Intermittent slow charge from home charger - MG5 SR

[Padaung]

Hi all,

I have a '21 plate MG5 SR. We have owned it from new.

Over the past 9 months, when using our home charger, we have experienced several very slow charges (2kW), when it was expected the car would charge at 7kW. This has meant we have had a car that hasn't charged enough for a return commute the following day.

The charger is an EO Mini Pro 2, purchased new and professionally installed by a local electrician who specialise in EV chargers.

An EO Charging support person has checked the data from our charger and has confirmed that the charger is offering the car a full 32amps (thus a 7kW charge rate) for the times we have had a slow charge.

1. The slow charge is intermittent, and relatively rare (it probably occurs around twice times a month). We cannot predict when it is going to happen.
2. On one occasion I was still awake at 12.30 when the overnight charge started. I saw that it was charging slowly (our smart meter showed 2kW) so I stopped the charge, waited a few minutes and then resumed the charge - it then charged at 7kW. The car was not unplugged in-between the two charge attempts, nor was the cable moved in any way.

Has anyone any thoughts on what could be happening and a possible solution?

When the car does under charge overnight it has often caused us a bit of a headache the following day.

Apologies if I've got any of the technical amp/kWh terminology wrong, I hope the meaning of my message is still clear.

Edit to clarify:
We use Octopus Go, which isn't an intelligent tariff from my understanding. It just offers us four hours of electricity overnight at a cheaper rate.

In addition to this, we never had this problem for the first two and half years using the same car, charger and electricity tariff.

 

[SimonomiS]

Are you on an intelligent tariff that might be remotely adjusting these charging rates itself?

 

[Padaung]

Are you on an intelligent tariff

Sorry, forgot to add this info.

We use Octopus Go, which isn't an intelligent tariff from my understanding. It just offers us four hours of electricity overnight at a cheaper rate.

In addition to this, we never had this problem for the first two and half years using the same car, charger and electricity tariff.

I've just added this info to my original post.

 

[MickeySw]

Sorry, forgot to add this info.

We use Octopus Go, which isn't an intelligent tariff from my understanding. It just offers us four hours of electricity overnight at a cheaper rate.

In addition to this, we never had this problem for the first two and half years using the same car, charger and electricity tariff.

I've just added this info to my original post.

That’s a strange one indeed, hard to differentiate which side is causing the problem especially with the low frequency this is happening, in an ideal world you would bring it to the dealer for investigation right after the issue occurs so they can look at the log files, but in reality that’s unlikely to happen given the experience of other owners.

So let’s look at the other end, a faulty load sensing circuit of the wall box could reduce the charge power, if you only plug in overnight it would be safe to disconnect the CT clamp temporarily and wait a month..

 

[5teep]

Might it be corrosion in the charge port on the car messing with communication? The only way to find out for sure is to get a garage to look at it while charging I suppose.

 

[Coulomb]

Apologies if I've got any of the technical amp/kWh terminology wrong,

I've corrected your post; charge rate is in kW, not kWh. kWh is for the energy that ends up in your battery over time (hence the h for hours).

As for your problem, try charging at a public AC charger; there you should get the full 6.6 kW if the problem is not your car.

If that works as expected, there may be an intermittent problem with your EVSE ("charger"). For example, the switch that selects the maximum current might be loose or corroded or faulty. It could even be the small resistor in the cable; the car judges the current capability of the cable by a resistor between the proximity pilot pin and earth. You can even measure this (with the power off of course) using a multimeter; for a 32 A cable it should be 220 Ω. The required pins are centre and north east, looking at the plug in the usual position:

 

[mailmannz]

I’m finding Octopus a bit hit and miss these days. Sometimes the charge will complete to schedule but far too often the charge will have stopped early for no apparent reason

 

[Lewis49]

I noticed my car had failed to start a charge late one night. I tried a different lead and it connected.
Next morning I tried my normal lead again but it still didn't charge on that. I tested the lead for both continuity and insulation resistance and it checked out OK. Next I opened the plugs on both ends and found condensation in both. Wiped them dry and left in the sun for a couple of hours, reassembled and it worked. Its been OK now for the last three months.