My EV will only accept single phase charging at 6.6kW. At the 230V supply this will be nominally 32A depending on actual line voltage.

I have a three phase supply to my house and have just installed solar panels with a 3 phase 10kW inverter. This can supply up to 4kW per phase, so around 17A.

If I connect an EVSE to a single phase in the house everything is easy except it will only charge at 4kW using solar unless I let the charger pull additional power from the grid. Unfortunately the metering in this country will not net off exports on the other two phases against the import on the phase supplying the car.

I know enough about power supplies to say that it is not good idea to connect the three phases together to attempt to get more power because I'll get a loud bang as the breakers trip due to the 400V line to line voltage being shorted (and each phase being 120 degrees out of synch). <nervous laugh/>

However - conceptually (I'm not about to plug anything together) - I could use a hefty transformer and wire the primary (delta style) across two phases, and then use the secondary to power the EVSE. I'm thinking the step down ratio would be something like 400/230, and it would need to be able to handle the 6.6kW load ( so 16.5A on the primary and 29A on the secondary). Looks like something a transformer specialist would need to custom design.
Is there anything else I should be thinking of before I starting emailing transformer suppliers ?

 

What you are discussing is what is called an open delta.
It is feasible, and you will be using all three phases, but they will be unbalanced. One phase will consume 58% more current than the other two. I am quoting the value from memory, it could be different.

 

I've googled an open delta which appears to be different to what I've got in mind. My computer running my normal circuit drawing tools is out of action so I've attempted to sketch what I had in mind with an online tool.

I propose a transformer with a single primary winding connected from P1 to P3 (400V line to line). P2 is ignored for this, but is shown as a Wye circuit because that is how our houses are wired with the centre of the Wye providing the Neutral reference (which is also tied to Protective Earth at the main switchboard). The secondary winding is over the same core with whatever ratio is required to achieve the 230V output across the winding.
I can see an issue though - normally the EVSE would be connected between a single phase and the Neutral, so I assume the Neutral (equipotentially bonded to PE) here would be floating. Probably not a great idea, although the transformer would provide some protection i.e. if a user was touching a single EVSE wire and ground there would be no circuit. However if they touch both EVSE wires then it would appear as a normal load to the primary so no RCD or MCB protection would trip.
I'm getting the feeling this is not a great idea !

 

Don't all EVs have 3-phase inputs at 22kW? What sort of connector does it have?

 

Transformers are readily available. Your applicable electrical code will guide you through an acceptable installation.

 

Don't all EVs have 3-phase inputs at 22kW? What sort of connector does it have?

No, not all. This is a Nissan Leaf. Older models had a 3kW charger. More modern have 6.6kW. The connector is the IEC type 2 which has 5 AC power connectors and two signal wires. The five power connectors are PE, Neutral and Three phases but on this car only one is wired in. I think I saw on the interwebs that the 6.6kW basically had two circuits in parallel, but on the one phase. The car is still under warranty so I'm not about to open the PDM to have a "poke around". Even if I did, I'm not keen on altering the wiring in the car.

 

Transformers are readily available. Your applicable electrical code will guide you through an acceptable installation.

Thanks, I will have a chat to a local transformer designer. I'm guessing the $$ will be way in excess of any amount I am going to pay in extra power bills. I have ordered an Open EVSE charger which has an API that will allow me to limit how much power the charger pulls. I will just need to set a rule so that it stays within the limits of the inverter output.
There is also an RS485 connection on the inverter so I'll need to experiment to see if I can tell it that there is a bigger load on the phase the charger connects to, so it can bias output towards that phase.
And for the few times where I really need to get the battery recharged I'll need to import from the grid and pay their "tax"

 

There could be another choice,which would be a standard transformer from each phase supplying 2.2 Kw, and with transformer isolation putting all 3 DC sources together in series would be very straightforward. And the transformers could all be standard types, probably. It will work if there is a DC charging input on the car. Not the simplest scheme but possibly the cheapest. It might even be the most efficient.

 

There could be another choice,which would be a standard transformer from each phase supplying 2.2 Kw, and with transformer isolation putting all 3 DC sources together in series would be very straightforward. And the transformers could all be standard types, probably. It will work if there is a DC charging input on the car. Not the simplest scheme but possibly the cheapest. It might even be the most efficient.

Thanks Bill. I had wondered about that. The only hesitation I have is concocting something to handle/control the DC.
The car is fitted with a Chademo DC plug, which is capable of handling up to 50kW. Voltage is in the region of 400V d.c.
As well as the charging current there is a CAN bus connector with a complicated handshake via the protocol to ensure the contactors in the battery activate so the current can flow. It looks like their is also some proximity signalling.
As far as I can see there is no commercially available Chademo EVSE in a size suitable for a home installation. They all appear to be commercially sized for fast charging and so typically runs to tens of thousands of dollars. By way of contrast an AC EVSE typically costs around $1,000.
The only other thing I contemplated would be a modification to the on board charger so it could use more than a single phase. However this has even more complications, and as the vehicle is still under warranty is not a possibility.

 

My EV will only accept single phase charging at 6.6kW. At the 230V supply this will be nominally 32A depending on actual line voltage.

I have a three phase supply to my house and have just installed solar panels with a 3 phase 10kW inverter. This can supply up to 4kW per phase, so around 17A.

If I connect an EVSE to a single phase in the house everything is easy except it will only charge at 4kW using solar unless I let the charger pull additional power from the grid. Unfortunately the metering in this country will not net off exports on the other two phases against the import on the phase supplying the car.

I know enough about power supplies to say that it is not good idea to connect the three phases together to attempt to get more power because I'll get a loud bang as the breakers trip due to the 400V line to line voltage being shorted (and each phase being 120 degrees out of synch). <nervous laugh/>

However - conceptually (I'm not about to plug anything together) - I could use a hefty transformer and wire the primary (delta style) across two phases, and then use the secondary to power the EVSE. I'm thinking the step down ratio would be something like 400/230, and it would need to be able to handle the 6.6kW load ( so 16.5A on the primary and 29A on the secondary). Looks like something a transformer specialist would need to custom design.
Is there anything else I should be thinking of before I starting emailing transformer suppliers ?

Have you heard about the Scott Connection?
https://circuitglobe.com/scott-t-transformer-connection.html

 

At this point the question is: charge with DC or power the internal charger with AC?? But since it seems that an adequate AC supply is not available, that leaves charging with DC as the way to charge at the maximum rate. The big challenge will indeed be talking to the car controller to have it accept whatever charge your system can supply. Probably the vehicle warranty is the biggest challenge. And simulating the commercial charger handshake process.

 

The big challenge will indeed be talking to the car controller to have it accept whatever charge your system can supply.

The other thing is the physical Chademo plug, which is likely to be $$$ even if I can find an open source design for the actual EVSE side.

 

It may be possible to add a second charging connection port to the vehicle, although probably the "safety" regulators have done their best to make every portion of the wiring inaccessible. And it might even be that some small business sells charging-only connectors that don't include the rest of the connections

But somewhere near the on-board charger may be a suitable access point.

 

The Chademo protocol uses for the (fast) DC charging is not open source.
I did find this series of blog post interesting though
https://www.evcreate.com/chademo-fast-charging-in-diy/

It may be possible to add a second charging connection port to the vehicle, although probably the "safety" regulators have done their best to make every portion of the wiring inaccessible. And it might even be that some small business sells charging-only connectors that don't include the rest of the connections

In our jurisdiction cars are required to pass an annual inspection, so anything which is obviously bodged will mean a fail. I think a solution external to the car is the way to go.

 

I was not suggesting a cobbled together hay-wired installation. Not at all. And, of course, certainly some inspectors are unable to think, and only able to compare with standard.

 

It looks like others have been down this path. I found a thread in the My Nissan Leaf website exploring the idea of creating a small "low" power DC charger. If I wanted to limit the input to what my solar array can provide I can envisage a 10kW device.
https://mynissanleaf.com/threads/mini-qc-rapid-charger-rc-project-for-leaf-qc-port.13349/