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Discussion Starter #1
Hello all from Turkey!

So I've been driving an EV at lease this past 1,5 years and I charge at our offices, which luckily is in an industrial zone so we have plenty of power. When lease began they put in their own EVSE but now lease is about to end so they'll take it away. I'm planning on buying the new ZOE ZE 40 after this lease so I'll need a new EVSE. Since we have a 40A three phase MCB available right next to where I park my car, I thought it would be a lot of fun to build my own EVSE, learn along the way and save plenty of money. I thought a tethered application would be the best and simplest. (Speaking of which, why aren't we seeing more commercial tethered EVSEs? Wouldn't it be much more easier than getting the cable from your trunk every time? You know when the cable is dirty, muddy or when it is raining it's not the easiest thing to handle. Reliability issues? Added cost? I seriously don't understand why people aren't going the tethered way.)

Firstly; I'm not an engineer and I've been researching, reading, watching fanatically this past week about building EVSEs and I've learnt a lot thanks to this wonderful community. I've started the plan for the project and wanted to run it down with you guys before moving on to make sure.

I'll be purchasing the ViridianEV EPC for the signal controls.(which seems to be the mainpine EPC Kevin Sharpe used at the EVSE Build day video) Theirs seem to be the most affordable and simple one. I only want the signalling, three phase 32A 22kW. Don't need any smart features.

I'll use an RCD-B 40A and a 40A 4 pole contactor. Reading the viridianev manual and all sorts of other stuff, here's the wiring plan I came up with.


Off to my questions;
- Cost is very important for me and I plan on just getting a Type 2 IEC 92196 Female connector and instead of finding the EV charging cable of 5G6mm + 1G0,75mm, I'll get a 5G6mm TTR + a 0,75mm cable(is it supposed to be cat6?) and put them through a cable cover together. Would this be OK? Would save a lot of money. Less stuff I get from abroad (i.e. not Turkey) the better, and there's no 5G6mm + 0,75mm cable made here I'm sure.
- I know I'm supposed to use 6mm cables for live and neutral wires but what about the others? For earth and other EPC relay cables? Cat6 signaling cables?
- I'll put it all in a DIN rail box and put it on the wall or on a stick I'll stick to the ground. I'll have a hook to hang the cable when not in use so I will save myself the hassle of unplugging, putting cable in trunk and having a hard time getting it to roll every Friday night after work. I suppose this will be all good too?
- If I'm not getting it wrong I can also in the future convert this box into a mobile one by connecting the MCB into the box, getting a male commando connector to the other end and adding a resistor selector to the IC input to change current right?
- Leaving the PP empty is OK I assume because this is a tethered setup? I remember reading this.
- For the free cable versions why do we need different 16-32-63A RCBO and contractors, tripling the cost? CP signals the max current and PP signals max current cable can take so the car doesn't pull more than that anyway. Why not just put the 63A RCBO and contactor?

Any advice is appreciated. I think this will be a lot of fun. Thanks in advance.
 

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I'm not an electrician, but here's my pennyworth: why have 16/32/64A Rcbos etc? Cost. If you know your car can only ever max out at 16A charging, the other 32 or 64 A Rcbos will be more expensive. As they have to be able to handle bigger currents, they need bigger contacts, thicker wiring etc = more expensive.

Think about the earth line. If something in the car's socket shorts out, you could get 250V feeding straight into it. And if you have a 32A Rcbo, that could be 32A for a few milisecs. So this should probably be a substantial wire, not just some Cat5 gauge thing. I recently blew up a Mainpine 32A ECU when my car socket failed. I think the Mainpines need extra circuitry to protect against 250V being fed back up the CP line! I have some ideas as to what might work, but haven't yet bought the bits to test this.
 

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Discussion Starter #4
I'm not an electrician, but here's my pennyworth: why have 16/32/64A Rcbos etc? Cost. If you know your car can only ever max out at 16A charging, the other 32 or 64 A Rcbos will be more expensive. As they have to be able to handle bigger currents, they need bigger contacts, thicker wiring etc = more expensive.
Thanks for chiming in. With the different current contactors and rcbos that wasn't what I'm asking per se. Say you want the "station" to have the ability to deliver max possible current(for others to charge too) which is 63A. Wiring diagram of Mainpine/Viridian suggest you use all 16-32-63 contactors and rcbos. What I'm saying though is just using the max equipment would make using less possible too.

As for earthing, maybe I could connect earth to 0V at EPC too for extra cp protection? I remember seeing a case like that.

Do you see anything wrong with the wiring? For relay cables to contactor coil and rcbo live what type of wire should be used?

Final question; it looks like it would be fairly easy and cheap to design a microcontroller signaling pilot in accordance IEC61851/J1772 protocols for an ee engineer. What keeps every one of them from starting a business? Where's the added value of evse/network companies?
 

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I'm hoping someone more qualified will chip in soon! For your wires from Mainpine ECU to operate the contactor coil, you need to know what current the contactor draws. But this will be small, maybe 1A? Maybe 4A? So simply use an offcut of the high-current stuff you have for free. Any wires carrying 64A obviously needs to be rated for that current.

An extra earth to 0V isn't going to protect Mainpine. Assume you feed 250V back down CP wire. Like my car did. ECU expects ±12V on that wire. 250 destroys it. Period.

Final qn, why doesn't every Tom, Dick & Harry make these ECUs? Why bother? Mainpine have already done it. At £75 there isn't a huge profit; There's noticeable cost in simply generating -12 as well as +12 V, etc. Viridian already know their ECUs need more short circuit protection and I would not be surprised to see it designed in soon.
 

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The reason why Viridian have an example showing multiple MCBs is because the max current signalled from the EVSE to the car is entirely down to the car to honour, and they're erring on the side of caution. EVSE advertises 16A, for instance, and the rather over-engineered example makes sure that the vehicle doesn't draw more than that, even if 32A is actually available on the upstream cabllng.
I don't think I've seen a single commercially produced EVSE with quite that level of safety checks.
 

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Discussion Starter #7
So they basically trust the car to function properly and don't undertake any liability on car's part. Makes sense. Beats me why Viridian over engineers it.

Getting back to my wiring diagram, everything seem OK right? I've done my research properly? I'm still not sure which wiring to use besides the 6mm high voltage wiring. For which ones do I have to use CAT6 signaling cables and for which I would just do with a 0,75mm regular TTR cable?
 

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So they basically trust the car to function properly and don't undertake any liability on car's part. Makes sense. Beats me why Viridian over engineers it.

Getting back to my wiring diagram, everything seem OK right? I've done my research properly? I'm still not sure which wiring to use besides the 6mm high voltage wiring. For which ones do I have to use CAT6 signaling cables and for which I would just do with a 0,75mm regular TTR cable?
The Viridian EPC requires the 0V connection to be connected to protective Earth as shown in their example schematic. It forms the return path for the pilot signal. I know this because mine did not work until I connected it.
 

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Discussion Starter #9
The Viridian EPC requires the 0V connection to be connected to protective Earth as shown in their example schematic. It forms the return path for the pilot signal. I know this because mine did not work until I connected it.
Do you mean the DIN rail mount earth block terminal they used at the EVSE Build Day video?

If I want to use seperate LED bulbs I need to also wire it into 0V. So do I parallel it with earth?
 

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Do you mean the DIN rail mount earth block terminal they used at the EVSE Build Day video?

If I want to use seperate LED bulbs I need to also wire it into 0V. So do I parallel it with earth?
It should be as shown in Section 5.2 if the Viridian EPC manual. The common wires of the LEDS and the 0V terminal of the EPC all connection to the Earth terminal block.

I also should have said in my last post that you have left out the resistor connection between 0V and the IC terminal of the EPC. This resistor determines the current signalled to the car over the pilot signal. The values of resistor to use are listed in the table on page 7 of the manual. The table assumes a single phase supply. For a Zoe you want a peak charge rate of 22kW which is 32A per phase. So you need a 732 ohm resistor.
 

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Discussion Starter #11
It should be as shown in Section 5.2 if the Viridian EPC manual. The common wires of the LEDS and the 0V terminal of the EPC all connection to the Earth terminal block.

I also should have said in my last post that you have left out the resistor connection between 0V and the IC terminal of the EPC. This resistor determines the current signalled to the car over the pilot signal. The values of resistor to use are listed in the table on page 7 of the manual. The table assumes a single phase supply. For a Zoe you want a peak charge rate of 22kW which is 32A per phase. So you need a 732 ohm resistor.
I thought leaving the 0V-IC empty meant max the controller can give, i.e. 32A for the tethered one I'm going to purchase. I thought the IC was to tune it down be it a fixed resistor or a potentiometer for mobile solutions. So I definitely need a resistor?
 

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The reason why Viridian have an example showing multiple MCBs is because the max current signalled from the EVSE to the car is entirely down to the car to honour, and they're erring on the side of caution. EVSE advertises 16A, for instance, and the rather over-engineered example makes sure that the vehicle doesn't draw more than that, even if 32A is actually available on the upstream cabllng.
I don't think I've seen a single commercially produced EVSE with quite that level of safety checks.
Note that there's also the consideration of providing fault protection for the cable itself (ie. in case the cable gets damaged and shorts out - you want a breaker to open before the cable catches fire).

IMO, relying on the car to draw no more than it is told by the pilot signal is OK - the car's charger is already a safety-critical component, with access to plenty of energy (from the battery) to cause trouble if it malfunctions.

So whether or not overcurrent protection is needed in the EVSE is mainly about protecting the cable. I believe Viridian's approach with multiple MCBs/contactors is probably over-cautious in the case of a 32A unit (a 32A breaker will probably clear faults on the sizes of cable likely to be used for 16A), but is probably juistified if you are going to build a unit with 63A output capability. Note that most commercial 63A units have tethered cables rather than sockets, quite possibly for this reason.

Concerning the other issues in @Emir 's build:
  1. The protective conductor (earth) in the main cable MUST be of substantial size - it needs to handle hundreds of amps in a fault condition until the breaker opens. For practical purposes, it should be the same size as the phase conductors (you could theoretically calculate a slightly smaller size, but probably can't find a cable with cores like that). So you should have that 6mm² green/yellow core in your flexible cable going to the earth block in your EVSE and a similar substantial connection from that earth block to the earth of the fixed wiring installation. You can then have a smaller wire from the earth block to the earth terminal on the Viridian unit. Your earth block might be a DIN-rail terminal or a separate earth block built in to the enclosure you are using.
  2. The CP core in the cable is only carrying a few milliamps, so does not need to be large for current-carrying reasons - 0.75mm² is normally specified for mechanical strength. Cat5 wire would work, but is not really ideal, and if you do it that way DO NOT put a parallel earth wire in the 'data' cable. The signaling over the CP wire is intended to prove that the safety earth is connected, by passing a small current around the loop Controller->CP wire ->car -> main earth wire in cable -> Earth block -> earth terminal on Controller. So if you put a parallel thin wire that would defeat the safety check that is trying to ensure the main earth is intact.
  3. Do you have suitable equipment for crimping the terminals on the Type2 connector? It is possible to buy Type 2 connectors with a length of suitable cable (5 cores 6mm² plus 1 core 0.75mm²), and I'd strongly recommend that as an alternative to crimping your own connector onto a make-shift cable. Quality of those crimps is critical for this application where it's going to draw 32A continuously for hours.
  4. Leaving the PP open isn't right for any configuration. If this is tethered (which I think you were proposing to do), then there needs to be a resistor CP->Earth (normally done inside the connector) - the car uses this to detect the plug being removed from the socket during charging, hence the name "Proximity pilot". If you are building a socketed EVSE to use with a loose cable, you need the appropriate version of the Viridian controller and the controller must sense the resistor that the cable connects to the PP pin.
 

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I thought leaving the 0V-IC empty meant max the controller can give, i.e. 32A for the tethered one I'm going to purchase. I thought the IC was to tune it down be it a fixed resistor or a potentiometer for mobile solutions. So I definitely need a resistor?
Yes you are correct. An open circuit on IC will limit the EPC to its peak design rating which is limited by firmware.

I would echo the comments made by @arg about the necessity for crimped connectors for all high current connections.
 

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Discussion Starter #15
Note that there's also the consideration of providing fault protection for the cable itself (ie. in case the cable gets damaged and shorts out - you want a breaker to open before the cable catches fire).

IMO, relying on the car to draw no more than it is told by the pilot signal is OK - the car's charger is already a safety-critical component, with access to plenty of energy (from the battery) to cause trouble if it malfunctions.

So whether or not overcurrent protection is needed in the EVSE is mainly about protecting the cable. I believe Viridian's approach with multiple MCBs/contactors is probably over-cautious in the case of a 32A unit (a 32A breaker will probably clear faults on the sizes of cable likely to be used for 16A), but is probably juistified if you are going to build a unit with 63A output capability. Note that most commercial 63A units have tethered cables rather than sockets, quite possibly for this reason.

Concerning the other issues in @Emir 's build:
  1. The protective conductor (earth) in the main cable MUST be of substantial size - it needs to handle hundreds of amps in a fault condition until the breaker opens. For practical purposes, it should be the same size as the phase conductors (you could theoretically calculate a slightly smaller size, but probably can't find a cable with cores like that). So you should have that 6mm² green/yellow core in your flexible cable going to the earth block in your EVSE and a similar substantial connection from that earth block to the earth of the fixed wiring installation. You can then have a smaller wire from the earth block to the earth terminal on the Viridian unit. Your earth block might be a DIN-rail terminal or a separate earth block built in to the enclosure you are using.
  2. The CP core in the cable is only carrying a few milliamps, so does not need to be large for current-carrying reasons - 0.75mm² is normally specified for mechanical strength. Cat5 wire would work, but is not really ideal, and if you do it that way DO NOT put a parallel earth wire in the 'data' cable. The signaling over the CP wire is intended to prove that the safety earth is connected, but passing a small current around the loop EVSE->CP wire ->car -> main earth wire in cable -> Earth block -> earth terminal on EVSE. So if you put a parallel thin wire that would defeat the safety check that is trying to ensure the main earth is intact.
  3. Do you have suitable equipment for crimping the terminals on the Type2 connector? It is possible to buy Type 2 connectors with a length of suitable cable (5 cores 6mm² plus 1 core 0.75mm²), and I'd strongly recommend that as an alternative to crimping your own connector onto a make-shift cable. Quality of those crimps is critical for this application where it's going to draw 32A continuously for hours.
  4. Leaving the PP open isn't right for any configuration. If this is tethered (which I think you were proposing to do), then there needs to be a resistor CP->Earth (normally done inside the connector) - the car uses this to detect the plug being removed from the socket during charging, hence the name "Proximity pilot". If you are building a socketed EVSE to use with a loose cable, you need the appropriate version of the Viridian controller and the controller must sense the resistor that the cable connects to the PP pin.
Thank you for your time and effort. I appreciate your feedback.

I've updated the wiring diagram taking into consideration your earth block terminal warning and I wanted to add a digital volt/amp metre to see the EVSE in action. (Inexperienced me assumed that shoving all three live wires through one current transformer would show me the total Amps. I have a feeling that is a wrong way to go and I need three phase meters or three different meters to get it done correctly. Did the drawing to tell what I have on my mind.


1) Noted. I'll use 6mm2 for all live, earth and neutral wiring. I'll only use 0,75mm with everything regarding the EPC except L, N and P1 which have connections to the 40A RCD.
2) Noted as well, thank you. Will just use 0,75mm. I'll use a 5G6mm2 cable, get a nice cable sleeve and put the 0,75mm2 + 5G6mm2 cables together from it to the car side connector.
3) Yes I will be crimping. If crimping is fine at the contactor side and RCD side it should be fine on the connector side too. Contactor and RCD will have sustained 32A passing through them as well.
4) I meant leaving the PP at the connector side unconnected. With the tethered EPC I'm buying there's no PP at the EPC side anyway. Right? PP pin's existance (PP-Earth resistance at the connector-car end) will signal the car not to move; proximity as you said. As far as I could learn, PP connection at the EVSE side signals the plugged in cable's (to the EVSE) max. current. Mine will be a tethered one like a petrol station anyway so no need. (Do regular charging cables have 5G6mm + 2G0,75mm for both PP and CP? Or is it pin's resistance doing the signaling as is my case, or am I getting this completely wrong?)

Thanks again for the feedback. This will be fun!
 

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You do not use any cat6 or twisted pair cable anywhere.

Just another note to use good quality cable (not solid core) - we use what is known as 'tri-rated' for anything carrying AC.

Sent from my SM-N9005 using Tapatalk
 

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DO NOT CONNECT THE PHASES TOGETHER AT THE VOLTMETER!!!

The ammeter won't read correctly if you run all three phases through the pickup. Measuring one phase will be close to what is going on in the other two. Or at least it should be. If you really want to measure all three, you need three meters or a 3-phase meter.
 

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  1. You do still need to do something about the PP. You have said that it's going to be a tethered cable, so presumably the T2 connector in your diagram is the one on the end of the tethered cable. The PP pin on the connector must be connected via a resistor to earth (often done on commercial cables by crimping one end of a standard 1/2 watt resistor in the earth pin alongside the earth core of the cable, then crimping the other end on its own to the PP pin.
  2. Sorry to keep going on about the crimping, but to get good quality results you really need a tool suited to the pin being crimped. I would not crimp a T2 connector myself, as none of the various crimp tools I have on hand are really suitable, and for just one connector it is cheaper to buy the connector and cable already assembled than to buy the right tool (or risk having to buy a 2nd connector if you botch the first one). If you are really sure your tool is OK then by all means go ahead, but this is by far the hardest part of what you are planning to do - and failure, apart from any safety implications, risks melting the inlet on the car too, which will probably be expensive to put right.
  3. I agree with the comments above about metering. If you put all three phase wires through the current sense coil, the meter should read close to zero (it will give exactly the same as if you put it round just the neutral). Measuring just one phase is probably enough to be useful.
 
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