I would like to know what are special requirements for an Electric Vehicle Charger. Specifically, how does it differ from a regular Battery Charger? I have heard of Level1, Level2, and Level3 charging. However, other than the side-band access to Vehicle capabilities and higher power levels, what other features would differ in an Electric Vehicle Charger? Also for getting to know the Vehicle capability, are there any standard data formats which are employed? One thing I could think of is pre-paid access to Charging power, what else?

Help me finalize a spec, Please :)

Best Regards,

Vishal Sapre

  • \$\begingroup\$ First thing what battery chemistry are you considering - as some have the three levels of charge you mention... Even “ordinary” battery chargers can regulate the output compared to time and state of charge. \$\endgroup\$ – Solar Mike Jan 31 '18 at 12:59
  • \$\begingroup\$ Spec for what? The battery charging circuits to go into an electric vehicle? Or the specs for a charging point to plug a vehicle into? Or something else? \$\endgroup\$ – Finbarr Jan 31 '18 at 13:47
  • \$\begingroup\$ If the vehicle uses regular batteries, then a regular charger is used. Early electric vehicles used lead-acid. I once drove from Boston to LA in a vehicle powered by nickle-cadmiums. So exactly what sort of batteries are you talking about? \$\endgroup\$ – WhatRoughBeast Jan 31 '18 at 13:47
  • \$\begingroup\$ @Finbarr: Spec for a Charging Station and a High Current Charger that we would like to make. \$\endgroup\$ – Vishal Jan 31 '18 at 15:22
  • \$\begingroup\$ @SolarMike: I think the Battery Charger makers, would have to consider both Lead Acid and LithiumIon Batteries. We have some e-scooters in India that use LeadAcid batteries, and also some which use LithiumIon batteries. Larger, 3 wheelers such as those used for moving items or people for small distances, invariably uses LeadAcid, because of the low price bracket that they have to cater. So I am looking at both the chemistries. \$\endgroup\$ – Vishal Jan 31 '18 at 15:31

Level 1 and level 2 are very simple: the charging station (not charger, the battery charger is built into the car) supplies a low voltage square wave where the duty cycle indicates the maximum current the car is allowed to draw. The car then connects a resistor between that signal and ground to indicate it is ready to draw current. The charging station then provides AC voltage to the car (at least in the USA, 120 volts for level 1 or 208/240 volts for level 2). That’s pretty much it. There’s no communication of car identity. Any authorization is done outside, using RFID cards or such. This is specifically how stations with the standard J1772 connector work.

In earlier level 3, the battery charger is actually in the station and provides high-voltage (as high as 500 volts) to the car under direction of the battery monitoring hardware in the car. This dynamically varies the voltage as required. I still don’t believe there is any in-band authorization. This is specifically for the Japanese Cademo stations.

Tesla has a separate connector and protocol for their stations, though I believe the voltages are the same. I’m not sure but I assume their Supercharger L3 stations do in-band authorization.

Additionally, there is now a variation on the J1772 for level 3 charging which adds two high-voltage, high-current pins to the connector. I don’t know how much the protocol changes with this.

All of the stations also use built-in GFCI to protect against faults that could hurt or kill the user. They also self-test the GFCI at the start of every session by leaking current to ground internally.

  • \$\begingroup\$ In the Level1 and Level2 Charging, How does the Charging Station understand that the vehicle is ready to accept AC current. Does the charging station detect some current flowing through its signal pin, to detect that the AC breaker has to be closed? \$\endgroup\$ – Vishal Jan 31 '18 at 15:24
  • \$\begingroup\$ @Vishal - have you done any research - you should have found this answer already... \$\endgroup\$ – Solar Mike Jan 31 '18 at 15:55
  • \$\begingroup\$ @Vishal that’s basically correct. Take a look here for more details: en.m.wikipedia.org/wiki/SAE_J1772#Signaling \$\endgroup\$ – DoxyLover Jan 31 '18 at 19:15
  • \$\begingroup\$ @SolarMike: Yes, I have done some research on these topics. But frankly speaking, there is so much information on Google, that it gets overwhelming to skim and filter to get the exact bits and pieces. My General thinking is that Experts (like yourself) would provide better pointers for such general questions. I really Thank You for your contribution. Best Regards. \$\endgroup\$ – Vishal Jan 31 '18 at 19:49

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