EVSE connections to car

According to https://guide.openenergymonitor.org/images/integrations/ev-charging/evse-build/evse-build-0.png.jpg etc. the PP output on the PCB is unused.

My Type 1 Leaf car certainly did not need it and the car lead, whilst containing an extra wire signal has it cut short and unconnected… But am now getting a Peugeot e2008 Type 2 car and changing over the charging lead. Do I definitely not need the PP output and if so what is it for?

What are the current capacities of the 230V and 12V outputs to contractor coils from the PCB? My PCB is 6 months old so presumably of the latest version.

As my car has a single phase connection can I assume that it is the L1 (Live 1) pin out of L1, 2, 3 that is the live pin to use in the charge lead?

Tethered EV cables don’t need PP connected to the EVSE controller. The PP connection is used when connecting to a non-tethered Type-2 socket where the EVSE needs the ability to detect the current carrying capability of the cable via an inbuilt resistor.

Yes, you have the latest version.

Correct. The cable should only have L1 connected, I wouldn’t recommend purchasing a three-phase cable if you’re only going to use it on a single-phase.

Don’t really understand this. Surely I can hard wire a tethered 16A cable to the EVSE (as I have now) and connect it to a 32A car and without the ESVE reading the resistor it will fry the cable unless the MCB trips. In practice my Leaf cannot draw more than 16A, but theoretically another car could plug itself in and try to draw 32A. Where is the resistor? In the car end plug? Do the cars read this resistor and limit their current accordingly?

I guess what you are saying is that the official ESVE kit has a 32A tethered cable so does not need to read the resistor.

If what you say is right (extremely likely!), as I have added a Type 2 socket to the enclosure to replace the tethered cable, I need to connect the PP to it. The Leaf will in future use a loose 16A cable and the e2008 a 32A one.

The car comes with a cable and I assume its a single phase 32A one.

It is not so difficult. The principle used in the UK for protecting electrical installations or equipment is the protective device which will normally be a circuit breaker or a fuse, but it could be something that incorporates a means of limiting the current, is rated so as to be able to supply the intended load. Then, all cabling downstream of the protection must be rated to carry the full load current and the prospective fault current during the time it takes for the protection to operate.

Therefore, if you have used a 16 A cable, and the EVSE is protected by a 32 A breaker, then you need to replace the breaker with a 16 A one, unless you have another means to ensure that the current is limited and does not cause unacceptable heating in the cable.

As you indicate, you must not rely on somebody (who does not know any better) not plugging in a car that demands 32 A, because if they do, the EVSE will supply it and the cable will be damaged and there will be a real risk of fire.

[In reality, the protection and cabling is often sized for convenience and availability, and that defines the maximum load - e.g. you can’t plug a kettle into a lampholder.]

Yes understand that. My installation was in practice protected by the 16A MCB plus a software limit of 16A. What’s puzzling me is that if you fit a tethered lead and don’t use the PP connection then you are not protected unless your tethered lead is at the max capacity on the software. Glyn said “Tethered EV cables don’t need PP” but surely they do if there is not some other means to limit the current to the lead’s capability. That was the bit I did not understand. Perhaps he meant “Tethered EV cables don’t need PP as they should be sized to meet the EVSE max current output.

Resistors in charging cables – CanZE says the PP resistor should be fitted to both ends so I should have added a >680 ohm from PP on the PCB to earth inside the ESVE and connected the PP wire.

That link content does not seem quite right as in one place is says the PP pins are not wired from cable end to end and later says the 2 resistors measure at half the resistance so they must be connected.

Now that I am uprating to 32A I need to be sure any 16A connected lead is protected.

That is correct, the assumption being that you MUST use the appropriate cable.

You must indeed.

Have uprated the point now to 32A and protected the non tethered leads by connecting the PP wire.

It worked at 28A but when I set 32A the control webpage said it had tripped on overcurrent. Why would that be? Could it be due to inaccuracies in the CT and measurement such that it actually draws say 32.5A when set to 32A? Thus it trips. Difficult to believe that explanation as below 16A it says it is delivering 1 to 2 A less than the set current. Never seen the current higher than the set value but maybe the new car is different.

I note too that the “App” has recorded 16 instances of no ground. Presumably that is cumulative times since new. Why would it log this when I am not ever aware of any earth faults or disconnected ground. Is it just glitches when the car plug does not quite connect well? E.g. the Leaf sometimes does not recognise the plugging in and it has to be repeated.

If you’re using a non-tethered socket then you need to use EmonEVSE controller firmware which has PP_AUTO_AMPACITY enabled which allows the controller to autodetect the current carrying capability of the cable. Connecting PP without enabling PP_AUTO_AMPACITY will do nothing.

Here is the lookup table used by `PP_AUTO_AMPACITY

e.g a 32A cable has a 220R resistor between PP and GND while a 20A cable has a 680R resistor.

Tethered cables don’t have resistors on the EVSE end of the cable since they are part of the fixed installation, the manufacturer of the EVSE should install a correctly sized cable to match the output capability of the EVSE. These days the cost difference between a 16A and 32A cable are minimal, so we only sell 32A cables.

Thanks for that. So do I have to edit the firmware and reload it? Or is there a version ready to go in GitHub?

Without the software mod there is no danger to my cars of overloading their cables as the Leaf is incapable of exceeding 16A . But conceivable an outsider could drive up my house and illegally (a moot point, is “stealing” someone’s electricity actually a crime?) connect their car and cable. Could be said that any resulting damage is their fault!

Very definitely. Catching them in the act and proving it (unless you have CCTV) could be tricky. But CCTV pictures and an emonCMS graph showing the power/energy abstracted would be a big help.

In the old days, people were prosecuted for “stealing Post Office electricity” for using the 50 V to trickle charge batteries, and BBC lore is that a farmer who lived near a long wave transmitter and erected a loop aerial in his barn to charge batteries (via a rectifier of course) also felt the full weight of the law.

Yes, a pre compiled emonevse.hex is available: https://github.com/OpenEVSE/open_evse/releases/download/8.2.0/emonevse.hex

See flashing instructions: GitHub - OpenEVSE/open_evse: Firmware for Open EVSE

That’s very unlikely! The risk vs reward of someone plugging in a car on your driveway is very low. They would need to be sat there for many hours to make any significant saving. More likely is that you have a visitor that plugs in. An easy way to protect against this is just to set the maximum current on the OpenEVSE to 16A.

I can attest to the power in a BBC Tx. I was once driving past the long wave BBC overseas service Tx at Rampisham in Dorset and heard a mid-European language wafting loudly across the field under the aerial masts. Something like Polish. Stopping to investigate this unusual noise, when no one was anywhere nearby, I noticed a bright blue flame about 3 feet high coming out of one of the feeders to a mast. It soon stopped.

What had happened as far as I could tell was that the feed power in the cable to the mast (possibly a large coax with an air core) had burnt through the cable, causing an external arc. As the radio power was AM modulated the arc was pulsing at the audio frequency of the transmitted sound. Thus sound was radiated. The Tx would have eventually detected the overload/short that had been created in the cable and tripped out.

There is/was loudspeaker design that used arcs to radiate the sound. As an arc has almost zero mass, unlike a speaker cone, it allegedly makes for excellent reproduction with no strange colourations caused by a cone resonating or distorting.

Had a brainwave. We don’t need car chargepoints at all. We just need to repurpose the LW transmitters, which are now largely unused, into RF chargers for cars. Each car can suck power out of the air on the move and when stationary.

Only joking. It would be hugely inefficient and I doubt enough transmitted power could be made available. And how would the car owner pay for the electricity collected this way?

Do you think they wouldn’t find a way, and then tax it as well? :rofl:

You might be nearer to the truth than you think - I am sure I’ve read about inductive loops under parking spaces, for charging.