Vehicle to PhotoVoltaic PV Inverter DC discharger available?

[codger222]

Anyone know of an aftermarket product that I can buy that will connect my Tesla Model X or Model S to a PV grid tied inverter and allow me to discharge vehicle battery at night? My battery warranty is over, so I'm not worried about voiding my Tesla battery warranty. I have unlimited lifetime super charging and would like to take advantage of that. My PV inverter can handle from 200 to 1,000 Volts DC and up to 15 amps on a circuit so I think it can handle the battery output. The product would connect to the DC inputs on my inverter via conduit I could run from my garage to the inverter. The product would ideally need to be able to control the power flow and limit total watts drawn per second and per night. I would want to pull say just 30 kW to 50 kW per evening or night. 400 volts DC x 20 amps = 8,000 W / hour discharge rate is what I would like to see to start. It might be even better to be able to spread the discharge out over more time (reduce the watts/hour) so that the discharge is gradual through the evening and night.
Codger222

 

[bobkart]

Welcome to Tesla Motors Club!

You're describing 'Vehicle-To-Grid' (V2G). Some EVs support this. Connecting directly to your Tesla's HV battery presents challenges. First, it's dangerous (wear appropriate gloves at least). And, the vehicle may detect the battery going down without seeing where the energy is going, and flag an issue. You need to find where to make that connection (safely).

I'll also suggest getting up to speed on power versus energy. Watts / kilowatts are units of power, and watt-hours / kilowatt-hours are units of energy. Specifically, 'watts-per-hour' is not a thing. So at 400VDC times 15A, you'd be drawing 6 kilowatts (kW) of power from your HV battery. Do that for ten hours and you've drawn 60 kilowatt-hours (kWh) of energy.

I'd be concerned that your PV Grid-Tied Inverter, while claiming to support up to 15A per circuit, might not *limit* the current to that, and the HV battery can supply considerable more than that, potentially leading to blown fuses (at a minimum). If your inverter will in fact only draw up to that current limit, then no issue there.

Are you already set up to feed back to your grid potentially more than you're using? I.e. 'meter running backwards'? If not, the power company could have an issue. If you're already set up for that (permits, agreement with power company, ...) then again, no issue. Just raising this as there's usually red tape in the way of just doing that.

 

[ucmndd]

There is no off the shelf product that does what you’re describing. The Tesla charge port isn’t bidirectional so you’re gonna have to do some major modification to the HV system to get direct access to DC power from the pack.

A whole lot of custom work just to steal some electricity from Tesla…

 

[codger222]

There is no off the shelf product that does what you’re describing. The Tesla charge port isn’t bidirectional so you’re gonna have to do some major modification to the HV system to get direct access to DC power from the pack.

A whole lot of custom work just to steal some electricity from Tesla…

Tesla did give us all early adopters life time unlimited charging. We paid a premium for it and helped get the company off the ground. I also doubt I would actually go to a super charger every day. Kinda not a very productive use of my time. It would though allow me to use the Model X battery like a huge power wall array and allow me to not have to use utility power during the day.

 

[codger222]

Welcome to Tesla Motors Club!

You're describing 'Vehicle-To-Grid' (V2G). Some EVs support this. Connecting directly to your Tesla's HV battery presents challenges. First, it's dangerous (wear appropriate gloves at least). And, the vehicle may detect the battery going down without seeing where the energy is going, and flag an issue. You need to find where to make that connection (safely).

I'll also suggest getting up to speed on power versus energy. Watts / kilowatts are units of power, and watt-hours / kilowatt-hours are units of energy. Specifically, 'watts-per-hour' is not a thing. So at 400VDC times 15A, you'd be drawing 6 kilowatts (kW) of power from your HV battery. Do that for ten hours and you've drawn 60 kilowatt-hours (kWh) of energy.

I'd be concerned that your PV Grid-Tied Inverter, while claiming to support up to 15A per circuit, might not *limit* the current to that, and the HV battery can supply considerable more than that, potentially leading to blown fuses (at a minimum). If your inverter will in fact only draw up to that current limit, then no issue there.

Are you already set up to feed back to your grid potentially more than you're using? I.e. 'meter running backwards'? If not, the power company could have an issue. If you're already set up for that (permits, agreement with power company, ...) then again, no issue. Just raising this as there's usually red tape in the way of just doing that.

Bobkart,
Thank you for the reply and correcting my use of watts and watt-hours.
Meter running backwards question: Yes. I have 2 Fronius grid tie inverters running and sending electricity back to the grid. I produced more electricity than I needed last year and should be getting a small ~$300 annual true up check from my utility fairly soon. So the utility is ok with me producing more than I need on any given day and annually.
I would rather purchase a product or kit rather than figure out the correct power drain interconnect, controls etc, I can't be the only one in my position. From this tridens web site I'm pretty sure there were about 180,000 of us Model S and Model X owners out there that have expired battery warranties and there will be another 50,000 to 68,000 of more added to that market population each year. I would like to contribute a small effort to the solution of helping to load shift from day to night every sunny day. Since I'm in a relatively sunny part of California I could contribute most days for the year and eliminate my draw on the utility grid nearly entirely.

 

[codger222]

Tesla did give us all early adopters life time unlimited charging. We paid a premium for it and helped get the company off the ground. I also doubt I would actually go to a super charger every day. Kinda not a very productive use of my time. It would though allow me to use the Model X battery like a huge power wall array and allow me to not have to use utility power during the day or night.

Also I have 2 other cars in the garage, so I could leave the Model X plugged to discharge at night and still have wheels to go places.

 

[bobkart]

Regarding using a Tesla for backup power, most approaches involve tapping into the 12V system as opposed to ~400V:

MASTER THREAD: Powering house or other things with Model 3

A typical approach is to tap into the DC-DC converter output, under the rear seat (in Model 3/Y), which is capable of ~2kW (at 14VDC - 16VDC for the new Li-Ion low-voltage battery). So an inverter is required, but be careful not to trip the e-fuse when the inverter's capacitors are initially filled up. Various circuits are explored in the above thread to work around the e-fuse tripping. Might be easiest to have another small 12V battery laying around that you connect the inverter to first (filling up the capacitors from it), then connect to the Tesla DC-DC converter before the capacitors discharge much. Apparently the e-fuse does reset after some time. And not all inverters exhibit the huge-initial-current-draw issue that can trip the e-fuse.

 

[SmartElectric]

Also I have 2 other cars in the garage, so I could leave the Model X plugged to discharge at night and still have wheels to go places.

If you have the money to sink into an idle Tesla, may I respectfully suggest selling one of the cars and getting powerwalls, they'd work right away and wouldn't require spending time daily to supercharge and return home ...

Our F150 Lightning has power backup to home via the Ford Charge Station Pro and Sunrun inverter, but I declined to spend $ to implement that in my own home because I already have a battery system for my solar, and that's been working for years and doesn't require hacking my car or leaving a spare car in the garage ... something to think about.

 

[ucmndd]

Tesla did give us all early adopters life time unlimited charging.

Which they most certainly did not intend to power your home.

 

[codger222]

If you have the money to sink into an idle Tesla, may I respectfully suggest selling one of the cars and getting powerwalls, they'd work right away and wouldn't require spending time daily to supercharge and return home ...

Our F150 Lightning has power backup to home via the Ford Charge Station Pro and Sunrun inverter, but I declined to spend $ to implement that in my own home because I already have a battery system for my solar, and that's been working for years and doesn't require hacking my car or leaving a spare car in the garage ... something to think about.

I think it is great that Ford has that Charge Station Pro feature in their F150 Lightning vehicles. I think that that might have caused Tesla to put that feature in their Cyber Truck. Tesla has been slow to add the 2 way charging option to any other of the other vehicles in their line up because I think they want to sell more power walls.

You are right about wasting time using the super charger credits. The 30 minute one way drive to the nearest super charger, plus the 50-60 minutes to charge plus the 30 minutes return for less than $30 of electricity is a poor use of my time.

My car is not really idle. It's idle when I'm sleeping. I use it all the time. I drive it to work, and run errands. It's just that the car is usually either at home, because most days I'm working from home, or back at home by 5-6 PM and not usually later than 10-11 PM. My 2016 Model X is nearly beyond the 8 year Tesla battery warranty and still probably has about 5 times the kWh capacity of a single 13 kWh power wall. I'd just rather not spend another $15k - $25k buying 2 or 3 power walls to limit my nightly electric utility usage when the there is a huge battery already there in my garage. If I could buy an after market adapter to allow me to discharge DC current to one of my PV inverters, I think it could help level out the demand on the grid.
Codger222

p.s. I have 2 solar arrays in my back yard connected to 2 separate PV inverters. The panels & inverters charge the 2 Teslas, and power the pool pumps, electric clothes dryer, washing machine, electric oven, lights, heat pump water heater and heat pump heater & AC here.

 

[codger222]

Regarding using a Tesla for backup power, most approaches involve tapping into the 12V system as opposed to ~400V:

MASTER THREAD: Powering house or other things with Model 3

A typical approach is to tap into the DC-DC converter output, under the rear seat (in Model 3/Y), which is capable of ~2kW (at 14VDC - 16VDC for the new Li-Ion low-voltage battery). So an inverter is required, but be careful not to trip the e-fuse when the inverter's capacitors are initially filled up. Various circuits are explored in the above thread to work around the e-fuse tripping. Might be easiest to have another small 12V battery laying around that you connect the inverter to first (filling up the capacitors from it), then connect to the Tesla DC-DC converter before the capacitors discharge much. Apparently the e-fuse does reset after some time. And not all inverters exhibit the huge-initial-current-draw issue that can trip the e-fuse.

Thank you for the link to the other thread "Powering house or ..." and this additional information. I found some DC converters on line that will boost a 12 volt source. I'll test my idea out with a simple stand alone 12 volt car battery.
Thank you again.
Codger222