MG4 V2L earth rod, TT system

Have some questions about earth rod, earthing and TT system when using MG4, V2L to power house. I’m using similar setup as Stageshoot (125 amp changer over switch, 10mm SWA to from C/O switch to a converted type 2 lead with 470 ohm resistor) … Any feedback would be much appreciated.

* Our home earthing is TN. Does the V2L earth rod, new TT system for MG4 connect to existing TN earthing or should earth Rod be connected separately? I have read conflicting comments on the V2L earthing.

• The type 2 lead we have converted has 470 ohm resistor connected to PP and PE pins. The CP pin/wire was/is not connected in our lead. Is this correct?

• Has anyone had any issues with car tripping. And if so what was the cause? Our MG4 has been tripping after short periods, and even when under low load of under 1000 watts.

Car, V2L is showing a power output of around 217 volt.

I noticed that the in car discharge screen constantly shows 17 hours of discharging time remaining. That is when the car battery is charged to 100%, which seems low when load is between 500w -1000w. Has anyone had same issue?

Stageshoot had posted helpful information which was pretty detailed on his installation, is there any other source anyone can direct me to which is more recent and that details installation.

Many thanks in advance for any feedback

Rick

I think the discharge is based on maximum rating of the V2L connection (vs whatever minimum % SoC you've set in the car).

As to your earthing queries ... perhaps @Ayoull may be able to offer some suggestions.

rick1942 said:

Our home earthing is TN. Does the V2L earth rod, new TT system for MG4 connect to existing TN earthing or should earth Rod be connected separately? I have read conflicting comments on the V2L earthing.

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You have to ensure that your TT earth is completely separate from the DNO earthing and most not press any potential onto a DNO earth without the DNOs express permission.

V2L is not designed to drive a full house and offers no protection afforded by true V2G systems.

You must under the electricity act, esqcr and ENA G88 ensure that any generation set (which the car is in this instance) does not pose a risk to anyone working on or around the DNO network, you can not pollute or distort another users supply at the point of common coupling on the DNO network inline with ENA EREC P2/9.

Basically you need to undertake a complete earthing study of your installation and submit to you DNO for permission to utilise the arrangement and confirm that it's safe, and not likely to kill anyone working on the DNO network.

Or the DNO reserves the statutory right to disconnect your service from the grid under the ESQCR and electricity act.

At NPg where I work V2G is not permitted on the network there were pilots done but the results lead to the senior engineers to decide the current implementations weren't viable or safe for the network.

And NPg don't permit islanding of generators unless that are solely for backup purposes and disconnect on restoration of supply once synchronized.

Edit: worth adding this is why G98, G99 and G100 exist to provide standards that generator systems that are intended to be connected to the grid, and ensure they work in a safe manner

rick1942 said:

• Has anyone had any issues with car tripping. And if so what was the cause? Our MG4 has been tripping after short periods, and even when under low load of under 1000 watts.

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The bidirectional onboard charger is officially only rated for 2.2kW on V2L, and that is assuming unity power factor, what you'll find is as soon as you start adding reactive loads in a house basically electronics chargers the power factor goes pretty bad.

In my home the power factor is around 0.6pf due to mobile phone chargers, laptop charger, a couple of raspberry pi's, flat screen TVs and a set top boxes.

So in my house 2.2kW would actually be 3.66kVA which a DNO grade transformer all the way through to a super grid transformer will happily take all day long.

So in your scenario 1kW draw and the car uses 200-300w just being turned on and running it's 12v systems means you're doing between 2kVA and 2.16kVA which is towards to upper limit of the official V2L rating wouldn't surprise me if they can restrict it in firmware and newer cars are limited.

siteguru said:

I think the discharge is based on maximum rating of the V2L connection (vs whatever minimum % SoC you've set in the car).

As to your earthing queries ... perhaps @Ayoull may be able to offer some suggestions.

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Thank you so much for the response

Thank you so much for the response

Ayoull said:

The bidirectional onboard charger is officially only rated for 2.2kW on V2L, and that is assuming unity power factor, what you'll find is as soon as you start adding reactive loads in a house basically electronics chargers the power factor goes pretty bad.

In my home the power factor is around 0.6pf due to mobile phone chargers, laptop charger, a couple of raspberry pi's, flat screen TVs and a set top boxes.

So in my house 2.2kW would actually be 3.66kVA which a DNO grade transformer all the way through to a super grid transformer will happily take all day long.

So in your scenario 1kW draw and the car uses 200-300w just being turned on and running it's 12v systems means you're doing between 2kVA and 2.16kVA which is towards to upper limit of the official V2L rating wouldn't surprise me if they can restrict it in firmware and newer cars are limited.

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Hey man, great info. What if I link it up to my 'off grid' solar system.

Basically I connect an auto change over switch and it switches between grid and car into the solar inverter which then feeds the house.

Before the car, the grid would 'take over' after my battery would be drained. Now I wanted to use the car battery to keep my home battery topped up as much as can be. So it would not be linked directly to the house load..

Several points in addition to the above:

Just because the 470 ohms resistor delivers more kilowatts than the stock 2000 ohm V2L cable doesn’t mean you should use it.

I expect that V2L use is recorded in the car’s software event log. A claim against the warranty for a blown inverter when the vehicle log shows the use of non-standard V2L cable may well be denied.

The MG4 does not like the “neutral” being grounded. The only way round this problem is the use of an isolation transformer so that the side towards the car is floating and the side toward the house can have a neutral to earth bond. Your idea of using the car via a PV system might work. Some PV multipoint trackers have miltiple input to support more than one string of panels.

This input obviously needs DC so you would need a power supply of some sort to convert the AC from the car.

Alternatively you might simply power a charger connected to your home PV battery.

But asking questions about earthing here is an indication that you shouldn’t be doing V2H.

Sorry if that sounds condescending but as pointed out above livening up the feed from your house back into the DNO’s network is a real risk, a danger to both life and property.

So limited V2L to cover power cuts where the individual appliances are connected directly to the V2L cable is safe enough.

Running a battery charger via the V2L cable to top off your PV system storage should be safe enough.

Powerer a sub main to portions of your house via an approved change over system with an isolating transformer may be OK depending on the specifics which you will not be able to glean from forum opinions (including mine). For that you should consult either the DNO or a licensed electrician.

I can confirm that the V2L voltage is 217V.

The isolation transformer is not a safety thing, the suggestion is simply to stop the MG4 from tripping.

This thread may be of interest: V2L Earthing - how?