AC charging loss

[MSvirus]

I have been charging in the cold these days. Efficiency goes down in the charging process as it gets colder, and is poor this time of year, with all the way down to 35% loss when it is really cold. For ok winter charging temps the loss on my IM6 is about 25%. So I tried a test with charging my MG4 in the same conditions too. Then I got 20% loss. So there is 5% more loss in the IM6 than my MG4. Is that due to the higher voltage? Or what can cause this? Should not newer cars be more efficient? And the result is not a one time off, it can be repeated and is stable.

On my car, I noticed too that the app is showing totally the wrong time for charging finishing time. Slow charging yesterday, it said finish at 1400 today. Same charging speed, and charged continually it now shows after midnight, and still climbing when I update the page. My MG4 has not this problem in the app, as that is almost accurate.

 

[T1 Terry]

Is the car inside out of the freezing weather? It might be warming the battery while charging it. If the slow charge is anything like the Aussie one, it draws 6 amps from the mains @ 230vac = 1380w. I believe the MG4 has a 10 to 15% loss just through the charging section, so say 140w, that now leaves 1240w to power the battery heater as well as charge the battery.
This means, every time the heater turns on, or the 12v battery is topped up, less that 1240w is available for battery charging, that is why the end charge time keeps climbing.
Faster charging like 10 amps or even 15 amps will be far more efficient, 15 amps @ 230vac = 3450w, less 10% =3,105w as opposed to 1240w using a 6 amp mains charger.

T1 Terry

 

[MSvirus]

My MG4 in summer is at the best with around 17% loss at 9,7A from grid, so about 300W of the 2230W, as about 1900W is entering the battery. In winter at about -5 to -10C, with the car stationary in that temperature over time, the loss is around 20%. Even worse if there is -25C, but that is not that often.

I have not tested IM6 charging (100 kWh version) in the summer yet. But when both cars have same cool down period, and is in the same temperature environment, the IM6 has a bigger loss than that, every time I check up the charging speed. Maybe the bigger battery (100 vs 64) needs to draw more power to be kept in an ok temperature then.

About the finishing time, it is nearly two hours since I wrote the initial post, and then it said some minutes over midnight to be finished. Now is says 0215. So two hours have passed, and two hours have been added to the finishing time. And it has charged at 1,6 kW on a 9,7A charger. That is about 600W loss. But the time added is 100% of the charging time the last two hours. It doesn't add up, as the percentage has risen accordingly to what is expected on 1,6 kW. The MG4 doesn't do this even in the cold.

 

[T1 Terry]

Is the 1.6kw measured at the charger or car's infotainment screen?
Or poverty pack MG4 51 takes about 3 days to charge from 5% to 100% with 6 amps set on the charger, over night set on 15 amps. The one time I used the 7kw AC charger where you need your own lead, the charger claimed it was feeding the full 7kW, but the car screen said 6.6kw, so only 400w was lost using the fastest AC charger input the MG4 could handle.
Under 1hr from 5% to 95% on a DC fast charger, but the charge rate is slowing at around that point, so no real value in hanging around waiting for the 100% to roll up

T1 Terry

 

[MSvirus]

That 1,6 kW is reported by the car, as into the battery, same time as I measured 2,23 kW from the grid, if my measuring devices is correctly calibrated

 

[T1 Terry]

Fair enough, that battery heater must draw quite a bit of power, but then, it does have a lot of heating to do keep the cells above 0*C .... I'm not sure what temp MG consider the ultimate for battery charging

T1 Terry

 

[Everest]

So there is 5% more loss in the IM6 than my MG4. Is that due to the higher voltage? Or what can cause this? Should not newer cars be more efficient? And the result is not a one time off, it can be repeated and is stable.

It has a bigger battery, so more metal to heat up and hence more powerful heaters, would be my best guess.

That 1,6 kW is reported by the car, as into the battery, same time as I measured 2,23 kW from the grid, if my measuring devices is correctly calibrated

That's a low charge rate, so not surprising losses are a big %. As T1 said, charge at a faster rate so the fixed rate losses become a lower % of the overall charge losses.