AC charge rate slowly decreases to 1kw

[TheMDawg]

I picked up a new MG4 Trophy Long Range on Saturday. Setup a charging schedule Saturday evening for the Octopus cheap rate window, woke up Sunday with the battery only charged less than 10%.

I’ve noticed a charge starts pulling 6.6kW but over the first 10 minutes of the charge this steadily decreases to 1.4kW (which would be 6amps). I’ve made sure the setting in the car is set to maximum current available so my hunch is fault with the car, is this common?

My home charger is an Andersen A2 (which granted is a piece of junk) that was installed 2020 and charges my other EV fine at 7kW.

 

[Martinonline]

I'm afraid more information is required.

a. Was the schedule set on the charge and/or the car?
b. What was the start level of the car's charge and what level was it set to reach?
c. Is charging successful with the granny charger?
d. Have you tried a public AC charger?

 

[TheMDawg]

a. Was the schedule set on the charge and/or the car?

Schedule was 23:30-05:30 and set on the car.

b. What was the start level of the car's charge and what level was it set to reach?

I can't remember the exact SOC but it was around 45% and reached around 55%. Limit is set at 80%. The rate shouldn't be getting throttled at that level of SOC.

c. Is charging successful with the granny charger?

Not tried with the granny cable.

d. Have you tried a public AC charger?

I haven't. I don't think there are any tethered AC chargers near me and unfortunately the dealer 'forgot' to put the Type 2 cable in the car (I've to pick it up this weekend). I'll have access to one this evening so I can try a public charger or try charge at a friends house.

As I say it starts fine but over the course of 10 minutes the charge rate dwindles down to around 1kW and stays there. If I stop charging and start again it goes back up and repeats.

 

[siteguru]

A 7kW charge point shouldn't get rate-limited at all (to any great degree) - even as you approach 100% SOC. The only "rate-limiting" that should happen is when balancing occurs.

 

[TheMDawg]

A 7kW charge point shouldn't get rate-limited at all (to any great degree) - even as you approach 100% SOC. The only "rate-limiting" that should happen is when balancing occurs.

Yeah, which makes me think its unfortunately a car fault. The Andersen A2 I have charges my other EV at 7kW. Nothing in my house draws a huge current (no electric showers, oven hasn't been on) so the charger isnt going to be balancing any load from the house. I don't have solar or batteries either to complicate matters.

Will try it on a public charger tonight.

 

[siteguru]

You need to try a public Type 2 (AC) charge point. (Just to be clear - trying a DC rapid charger won't prove anything).

 

[AndyL61]

Because your EVSE charges your other EV ok then it must be either a fault or a setting on the car . You need to confirm by using another 7kw AC EVSE , if it still behaves the same it's a trip to the dealership, then a wait while they confirm what you've told them , then another wait for MG to confirm a warranty claim , then another wait for any parts required.

 

[siteguru]

Good point re. setting. @TheMDawg have you looked under the battery tile in the car and checked what charge current is set in the car? (Mine is set for Maximum Current, but lower levels can be set).

 

[PeteC]

Good point re. setting. @TheMDawg have you looked under the battery tile in the car and checked what charge current is set in the car? (Mine is set for Maximum Current, but lower levels can be set).

@TheMDawg says so in his post, so not that!

I’ve made sure the setting in the car is set to maximum current available

 

[GrayCat]

Check the temperature of your Mains Plug (and socket). Modern EVSE's have T°-sensor in the plug, and shut off or lower current if it's heating.

 

[DBedford]

I was just going to say check for any hotspots on your leads/ plugs.

 

[TheMDawg]

A whopping 1.1kW on a local PodPoint charger. Must be a problem with the car

 

[benflugel]

This AC charging problem seems to be getting more common.

 

[Rolfe]

I'm getting suspicious that every single one of the phase 1 NMC-battery cars is going to get this.

 

[TheMDawg]

This is a brand new 24 plate picked up Saturday. I have the rear wiper, body colour roof and centre headrest.

 

[Rolfe]

Mmm. Maybe it's something else then. With a car that new, you really need to go back to the dealer ASAP.

 

[pecker]

This is a brand new 24 plate picked up Saturday. I have the rear wiper, body colour roof and centre headrest.

It’s simply not good enough, have you spoken to your dealer

 

[fnegroni]

One thing to note:
You are AC charging at 4C outside temp.
If the battery pack is cold, the battery heater might have kicked in to avoid damaging the battery.
The charge rate being displayed shows what goes in the battery, which is the difference between what is being supplied (6.5kW) and what is consumed by the battery heater and other accessories.
You seem to have the HVAC on and judging by the time of day, possibly the lights too.
So that’s 300W + 3kW for the battery heater + 0.5 to 1.5 kW for the A/C plus 0.5 to 3kW for the PTC heater.
6.5kW minus between 4 and 7kW.
I’m not saying that this is definitely the problem, but whenever charging on a type 2 charger you must take that into account.
To make matters worse, the type 2 cable you are using might be single phase or triple phase 16Amp cable.

 

[TheMDawg]

The cable and Andersen have charged my Model 3 fine and at these temperatures (or lower) no problem. I don’t think it’s realistic that overnight it drops to 1kW and never goes back up at all.

I’ve spoken to the dealer but they won’t have a courtesy car available until Tuesday next week. It is the Easter weekend to be fair.

 

[fnegroni]

The cable and Andersen have charged my Model 3 fine and at these temperatures (or lower) no problem. I don’t think it’s realistic that overnight it drops to 1kW and never goes back up at all.

I’ve spoken to the dealer but they won’t have a courtesy car available until Tuesday next week. It is the Easter weekend to be fair.

i was talking about the pod point charging session.
I didn’t know how long you had been charging for, and what cable you had been using.