3 ms·

I don't think that that is true. The inverters are designed for power and cost efficiency, so I'd say it is unlikely that are capable at outputting anything ot

by LeonM 6y ago

I don't think that that is true. The inverters are designed for power and cost efficiency, so I'd say it is unlikely that are capable at outputting anything other than the high-voltage, high-frequency power intended for the electric motor. The electric motors in most EVs are 3-phase, 400V motors. I expect them to operate at quite high frequencies for efficiency (I'm not sure about that though). So I expect that 115V/50Hz or 230V/60Hz is just way outside of the design envelope of car inverters.

cmrdporcupine 6y ago
Yes it would be very difficult to go from the full 3 phase AC, that runs the drive train, to 120v or 220v 2 phase AC. Third party adapters that do this usually run off the 12v DC accessory battery, which already is hooked up to a DC to DC converter from the car's LiOn battery. Going from 12v DC to 120V AC is obviously already a very solved problem.
- LeonM 6y ago
  That would be very inefficient, and I also doubt that the build-in 12V DC-DC converter is capable providing the current required to run the inverter. So, since it requires retrofitting anyway, it would make much more sense to have an inverter running directly of the high voltage battery. I guess this all comes back to my original statement: Currently available EVs certainly do not have suitable electronics for 115V or 230V output. It will require hardware retrofit, not just a magical software update to make it work.
  - serf 6y ago
    > I also doubt that the build-in 12V DC-DC converter is capable providing the current required to run the inverter. that's not how it works; the current is provided by the 12v battery, not the charging inverter. Now, obviously the charging inverter isn't going to keep up for long, but as far as high current is concerned as 12v car battery can usually provide around 400-700 amps if given the proper leads, with a capacity of (typically) at least 45aH. that's a lot of juice. even with the inverter inefficiency you should be able to get some fairly major work done if the inverter can supply the amperage -- especially if the EV systems are working alongside to maintain the battery. >That would be very inefficient absolutely. >So, since it requires retrofitting anyway, it would make much more sense to have an inverter running directly of the high voltage battery. that'd be nice, but I think EV groups would rather you wear out the cheaper replaceable battery with the erroneous usage. Sure, the loads still load the EV battery, but those charge/discharge rates can be more closely monitored or denied all together -- something that'd be harder to implement if the inverter had straight access to the ev primary battery.
    - LeonM 6y ago
      I didn't realize EVs still have a 12V battery, I always assumed 12V accessories are ran directly of the DC-DC converter. Thanks for pointing that out!
      - cmrdporcupine 6y ago
        So I'm not even sure in my Volt if the 12v battery even powers the accessories directly, because it's at the _back_ of the car, not up in the front by the accessories. It's super handy for boosting other vehicles.
londons_explore 6y ago
> The inverters are designed for power and cost efficiency, so I'd say it is unlikely that are capable at outputting anything other than the high-voltage, high-frequency power intended for the electric motor. You could use the motor inverters for this, if only they weren't already connected to the motors. You can't have your wheels spinning just because you want to hook up an AC device. Instead you'd use the charging inverter. Large modern chargers are combinations of MOSFETs, capacitors, and inductors, which are all components where the power flow is reversible. There is also an isolation transformer which the motor drive inverters don't have, and is important for detecting potentially dangerous faults. This isn't true with say your laptop charger, since it's input stage typically uses diodes rather than MOSFETs for the initial rectification, which means you couldn't run the whole thing in reverse to make AC off your laptop battery, even with new firmware.

by LeonM 6y ago

cmrdporcupine 6y ago

Yes it would be very difficult to go from the full 3 phase AC, that runs the drive train, to 120v or 220v 2 phase AC. Third party adapters that do this usually run off the 12v DC accessory battery, which already is hooked up to a DC to DC converter from the car's LiOn battery. Going from 12v DC to 120V AC is obviously already a very solved problem.

LeonM 6y ago
That would be very inefficient, and I also doubt that the build-in 12V DC-DC converter is capable providing the current required to run the inverter. So, since it requires retrofitting anyway, it would make much more sense to have an inverter running directly of the high voltage battery. I guess this all comes back to my original statement: Currently available EVs certainly do not have suitable electronics for 115V or 230V output. It will require hardware retrofit, not just a magical software update to make it work.
- serf 6y ago
  > I also doubt that the build-in 12V DC-DC converter is capable providing the current required to run the inverter. that's not how it works; the current is provided by the 12v battery, not the charging inverter. Now, obviously the charging inverter isn't going to keep up for long, but as far as high current is concerned as 12v car battery can usually provide around 400-700 amps if given the proper leads, with a capacity of (typically) at least 45aH. that's a lot of juice. even with the inverter inefficiency you should be able to get some fairly major work done if the inverter can supply the amperage -- especially if the EV systems are working alongside to maintain the battery. >That would be very inefficient absolutely. >So, since it requires retrofitting anyway, it would make much more sense to have an inverter running directly of the high voltage battery. that'd be nice, but I think EV groups would rather you wear out the cheaper replaceable battery with the erroneous usage. Sure, the loads still load the EV battery, but those charge/discharge rates can be more closely monitored or denied all together -- something that'd be harder to implement if the inverter had straight access to the ev primary battery.
  - LeonM 6y ago
    I didn't realize EVs still have a 12V battery, I always assumed 12V accessories are ran directly of the DC-DC converter. Thanks for pointing that out!
    - cmrdporcupine 6y ago
      So I'm not even sure in my Volt if the 12v battery even powers the accessories directly, because it's at the _back_ of the car, not up in the front by the accessories. It's super handy for boosting other vehicles.

londons_explore 6y ago

> The inverters are designed for power and cost efficiency, so I'd say it is unlikely that are capable at outputting anything other than the high-voltage, high-frequency power intended for the electric motor. You could use the motor inverters for this, if only they weren't already connected to the motors. You can't have your wheels spinning just because you want to hook up an AC device. Instead you'd use the charging inverter. Large modern chargers are combinations of MOSFETs, capacitors, and inductors, which are all components where the power flow is reversible. There is also an isolation transformer which the motor drive inverters don't have, and is important for detecting potentially dangerous faults. This isn't true with say your laptop charger, since it's input stage typically uses diodes rather than MOSFETs for the initial rectification, which means you couldn't run the whole thing in reverse to make AC off your laptop battery, even with new firmware.