Driving with headlights off any advantage in certain sit?

[DeafSoundGuy]

MY former question about where does he headlights get their power from and the answer from a poster "the 12v battery for sure" still leaves me with the question of: Does it help to not have them on when you can get away from not having them on? (as stupid at it might be...)

I thought the 12volt battery for sure too, but was wondering when I made a 2-part experiment a few days ago. My estimated range was 31 miles, and it was going to be at least 80% all uphill, and I was going 30 miles (at night). The first part of the experiment was driving with the headlights off as much as I could and in EcoPro (not+). With the lights of the big city, and being in the slow lane behind a semi lets say where it doesn't matter if your headlights are on or not because you're in your space between 2 fixed speed (on the freeway) vehicles, it's pretty easy to not have them on with how bright the U-shaped LED running lights are. Or, when you're at long stop lights and also no reason to have headlights on too I only kicked them on when I was entering the freeway at at certain intersections. Even though I climbed the uphill route most of 15 miles, I was still able to beat the estimate by 3 miles indicated. So was it wacky i3 estimate that I seemed to get better range, or did the lights off mode help? It would seem like there would still be a alternator (or generator) powering the 12volt battery, so me thinks that there might lurk the possibility that if the alt/gen isn't putting recharge current into the 12v system, then there would be the possibility of the juice instead going to the HV battery. Of course I could be totally high on this...

The return trip was mostly downhill and this time in comfort mode with little cabin heat and driven sensibly (tough). I couldn't make the same distance even driving downhill mostly and at grandpa speeds. Me wonders....

The other part of the experiment was "just how bright are those U-shaped headlights and are they good enough for visibility for non carrot challenged other drivers? Since those little guys are pretty bright and they alone illuminate road signs pretty good on their own at shorter distances, one would think that other drivers could see them pretty well....

So the (2nd) question was, a night of mostly headlight off driving on all sorts of streets and freeways - would I get flashed from other drivers that
"hey, your headlights are off moron"? I didn't get flashed once - an interesting (although maybe stupid) experiment.

 

[jadnashuanh]

While driving and while recharging, the 12vdc battery gets recharged from a DC-DC power supply in the car from the main batteries. The only time it isn't being recharged (or maintained, at least as I understand it) is while the car is off or not charging. So, since power is power, I guess it makes some sense that it would make a little difference in range, but not much, depending on the duration of your drive. Count in the visibility factor of having them on, and some areas require daylight running lights, and the safety factor would seem to override the very slight gain by not running them. The LED's are pretty efficient, and the daylight running lamps aren't all that power hungry.

 

[Jeffj]

The power consumption of LED 's is really low, on the order of single digit to low double digit watts. If you assumed 25 watts (which is probably high) then you would have to run your lights for 40 hours to consume a key of battery. So yes, using the lights will reduce range, but it's probably not measurable outside of a lab. The heater, on the other hand, probably consumes 20x or more times the power of the headlights.

 

[tiburonh]

MY former question about where does he headlights get their power from and the answer from a poster "the 12v battery for sure" still leaves me with the question of: Does it help to not have them on when you can get away from not having them on? (as stupid at it might be...)

I thought the 12volt battery for sure too, but was wondering when I made a 2-part experiment a few days ago. My estimated range was 31 miles, and it was going to be at least 80% all uphill, and I was going 30 miles (at night). The first part of the experiment was driving with the headlights off as much as I could and in EcoPro (not+). With the lights of the big city, and being in the slow lane behind a semi lets say where it doesn't matter if your headlights are on or not because you're in your space between 2 fixed speed (on the freeway) vehicles, it's pretty easy to not have them on with how bright the U-shaped LED running lights are. Or, when you're at long stop lights and also no reason to have headlights on too I only kicked them on when I was entering the freeway at at certain intersections. Even though I climbed the uphill route most of 15 miles, I was still able to beat the estimate by 3 miles indicated. So was it wacky i3 estimate that I seemed to get better range, or did the lights off mode help? It would seem like there would still be a alternator (or generator) powering the 12volt battery, so me thinks that there might lurk the possibility that if the alt/gen isn't putting recharge current into the 12v system, then there would be the possibility of the juice instead going to the HV battery. Of course I could be totally high on this...

The return trip was mostly downhill and this time in comfort mode with little cabin heat and driven sensibly (tough). I couldn't make the same distance even driving downhill mostly and at grandpa speeds. Me wonders....

The other part of the experiment was "just how bright are those U-shaped headlights and are they good enough for visibility for non carrot challenged other drivers? Since those little guys are pretty bright and they alone illuminate road signs pretty good on their own at shorter distances, one would think that other drivers could see them pretty well....

So the (2nd) question was, a night of mostly headlight off driving on all sorts of streets and freeways - would I get flashed from other drivers that
"hey, your headlights are off moron"? I didn't get flashed once - an interesting (although maybe stupid) experiment.

As strong as the carbon fibre body may be, it's not going to save you from death when some massive SUV or semi truck runs into you some night because they didn't see your tiny i3 with its lights off. Maximizing range is a great thing to do - but only within limits!

 

[HomelessDude]

Ballpark number, the pair of headlights probably draw about 5 amps total. Not sure what that loss translates to in terms of reduced range. My shortest recorded range on a single charge was 73 miles, all highway 70mph with headlights and a/c running.

 

[noakey]

Maybe if you robbed a bank?

Sorry... couldn't help it!

 

[DAZ]

I can give you a apple and oranges reply. i have a 2012 Prius Plug In that I've had for almost two years. The EV range on my Prius is between 10-14 miles. Most days, after charging, my Prius will report ten miles EV range available. My work commute is 9.8 miles. With conservative driving, I can make my one way work commute all EV.

In winter months, I'm hard pressed to make it. I noticed, even with shorter winter days, driving with the LED headlights on, makes no measurable difference in my EV mileage. My Prius Plug In has the LED headlights, not all Prius do.

The Prius plug In has a 4.4kWh battery, and very low EV range. If LED headlight use has virtually no effect on Prius EV range, than I would assume NO measurable negative impact on the i3 with a much larger battery pack.

To conserve range in my Prius, I've reduced my speed, regen as much as possible, virtually never use heat. Note, even using AC in summer months have little effect on Prius EV range. I must admit, trying to drive EV in my Prius is work. With over 10,800 total miles, 75% of my mileage was all EV.

My 13 BEV EV experience is more enjoyable, with less effort.

 

[mindmachine]

In short though disregarding safety needs, the juice for the headlights comes from the traction battery and using them reduces your range by some small amount. So if it is safe not to use them then don't, like for example some people run with their headlights on all the time. Doing that in the i3 would waste power and hence impact range negatively.

 

[noakey]

In short though disregarding safety needs, the juice for the headlights comes from the traction battery and using them reduces your range by some small amount. So if it is safe not to use them then don't, like for example some people run with their headlights on all the time. Doing that in the i3 would waste power and hence impact range negatively.

Anyhow, the i3 has running lights on all the time, so unless its dark these should suffice.

 

[WoodlandHills]

The running lights on US i3s can be turned off in iDrive.

 

[noakey]

The running lights on US i3s can be turned off in iDrive.

ah I see... I didnt realise... thank you for the correction. Its amazing how different the same car can be in different countries.

 

[DeafSoundGuy]

Just a quick note that anyone wanting to drive with the U-shaped lights only when it's getting dark, remember that the light switch when it's in Noon position will be front running lights only - you will be dark as Dracula in back :evil: . I didn't realize that at first. You have to turn the light switch to the 2:00 position to get all the running lights and no headlights.

And yes, I agree that robbing a bank would be an excellent example of running the switch in the Noon position :!: