[Dmitri]

On my way back from DC, encountered a heavy rain for 600 miles. Kept the same driving stile as on the way to DC, the car was about 300 lbs. lighter.
On average the consumption dropped almost 1 mile per kWh. (280 miles to 180 miles of range)

1800 miles Road Trip in i4 | BMW i4 Forum (i4talk.com)

Interesting if anyone have a similar experience?
Any difference during heavy rain on eDrive 40 vs M50?

 

[Mark287]

I have had a similar experience with an M50. Highway speeds and heavy rain drops my efficiency way more than cold weather.

 

[thev]

Yeah, I noticed the same. I feel it makes sense as water is heavier than air, so thousands of droplets hitting the car will tend to slow it down and increase the drag it has to overcome. Also, energy loss due to wet roads. I haven't driven through a lot of storms but when I did I observed an "up to" 50% decrease in efficiency.

It made me wonder whether rain was less impactful with my old ICE car... or was it simply that I wasn't so bothered to obsessively monitor efficiency on a trip-by-trip basis.

 

[Grawyl]

The loss of range does make sense while driving in the rain due to the mass of the rain hitting the car and increased rolling resistance due to the tires having to push the water on the road out of the way. What doesn't make sense is the scale of the reduction in range. 30%+ seems extreme and I've never notices anything close to this in an IC vehicle.

 

[ashley1960]

I did notice the difference driving in the rain with an ice car of about 10%, I think maybe ignoring cold weather and heavy wind and faster driving, the effect of just the rain would be around 10%, cold weather may be another 10% on it’s own and driving at 80 instead of 60 may be 25% plus wind etc. Adding everything up you could go from 200 miles with all these things to 300 miles on a warm day no wind dry roads at slower speeds, everything added up would be a big range penalty, excess speed the worst of all. Also I find that my car starts to be most economical after the first 50 miles of a long journey I have not found pre conditioning that much of an advantage myself.

 

[cruzer666]

On my 3 day 1100 miles road trip I drove during heavy rain most of the time. The efficiency dropped from 3.5 to 3.1 miles/kWh. However, it was also cold and I had passenger and luggage which I normally do not have when I get 3.5.

I would say an effective drop of 5-10% due to heavy rain. The main reason for decrease in efficiency is increase in rolling resistance due to the car pushing through water.

 

[Grawyl]

On my 3 day 1100 miles road trip I drove during heavy rain most of the time. The efficiency dropped from 3.5 to 3.1 miles/kWh. However, it was also cold and I had passenger and luggage which I normally do not have when I get 3.5.

I would say an effective drop of 5-10% due to heavy rain. The main reason for decrease in efficiency is increase in rolling resistance due to the car pushing through water.

12% decrease in range due to rain makes sense. A 36% decrease due to rain seems very excessive unless other factors are at play.

 

[Dmitri]

I have had a similar experience with an M50. Highway speeds and heavy rain drops my efficiency way more than cold weather.

Highway speeds and cold weather had a minor impact on my range (10%)
Rain (30%)

 

[Dmitri]

The loss of range does make sense while driving in the rain due to the mass of the rain hitting the car and increased rolling resistance due to the tires having to push the water on the road out of the way. What doesn't make sense is the scale of the reduction in range. 30%+ seems extreme and I've never notices anything close to this in an IC vehicle.

I was driving through a storm. The rain was so heavy, that most of the traffic had to slow down or pull over. The vipers were engaging at the max speed at all times. I kept the constant speed at 75mph.
I assume, that a similar condition cause a less effect on a more powerful car.

 

[BMWdav]

12% decrease in range due to rain makes sense. A 36% decrease due to rain seems very excessive unless other factors are at play.

I think 30%+ seems reasonable from some rough math if there is heavy rain, it increases the rolling resistance and the drag by a lot it seems.

 

[thev]

I think 30%+ seems reasonable from some rough math if there is heavy rain, it increases the rolling resistance and the drag by a lot it seems.

Yes, it definitely seems reasonable. I mean, we already know the cold has a 10-20% effect on range because cold air is denser and harder to push through than warm air (and it's not because of heating the cabin in winter).

And you know what's even denser and even harder to push through than cold air? Water.

 

[BMWdav]

Yes, it definitely seems reasonable. I mean, we already know the cold has a 10-20% effect on range because cold air is denser and harder to push through than warm air (and it's not because of heating the cabin in winter).

And you know what's even denser and even harder to push through than cold air? Water.

Yeah, although it seems to be hard to find any sure figures on just how much it does increase.

The figures I found for rolling resistance was that just the water on the road would easily be able to account for around 40% higher rolling resistance, so if rolling resistance stood for 30-40% of the total energy required to keep the car at speed (which would be the case at say 75-85 mph in a car with low drag) before the rain that alone is an increase of 12-16% of the total.

 

[J_P]

I assume, that a similar condition cause a less effect on a more powerful car.

Not really. It is all to do with accelerating the mass of water to the speed of the car. When a raindrop hits a car it is travelling at a horizontal speed of 0 MPH, the car has to accelerate the drop to the speed of the car - it is in effect pushing the raindrop. In a really heavy rainstorm that is a big weight that you are having to accelerate to your speed and of course that is a constant force you have to apply because there is always new rain coming down that is travelling at 0mph until you car hits it. Many years ago, I had a Physics exercise that was about calculating the additional force that was required to keep a car at a constant speed in rain.

A more powerful car would suffer the same effect. A less powerful car may not have enough reserves of power to do all this additional work and may slow down in really heavy rain.

 

[ashley1960]

Not really. It is all to do with accelerating the mass of water to the speed of the car. When a raindrop hits a car it is travelling at a horizontal speed of 0 MPH, the car has to accelerate the drop to the speed of the car - it is in effect pushing the raindrop. In a really heavy rainstorm that is a big weight that you are having to accelerate to your speed and of course that is a constant force you have to apply because there is always new rain coming down that is travelling at 0mph until you car hits it. Many years ago, I had a Physics exercise that was about calculating the additional force that was required to keep a car at a constant speed in rain.

A more powerful car would suffer the same effect. A less powerful car may not have enough reserves of power to do all this additional work and may slow down in really heavy rain.

Great answer, when you are driving in the rain you can physically feel the car being pulled back especially during heavier rain, driving through puddles, heavy winds make a big difference, if you are driving at 60 mph on a dry day against the wind at 20 mph it’s more or less like driving at 80, and when the wind is with you it would almost be like driving at 40 mph! It will be intesting driving in Summer in the dry comparing against what we are getting now. I am doing around 3.5 miles per kWh, but on short trips about 3.0, I am hoping in Summer to get 4.0 miles but will have to resist the temptation to drive faster when it’s safer, I can see me averaging about 10 mph faster so will probably end up with the same consumption as Winter!

All of us drive differently to each other, some say they can’t get 200 miles range, and others can get over 300 miles, it’s not our cars are different it’s about how we drive them, if I want good range I drive very carefully and very slowly, when I speed up the consumption fall dramatically, but then where is the fun at driving at 55 mph, I sometimes wish I could just drive a bit faster all the time but it’s now become a habit to see how far I can get and I now get scared at speeds I used to consider too slow. That’s when I know I have got old!

 

[BaronofGreymatter]

Our e40 msport averages 4.0 mi/kWh in good weather. Drops to ~3.5 with heavy rain or temps in the 30s F and as low as 3.0 with temps in the teens. Our longest typical drives are about 150 miles round trip, so even in winter we can make that and still keep the battery between 20-80%.