Will my car be damaged if I do this?

[Simboid]

Hi, I'm getting an MG5ev delivered in a few weeks and I was considering charging options. I don't drive very far for work so will only really need to charge once every two weeks ish over a weekend.

I'm lucky enough for my house to have solar panels and I'm techy enough to be thinking of constructing a system to switch on and off a 13A socket when my solar output current reaches certain thresholds (A cheap Zappi if you will). Therefore I will be able to plug in the granny charger at the weekend and charging should be mostly free (weather and time of year dependant)

My question for you good people is am I likely to cause damage to my car if the system switches power on and off randomly (say a few times an hour if its cloudy) ?


Has any one tried something like this?

Thanks

Simboid

 

[Jomarkh]

The granny only pulls 2.2kw could you not just set the timer for strong daylight hours?

 

[smokie]

This was discussed on another forum I used to use and it wasn't thought to be damaging.

Your problem is likely to be much more rapid switching than you expect, particularly if you have it set to go on over a set value and off under that value. You need to a bit of a buffer to stop constant switching when your output is borderline.

Also ( - and I suspect you've thought of this from the wording of your post) some of the cheaper switches may not be man enough for sustained high throughput so ideally you'd use your technology to drive a contactor which would actually do the switching. For instance I think the older Sonoff sockets (S20, S26) are rated at 10A but you can find pics online where they've caught fire - maybe by being overworked - but better safe than sorry.

EDIT to say that you won't get a lot from the granny though, my notes say about 7 miles per hour, so you'll probably need to find another source too.

 

[Simboid]

I Plan to use an adjustable current sensor so I can fettle the current levels.

My plan is to see how I get along with the idea and to fit a bypass switch for overnight charging if I need it.


If that is not enough I will look into a 7Kw

 

[weedavemac]

I Plan to use an adjustable current sensor so I can fettle the current levels.

My plan is to see how I get along with the idea and to fit a bypass switch for overnight charging if I need it.


If that is not enough I will look into a 7Kw

The bypass switch for overnight charging should be more than enough for the limited driving that you are expecting to do.

Enjoy the car.

 

[smokie]

You're not using Home Assistant are you? I can see my solar output (I think 30 sec delay) in that and cause all manner of actions based on the value (and other factors if required). I've not bothered using it though as my excess generation is soaked up by an iBoost anyway, and I already use the 7kW charger overnight to charge.

 

[BugEyed]

If you turn off the 13A socket mid charge you risk both the car and the charge point. The on board charger on any car has massive inductance and will send back a significant voltage spike if you do this. Replacement will run into £k and the logs on the ECU will record how often it's been done.
To achieve what you want you need to arrange to interrupt the Control Pilot and Earth that via a resistor.

Edit: Don't forget that solar in the UK fluctuates significantly due to clouds, so turning on and off every five minutes would not be unusual. Proper solar charge points offer a mode where they have a minimum low level of 1.4kW from the mains where required and use as much solar as possible.

 

[Deep purple]

I have PV too plus I have economy seven overnight (not the really cheap EV tariff, just the standard one) so I pay about 20p for 7 hours off peak and 30p on peak.
Assuming the granny charger takes about 2.2KW (based on experience) then I charge the car whenever the PV output gets above about 1.3 KW, This is on the basis that I am getting 2.2 KWhr for about 42p (buying 1.4 KWhr @ 30p allowing about 0.5 KW for household base load) which is therefore the breakeven point between charging using PV rather than off peak. which would cost 44p for 2.2 KWhr
Sorry the sums are a bit convoluted.
My main challenge is my control of charging is manual and other people in the house see it is sunny and use the washing machine. Even a Dyson mains vacuum is an issue as they take 1.6KW.
The best solution is to have PV with battery storage and a smart charger, but that doesn't come cheap.
In the 2 months I have had the car I never had to pay for a charge except on my overnight cheap rate.

 

[smokie]

If you turn off the 13A socket mid charge you risk both the car and the charge point. The on board charger on any car has massive inductance and will send back a significant voltage spike if you do this. Replacement will run into £k and the logs on the ECU will record how often it's been done.
To achieve what you want you need to arrange to interrupt the Control Pilot and Earth that via a resistor.

Edit: Don't forget that solar in the UK fluctuates significantly due to clouds, so turning on and off every five minutes would not be unusual. Proper solar charge points offer a mode where they have a minimum low level of 1.4kW from the mains where required and use as much solar as possible.

How would you turn off a charge on a socket other than abruptly?

 

[m4rmite]

Diodes should stop any reverse travel if designed within electrical items

 

[BugEyed]

How would you turn off a charge on a socket other than abruptly?

Via the car by unlocking it.

Edit, to be fair the manual doesn't expressly mention the switch on the 13A socket but is clear that you end the charge by unlocking the car.

Residential Charging
Your vehicle will have been supplied with a residential charging device. This device can be plugged into a standard household 3 pin socket. During the charging operation the vehicle power system must be OFF. Carry out the following procedure to charge the car using the charger supplied with the vehicle:
1 Ensure vehicle power system is OFF and all doors are closed.
2 Open the charging port door, remove the waterproof plug cover from the 7 pin charging plug connector. Ensure the surroundings are clean, dry and free from debris.
3 Connect the 7 pin charging plug to the socket on the vehicle.
4 Connect the charging device 3pin plug to the domestic electricity supply. Lock the vehicle.
5 On completion of the charge unlock the vehicle, disconnect the charging cable from the vehicle, and then the domestic plug.

 

[smokie]

You live and learn

 

[MarkLynn]

I charge with a granny charger all the time when at home or work, I only ever use 7kw or rapid chargers if on a trip or if they are free when shopping. This works for me as I have solar system with a battery storage. The battery storage negates the issue with having to turn off the charger when the sun goes in. I'm not sure of the effect of turning the charger on and off, would be interesting to know how you get on with this.

 

[BugEyed]

The battery storage negates the issue with having to turn off the charger when the sun goes in.

An ideal situation. But my inverter "only" manages 3.5kW so any load in addition to the 2.3kW of a granny and my summer baseload of 0.6kW (don't ask) might result in import which I'm stupidly obsessed about avoiding. But by luck and before I had solar I got a cheap Chinese charge point that handles solar well.

 

[amackayj]

I have solar panels and a 3.6 KW inverter. I looked at the Solar Edge inverter with built in EV charger which works a bit like the Solar iboost hot water system (detects when you are exporting and diverts it to the car) but opted for the cheaper Solis inverter, as I didn't have an EV at the time.

Slightly regretting that decision now that I have an EV. I'm using a smart plug to time the granny charger so that it's on at the time of day when the panels are likely to be producing over 2kw and I can switch the granny on and off with the app if it's cloudy or if there is something else which needs power. It's a bit manual, but does the job.

 

[amackayj]

I have solar panels and a 3.6 KW inverter. I looked at the Solar Edge inverter with built in EV charger which works a bit like the Solar iboost hot water system (detects when you are exporting and diverts it to the car) but opted for the cheaper Solis inverter, as I didn't have an EV at the time. Slightly regretting that decision now that I have an EV. I'm using a smart plug to time the granny charger so that it's on when the panels are producing over 2kw. It's a bit manual, but does the job.

I can see what my PV system is generating on an android app and can switch the granny on and off via another app, so what I'd really like is an app which can read the PV output and switch the smart plug off when the PV output drops below a threshold.

If I can find someone to develop this app, then would there be any interest here?

You'd need an inverter which broadcasts it's output via WiFi and an outdoor WiFi three pin socket.

 

[BugEyed]

Dragging the thread back to its title, switching power to a charge point on and off will likely lead to damage to the charge point and the car. If you build your own integration make sure that you follow the standards and signal to the car via the Control Pilot line to interrupt the charge - that's the intended way for this to be done.

 

[amackayj]

Hasn't done mine any harm so far. I'll let you all know if it does!

 

[johnd973]

We have solar and battery storage and do most of our home charging with the granny charger when we produce excess power.

We have a CT sensor on the meter cable and a sensor on the house battery. When we start putting power back to the grid the outdoor socket which the granny Charger is plugged into is switched on by a raspberry pi, its then switched back off if the house battery falls below 70% or the time gets to 30mins before sunset. This stops the constant switching you might otherwise get. I did try switching the charger off based on a light sensor but this caused constant switching whenever a cloud passed overhead.

Doesn't seem to do the car any harm at all and I wouldn't think small occasional charges would otherwise the regen when driving would damage the battery wouldn't it!

 

[amackayj]

That's a very clever system. We didn't go for battery storage because we dump excess energy in hot water and after charging two cars (the MG and a Mitsubishi Outlander PHEV) there wasn't going to be enough going into battery storage to justify the cost... We exported about 100kwh per month before we got the MG, I suspect that is going to decrease dramatically!

Would you mind sharing a link to or details of your pi system? If it provides a way to stop the car charging when the draw from the grid exceeds a threshold and if there's a way to set a limit between switches (to give the car time to settle down), then I'd be interested in giving it a go!