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You're not writing the software controller for your switch. You're not interfacing with the firmware of your giant lithium battery parked in your house. You're

You're not writing the software controller for your switch. You're not interfacing with the firmware of your giant lithium battery parked in your house. You're not soldering anything, or dealing with more than 15a or so. It's really not the same.

HeyLaughingBoy 3y ago
The software controller for that switch was probably written by the new guy fresh out of college with maybe a bit of oversight from his manager. You're not wasting your experienced Staff engineers on stuff like that.
manchmalscott 3y ago
An EVSE (what this project is) only does three things. It advertises the maximum amperage supported by the circuit, it listens for the car to say that it’s ready to charge, and then it supplies 120-240V AC line voltage across the main pins. No EVSE ever, including storebought, is “interacting with the firmware of your giant lithium battery”, the actual charger that turns the AC into DC and shoves it in the battery is built in to the car. You’re probably thinking about DC fast charging, where the charger is external to the car and connects directly to the battery. Nobody should be trying to make _that_ themselves with an Arduono, sure.
- bastawhiz 3y ago
  If the EVSE is talking to your car but not the firmware of the car, then please explain what the hell it's talking to. Is it in the cloud? Is there a little man that lives in my car that replies? Getting the amperage wrong or sending power when the car is not ready both sound like astoundingly dangerous failure modes for a DIY project, even if the most damage is bricking your car's battery controller.
  - manchmalscott 3y ago
    if I plug in my phone and my phone isn't ready to start charging (say it detects an overheat, common in Arizona), it just… doesn’t start charging. Just because the cars onboard charger now has power available to it doesn’t mean it has to start charging the battery. The EVSE is talking to the onboard charger, the on board charger is what actually interacts with the batteries. The EVSE has a specific resistance inline with a comm pin to indicate presence (even when unplugged from the wall) and modulates a frequency on the comm pin to indicate max amperage. The car puts a specific resistance on a different comm pin to request that the contactors close to connect the charger to wall power. Any problems or bugs thereafter are with the onboard charger, not the EVSE.

HeyLaughingBoy 3y ago

The software controller for that switch was probably written by the new guy fresh out of college with maybe a bit of oversight from his manager. You're not wasting your experienced Staff engineers on stuff like that.

manchmalscott 3y ago

An EVSE (what this project is) only does three things. It advertises the maximum amperage supported by the circuit, it listens for the car to say that it’s ready to charge, and then it supplies 120-240V AC line voltage across the main pins. No EVSE ever, including storebought, is “interacting with the firmware of your giant lithium battery”, the actual charger that turns the AC into DC and shoves it in the battery is built in to the car. You’re probably thinking about DC fast charging, where the charger is external to the car and connects directly to the battery. Nobody should be trying to make _that_ themselves with an Arduono, sure.

bastawhiz 3y ago
If the EVSE is talking to your car but not the firmware of the car, then please explain what the hell it's talking to. Is it in the cloud? Is there a little man that lives in my car that replies? Getting the amperage wrong or sending power when the car is not ready both sound like astoundingly dangerous failure modes for a DIY project, even if the most damage is bricking your car's battery controller.
- manchmalscott 3y ago
  if I plug in my phone and my phone isn't ready to start charging (say it detects an overheat, common in Arizona), it just… doesn’t start charging. Just because the cars onboard charger now has power available to it doesn’t mean it has to start charging the battery. The EVSE is talking to the onboard charger, the on board charger is what actually interacts with the batteries. The EVSE has a specific resistance inline with a comm pin to indicate presence (even when unplugged from the wall) and modulates a frequency on the comm pin to indicate max amperage. The car puts a specific resistance on a different comm pin to request that the contactors close to connect the charger to wall power. Any problems or bugs thereafter are with the onboard charger, not the EVSE.