Mythbuster- "Your EV will die if you are stuck on the Motorway"

Ok, we've all seen clickbait titles like this one in the usual daily rags. Those of us in the EV community know that if you are stuck on the motorway in traffic &/or cold weather, your car will NOT DIE in 5 mins leaving you to freeze to death. This week, sadly, I had the opportunity to test this. I thought I would share the experience with the community, especially for newcomers to the EV world who may have read such headlines and been worried.

I live on Anglesey, North Wales and my daily commute to Bangor is around 18 miles/ 25minutes. Early hours Thurs morning there was a traffic accident involving 2 lorries and 2 cars, closing Britannia Bridge completely ( the main A55 link to the mainland). Sadly one local person died in the crash and another was seriously injured.

I set out at my usual 7:30 am temp about 1degC at home battery around 96%. I hit the traffic jam at around 7:45 and remained in that until 11:45. It wasn't until an hour later I thought about recording the data so the following starts at 8:52.

Basic info:-
Car- MG5 LR
Configuration- in Normal with no eco settings, heating set at 20 degC Auto at all times.
Weather- Clear & dry temp remained at 3 degC for the rest of the day


8:52- 92%, 3dC


Traction Battery drawing typically 1-2 amps (mostly drawing 1 amp, but occasionally flickering 2/3a)


Status of Heating etc- just left it set at this the whole time stationary. Air was set to recirc mainly due to the old diesel Audi in front of me appearing to have been converted to coal burning- lovely plumes of blue/black smoke spewing out for everyone to enjoy!


10:16- Finally dropped 1%


10:55 burning through the battery! now at 90% (did move a third of a mile as well)


11:43 Another hour and we're at 89% and 4/10 of a mile further on. At this point they had opened the eastbound lane and we started to move.

Things learned from this?
If we assume a 1% loss per hour then I could have about 70 hours cozy sitting and still have around 20% / 30 ish miles to get me somewhere. Obviously if the weather was sub zero these figures would reduce. The point is, once the car is warm, it takes less energy to maintain a comfortable temp than keep heating and cooling.

Ironically, when I got to work at mid day, a collegue was talking to his daughter on the phone. She was still stuck in the traffic coming from Caernarfon in an ICE car. Her problem? Even though she was only a few miles from a petrol station she was worried she would have enough fuel to make it there and so was sat freezing with the engine off. Should get an EV- far more reliable!

One final note after sitting in the MG5 for near enough 8 hours (it took me 3 1/4 hours to get home via Bangor & Menai Bridge in the afternoon !)- I find it REALLY comfortable!

I hope you had the foresight to have a newspaper or good book to read? Did you play the radio? What effect does that have, I wonder?

Great post @Big Nige !.
I did see the report of the accident, very sad.
I live in North Wales, about 50 miles in the other direction from yourself.
Our ZS EV was purchased from the MG dealer on the island, about two years ago now.
I have noticed that the most amount of drain from the HV battery, is when the heater when it is first turn on.
As the cabin warms up, the demand is reduced, because you tend to adjust the heat demand and especially if you are standing still in traffic.
The use of heated seats ( if available ) makes a big difference over the use of the cabin heater.
The heated seats are a very low consumer of power from the 12 volt battery, where as the cabin heater is drawing juice from the traction battery.

bwanamdevu said:

I hope you had the foresight to have a newspaper or good book to read? Did you play the radio? What effect does that have, I wonder?

Click to expand...

Yes- I used the time to finally read the handbook ! And yes, the radio was on all the time- I’m fairly sure the ancillaries draw off the 12 v system. Also spent the time to learn about apple car play and listened to an audiobook off my phone.

Big Nige said:

Yes- I used the time to finally read the handbook ! And yes, the radio was on all the time- I’m fairly sure the ancillaries draw off the 12 v system. Also spent the time to learn about apple car play and listened to an audiobook off my phone.

Click to expand...

So quite a productive few hours then! Glad to read you spent the time wisely. Reading the handbook? How few of us ever do that except when we are stuck with something.

Lovemyev said:

Great post @Big Nige !.
I did see the report of the accident, very sad.
I live in North Wales, about 50 miles in the other direction from yourself.
Our ZS EV was purchased from the MG dealer on the island, about two years ago now.
I have noticed that the most amount of drain from the HV battery, is when the heater when it is first turn on.
As the cabin warms up, the demand is reduced, because you tend to adjust the heat demand and especially if you are standing still in traffic.
The use of heated seats ( if available ) makes a big difference over the use of the cabin heater.
The heated seats are a very low consumer of power from the 12 volt battery, where as the cabin heater is drawing juice from the traction battery.

Click to expand...

Yes it takes less energy to maintain a temperature than to heat up. The example I use to use in my surveyor days was a boiled kettle. Fill a jug kettle up, time how long it takes to boil, then 30 seconds later time it to boil again. You can apply the principal to home heating. Can’t remember the schoolboy physics & formulae now ( brain getting old).

Heated seats are great. Many years ago I had a Smart Fortwo with them and used them all the time. Very pleased to have them back in the MG5.

I spent 2 hours stuck on the M4 at 1C in the dark due to a jumper.

1% per hour was lost, the same.

Lots of abandoned ICE cars out of fuel on the hard shoulder!

And don't forget the thermite underwear.

Keeps you VERY toasty.

Lovemyev said:

Great post @Big Nige !.
I did see the report of the accident, very sad.
I live in North Wales, about 50 miles in the other direction from yourself.
Our ZS EV was purchased from the MG dealer on the island, about two years ago now.
I have noticed that the most amount of drain from the HV battery, is when the heater when it is first turn on.
As the cabin warms up, the demand is reduced, because you tend to adjust the heat demand and especially if you are standing still in traffic.
The use of heated seats ( if available ) makes a big difference over the use of the cabin heater.
The heated seats are a very low consumer of power from the 12 volt battery, where as the cabin heater is drawing juice from the traction battery.

Click to expand...

Yes bt the traction battery will need to top up the 12v….

I was stuck in a jam for several hours recently (posted elsewhere) and my experience was pretty much the same. In my case it was cold, wet and dark so the load also included wipers and lighting. Cabin temperature was also set to 20 Deg C. My energy consumption was around 1%/hour (Standard Range car).

StEvnut said:

Yes bt the traction battery will need to top up the 12v….

Click to expand...

Agreed, but the traction battery is only charging the 12 volt battery at around 14.5 volts ( same as an alternator in a ICE car ) this demand is significantly less than the demand required for the electric cabin heater.
The demand to run the heated seats and keep the 12 volt battery charged, will only reduce the range on the GOM by around 1 - 2 miles.
The cabin heater will pull around 10miles plus, from the range on he GOM.
It is extremely greedy beast .
A/C in the summer a LITTLE less so.