-750W. The car can be happy to accept more power, but I don’t think there’s anything to overload, The solar is providing whatever it provides. Even if you short the connection, it can still only provide 500W (or whatever the sun allows). It’s not like a household circuit which will provide as much power as it possibly can until (hopefully) a breaker trips, or (less good) something melts.
So optimistically/realistically - and to keep the math simple - say 1,000 … which means a 50kw battery in 50 (peak-sun)hours … so 7-10 days w/ all unfolded.
Or … (and that rationale sounds better to me) … you can re-gain about 15% of charge while having it parked on a suitable parking-space outside your office.
