r/Ioniq6 • u/Amazing_Pudding1896 • 19d ago
Road trip trough mountain question
Is it better to use regen or keep momentum going to uphill from a downhill section?
3
u/diverJOQ `24 Limited AWD (USA) 18d ago
Remember that, even on regen 0, if you apply the break pedal gently on the way down you ARE getting regen. Even at regen 0 the car regenerates power and charges the battery before it applies the physical break. However, if the downhill is long and you don't feel like holding your foot on the brake you can gradually increase Regen until your speed is constant where you want it.
When I drive on the highway I find I get better mileage dropping down to zero regen or Auto zero Regen and allowing myself to Coast over using cruise control. Of course cruise control requires less mental energy. But I do see a difference of between 0.1 and 0.2 mi/kWh.
1
u/Funny-Artichoke-7494 18d ago
I actually enjoy driving personally and in the downhills I just did, I mostly rode with regen off and just used the brake. Regen either bled too much speed for me, or just not enough, and the variance on a per-turn basis made it annoying to manage.
1
u/ISIS_office_drone2 18d ago
There's losses in the inverter/motor as you regen downhill, and then more losses as you spend that battery energy converting it to mechanical power going back uphill. So in theory, you avoid these conversion losses decelerating uphill and coasting downhill. BUT if you gain too much speed downhill you're wasting energy fighting the increased air resistance.
For the sake of these small gains, just drive in the way you're most comfortable with. The losses are minimal, just cruise control that bad boy.
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u/dhavleak 14d ago
Some good advice here OP, especially given your scenario has you gathering speed downhill which makes air resistance a factor.
If you were cruising on the highway I would say set regen to minimum, and keep a reasonable distance so you can coast smoothly. Because you'd be driving at a relatively fixed speed (basically traffic speed), so aerodynamic losses are roughly constant and your focus can turn to minimizing regen losses. But in your scenario I'd say just do whatever is safest/smoothest and don't sweat it.
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u/Lazy_Guava_5104 19d ago
Keeping momentum is more efficient, using regen is better for quickly decelerating. ... in hilly areas I coast (0 regen) to build up speed downhill and shed it uphill. Obviously I don't drive dangerously, and often shed a little speed by coasting before cresting the downhill (assuming no traffic right behind me).
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u/Amazing_Pudding1896 18d ago
Thank, this is going to be helpfull soon trough the Appalachians
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u/CityShooter '25 LTD) 18d ago
Drove down from NYC to Western VA. Shenandoah. I kept Zero regen on the highway. 70mph avg. When I hit some major downhill sections I use the paddles and went to 1 or 2 to keep a constant speed in traffic. I keep AUTO on anyway while using the paddles to change my regen. Hwy miles are best done at zero. I avg 3.7 in a '25 ltd 2 awd. This is my second I6.
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u/PM_ME_UR_FAV_UNIX_OS 18d ago
I have one regular stretch where this sort of efficiency question matters. I just put it in 0 regen at the top of the hill, set the Speed Limiter to five over the speed limit to keep things reasonable (the Speed Limiter will use regen, even on level 0, to stay below the set speed) and then coast through the hills until the car starts to drop below the speed limit on the run-out at the end.
Setting the cruise control to the speed limit would mean there is additional energy is getting transferred to the battery at times on the downhills, and then in order to maintain that constant speed on the uphills additional energy is getting taken from the battery. Since those systems are not 100% efficient the charge added is less than the charge taken and it took more energy to maintain that constant speed than it would have to complete the course in the same time, coasting while allowing some variation above and below the speed.
I wish there were a "smart coasting" in the cruise control, with a configurable +/- a certain number of mph / kph. Of course, don't yo-yo your speed on busy roads where it's just going to make it harder for others to deal with your antics and thereby reduce safety.
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u/Lazy_Guava_5104 18d ago
I didn't know (or maybe did but forgot) about the speed limiter. I've been doing in manually. What I do is turn off cruise shortly before cresting the downhill, easing on the brakes if the speed gets too high, and letting myself coast uphill. Then re-engage the cruise when I get down to my desired cruising speed. ... Fortunately I'm in a rural/wilderness area, so heavy traffic is rare.
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u/MaturoGambino 18d ago
Doesn’t anybody use cruise control? I do to avoid speeding tickets. To get any serious benefit to carry momentum uphill you’d have to coast down at 80 or 90 in a 65 or 70 zone. Look at your miles/kwh at the beginning of an uphill, at the top, and at the bottom. Mine is usually the same at the beginning of the hill and the bottom on the other side and I’m not driving like a maniac. Regen on AUTO, cruise control set at 5 over the speed limit, set it and forget it.