Battery usage on highway

[khurram]

Hey! I recently got a MG HS PHEV -- the older shape not the 2025 one in UK. Fairly happy with in terms of the electric / petrol usage. I recently got to take it on a longer trip (400 km one way) at constant 120km/h. I drove the car on hybrid mode for the most part for the first 1500km and charged it every third day or so. I would typically get about 4L/100km in the city.

On this longer trip I again drove the car in hybrid mode. I remember getting on the highway with the batter at 80%. The drive throughout was at around 120km/h. The charging mode was set to default (not high or medium). What I expected was that the car would gradually use the battery and eventually it would be depleted. That's what other people had mentioned in this forum as well. The usage graphic agreed with this and showed both the engine and the motor driving the wheels. Only sometimes did it change to the state where the engine was shown to charge the battery when I had to brake or there was a gradual downhill section. I got off the motorway after about 400km with the battery at 90%! The petrol usage came out at about 7.5L/100km which is decent for a car of this size plus I had gained 10% on the battery. This was very weird for me since I expected the battery to be used and the petrol usage to possibly be around 6L/100km had it been used.

The drive back was similar. I ended up using the battery in the city at my destination. When I got on the motorway I was at about 20% and it was at 25% by the time I got off. The petrol usage was again around 7.5L/100km. Has anyone else experienced this? Could it be because while I was on the motorway I was constantly around 120 km/h and at no time I was under 90km/h ??

While I can live with this, I would have preferred if the battery was used on the motorway and I could have just recharged at my destination which would have made the trip more efficient possibly bringing down the petrol usage to 6L/100km. I do understand that PHEVs are not the most efficient on longer drives -- just wanna understand this behavior and confirm that other people have observed something similar. Cheers!

 

[ronmaz]

This is normal. Even in default mode the battery will very slowly charge if you are driving constantly regardless of speed and not in stop-start traffic. You can see this if you switch to the hybrid screen while driving, you will see the amps go into negative values that means charge is going back into the battery. It's very slow in default mode as you've noticed, only about 5% for every hour of driving approximately.

If you want all the battery to be used by the time you get to your destination then simply switch to EV mode for the last part of the trip. e.g. if you know you are 20kms from your destination, and the car says you have 20-ish km range of electric left, then simply switch to EV mode by pressing the EV button. You don't have to stop the car to do that, it can be done while driving.

 

[khurram]

I see -- so essentially that means that the motor is not really driving the wheels at constant high speeds? And that the battery just gets charged sometimes whenever the load on the engine is less due to slight downhill or braking conditions?

And yes that EV option is always there towards the end of the trip. I was just a little surprised because I would have expected the motor to contribute a little towards driving the wheels and eventually the battery being depleted.

 

[New to MG]

Hey! I recently got a MG HS PHEV -- the older shape not the 2025 one in UK. Fairly happy with in terms of the electric / petrol usage. I recently got to take it on a longer trip (400 km one way) at constant 120km/h. I drove the car on hybrid mode for the most part for the first 1500km and charged it every third day or so. I would typically get about 4L/100km in the city.

On this longer trip I again drove the car in hybrid mode. I remember getting on the highway with the batter at 80%. The drive throughout was at around 120km/h. The charging mode was set to default (not high or medium). What I expected was that the car would gradually use the battery and eventually it would be depleted. That's what other people had mentioned in this forum as well. The usage graphic agreed with this and showed both the engine and the motor driving the wheels. Only sometimes did it change to the state where the engine was shown to charge the battery when I had to brake or there was a gradual downhill section. I got off the motorway after about 400km with the battery at 90%! The petrol usage came out at about 7.5L/100km which is decent for a car of this size plus I had gained 10% on the battery. This was very weird for me since I expected the battery to be used and the petrol usage to possibly be around 6L/100km had it been used.

The drive back was similar. I ended up using the battery in the city at my destination. When I got on the motorway I was at about 20% and it was at 25% by the time I got off. The petrol usage was again around 7.5L/100km. Has anyone else experienced this? Could it be because while I was on the motorway I was constantly around 120 km/h and at no time I was under 90km/h ??

While I can live with this, I would have preferred if the battery was used on the motorway and I could have just recharged at my destination which would have made the trip more efficient possibly bringing down the petrol usage to 6L/100km. I do understand that PHEVs are not the most efficient on longer drives -- just wanna understand this behavior and confirm that other people have observed something similar. Cheers!

Hello Khurram,
I did find that surprising, as you did.
I have the MY23 MG HS + EV (PHEV) in Sydney. My figures suggest these for 'hybrid' driving [referred to as 'Auto' in this car].

On Motorways / Freeways outside Sydney

• The 16.6 kWh battery depletes @2.1 kWh per 100 km of travel.
• The full battery charge starts at a reading of 62-63 km (for EV only driving), drops by 1 for every 13 km, to drop down to 2-3 km reading after about 780 km of travel in hybrid (“auto”) mode. So, the fully charged 16.6 kWh battery should be almost fully consumed after about 780 km of travel on MOTORWAYS in hybrid mode.
• My average travel speed on motorways in NSW : 105 kph.
• The petrol consumption on this long motorway drive in hybrid (“auto”) mode is around 6 L per 100 km of travel.
  

On Urban A & B roads

• The 16.6 kWh battery depletes @6.5 kWh per 100 km of travel.
• The full battery charge starts at 62-63 km reading (for EV only driving), drops by 1 for every 4 km travelled, to drop down to 2-3 km reading after about 245 km of travel in hybrid (“auto”) mode. The fully charged 16.6 kWh battery (if not recharged), would be almost fully consumed after about 245 km of travel on URBAN 'A' and ‘B’ roads in hybrid mode.
• Average travel speed : 37 kph
• The petrol consumption on these longer drives on Urban ‘A' and 'B’ roads is around 5.5 L per 100 km. A lot of the low speeds, slowdowns, traffic lights, round abouts etc is done on the HV battery, with little petrol use.

 

[khurram]

Hello Khurram,
I did find that surprising, as you did.
I have the MY23 MG HS + EV (PHEV) in Sydney. My figures suggest these for 'hybrid' driving [referred to as 'Auto' in this car].

On Motorways / Freeways outside Sydney

• The 16.6 kWh battery depletes @2.1 kWh per 100 km of travel.
• The full battery charge starts at a reading of 62-63 km (for EV only driving), drops by 1 for every 13 km, to drop down to 2-3 km reading after about 780 km of travel in hybrid (“auto”) mode. So, the fully charged 16.6 kWh battery should be almost fully consumed after about 780 km of travel on MOTORWAYS in hybrid mode.
• My average travel speed on motorways in NSW : 105 kph.
• The petrol consumption on this long motorway drive in hybrid (“auto”) mode is around 6 L per 100 km of travel.

On Urban A & B roads

• The 16.6 kWh battery depletes @6.5 kWh per 100 km of travel.
• The full battery charge starts at 62-63 km reading (for EV only driving), drops by 1 for every 4 km travelled, to drop down to 2-3 km reading after about 245 km of travel in hybrid (“auto”) mode. The fully charged 16.6 kWh battery (if not recharged), would be almost fully consumed after about 245 km of travel on URBAN 'A' and ‘B’ roads in hybrid mode.
• Average travel speed : 37 kph
• The petrol consumption on these longer drives on Urban ‘A' and 'B’ roads is around 5.5 L per 100 km. A lot of the low speeds, slowdowns, traffic lights, round abouts etc is done on the HV battery, with little petrol use.

Hello! I remember reading a similar response earlier -- it was probably yours. That's exactly why I thought that the battery will deplete gradually as I keep on driving. Very different observations between you and me. Maybe other people can chime in.

Anyways it is what it is. I will be going on another trip in a few weeks. Will post here if the car behaves differently this time around.

 

[New to MG]

Hello! I remember reading a similar response earlier -- it was probably yours. That's exactly why I thought that the battery will deplete gradually as I keep on driving. Very different observations between you and me. Maybe other people can chime in.

Anyways it is what it is. I will be going on another trip in a few weeks. Will post here if the car behaves differently this time around.

Hi Khurram,
BATTERY
On your next long trip it would be good if you could "stage" readings a bit like this when driving in 'auto' / hybrid.

• After 0 km of travel on motorway battery reading _ _ km (at entry point of motorway). _ _ %.
• After 100 km of travel on motorway battery reading _ _ km. _ _ %.
• After 200 km of travel on motorway battery reading _ _ km. _ _ %.
• After 300 km of travel on motorway battery reading _ _ km. _ _ %.

Show the km rather than the %. Or both.
PETROL
Would also be interested to see what you get as petrol consumption __ L per 100km : after a 200 or 300 km on the motorway. Would be a good idea to stop, park, and 'reset' the reading for current journey JUST BEFORE entering the motorway.