Running a Tesla after Irene took the power

[rabar10]

I wasn't proposing meeting the full Level-3 current capability of CHAdeMO, just using the direct-DC connection to charge the car with whatever power IS available from the solar array, without using an intermediate storage mechanism. I'll go research the CHAdeMO protocol to see if the car would allow this...

 

[mpt]

You need to sustain 440V at 200A DC for 45 min for CHAdeMO. (or any LV 3 for that matter)

Are you sure? My understanding is that the CHAdeMo standard calls for an off-board charger that is handed, in effect, the connection to the battery; what you send down there is between you and the cells no?

 

[W.Petefish]

Good luck to ya. I was just figuring for a full charge with a large charge dump from a BIG battery. I'd be interested to know what you can come up with and how large the array you would need to reach 440V. Questions to answer:

How big of an array would you need?
What is the cost of such an array?
Any easier way?

Admittedly my CHAdeMO knowledge is a bit rusty, and stale.

 

[TEG]

Are you sure? My understanding is that the CHAdeMo standard calls for an off-board charger that is handed, in effect, the connection to the battery; what you send down there is between you and the cells no?

What happens exactly isn't published publicly.
For a typical L1 or L2 AC charge, the AC current goes into a charger in the car that turns it into DC to charge the batteries.
For the DC L3, I think the offboard charger sends the DC direct to the batteries (like you said), but the voltage applied may be under control of some electronics in the car. In the Leaf, for instance, I think the car charger device talks through some CHAdeMO CAN type bus to the CHAdeMO charger and gives it some hints on how to best charge the batteries. At a mininum, I think the car has a better idea of what is 80% SOC to tell the offboard CHAdeMO L3 when to stop.

 

[TEG]

By the way, I think most chargers are designed with an assumption that constant current (and relatively stable voltage) is available from the line, so hooking solar panels directly to a charger is unlikely to work in most cases. But, it is certainly possible to design a charger that can run off of solar panels, and charge the batteries as it can. Plenty of home brew conversions, and solar racer teams have done this. If there was a big enough market for it, I am sure we could see such systems on the market.

Just due to available equipment most "solar car ports" are just grid tied, and then the car charges from the grid. So if the grid power is down the solar car port doesn't work either. On the other hand, it is a better system most of the time as the solar power is going somewhere useful even when there is no car parked there.

 

[mpt]

I'm sure that, from a design perspective, the switched mode inverters in the car could operate on almost any voltage; I suspect that, from a design stance, that's what they do. I've charged on power from 100v-128v, 190v-210V & 228v-246v. I imaging that it's only the safety systems that monitor line voltage drop due to possible over current that stopt me. I wonder if Tesla would consider a 'Just pull what you can up to nn Amps' safety override mode.

The only crack I see in my train of thought is that they do seem to track frequency closely. I don't understand why that's important to a switching inverter that's running at, I don't know, many Khz?

 

[TEG]

My guess is that it boils down to some design assumptions about only running on grid power. Maybe they save a small amount of costs by not having to add the extra flexibility to handle a wider range of power sources.

Also, they probably do all their testing based on the range of expected grid outputs.

 

[Doug_G]

All I can say is, "it's fussy". I guess it's hard to blame them; you don't want to risk damaging the ESS or start a fire due to a dodgy power source.

 

[vfx]

By the way, I think most chargers are designed with an assumption that constant current (and relatively stable voltage) is available from the line, so hooking solar panels directly to a charger is unlikely to work in most cases. But, it is certainly possible to design a charger that can run off of solar panels, and charge the batteries as it can. Plenty of home brew conversions, and solar racer teams have done this. If there was a big enough market for it, I am sure we could see such systems on the market.
....

A Roadster can indeed charge from all sort of voltages from 110V 12A and up to 220V 70A.
Voltage drops down to 100V and the car does not like it. So who is going to buy a wrecked car and use a Tesla battery to be house backup?

 

[TEG]

Have to read carefully on press releases that say "solar powered EV charger"...

B'More Green: Solar-powered EV charger debuts - Going Green: Environment, energy, living green, conservation and more in Baltimore, the Chesapeake Bay and beyond - baltimoresun.com

Solar-powered EV charger debuts
...
The power generated is fed to the grid, and the charger draws from the grid to recharge electric vehicles - so no one's Volt goes hungry just because the sun isn't shining...

(but they will go 'hungry' if the grid isn't energized.)

 

[TEG]

Is the Sanya Skypump grid tied too?
Sanya Skypump Brings EV Charging To Parking Lots, Uses Renewable Energy
Skypump: Renewable Energy-Based EV Charger: Enviro News
with wind | Grist
Sanya Skypump wind turbine is getting set to charge EVs and PHEVs

intended to take plug-in cars off the grid

 

[rabar10]

Competing forces:

- When green power generation could exceed local consumption, it's more environmentally-conscious to have local, green power generation tied to the grid so that all green energy is used to offset other generation
- Nearly all of these systems disconnect and shut down when the utility grid goes down

- "Off-the-grid" advocates want a power source available that is completely separate from the grid, for various reasons including independence, survivalism/disaster preparedness, or economic (if you're too far away to cheaply connect)
- Nearly all "off-the-grid" systems use local storage batteries to balance fluctuations between generation and consumption.

 

[Slackjaw]

.. So who is going to buy a wrecked car and use a Tesla battery to be house backup?

Why a wrecked one? I know it says in the manual that you specifically cannot use the Roadster as a "generator" to power your home or whatever. But if you could, wouldn't that be cool. We've paid for the 53kWh capacity pack, so maybe the next step for the "smart grid" is to let everyone store spare kWh in their EVs and use them as mobile UPSs. I was blacked out just like MPT and considered trying to run some lights from the 12V line on the Roadster but we already have some battery backup UPSs which (coupled with LED light bulbs) last longer than most blackouts.

If the Roadster could be used as a "generator" MPT could literally have carried 40kWh (or whatever's left over after driving about) of charge home from Rutgers to run his home. Like Doug_G said though, I suppose we can't blame Tesla for not letting us do this. Maybe a few EV generations from now though. I noticed one person running a 110v extension cord from the front of their Subaru Outback (the socket was on the end of a wire, hanging from the front grille); I think that's a standard feature on the 2011 model now.

 

[NigelM]

(but they will go 'hungry' if the grid isn't energized.)

Not necessarily. It depends on the installation:

We have a bi-directional metering system so we over-produce during the day and draw from the grid at night (or in bad weather). We are also registered with the local emergency authorities and the utility company as we can still keep pumping out our excess power even if a power line goes down. On the side of our house there's a huge cut-off lever in bright red so that it can be turned off in the event of technicians working on the lines. It just so happens that we are in the middle of our rainy season and we had a stormy day yesterday which led to a power out at 3.55pm. See the production graph below; it was a very erratic day with storms coming and going. It was cloudy and semi-dark but we carried on producing power and the "dip" in current caused my computer to restart but we didn't lose power completely as our neighbors did - the power out only lasted a minute or so but with clear skies we could have kept going with HVAC and everything so long as we had sunshine and the technicians didn't require we shutdown. Having said all that, it's quite possible that a bi-directional meter was just too expensive to install for one public charging station.

 

[TEG]

Where I live in California, they require that the inverters shut down if the grid power goes off.
You can make an isolated "island" system that isn't grid tied at all, but for grid-tied systems the grid must be up.

 

[Doug_G]

It is standard practice for power line workers to check the line even if they "know" it's offline. People often connect generators to their house wiring with back-to-back plugs and then forget to turn off the main breaker. Then the poor power worker comes along to hook their house back up and gets electrocuted. I think paranoia would be a requisite qualification for these guys.

 

[Norbert]

That's something that I learnt this last week; charging up the car to just 15 miles means I'll be home, as normal, no problem... with a buffer!

I used to have range anxiety, as much as I denied it. Now, I have "Range Confidence".

I know it is not exactly what you mean, but I think you are beginning to see the value a charging infrastructure has for many people!

Also beyond emergency situations and back-to-nature trips, that is...

 

[doug]

I used to have range anxiety, as much as I denied it. Now, I have "Range Confidence".

 

[JRP3]

Great story! Around here when the power goes out, the gas stations don't work either, which is a harder problem to solve since it's inconvenient to move the gas station to a working outlet.

I recommend getting a propane genset for that reason. You can always get a full BBQ tank at a hardware store, convenience store, etc., even without power, plus the fuel won't go bad over time.

 

[vfx]

I recommend getting a propane genset for that reason. You can always get a full BBQ tank at a hardware store, convenience store, etc., even without power, plus the fuel won't go bad over time.

Except the tanks are one of the first things to go in an emergency. Those outdoor BBQs become the only cooking surface.