Optimal cruising speed

[Neilio]

Apologies for the noob question but, having never had an EV, does the M3 have an optimal cruise speed for battery efficiency?

I ask because on ICE cars it's always at a low-ish speed in top gear. I worked out my current car returns best MPG at about 55mph in 9th gear.

Wondering if the M3 (and all EVs) has such an optimal cruise speed or, due to the nature of the power delivery and single gear is it just a case of faster is worse for the battery?

 

[oneonorder]

pretty much faster is worse is my experience.

that said you’ll find yourself tracking the trip view graph and when you realise you have charge to spare to get to your destination you’ll drive faster.

overall it’s worse if you drive with a lot of hard accelerations. much like your 9spd.

 

[Neilio]

pretty much faster is worse is my experience.

that said you’ll find yourself tracking the trip view graph and when you realise you have charge to spare to get to your destination you’ll drive faster.

overall it’s worse if you drive with a lot of hard accelerations. much like your 9spd.

Yeah I think it's true of all cars that having hard acceleration makes the economy worse, I was more thinking of cruise speeds on long trips. I thought it might be a case of faster is worse.

And you're absolutely correct, If I'm going to have plenty of charge spare at my destination on a long trip, it'll be acceleration mode out of chill and right foot to the floor!

 

[MrBadger]

Various charts and info here - Model 3 Consumption and Charging although some info may be a little dated

 

[Jason71]

Yeah I think it's true of all cars that having hard acceleration makes the economy worse, I was more thinking of cruise speeds on long trips. I thought it might be a case of faster is worse.

And you're absolutely correct, If I'm going to have plenty of charge spare at my destination on a long trip, it'll be acceleration mode out of chill and right foot to the floor!

There are no gears so there are no magic sweet spots. Faster is worse, and its a squared relationship so every MPH faster uses more energy than the last one.

 

[tsh2]

There are no gears so there are no magic sweet spots. Faster is worse, and its a squared relationship so every MPH faster uses more energy than the last one.

Not entirely true. There is a constant 'CPU on' cost, so somewhere below 10 or 20 mph, more energy goes into compute than traction. Worse if you also have AC or heating.

 

[Neilio]

Thanks guys, I mean, I'm still going to floor it everywhere but it's good to know what I need to do to conserve energy if needs be!

 

[NorfolkMustard]

Click on the energy graph and you’ll see the instant energy usage and how that compares to the normal line which equates to about 250wh/mile I think.

 

[Lickrob]

For long distance driving (specifically motorway driving) the car will tell you to slow down if it calculates you won't make it to the next SuperCharger at your current speed.

 

[Jason71]

Not entirely true. There is a constant 'CPU on' cost, so somewhere below 10 or 20 mph, more energy goes into compute than traction. Worse if you also have AC or heating.

OK you got me . But the question was about "cruise speed" and I don't think 10-20 mph qualifies so within the reasonable bounds of the question that was being asked I stand by my answer.

 

[Jason71]

For long distance driving (specifically motorway driving) the car will tell you to slow down if it calculates you won't make it to the next SuperCharger at your current speed.

Which would be a lot more useful if the system had way points since often my programmed destination is not my final destination where I will be able to charge.

 

[Adopado]

Apologies for the noob question but, having never had an EV, does the M3 have an optimal cruise speed for battery efficiency?

...and you could also take a different angle on optimal i.e. what speed should you travel at from point A to point B on a long trip (that is going to include supercharging) to ensure the shortest overall journey time. Even though you go through the battery charge at a much higher rate at high speeds it turns out (I believe) that so long as you have the Superchargers available it can be "faster is better" because the longer time spent charging is shorter than the time you lose by driving slowly. I imagine that it will be very "trip dependent" because of Supercharger spacing and perhaps being able to miss a charge stop completely by hitting the speed sweetspot. (This also doesn't include the time speaking with the nice police officer at the side of the road.)

 

[Neilio]

...and you could also take a different angle on optimal i.e. what speed should you travel at from point A to point B on a long trip (that is going to include supercharging) to ensure the shortest overall journey time. Even though you go through the battery charge at a much higher rate at high speeds it turns out (I believe) that so long as you have the Superchargers available it can be "faster is better" because the longer time spent charging is shorter than the time you lose by driving slowly. I imagine that it will be very "trip dependent" because of Supercharger spacing and perhaps being able to miss a charge stop completely by hitting the speed sweetspot. (This also doesn't include the time speaking with the nice police officer at the side of the road.)

That's a good point too. Thanks for that. I actually enjoy planing road trips so supercharger stops will just be another part of it. TBH I don't mind a long, say 40 minute, charge at a supercharger because on any trip over 4 hours (such as my one to my family) I'll always stop for food and drink anyway.

Oh and It'll never be over 70 mph of course (Unless I need a wee, in which case all bets are off)

 

[Dilly]

For long distance driving (specifically motorway driving) the car will tell you to slow down if it calculates you won't make it to the next SuperCharger at your current speed.

The car won’t get to tell me before the wife does!

 

[GT_M3]

...and you could also take a different angle on optimal i.e. what speed should you travel at from point A to point B on a long trip (that is going to include supercharging) to ensure the shortest overall journey time. Even though you go through the battery charge at a much higher rate at high speeds it turns out (I believe) that so long as you have the Superchargers available it can be "faster is better" because the longer time spent charging is shorter than the time you lose by driving slowly. I imagine that it will be very "trip dependent" because of Supercharger spacing and perhaps being able to miss a charge stop completely by hitting the speed sweetspot. (This also doesn't include the time speaking with the nice police officer at the side of the road.)

Agree. Play with A Better Route planner for a while and try different speed settings. I had a 280 mile trip and at 110% speed it took slightly less time overall than at 100% to reach the destination even though it needed more supercharging. Then setting the max speed to 60mph dropped one whole supercharger stop, but actually added 30 mins to the overall time taken. Of course if you have to wait to use a supercharger any time saving could be lost by doing the 'sprint and charge' option and of course it helps if there are superchargers conveniently en-route.

My takeaway was that there was no point in artificially limiting the speed to 60mph to get better efficiency and range, and being a bit of a hazard on the road, but to just drive with the flow of traffic. Normally roadworks and slow traffic restrict the speed anyway.

The only other thing to mention was that I was not brave enough to follow the departure charge % to the letter. If a BRP said to leave with 70% charge but I was still getting a reasonable charge rate at that percentage I'd probably sit for longer and leave at 80-85% to have a bigger buffer. Not optimal in terms of time but better for any range anxiety.

 

[Adopado]

If a BRP said to leave with 70% charge but I was still getting a reasonable charge rate at that percentage I'd probably sit for longer and leave at 80-85% to have a bigger buffer. Not optimal in terms of time but better for any range anxiety.

Yes, definitely that ... a bit of extra buffer is always nice ...