[Bruno]

Apologies if this question is asked and answered many times on this forum. I charge my Bolt at home with a hard wired ChargePoint 32 A unit. My question is whether the AC power supplied to the charger is rectified by the charger unit before going on to the Bolt as DC, or is AC power sent on to the Bolt and rectified onboard to charge the batteries.


I envision the day, hopefully soon, when we're able to use our EV's as "mobile batteries" to buffer and time-shift the energy exchange relationships between our EV's, our home PV systems, and the grid to mutual benefit for grid scale load leveling, etc. So I'm wondering about the possibility of my present Bolt being adapted to that back and forth power exchange in the future, or whether I'll need to trade up when the time comes to an EV with that capability built in by design. Thanks for your thoughts.

 

[redpoint5]

The EVSE is essentially an extension cord with extra safety and the ability to communicate the amperage rating back to the car. So it supplies AC into the car unmodified, and the onboard charger (inside the vehicle) rectifies and steps up the voltage to charge the battery.

I don't know how difficult it would be to modify the Bolt charger to send electricity back to the grid, but my guess is fairly difficult. While it's probably a modest extra expense to design it from the beginning to feed back to the grid, there's simply no reason to build it before there's demand, especially when there's so much extra liability involved.

I'm excited for EVs to provide grid stabilization and act as emergency power too, but we're probably a long way off from that. EVs would need to account for a sizable percentage of vehicles before infrastructure was built to take advantage of their storage, and then there'd need to be incentive (payment) offered to customers to sell energy back to the grid. Maybe in 25 years?

 

[Bruno]

Thank you for educating me on that, redpoint5.



I guess what I envision then will require an inverter and voltage transformer onboard my future EV to interact - through a bi-directional EVSE - with my home loads and/or the grid in the common currency of 240V 60Hz AC (in the US). And the home system would need a smart load manager module to charge or draw down the EV battery at times and by kWhr amounts as appropriate to balance the prioritized needs.

 

[redpoint5]

Yes, it's all technically feasible and seems like a good idea to me.

I dabble in electronics and have no formal education, so I might be mistaken, but I believe much of the onboard charger (converter) could be run backwards to take the high voltage DC and supply AC (inverter).

You need other electronics too for safety. If using the vehicle to act as emergency power when the grid goes down, you need something to disconnect the house from the grid before supplying the house with power.

For feeding power back to the grid, you'd need electronics that monitors phase (and probably other parameters) so the energy fed back is clean and harmonious.

Grid tied solar already has these functions built in, so then it's just a matter of interfacing the vehicle with those electronics, and a control circuit that can manage all of the functions based on the needs of the grid and parameters defined by the owner.

BTW- San Francisco piloted a program with BMW i3 owners where the utility could request to delay charging during certain peak times, and the owners could either participate in the delayed charging, or opt out.

http://www.pgecurrents.com/2017/06/08/pge-bmw-pilot-successfully-demonstrates-electric-vehicles-as-an-effective-grid-resource/

 

[Bruno]

Part of my motivation relates to the politics and regulation of grid-tied home PV systems. As more of these systems come online, we begin to cause timing problems with the utilities' load demand curves, and they will be inclined to impose more restrictive rate structures for our connections. NH, for example, is doing away with the "net metering" (at retail) structure I presently enjoy by grandfathering, and replacing it with a less generous scheme for new PV installations. Right now, I think the utilities see home PV as unwelcome to their business operations.

Since the potential is there to cooperate with the grid by introducing some time shifting capability in our home PV-EV systems, I think it's a good idea for us to lead this technology and product development effort, rather than wait for demand to bring it about. Because I agree with your 25 year estimate otherwise. By which time I don't expect to be on the planet.
As far as incentives go, real time pricing on utility power and in/out power flow with our EV batteries - at our control - can put us all in the business of making money while leveling the grid load to boot.

 

[GregBrew]

Apologies if this question is asked and answered many times on this forum. I charge my Bolt at home with a hard wired ChargePoint 32 A unit. My question is whether the AC power supplied to the charger is rectified by the charger unit before going on to the Bolt as DC, or is AC power sent on to the Bolt and rectified onboard to charge the batteries.


I envision the day, hopefully soon, when we're able to use our EV's as "mobile batteries" to buffer and time-shift the energy exchange relationships between our EV's, our home PV systems, and the grid to mutual benefit for grid scale load leveling, etc. So I'm wondering about the possibility of my present Bolt being adapted to that back and forth power exchange in the future, or whether I'll need to trade up when the time comes to an EV with that capability built in by design. Thanks for your thoughts.

V2G seems to share a characteristic with fusion power...it's perpetually twenty years from being realized. V2G has been discussed in EV forums since at least the late '90s.

 

[redpoint5]

My money is on V2G before fusion though, because the setback of V2G has more to do with adoption than a technical hurdle to solve. The technology is there, it's just that the economics to justify it aren't.

I like win/win/win scenarios like what is proposed in this thread. The grid can be stabilized, which is a win for the utility, the EV owners can get a little compensation for their participation, which is a win for them, and the consumer wins by having lower rates during peak demand. This tends to decentralize or at least reduce the reliance on centralized infrastructure which builds a more robust grid; less prone to outage and hardened against terrorist activity.

I had a roommate that had a doctorate in EE, and he works for a company that provides power management strategies for utilities. I should have had a discussion with him about V2G before he moved to the East Coast.

 

[psyflyjohn]

I'm sure a bi-directional EVSE is not only possible, but ready in the wings. I use a tiny version of it by powering some appliances off of the aux. battery through an inverter. Feeding directly into the house circuit with the main battery would require some type of converter. It's the same process of saving electrical power with a Tesla wall battery. The only thing that is holding automakers back is the extra cost is not justified by low current customer demand.

 

[GJETSON]

Added cost is certainly a part of it. But much of the delay involves two old industries, happy to continue as they have for a century.

 

[GetOffYourGas]

One of the advantages of the CHAdeMO standard over the Bolt's CCS is that it currently supports V2G. There is nothing that I know of that prohibits CCS from adopting this in the future, but they have not done so yet. Meanwhile, Nissan has demonstrated this capability already in Japan and South America.

 

[billatq]

I don't know how difficult it would be to modify the Bolt charger to send electricity back to the grid, but my guess is fairly difficult. While it's probably a modest extra expense to design it from the beginning to feed back to the grid, there's simply no reason to build it before there's demand, especially when there's so much extra liability involved.

I read somewhere that the DC-DC converter built into the Bolt is capable of doing up to 1.6kW from the high voltage battery to the 12V system already, so you could do this in principle with the right grid-tied inverter system.

If you do the trick mentioned here, you should be able to do that for some amount of time: https://www.chevybolt.org/threads/camping-mode-test-results.17722/

I did buy an 1600W pure-sine inverter to use in the event that my power is out and I don't want the contents of my fridge to spoil, though I'm just running a long extension cord instead of bothering with a transfer switch.

To really do this properly would require some equipment that can go directly from the HV battery over to a large inverter and work with the vehicle off, but I'm not sure it's worth it over just buying dedicated batteries for this purpose. If your employer lets you charge for free, I guess you could subsidize your power bill, but I can't imagine that would last for long.

 

[wesley]

One of the advantages of the CHAdeMO standard over the Bolt's CCS is that it currently supports V2G. There is nothing that I know of that prohibits CCS from adopting this in the future, but they have not done so yet. Meanwhile, Nissan has demonstrated this capability already in Japan and South America.

CharIN e.V., the industrial consortium pushing the CCS standard, has a roadmap to bring V2G by 2025.

CharIN: CCS Combo Standard To Offer V2G By 2025

CharIN e.V. has released the roadmap for grid integration (V2H, V2G) of charging systems based on the Combined Charging System (CCS).

insideevs.com

So yes, it looks like CCS will eventually get V2G capability. But it isn't being seen as much as a priority as the guys at CHAdeMO, it seems.

 

[GetOffYourGas]

CHAdeMO is dominant in Japan. I have heard that their grid is unreliable these days (could be purely hearsay). Maybe that is what is driving V2G with CHAdeMO?

 

[wesley]

CHAdeMO is dominant in Japan. I have heard that their grid is unreliable these days (could be purely hearsay). Maybe that is what is driving V2G with CHAdeMO?

Normally speaking, Japan has a very reliable grid even today. But the land is prone to lots of natural disasters, namely earthquakes and typhoons, which can cause grid disruptions. One extreme example was the 2011 Tohoku Earthquake and the subsequent Fukushima incident that caused power shortages in the Tokyo Metropolitan Area. So yes, grid reliability is a driving factor for developing V2G, but not quite in the manner that you thought.

As one of the major power utilities in Japan and also one of the key companies behind CHAdeMO, TEPCO is quite interested in developing V2G capabilities as a means to mitigate such problems. So far, the V2G capability isn't quite "standard" in that it's basically a Nissan-only feature. We'll see how it evolves.

 

[GetOffYourGas]

Thanks for the elaboration. I almost liked your post, except for the presumption of “how I thought” the grid was unreliable. It is the natural disasters I was thinking of. There was a surge of interest in V2G after Fukushima IIRC.

 

[GJETSON]

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Any of these will run just fine off the 308-402 volts from your Bolt's pack. You just need to run two cables from the positive, and negative ends of your pack, behind the computer controlled relays at the front of the pack, out to a pair of connectors.

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