-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
Wall connector and generator
- Thread starter davidr7876
- Start date
I wouldn't worry about it. If you have an automatic backup generator it'll probably have good enough output power quality to not upset the Tesla.
I assume the car would actually be fairly kind to the generator, even. Assuming there's an outage, charging will stop, and there will be a random delay of 3-5 minutes(after the generator start) before it restarts. When it restarts it will ramp up from 0 amps as usual.
Side note: it's not uncommon to have an EV charger >not< on the generator output, but if its big enough its not a big deal.
I assume the car would actually be fairly kind to the generator, even. Assuming there's an outage, charging will stop, and there will be a random delay of 3-5 minutes(after the generator start) before it restarts. When it restarts it will ramp up from 0 amps as usual.
Side note: it's not uncommon to have an EV charger >not< on the generator output, but if its big enough its not a big deal.
ATPMSD
Active Member
I suggest there are two problems with generators.
The first is voltage control; generators monitor voltage to control the load, as they load up voltage drops before the generator can satisfy the load, and when a load is reduced there can be a voltage spike. Neither of these is good for the car, or other appliances in the house. As noted by @Sophias_dad, if the generator is large enough your should be OK.
The other is frequency; electronics need fairly clean power so you will want to ensure the total harmonic distortion is less than 5% and preferably less than 3%.
Personally I would avoid plugging your expensive car battery into a generator. Also note, because Tesla cautions against a generator, if something happens your warranty may be void.
Finally, to be fair, the caution probably refers to small standby generators and not to large whole house generators.
The first is voltage control; generators monitor voltage to control the load, as they load up voltage drops before the generator can satisfy the load, and when a load is reduced there can be a voltage spike. Neither of these is good for the car, or other appliances in the house. As noted by @Sophias_dad, if the generator is large enough your should be OK.
The other is frequency; electronics need fairly clean power so you will want to ensure the total harmonic distortion is less than 5% and preferably less than 3%.
Personally I would avoid plugging your expensive car battery into a generator. Also note, because Tesla cautions against a generator, if something happens your warranty may be void.
Finally, to be fair, the caution probably refers to small standby generators and not to large whole house generators.
I think they say that so people don’t take generator and directly plug the car into it. I have a full house standby generator that’s 20kw Kohler. Runs the whole house with no issues. I’ll have to see when I get my MYP if it works or not.
Both the Mobile Connector manual and the Wall Connector manual have the same caution statement: CAUTION: Do not use private power generators as a power source for charging.
Perhaps it is a question of safety, i.e. not having a proper earth ground when using a portable generator.
If the standby generator becomes overloaded it would shut down or if it has a load shed module or modules the whole house standby power system would start shutting off circuits.
If the private power generator causes damage to the charging system in the Tesla vehicle it would not be covered under the warranty.
In most cases you would know that the standby power generator was running. You could defer charging the Tesla vehicle until grid power was restored. If you need to charge the Tesla vehicle and can't wait you can proactively turn off other high amperage draw circuits such as the HVAC system, water heater while charging. You could also temporarily reduce the charging amperage for the charging session.
Perhaps it is a question of safety, i.e. not having a proper earth ground when using a portable generator.
If the standby generator becomes overloaded it would shut down or if it has a load shed module or modules the whole house standby power system would start shutting off circuits.
If the private power generator causes damage to the charging system in the Tesla vehicle it would not be covered under the warranty.
In most cases you would know that the standby power generator was running. You could defer charging the Tesla vehicle until grid power was restored. If you need to charge the Tesla vehicle and can't wait you can proactively turn off other high amperage draw circuits such as the HVAC system, water heater while charging. You could also temporarily reduce the charging amperage for the charging session.
The issue would be I go to bed and car is set to charge at say 11pm and middle of the night the power goes out. Generator kicks on within minutes or less and what does that do to the car charger. They need to specify portable small generators that would be dangerous to use and the whole house 20-30kw ones. A lot of people have whole house generators.
I honestly think this is just a case of CYA. I have viewed videos, one recently, of someone who drained a Tesla (Model ?) down to where it would not drive. They pulled a portable generator from the hatch (like a Honda generator) started the generator and plugged in the Mobile Connector into the generator and into the Tesla's charging port. The Tesla started charging. I realize this was just a stunt. (Sort of like the movie Airplane when the captain, George Kennedy, revs the engines of a Boeing 747 to full power to get the airplane moving when the runway was covered in deep snow. The co-pilot cautions that the manual states that the plane cannot handle full power when stopped. Kennedy replies "Good thing airplanes can't read the manual" and the 747 breaks free and starts to roll.)
I think that Tesla needs to clarify this issue. When I posted a question about being away for a month on a non drive vacation it was recommended that I leave the car plugged in. What happens if the power goes out for days and my generator (Honda 20kw) is powering the house and charger?
The Tesla vehicle will only charge when the state of charge falls ~5% below the set charge level. If this is really a concern you could have your electrician install a load shed module, take the EV circuit off line whenever the generator is running.
The discussion about generator charging does not address an important point. Some generators, usually the more expensive ones, put out a pure sine wave. I would bet that having a stable voltage and current capacity to the T3, it wouldn't know the difference between a generator and a Level 1 or Level 2 house feed.
On the other hand, APC, the manufacturer of a wide range of Battery Backup Systems, says that it sees a modified sine wave as "dirty" and won't accept it.
What does Tesla say about "Pure Sine Wave" vs "Modified Sine Wave". No one at my local service center has any idea what I'm talking about, and repeated queries to Tesla have gone unanswered...that's why I'm here.
On the other hand, APC, the manufacturer of a wide range of Battery Backup Systems, says that it sees a modified sine wave as "dirty" and won't accept it.
What does Tesla say about "Pure Sine Wave" vs "Modified Sine Wave". No one at my local service center has any idea what I'm talking about, and repeated queries to Tesla have gone unanswered...that's why I'm here.
ATPMSD
Active Member
Since Tesla cautions against using generators I doubt you will find anything, I have seen videos where people used a generator, but the voltage had to be stable and the THD had to be less than 5%, and preferably 3%.
minor correction - Airport, not Airplane.
For those us us born later than this 1970 release and more likely to have seen Airplane, the 4 Airport movies are fun, and very explanatory for the (slightly more) comedic one with Liam Nielson and Robert Hays.
Along similar lines, does anyone know what the car does when the supplied voltage starts dropping, as during a "brownout"? Does it progressively cut back on current as voltage drops or shut off completely at some point? If so, does it automatically start charging again when the voltage returns to a certain value? Any information on actual values? (I'm not talking about complete loss of input power.)
A square wave has only two voltages, high and low, alternating at a frequency of 50Hz or 60Hz. A modified sine wave (which in my opinion should be called a modified square wave) has three voltages, high, medium, low, medium, high, medium, low, etc. with 50 or 60 cycles per second. A sine wave has continuously varying voltage, approximating a sine function, but with some distortion.
All generators driven by a rotating engine produce a sine wave, not a modified sine wave. The only things that will produce a modified sine wave (or a square wave) are some very cheap inverters. However, the sine wave of an ordinary generator can have total harmonic distortion of up to 20%. A good oscilloscope will be able to measure the THD of your generator. 20% THD won’t damage the car’s battery, but it might damage the car’s onboard charger and it might damage the electronics in the wall connector. An inverter generator (a generator with some extra electronics to filter the output) will have THD below 5%, maybe below 3%.
If you’re going to use a generator to charge an EV, I would recommend either using an inverter generator or, if you already have a generator, using the generator to power an inverter and then the inverter to power the wall connector.
Loads can be either constant current, constant power, or constant impedance. L2 EV chargers are constant current loads (i.e. the current stays constant as the voltage varies) up to the maximum power capacity of the onboard charger. If one configures a wall connector for 48A, it will draw 48A all the way down to well below 200V and up to around 260V, above which the onboard charger becomes a constant power load (12.5kw unless the onboard chargers have changed recently) up to the cutoff voltage (somewhere around 290V to 300V). An example of a constant impedance load would an incandescent lightbulb (current rises and falls through a lightbulb as the volt does).
If the wall connector or, more likely, the onboard charger shuts down due to insufficient voltage, it will restart after a delay when the voltage returns to acceptable levels.
I am in the exact same situation with Kohler 20kw. My car has not been plugged in during several outages. Will try charging during next outage or do a trial run next time the unit is serviced while tech is here.
Gen2 HPWC and model 3 was perfectly happy with 277+. I myself have seen them at ~289/48A... it was great...13.8kw. Sadly, they made the Gen3 277V-incompatible.
The car and HPWC is also fine with L2 charging down around 190V. I'm not sure how low it will go before startup/cutoff.
Both those said, I think the car itself will stop charging if it notices a wide swing in voltage AFTER charging starts, like if you plug in and get 235/48A but then it drops to 190V
Similar threads
