[cricketo]

you should look at something like Midnite Solar charge controllers. DC-DC from PVs is a bad solution.

 

[Allan56]

I'll check out Midnite Solar charge controllers, thank you.

Can you say what would be wrong with DC to DC from solar panels? I think in the case of using a Zivan on DC input, (if that turns out to be possible) the Zivan would be the "charge controller" but with the right output voltage and algorithm. From what I understand, it's hard to find a solar charge controller with an output higher than 48 volts.

 

[cricketo]

You may have heard the term MPPT, here is an article with a better explanation than I can provide Maximum power point tracking - Wikipedia

 

[Allan56]

Wow! Okay, we need the mppt function of a solar charge controller, one way or another. The Zivan doesn't have that. And a charge controller is essentially a battery charger so it's a matter of finding a solar charge controller that can output the voltage that matches the charge requirements of the EV stack.
Thanks for the info cricketo, it's all hinew to me.
I would have thought that the PV and EV worlds would have really common overlap but it doesn't seem to be that way.

 

[BAstereo]

That's because of the difference in power levels. A good solar panel is about 1 meter x 2 meters and makes 400 watts on a great day, angled right at the sun.

An EV might use 10-20kw to cruise on the highway?
So, you'd need 2-3 semi trailers covered in panels to cover driving on the freeway.
Alternatively, a single 400 watt panel would need 25+ sun hours to get an hour of freeway driving.

In short, the math just isn't there.

I've got 20 - 325 watt panels on my house and a set up to limit charging to use just extra output from the panels, even those 20 panels is just enough to do school drop off and pick up plus a quick in town errand.

 

[Allan56]

Okay, good point. I've used that "semi-trailer of solar panels" example before with people who wondered about solar powered electric cars. But that's what it would take to generate the power that the car uses at the same rate as the car is using it.
The person who I'm researching this subject for lives in New Mexico and has been a solar contractor for decades. He has access to plenty of hardware so it might make enough sense in this case. But I see your point. Thank you!
When you charge your car with solar power for those short trips, are you converting it to AC and then back to DC to charge? Or do you have a DC to DC setup? If the latter, I'd be interested in what sort of hardware you use. My friend in New Mexico is entirely off grid so is real interested in DC to DC.

 

[BAstereo]

It's DC from the solar to 240vac, then the car converts to DC with it's onboard charger.

A DC charger compatible with CCS1 is in the $50,000 range. And that's coming from 480 3-phase. I can't imagine what it would cost coming from the variability of PV DC. With how low the production/demand would be, that feels like an unobtainable product.

I'll take the efficiency hit and use my $400 EVSE.

 

[remy_martian]

Okay, good point. I've used that "semi-trailer of solar panels" example before with people who wondered about solar powered electric cars. But that's what it would take to generate the power that the car uses at the same rate as the car is using it.
The person who I'm researching this subject for lives in New Mexico and has been a solar contractor for decades. He has access to plenty of hardware so it might make enough sense in this case. But I see your point. Thank you!
When you charge your car with solar power for those short trips, are you converting it to AC and then back to DC to charge? Or do you have a DC to DC setup? If the latter, I'd be interested in what sort of hardware you use. My friend in New Mexico is entirely off grid so is real interested in DC to DC.

1. Which model of electric car does your "friend" have and

2. why is he using a middleman on this forum that appears to know less about solar systems (like MPPT) than he should?

 

[Allan56]

My friend is thinking about an EV conversion of a Toyota pickup and I'm helping with the early planning stages. I've been doing ev conversions for 30 years or so but never had experience with solar. He's the opposite. Plus, his internet access is not good right now so I'm finding out what I can. I thought this forum might be a good place for that. This issue of how he'll charge the truck off grid is where we're at in the planning right now.

 

[remy_martian]

He needs to charge the truck as if it was on grid because it will need to be able to get charged on the grid, if only when it's at the neighbors. Loaded, it may only make a one way trip into town.

All of his household appliances run off the inverter. The truck is just another 240VAC or 120VAC appliance that has to be compatible with the components of the offgrid system.

Most of all, it cannot damage the offgrid system or there's no water coming out of the well. It's not something to fuck with, as we say in engineering.

For offgrid, the only cost of inefficiency is a larger solar collector.

For an EV, it's just extra charging time.

You don't have a case for DC-DC here that I can see that isn't fantasyland blue sky stuff.

 

[Allan56]

Yup, I'm getting that idea loud and clear. No wonder I was having trouble finding much on the subject. I'll pass this information along. Thank you all for your help!

 

[Electric Land Cruiser]

Sorry these guys are giving you a hard time without substance.

I have not found an example of solar to EV charging that does not use batteries as an intermediary between the panels and the EV battery. In this case your friend's experience with solar off-grid systems he should be able to build a battery back-up, if he doesn't already have one. Then he can plug in a normal EV charger/EVSE into his normal 240VAC off-grid system and charge like normal.

The most efficient is using microinverters on each panel into a 240VAC circuit powered by batteries and a pure sine inverter.

 

[Allan56]

Yup, that's what I've been reading. I appreciate the information!
I think overall my friend in New Mexico with his years of off-grid experience is used to staying with DC if he possibly can, going to AC if there's no good DC alternative. That just makes sense.
To me, a rank solar-power amateur, DC-DC charging is something that makes intuitive sense. I do appreciate people bothering to point out to me what to them is obvious.
It reminds me of when I was selling EV conversions in the '90s and people would try to convince me that if I would just mount alternators on each of the wheels, the car would surely charge its battery as it drove down the road... They had proof because that's how their gas cars worked every day.
Except in that case I would just nod and smile.

 

[cricketo]

I don't know how this conversation got derailed, but there is no need for AC to be involved with charging batteries from PVs. Solar inverters all do the same thing as the solar charge controllers, plus the inverting stage. Merely having a string of PVs at the proper OCV and a charge controller that can take that OCV and regulate to the required battery voltage should be sufficient.

 

[Electric Land Cruiser]

AC microinverters are the new hotness in PV. They convert to 240VAC right at the panel on each individual panel. Better efficiency than hooking them into a DC circuit. Also with DC the panels are wired in series which causes a the whole string to go down when one panel is covered by shade.

Solar DC to charging an EV you have to convert the voltage multiple times and if you are using a normal EVSE then you need AC power anyway. If you are charging with batteries in the loop then you will most likely have a 48v system that's going to need either a step up for custom DC chademo or you're using an AC inverter, again making microinverters the best choice.

e. With the batteries producing the AC sine wave through an inverter; the microinverters sense that power and automatically produce slightly higher voltage. In this case when the solar is producing enough power to charge the car, the batteries will just be floating the inverter and the majority of power will go to the EV directly from the solar panels. I.e. the most efficient solar charging setup.

 

[cricketo]

AC microinverters are the new hotness in PV. They convert to 240VAC right at the panel on each individual panel. Better efficiency than hooking them into a DC circuit. Also with DC the panels are wired in series which causes a the whole string to go down when one panel is covered by shade.

Solar DC to charging an EV you have to convert the voltage multiple times and if you are using a normal EVSE then you need AC power anyway. If you are charging with batteries in the loop then you will most likely have a 48v system that's going to need either a step up for custom DC chademo or you're using an AC inverter, again making microinverters the best choice.

e. With the batteries producing the AC sine wave through an inverter; the microinverters sense that power and automatically produce slightly higher voltage. In this case when the solar is producing enough power to charge the car, the batteries will just be floating the inverter and the majority of power will go to the EV directly from the solar panels. I.e. the most efficient solar charging setup.

I would propose that you're a bit confused. So first of all, microinverters have been around for a decade. They have their place, but also they have their drawbacks. The main thing is that conversion efficiency is affected by the voltage differences. So like when 300VDC gets converted to 240VAC, efficiency is a lot higher than when 30VDC gets converted to 240VAC. For that reason microinverters are only installed in case you're describing - when partial shading is likely to cause more issues than reduced inverter efficiency.

If you're using onboard charger that takes AC input to charge the vehicle, then it's a different story irrelevant to the original question. I will just add that you're making some conflicting statements regarding hybrid systems with both battery and solar inverters coupled via AC path.

 

[Electric Land Cruiser]

I would propose that you're a bit confused. So first of all, microinverters have been around for a decade. They have their place, but also they have their drawbacks. The main thing is that conversion efficiency is affected by the voltage differences. So like when 300VDC gets converted to 240VAC, efficiency is a lot higher than when 30VDC gets converted to 240VAC. For that reason microinverters are only installed in case you're describing - when partial shading is likely to cause more issues than reduced inverter efficiency.

If you're using onboard charger that takes AC input to charge the vehicle, then it's a different story irrelevant to the original question. I will just add that you're making some conflicting statements regarding hybrid systems with both battery and solar inverters coupled via AC path.

The battery powered inverter is only needed in order to produce a 60hz sine wave to activate the microinverters. If you have another idea on how to charge an EV at home on solar other than "AC input EVSE" then please describe it!

 

[cricketo]

The battery powered inverter is only needed in order to produce a 60hz sine wave to activate the microinverters. If you have another idea on how to charge an EV at home on solar other than "AC input EVSE" then please describe it!

I already did describe it. You charge the EV battery the same way you'd charge the battery of a stationary system - using an MPPT charge controller. For factory EVs that may be a bit complicated due to higher voltage and no easy way to get into the DC path, but theoretically possible. In the OPs case though the voltage is much lower, from which I concluded it's a DIY project so it's definitely doable.

 

[Electric Land Cruiser]

I already did describe it. You charge the EV battery the same way you'd charge the battery of a stationary system - using an MPPT charge controller. For factory EVs that may be a bit complicated due to higher voltage and no easy way to get into the DC path, but theoretically possible. In the OPs case though the voltage is much lower, from which I concluded it's a DIY project so it's definitely doable.

Didn't think so