PeteSchwartz
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Direct DC Charging with Solar Panel

Fri Jul 06, 2018 3:54 am

I bought a 2014 Leaf yesterday.

At Cal Poly, my research students and I are developing ways to directly use DC electricity from solar panels. I’m interested to innovate a way to charge the Leaf directly from solar panels - both from my (not grid tied) home system as well as with onboard PV that we will design. How can I do this?:
1) Where can I learn the details of the charging system?
2) If the first thing that the AC charging system does is rectify the input power (which I don't know is the case), then could I not just run the DC output from solar panels into the AC port? If the subsequent processing is to transform the rectified electricity to high voltage for the battery pack, then could the input voltage be lower than 110 V?

Thanks
Pete

Pete Schwartz
Cal Poly Physics, Sustainability
805-756-1220
pschwart@calpoly.edu

Faculty webpage: http://www.physics.calpoly.edu/node/94

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RegGuheert
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Re: Direct DC Charging with Solar Panel

Fri Jul 06, 2018 6:19 am

PeteSchwartz wrote:I bought a 2014 Leaf yesterday.
Congratulations and welcome to the LEAF forum!
PeteSchwartz wrote:At Cal Poly, my research students and I are developing ways to directly use DC electricity from solar panels. I’m interested to innovate a way to charge the Leaf directly from solar panels - both from my (not grid tied) home system as well as with onboard PV that we will design.
I'm not a fan of PV-based direct-DC charging. You can read some discussion of that topic here. Even if your home is not grid tied, there may be real benefits to using AC instead of DC for charging the LEAF.
PeteSchwartz wrote:How can I do this?:
1) Where can I learn the details of the charging system?
There are bits and pieces of data throughout this forum. I'm not sure where there is a detailed, comprehensive set of data on the LEAF's OBC. OTOH, the ChaDeMo (DC) port should follow a standard which is published and public, so that may be a place to start.
PeteSchwartz wrote:2) If the first thing that the AC charging system does is rectify the input power (which I don't know is the case), then could I not just run the DC output from solar panels into the AC port?
Probably not, since the *first* thing that is likely done is to verify that the signal is a proper sinusoid meeting certain specifications *before* the EVSE even connects the AC to the vehicle.
PeteSchwartz wrote:If the subsequent processing is to transform the rectified electricity to high voltage for the battery pack, then could the input voltage be lower than 110 V?
No. The input voltage needs to be within certain ranges (one range for 120 VAC and one range for 240 VAC input). The current drawn depends upon in which range the voltage is found (lower current for 120 VAC and higher current for 240 VAC).

I think a related, similar project would be to look at the LEAF not only as a load, but also as an integral part of the energy system for the house. Nissan has made some overly-expensive efforts in this direction for the Japanese market. Search here and on the web for "LEAF-to-Home".

As for me, I would like to have a 2500-VA (or higher) bidirectional charger/inverter for the ChaDeMo port. I could find a lot of uses for such a device.

Finally, please have a look at the Solar subforum down below in the listings. We have discussed many topics related to homes, PV, batteries, etc. This topic has been raised a few times there, including in the thread I linked above.

Good luck with your projects...and be careful to not let the smoke out of your LEAF!
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

TexasLeaf
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Re: Direct DC Charging with Solar Panel

Fri Jul 06, 2018 8:48 am

The Nissan Leaf battery pack operates at over 300 volts. The on-board AC charger of the Leaf has an inverter that rectifies the 120v/240v AC power and kicks the DC power up to over 300 volts so that it can power the Leaf battery pack. If you really want to DC charge a Leaf using PV panels then you will have to generate over 300 volts DC from the panels.


If you really want to do this then you should get a copy of the Leaf service manual and study system operations and the wiring diagrams. There are plenty of off-the-shelf PV systems that generate 120v/240v AC power. Unless you are really committed to a DC system, you might be better off just getting your hands on one of the off-the-shelf systems and letting your grad students figure out how to charge a Leaf with it.

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davewill
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Re: Direct DC Charging with Solar Panel

Fri Jul 06, 2018 11:27 am

There was a project on here to do a home CHAdeMO at one point. I think that the JuiceBox folks were involved. That would be the approach to take since you have to have a charger than can generate the exact voltage the battery requires. It might be possible to hack the LEAF's internal charger, but you'd have to do a LOT of hacking. There's no way you'd simply be able to connect DC to the existing port and get it to work.

BTW. I've never understood why this concept keeps coming up so regularly. Since the charger has to do DC to DC conversions anyway, I can't believe there's any significant efficiency improvements to be gained. Certainly none worth this kind of effort, yet folks get all hot for it on a regular basis. Now a true car to home interface through the CHAdeMO would be more interesting, although if you actually drive the car, it's utility is kind of limited to emergency uses.
2014 Rav4 EV, Blizzard Pearl White
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WetEV
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Re: Direct DC Charging with Solar Panel

Sun Jul 08, 2018 8:20 am

davewill wrote:BTW. I've never understood why this concept keeps coming up so regularly. Since the charger has to do DC to DC conversions anyway, I can't believe there's any significant efficiency improvements to be gained. Certainly none worth this kind of effort, yet folks get all hot for it on a regular basis. Now a true car to home interface through the CHAdeMO would be more interesting, although if you actually drive the car, it's utility is kind of limited to emergency uses.


There is a smaller number of conversions, so the efficiency would be somewhat higher. Practical difficulties are huge. Perhaps at some time in the future...

This would be around 90% efficient:
Solar DC : DCDC -> Battery
Would require designing and building high power safety critical electronics, a bunch of nontrivial control logic and more.

This would be around 80% efficient:
Solar DC : DCAC -> : ACDC -> Battery
Off the shelf.

Yes, I'm oversimplifying. For example, some type of energy store or a grid connection is needed in both designs to deal with ramp up and ramp down when clouds change the solar output abruptly. And other complexities.

So what is the value of a direct charger? Yearly return would be less than 10% of your total charging cost. I use about $300 worth of electric power per year, so it would save me at most $30 per year. At a 6% return, this custom solution would be worth at most a few hundred dollars more than an off the shelf solution. There is no way at all that you could design, build and debug one for anything close to that until you get to fairly large production volumes.
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speedski97
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Re: Direct DC Charging with Solar Panel

Sun Jul 08, 2018 9:28 am

There was a solar powered DC fast charger powers by solar panels in Twentynine palms. The unit charged directly off the panels, and the rate would change with clouds and output of the panels. The DC charger is closed now but i am sure the owner is still there and has a lot of info.I think his name was Dave and was super nice. if anyone has info on him.

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JeremyW
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Re: Direct DC Charging with Solar Panel

Sun Jul 08, 2018 9:56 pm

If you want to do DC via the CHAdeMO port, you'll need a DC/DC that can keep the panels voltage in the maximum power point [tracking] (MPPT) region, as well as output near the pack voltage. There's not a lot of off the shelf parts (anything, really) that do that. High voltage DC tends to be rather specialized. The other thing you'll have to deal with is sudden drops in output. The Leaf expects output to remain relatively stable (close to the commanded value) over the course of a charging session. Drop offs in output will often lead to an aborted session. Any cloud could cause enough drop in say a second or two to cause the leaf to end the session. CHAdeMO isn't exactly graceful in this respect- it was made more for DC fast charging and not slow, variable sessions.

I would guess that while in theory you could feed 200-300V DC in via the L2 port, the car expects a fairly strong source, not one that can vary quickly over time. Yes, you could build a fancy circuit that modulates the J1772 pilot, but I would suspect that you need a pretty tight (<100ms) control algorithm and you may hit limitations in the leaf's charger control circuitry that won't respond fast enough. I don't know the leaf's exact specifics but most other cars are between 500ms and 2 seconds on J1772 throttle-ability. Without a battery buffer, I imagine your voltage is going to collapse rapidly with any approaching cloud cover.

My suggestion is to get in touch with the folks at Envision Solar. They've done the most practical version of what you're describing. There is a battery within the unit and an off grid inverter, along with a standard J1772 EVSE. You could try to minimize the battery, work on new control algorithms, etc.

After spending some time "in the industry" I've come to the conclusion that solar direct to EV with no buffer or grid whatsoever is just not a great use of resources. When it's a perfect sunny day, yes, you could use a DC/DC or have a very small battery buffer and an off grid inverter and it would work. But due to how much energy and power we are talking about, any sudden drop in solar output is going to collapse the system. The CHAdeMO standard as implemented on your 2014 leaf is just not meant to handle high variability. It's meant to charge the car rapidly with a high powered charger.

However, I don't want to discourage too much here. It would be a good exercise to see what the practical limit is on initiating and keeping a CHAdeMO session running, and I would like to support in any way I could. You can PM me for my contact info if you would like.
Former 2012 SL leasee 6/23/12 - 9/23/15
Now driving Honda Fit EV, License plate: CHADEMO
2000 Honda Insight for long trips

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Marktm
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Re: Direct DC Charging with Solar Panel

Sun Jul 22, 2018 11:20 am

Agree with most of the comments:

- Setec Power makes a mppt based solar charger that is CHAdeMO compliant. They have offered a 10kW unit, but is quite expensive. It could be worth the money if used in bidirectional mode via a standard inverter with the buffer battery system?? Setec said it is possible, but I could not get any basic unit specs, let alone specs for additional functionalities. It does apparently use a 48 VDC li tech battery buffer.

- Setec does make a useable V2H unit based on CHAdeMO (and CCS - at least claimed). It's not directly compatible with US household electricity and is certainly not integrated with home solar systems - at least out of the box.

- Princeton Power makes a 10kW and 30kW bidirectional charger/converter/inverter that is CHAdeMO compliant with Nissan vehicles and typical US power. (no actual personal experience).

- Nissan has a V2G unit advertised that almost seems to be "vapor-equipment". Best I can describe it. They do have a "wall" battery that they claim is being offered in Europe:
https://electrek.co/2017/10/04/nissan-ev-ecosystem-free-power-leaf-vehicle-to-grid/

- Anyone have additional information/experience.= in related equipment - I am very interested.
2012 Leaf SL; 36,000 miles. Battery replaced November 1st, 2016.

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