MG4 trickle charging

[WonkoTheSaneUK]

You have to tap on "Maximum Current" on the battery screen and select your desired current.
See around 30 seconds into the video below

 

[Rolfe]

In principle 8A should give you about 1,8 to 2kW.
Is there something else that could drain current during the charge (heater, battery heater, etc)?

That's exactly what I get - maximum I've seen is 1.88 Kw. Just using the supplied lead and a 13A socket without changing any settings.

 

[fnegroni]

The OP is in New Zealand.
The first picture shows a car with no HVAC running and 19C outside temperature.
An mg4 draws around 300W at rest when switched on (and dipped beam headlamps off)
Even assuming a limit of 8Amp on the granny charger for whatever reason (idk, NZ regulations?) and a 220v supply,
Times 0.85 because efficiency, and minus 300W because the car is switched on, should still charge at around 1.2kW
But it looks even lower than that.

 

[edcquintana]

You mean they tested the other showroom mg4 with your granny charger?
If so, and both are only getting 1.1kW, it seems to me either your granny charger is defective, or incorrectly set to a lower amp rating.
What is the granny charger normative in your country? In the UK it’s 10amp, giving a draw of around 2.2 kW and supplying the battery with around 1.8 to 1.9 kW.
It seems yours is configured for 6amp draw which would show 1.1kW in the car accounting for losses.

That's right. They also tested both cars on a wall charger they had at their showroom and they got similar input, somewhere around 4.8kWh. I mean the MG service fella was nice and all but I'm not too sure he knew much about this subject, since he pretty much told me all MG4 would have the same limitations and what people have reported here is quite different.

 

[edcquintana]

The OP is in New Zealand.
The first picture shows a car with no HVAC running and 19C outside temperature.
An mg4 draws around 300W at rest when switched on (and dipped beam headlamps off)
Even assuming a limit of 8Amp on the granny charger for whatever reason (idk, NZ regulations?) and a 220v supply,
Times 0.85 because efficiency, and minus 300W because the car is switched on, should still charge at around 1.2kW
But it looks even lower than that.

I don’t think it would be NZ regulation as a mate of mine owns a Kia EV6 and his granny charger is rated at 10A - with his cable I was able to get 1.3kWh by the way.

In any case here are some other photos, of my car setup (it’s currently max current and intelligent battery heating off) and the cable MG provided.

 

[siteguru]

You really should get out of the car and lock it, and check any charging rate via the app. That'll rule out any losses caused by the car being powered on.

 

[edcquintana]

You really should get out of the car and lock it, and check any charging rate via the app. That'll rule out any losses caused by the car being powered on.

I've always gotten different readings on the app. For example if the car screen displays 1kWh, the app instead would show 1.3kWh at the same time - that is with me in the car, car obviously unlocked etc.

Now that the car is locked I just checked the app and it shows 1.3kWh. Is that normal?

 

[Headgas1]

Mine is charging right now @1.9 kWh as we speak yours @edcquintana does sound really low but I don’t know how it works in NZ

 

[fnegroni]

I've always gotten different readings on the app. For example if the car screen displays 1kWh, the app instead would show 1.3kWh at the same time - that is with me in the car, car obviously unlocked etc.

Now that the car is locked I just checked the app and it shows 1.3kWh. Is that normal?

Still a little low tbh. Should be more like 1.5 at 8A which makes me think somehow yours is 6A

 

[fnegroni]

I don’t think it would be NZ regulation as a mate of mine owns a Kia EV6 and his granny charger is rated at 10A - with his cable I was able to get 1.3kWh by the way.

In any case here are some other photos, of my car setup (it’s currently max current and intelligent battery heating off) and the cable MG provided.

The photo shows your granny is 8A, maybe you’re friends isn’t an official one but off eBay Amazon.

 

[edcquintana]

Still a little low tbh. Should be more like 1.5 at 8A which makes me think somehow yours is 6A

Sounds like it's low indeed. I'm pretty convinced there's something wrong with the car as it's not just trickle charging. That's probably the most pressing one to me as I do it everyday, but even if I go to DC charging stations, I never get the full input. For example 25kW charger, I get 20kW, likewise 50kW charger, I get 44kW.

Sad thing is taking the car to the dealer did nothing so I guess I'm stuck with a slow charging car ha!

 

[ozzz]

Hi all,

Has anyone been able to get more than 1kW when using the granny charger? I’ve tested multiple different power outlets and couldn’t get more than that. Convinced there was something wrong, I took the car to the dealer and they tested my car against another brand new MG4 and that also came back with 1.1kW. Seems awfully low?

For context I have the MG4 51kWh.

Thanks

Hi I charge at 1.3-1.4 kW all day and every day and during day time it would be using my solar system 6kW.

 

[tsedge]

Sounds like it's low indeed. I'm pretty convinced there's something wrong with the car as it's not just trickle charging. That's probably the most pressing one to me as I do it everyday, but even if I go to DC charging stations, I never get the full input. For example 25kWh charger, I get 20kWh, likewise 50kWh charger, I get 44kWh.

It is normal not to get the full output due to rounding and losses. So long as you are getting close to it - as you are on your DC figures - that should be fine.

 

[VAG]

Sounds like it's low indeed. I'm pretty convinced there's something wrong with the car as it's not just trickle charging. That's probably the most pressing one to me as I do it everyday, but even if I go to DC charging stations, I never get the full input. For example 25kWh charger, I get 20kWh, likewise 50kWh charger, I get 44kWh.

Sad thing is taking the car to the dealer did nothing so I guess I'm stuck with a slow charging car ha!

Another thing to consider is that these chargers are not always providing the maximum power of what they announce.
It is frequent that a 50kW charger gives quite lower from this and 44kW that you get doesn't seems exceptional.

 

[Corindikev]

None of this is rocket science. You should plug the charger in to a socket that is capable of delivering 10 amps. Most are but if you can get that tested then you will know.

The granny charger supplied by MG is rated at 8 Amps.

The nominal voltage in NZ is 230 Volts.

Volts multiplied by Amps equals watts. This means 230 x 8 = 1840 Watts or 1.84 kiloWatts. There will be losses from heat and resistance (Ohms) but I won't go in to that.

The IEC standard allows for AC voltage to fluctuate between plus 10% and minus 6% of standard so voltage can be as high as 253 volts or as low as 216 volts at 50 hertz.

At 253 volts maximum power delivery will be 2.024 kiloWatts
At 216 volts maximum power delivery will be 1.718 kiloWatts

I have only ever used my granny charge once and that was to test that it worked when I bought the car so I didn't check its output to the car. You will get somewhat less than the values above due to losses I mentioned.

My car is on charge at the moment from my 7kW CJBeny wall charger. It is consuming 7.1 kW (current voltage is 237 volts) and the car is reporting 6.59 kW at its internal charger.

 

[tsedge]

All good points - also consider resistive losses are a higher percentage with granny chargers due to the small diameter cable.

The lower the charge rate, the higher the percentage losses.

 

[Coulomb]

even if I go to DC charging stations, I never get the full input. For example 25kW charger, I get 20kW, likewise 50kW charger, I get 44kW.

That's probably the case with many vehicles. DC chargers have three separate limits, for total power, maximum voltage, and maximum current. The voltage is set by your battery's present voltage; the DC charger has no control over that.

A 50 kW charger for example might be rated for 120 A max, 500 V max, and 50,000 W max (so you can't have 120 A at 500 V, you are limited to 50,000 / 500 = 100 A so as not to exceed the power limit).

Most vehicles have a nominal 400 V battery, which might be at say 367 V when at a low SoC. Now the current limit kicks in; you can only get 367 x 120 = 44,040 W or 44 kW.

The upshot is that you almost never can get full nameplate power from a DC charger.

So this isn't part of your slow charging problem; your slow charging is something to do with the On Board Charger or associated equipment, or maybe your EVSE (AC "charger") or cable.

 

[Buster72]

All good points - also consider resistive losses are a higher percentage with granny chargers due to the small diameter cable.

The lower the charge rate, the higher the percentage losses.

Exactly. The losses are heat.

 

[fnegroni]

Exactly. The losses are heat.

Still doesn’t add up. 2.2kW (220v x 10 amps) at 85% efficiency makes 1.87kW which is what we see in UK.
In NZ they are limited by the 10amp plug to 8A charging, x220v at 85% efficiency makes 1.5 kW not 1.1 or 1.2
1.1 or 1.2 would be an 8A supply and the car switched on with no heater or dipped beam (~300W).

 

[Corindikev]

The granny charger is rated at 8 amps not 10 amps so its maximum at the nominal 230 volts is 1.84 kW so assuming 85% efficiency it is 1.56 kW.