Start with full charge at top of hill

Start with full charge at top of hill

This question is more a matter of interest than of practical import.

If one has a 100% charge beginning at high elevation (unlikely I concede) and one immediately begins driving down the hill, of course the battery will have no capacity for further charge. Does this mean that the regenerative braking that one can normally expect won't occur. If it does "brake" where does the energy go?!

tylerhen | 18. September 2013

Regen braking does not work when you do a full charge. I have only done a range charge twice and both times for the first 10 minutes of driving, there is a dotted line on the energy usage meter that prevents you from regenning too much.

vlsidude | 18. September 2013

When the dotted line shows up you will get significantly less regenerative braking and hence have to use your friction brakes on steep hills - wasting energy and eating your brake pads. To avoid this I make a point of only charging to 90-95% before I start back from Tahoe - despite having a 230-250 mile trip ahead of me (depending on route and whether I make a side trip). That way I still get good regenerative braking and avoid using the friction brakes on the descent.

cpetrush | 18. September 2013

I live at the top of a big steep hill and when I max charge at home I have no regen braking until I am down hill and have used up some energy.

Velo1 | 18. September 2013

These replies are helpful, as I live at 8,000 feet and only have to drive 3 miles before I have a long descent (7 miles) down to 5,000 feet. I always charge at 80%, so have never experienced the dotted line or the less-than-usual regen, but will be aware of this if and when we do a full charge for an extended trip out of town.

rodhoffman | 18. September 2013

Velo: +1

I live at 8,500 feet in Evergreen, have a small hill to climb and then the big I-70 energy add. I always get energy add down hill and usually end in Denver with the rated charge I start with. I charge to 80% and only range charged once when doing a 200 mile trip to Ft. Collins. It was not needed however because New Belgium has a charger!

Went to Vail last week and charged at the Mountain House - the GM is an owner of a roadster and they have a conversion cable for the S.


jjb94941 | 18. September 2013

Thanks for all the helpful responses. It's good to bear in mind that one doesn't enjoy regenerative braking when charge is very high, because eventually one expects it as a part of one's daily driving and its absence can threaten at least a fender-bender.

hfcolvin | 18. September 2013

Also bear in mind that regen is limited when the battery is cold. I'm not sure if the newer software will condition the battery on shore power to make this less of an issue. Winter's coming folks!

lammersc | 18. September 2013


I have only charged the battery fully a few times, however, I get full regenerative braking within a 7-10 miles of battery usage. You could try charging to a lower amount (95%), and see how well regenerative braking works for you on the way down. Will it actually increase your batteries charge level. I would be interested to know.

DTsea | 18. September 2013

Just dont charge all the way full. You shouldnt do that daily anyway.

And yes, if long and steep enough it can actually increase total state of charge.

JZ13 | 18. September 2013

One concern to be aware of is if you use cruise control. I use cruise control to manage my speed for 90% of my driving. I live at the top of a steep hill and set the cruise out of habit. On the rare occasions that I have max charged I found myself speeding because I set the cruise but the regen doesn't kick in which the cruise control depends on to slow the car. Surprisingly my brakes don't take over for speed management. I could easily have received a speeding ticket before I realized the speed and corrected it.

cerjor | 18. September 2013

The first mile I drive after leaving home is downhill. When I get to the bottom I will have used negative watts/mile meaning I have more energy than when I started. Too bad I need to go uphill from there.

shs | 18. September 2013

I live up, and start most all drives by going down 3000' in about 15 miles. If we do a max charge before leaving home then we don't have regen most of the way down. That said, we do end up with more miles of range at the bottom of the hill with a range charge than with a standard (235) mile charge, as the grade is not steep enough to generate range, but we don't lose much range either. Charging to 245-250 gives sort of the best of both worlds for this drive as regen is active and we still have a good almost full charge at the bottom of the hill for the rest of the trip which often exceeds 200 miles without charging.

soma | 18. September 2013

Anyone know how many extra miles of range gained per 1000 ft of altitude? (in an ideal sense)

Brian H | 19. September 2013

Early guesstimates were about 7 mi.

Charging so much you can't use regen is a real waste; you're paying to heat up your brakes for a while, basically.