remarquian
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Go from Denver to Eisenhower Tunnel in one Charge

Mon Jul 25, 2016 9:29 am

I'm planning a trip to Frisco/Silverthorne with our 30Kwh 16' SV.

I'm wondering if someone has gone from Central Denver the the Eisenhower tunnel in once Charge (or knows how many Kwh it will take).

The EV planner says I cannot make it, but I'm not so sure.
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AlanSqB
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Re: Go from Denver to Eisenhower Tunnel in one Charge

Mon Jul 25, 2016 10:25 am

That's going to be tough due to the elevation change.

Maybe stop in BeauJo's in Idaho Springs for a meal and let the car charge for an hour or two.

Coming back down probably will be ok.
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remarquian
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Re: Go from Denver to Eisenhower Tunnel in one Charge

Mon Jul 25, 2016 11:31 am

That's what I was planning on doing initially and taking battery charge measurements with LeafSpy to see how much energy it takes.

Just wanted to know if I could avoid it.

Thanks.
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dgpcolorado
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Re: Go from Denver to Eisenhower Tunnel in one Charge

Mon Jul 25, 2016 1:33 pm

Some numbers for you:

Distance, about 60 miles, depending on where in the Denver area you start, and the elevation gain is about 5600 feet.

Using Tony Williams' venerable Range Chart, the energy consumption at 65 mph would be about 3.6 miles/kWh at 70ºF. The energy consumption for the elevation gain would be about 1.5 kWh/1000 feet. So:

60 miles ÷ 3.6 mile/kWh = 16.7 kWh
5600 feet ÷ 1.5 kWh/1000 feet = 8.4 kWh
Total = 16.7 kWh + 8.4 kWh = 25.1 kWh

Some caveats:
1) If temperatures are lower than 70º, as is very likely at higher elevation, the energy use will increase.
2) If speeds higher than 65 mph are used the energy use will increase; conversely, slowing down will reduce energy consumption significantly for several reasons. The speed limit is higher than 65 over much of that route so if you drive the limit you won't make it without a lot of extra charge on the way.
3) If a headwind is encountered energy use will increase drastically. Been there, done that.
4) Tires will have less rolling resistance if the pressure is at least 40 PSI; Nissan's recommended 36 PSI is too low for best efficiency. (But tire pressure increases with elevation, and vice versa, something those of us who drive mountains all the time need to keep in mind, so don't put the pressure up at 50 or something like that.)


Can you make it? Perhaps, in warm weather, driving gently and fairly slowly, despite traffic going much faster. I wouldn't think it would be much fun without a good long charge stop in Idaho Springs. If you could start with a full charge in Golden and then take US-6 until it merges with the freeway, it might make the trip easier.

FWIW.
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remarquian
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Re: Go from Denver to Eisenhower Tunnel in one Charge

Tue Jul 26, 2016 8:38 pm

That is interesting.

When I went up Mt Evans with two adults and three children in the car, which took me 9.9 Kwh (via leafspy) to get to Idaho Springs. It was 70ish and I went 55 uphill. Using your calculations, I should have used 12.8 Kwh. [((7526ft - 5280ft)/1000) * 1.5) + (34 / 3.6)].

So that checks out in my benefit.

Then 25 miles from Idaho Springs to the top of the Eisenhower Tunnel (27 / 3.6 = 7.5 Kwh) and an elevation gain of 3631 (3.63 * 1.5 = 5.5Kwh) is about 12.95Kwh.

So about 25.7 Kwh, with a budget of ~27.5.

So how does this sound as a strategy?

If I've got around 17Kwh on the battery at Idaho Springs, just go for it, else charge at Beau Jo's for an hour. The rational being that I'm under budget, and will continue probably to be so. If things start looking crazy, I can always bail and go back to Idaho Springs, it is all down hill.
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dgpcolorado
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Re: Go from Denver to Eisenhower Tunnel in one Charge

Wed Jul 27, 2016 10:59 am

remarquian wrote:That is interesting.

When I went up Mt Evans with two adults and three children in the car, which took me 9.9 Kwh (via leafspy) to get to Idaho Springs. It was 70ish and I went 55 uphill. Using your calculations, I should have used 12.8 Kwh. [((7526ft - 5280ft)/1000) * 1.5) + (34 / 3.6)].

So that checks out in my benefit.

Then 25 miles from Idaho Springs to the top of the Eisenhower Tunnel (27 / 3.6 = 7.5 Kwh) and an elevation gain of 3631 (3.63 * 1.5 = 5.5Kwh) is about 12.95Kwh.

So about 25.7 Kwh, with a budget of ~27.5.

So how does this sound as a strategy?

If I've got around 17Kwh on the battery at Idaho Springs, just go for it, else charge at Beau Jo's for an hour. The rational being that I'm under budget, and will continue probably to be so. If things start looking crazy, I can always bail and go back to Idaho Springs, it is all down hill.
If you are willing to drive 55 I would think you could make it fairly easily; speed makes a huge difference in aerodynamic drag. Since you have several options, including turning around if the charge level gets too low for comfort, you ought to give it a try. Even if you make the tunnel well below Low Battery Warning you should be ok, although you won't really be able to regen your way downhill until you clear the tunnel. Having Leafspy will allow you to use the lower part of the battery with confidence. Keeping your speed down on the downhill run will allow you to regen more on the way to Silverthorne or Frisco (this doesn't work in cold weather because regen is severely limited when the battery is cold IME, not that it will be a problem this time of the year).
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remarquian
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Re: Go from Denver to Eisenhower Tunnel in one Charge

Wed Jul 27, 2016 2:11 pm

Going 55 only adds about 10 minutes onto the trip versus an hour charging stop, so it doesn't bother me.

Temperature and the battery is interesting. Would the regen warm up the battery? A Quick Charge? Would it stay "warm" driving around in freezing weather?
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nickandre
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Re: Go from Denver to Eisenhower Tunnel in one Charge

Wed Jul 27, 2016 2:26 pm

Boosting battery temp is simply a matter of charging to end just before departure. Also note that you generate heat during normal driving and a transient decrease down 10-20 degrees will take a long time to cool the pack down, especially if you have heat input from battery use (driving).

People have suggested that driving in ECO mode without cruise control and allowing some variation in speed produces better efficiency (gain speed up to 60 downhill, slow to 50 uphill instead of 55 constant). I'm inclined to agree, but more testing would be necessary. I've seen efficiency on highways (I-93 out of Boston then I-95 north to the state line) up to 4.6 mile/kWh using this method though it's highly elevation-dependent. I usually map out what efficiency I "need" to make the next charger and then don't really bother to try and exceed that to a great extent. Note that taking a back road instead of a highway can have a dramatic increase in efficiency, mostly the same as dropping your speed down to the optimal range which is closer to 40-50 (probably below that, but ain't nobody got time for that).

I've considered making a sign for the back of my car that says "hyper-mile-ing EV, please pass on left, so sorry" ;)

PS: What would _really_ be cool is intelligent cruise control to optimize for efficiency, maybe even input map data. (One can dream, right? Plans for my Leaf once the value descends below $5k.)

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dgpcolorado
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Re: Go from Denver to Eisenhower Tunnel in one Charge

Thu Jul 28, 2016 3:13 pm

remarquian wrote:Going 55 only adds about 10 minutes onto the trip versus an hour charging stop, so it doesn't bother me.

Temperature and the battery is interesting. Would the regen warm up the battery? A Quick Charge? Would it stay "warm" driving around in freezing weather?
The tremendous climb up to the tunnel would warm the battery quite a bit. As nickandre says, arranging charging so that it ends right before you leave helps to start with a warmer battery. And, yes, quick charging warms the battery quite a bit.

I've had the experience of very good regen descending from Red Mountain Pass, 11,018 feet, to Ouray in September and very little regen when doing so in January. But I started at Silverton, ~9200 feet, after slow charging overnight at -8ºF, with the battery showing between one and two temp bars (so, fairly cold). That wouldn't be a problem with the climb up from Denver, even in winter. But a return trip from Frisco after a night at below zero temperatures might have limited regen on the way down from the tunnel. The problem with limited regen on big downhill runs is that one must use friction brakes to control speed on very steep grades. This is very hard on the brakes!

Just be aware that things are different in cold weather, as opposed to the current warm weather. Even a 30 kWh LEAF is not a practical car to visit the ski areas in winter IMO.
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Nfuzzy
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Re: Go from Denver to Eisenhower Tunnel in one Charge

Sat Aug 06, 2016 6:55 pm

If you are doing this now in warm weather I think it is doable depending on exactly where you mean by central Denver. I used roughly 12kwh from Idaho springs to Eisenhower back when I did my Breckenridge trip. Details posted under the Denver to grand junction thread.
If you do the trip, post details!
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