Resistors in charging cables

Posted on Posted in Hardware

The AC charger cables have a resistor between protective earth (PE) and the proximity pin (PP) pin to indicate

  • that the plug is inserted
  • that the plug can therefore be locked (type 2 only)
  • the gauge of the cable, and thus the maximum current

Note that the PP pins are NOT wired through the cable. The most common resistor values and also those of your standard Renault cable are 220 ohms, corresponding to 6 mm2 and 32 amps continuous, and 680 ohm, corresponding to 2.5 mm2 and 20 amps continuous. These are per strand values and the power varies given the number of phases used.

These PP-PE resistors should be installed on both ends of the cable, which I had not realized before. Yesterday I helped a friend changing his home charger from a socket type to a fixed cable type, so that he didn’t have to get the cable from the trunk every evening. The cable came pre-wired with the resistor in the plug, but it didn’t work. Only when we installed a PP-PE resistor in the charger itself, indicating the cable was inserted on that end, the charger started the process. The other side effect is that if you measure the connectivity between the PP pins on your standard Renault cable, you’ll measure a confusing 440 ohms. That’s because both ends are wired to the ground lead with 220 ohm resistors.

1500 Ω resistor – 13A cable
680 Ω resistor – 20A cable
220 Ω resistor – 32A cable
100 Ω resistor – 63A cable

11 Comments on “Resistors in charging cables”

  1. I will put additional resistor of 460 Ohm with switch in serial with existing one, in to charging cable for manual selection of cable type. Must I put it on the car’s side or on the charger port’s side for maximal power selection (32 or 20 A)?

  2. Either one should do. If you put it car side, the car will throttle. If you put it charger side, the charger should not set it’s PMW signal above said current, and the car should adhere to that too. Cool mod.

  4. Just to emphasize: the currents we are talking about are “true” currents. Cables don’t care if the current is phase shifted with the voltage. Since ZOE (at least the Q version) draws roughly 6 amps reactive current because of filter capacitors (see https://canze.fisch.lu/charging-currents-single-phase/ ) , especially at low currents, the actual power uptake is lower than the expected amps times 230 volts.

    • You can’t. It’s just that table. AFAIK it’s like that in the specs. Cars might “step” between the currents or adjust in a linear fashion, but I am fairly sire these are “the” values and that’s it.

      • Question , if you fit larger than 1500 ohm resistors will it get lower or is this the max

        • Apologies for the late reply. See https://en.wikipedia.org/wiki/SAE_J1772 The standard defines discrete current values, so a chargepoint following the standard would not gradually change it’s max current. But who knows what your chargepoint (or the ZOE) does. If you want to use this to control charge current real time: please don’t. Nowhere it is stated that either the car or chargepoint monitors this real time. You really need to implement that through the CP, using for instance OpenEVSE.

  6. Hello all, I will make cable 16A 230VAC directly to car so I have intention to charge by AC – but not sure if I need still resistor and if yes what value that should be
    Please