Hill Climb -- the Mt Baldy run

[edatoakrun]

Three bars of SOC at the top and 3 bars at the bottom. Cranking 10-30 kW of regen the whole way down.

Unless there's a software glitch, EVNow's theory seems to explain this best (a bigger SOC spread than expected within "bar 3" due to different charge/discharge thresholds). The spread between 20% SOC and 32% SOC would be about 2.9 kWh. The descent from Mt. Baldy Village (~4200') to Baseline Rd. (~1480') in Claremont is 9.2 miles and about a 2720' drop. At 1.3 kWh per 1000', that would be 3.5 kWh in potential energy. At 50% efficiency, you'd pick up 1.8 kWh in regen, well below that 2.9 kWh possible spread for "bar 3". Also, perhaps Carwings would indicate the total regen kWh on that drive.

Maybe someone needs to try a bigger climb/descent to see regen add a bar to the display! Start the climb with more charge and do the Mt. Baldy ski lifts next time? ;-)[/quote]

If these numbers are correct, there are not many road grades CONSISTANTLY steep enough with a total elevation drop to put a bar on the display. Too steep, and you lose regen potential to the brake pads. and any flat or uphill stretches reduce regen gains over the total drive.

I doubt any roads in my area would do it. Seems to me the only likely place to give it a try would be the Eastern Sierra descents on highways 120 or 108, from Tenaya or Sonora pass.

One of you grade/elevation experts take a look at them.

Then figure your charge path to get to the top...

 

[abasile]

On the way down from Mt. Baldy village, there are two places where Sparky might have used the accelerator a little. There's a short but steep uphill between the Mt. Baldy elementary school and Hog's Back, and then another flat spot and small uphill below the tunnels. On the other hand, with extra momentum (from briefly letting my downhill speed get over 60mph in an ICE car) and no one else on the road, I've barely coasted over both of those humps without touching the accelerator. Other than those spots, the road seems plenty steep for continuous (but sometimes very gentle) regen.

 

[abasile]

If these numbers are correct, there are not many road grades CONSISTANTLY steep enough with a total elevation drop to put a bar on the display. Too steep, and you lose regen potential to the brake pads. and any flat or uphill stretches reduce regen gains over the total drive.

I doubt any roads in my area would do it. Seems to me the only likely place to give it a try would be the Eastern Sierra descents on highways 120 or 108, from Tenaya or Sonora pass.

One of you grade/elevation experts take a look at them.

Then figure your charge path to get to the top...

"Charge path"...now that's key! Given existing charging infrastructure, mountain climbing experiments are probably best conducted in Southern California at the moment, where we have significant mountains very close to urban centers (and LEAF owners). But be forewarned; we in the SoCal mountains are expecting snow this week!

Perhaps this summer after the snow has melted, LEAF owners desirous of making Eastern Sierra climbs can find nearby campgrounds or RV parks with power!

 

[garygid]

We need convenient QC stations at the base of there "climbing" roadways, and perhaps another midway and at the top.

Many will use most of a full e-tank to just get to the base of the climb.

 

[abasile]

We need convenient QC stations at the base of there "climbing" roadways, and perhaps another midway and at the top.

Many will use most of a full e-tank to just get to the base of the climb.

That's why I keep saying we SoCal people need a QC station in Redlands or thereabouts, near I-10. That could allow for trips to both Big Bear and Palm Springs. Put another one in Fontana or thereabouts, to support driving over Cajon Pass (I-15) to Victorville, or as an alternative for trips to Lake Arrowhead. We'd also want a QC station in the Valencia area to support driving over the Grapevine (Tejon Pass via I-5) to Bakersfield.

The idea would be to really open up the region to LEAF owners, since getting out of LA/OC often involves mountain climbing. And extend this concept to other metro areas.

 

[EVDRIVER]

Regen efficiency is not 50% in terms of generation, if you are dumping 1kw you are getting 1kw less a small margin of loss of about 10%. So it is about 90% efficient during generation and into the pack.

 

[wsbca]

We need convenient QC stations at the base of there "climbing" roadways, and perhaps another midway and at the top.

Many will use most of a full e-tank to just get to the base of the climb.

It won't be right away, but once more cars are on the road and if the whole infrastructure thing actually happens I'd bet the Pala Casino near the base of Mt. Palomar will get some chargers to entice customers, making a drive up the South Grade to Mother's Kitchen for a bowl of chili (22 miles each way, 4000 feet of vertical) a potentially feasible regen experiment. I wonder if coming back down the east grade (gentler slope, more wide open) to Lake Henshaw would actually give more usable juice than the switchbacks on the south grade which would require friction braking. Of course then you're 25 miles away from the casino, with some climbing to get back there.

 

[abasile]

Regen efficiency is not 50% in terms of generation, if you are dumping 1kw you are getting 1kw less a small margin of loss of about 10%. So it is about 90% efficient during generation and into the pack.

That makes sense. However, of one's total potential energy at the top of a descent, I'm roughly guessing that no more than 50% would make it back into the pack via regen, due to wind resistance and friction losses. And that's of course highly dependent on terrain and speed.

 

[LEAFer]

Regen efficiency is not 50% in terms of generation, if you are dumping 1kw you are getting 1kw less a small margin of loss of about 10%. So it is about 90% efficient during generation and into the pack.

That makes sense. However, of one's total potential energy at the top of a descent, I'm roughly guessing that no more than 50% would make it back into the pack via regen, due to wind resistance and friction losses. And that's of course highly dependent on terrain and speed.

Something going "forgotten" here ... the energy used to drive the actual miles should still be accounted for separately. In other words ... in my original posting (where I posit the 1.3kWh/1,000') I believe I explicitly state that the energy needed to climb that elevation is IN ADDITION to the flat-land-miles you travel. Using said methodology also allows one to ignore the steepness of the grade (thus %grade does not factor into the energy use so long as the vehicle can actually climb that grade, and so long as (pointed out above by someone else) the friction brakes are not in use (voiding some of the regen efficiency)). The flat-land-miles traveled is subject to all the variables and normal factors as usual.

Therefore ... the 90% factor (from regen after minor losses) *DOES* apply only to the Potential Energy regained and stored back into the battery. The rest of the energy used to "go the distance" is assumed to be "flat-land-miles" with all of its variability

 

[LEAFer]

As a separate post ... to clarify conceptually ...

• The Energy Needed From the Battery ... call it (BE) ... is
  + Energy needed to "move" car on a flat surface under current ambient (wind, temp, speed, weight, etc) conditions, call it (KE);
  + Energy needed to climb (PotentialEnergy as previously posited based on mass*g*height, call it (PE);
  - Energy regen'ed (asumed to be (for example) 90% of (PE)) in descent.

Or,

(BE) = (KE) + (PE) - (90% * PE)

(Note that (KE) may also include some regen when slowing on a flat surface, but this severely complicates any calculation. Try to keep that portion as simple as possible.)
(Also note, this is VERY conceptual. And I am not implying that the two (PE) terms in the equation are identical, unless the elevation gain and drop are identical.)
(No jokes about bekepepe, please :lol: )

So ... most of the PE is returned (on a round trip or return to same elevation), but you can't get around the KE needed ...

 

[abasile]

Therefore ... the 90% factor (from regen after minor losses) *DOES* apply only to the Potential Energy regained and stored back into the battery. The rest of the energy used to "go the distance" is assumed to be "flat-land-miles" with all of its variability

Thank you for setting my thinking straight. In that light, let's re-think the descent from Baldy village to Baseline Rd. in Claremont (2720' over 9.2 miles). Total potential energy is just over 3.5 kWh. Assuming a moderate average speed, that descent also requires roughly 9.2 "flatland" miles of energy, or 2.2 kWh, to overcome wind/friction losses. The remaining potential energy available for regen is 1.3 kWh. 90% of that is just under 1.2 kWh back into the pack. That could easily explain why Sparky didn't light the 4th bar of charge.

 

[EVDRIVER]

Therefore ... the 90% factor (from regen after minor losses) *DOES* apply only to the Potential Energy regained and stored back into the battery. The rest of the energy used to "go the distance" is assumed to be "flat-land-miles" with all of its variability

Thank you for setting my thinking straight. In that light, let's re-think the descent from Baldy village to Baseline Rd. in Claremont (2720' over 9.2 miles). Total potential energy is just over 3.5 kWh. Assuming a moderate average speed, that descent also requires roughly 9.2 "flatland" miles of energy, or 2.2 kWh, to overcome wind/friction losses. The remaining potential energy available for regen is 1.3 kWh. 90% of that is just under 1.2 kWh back into the pack. That could easily explain why Sparky didn't light the 4th bar of charge.

This is why I find the bars to be far to basic since they don't teach new EV drivers about their habits and they don't give enough for those watching closely. Even the motor consumption bars are too broad and the regen up/down bar is about as good as a toy IMO. Once you get a boost in mies it still is misleading on the way down as it is averaging your downhill state and then you get to the flats and it all changes. Watching a accurate SOC up and down gives one nice behavior indicators to compare to the provided "bars". Regardless, seeing actual detail on up and down to the pack is far more comforting to many and less confusing at times. I think both tools together are a good approach.

 

[JimSouCal]

This is why I find the bars to be far to basic since they don't teach new EV drivers about their habits and they don't give enough for those watching closely. Even the motor consumption bars are too broad and the regen up/down bar is about as good as a toy IMO. Once you get a boost in mies it still is misleading on the way down as it is averaging your downhill state and then you get to the flats and it all changes. Watching a accurate SOC up and down gives one nice behavior indicators to compare to the provided "bars". Regardless, seeing actual detail on up and down to the pack is far more comforting to many and less confusing at times. I think both tools together are a good approach.

This might not make sense to some, but if you've ridden a bicycle up and down hills, without using the brakes at all, the way the energy is utilized, well, you can feel it in your legs. The coasting downhill is often at energy equilibrium, and I don't see how a car would be an exception to this.

I agree, my preference is for details on energy flux and not simplistic displays that are prone to mislead.

 

[abasile]

This might not make sense to some, but if you've ridden a bicycle up and down hills, without using the brakes at all, the way the energy is utilized, well, you can feel it in your legs. The coasting downhill is often at energy equilibrium, and I don't see how a car would be an exception to this.

The difference is that a bicyclist has a much higher coefficient of drag than a car, especially an aerodynamic vehicle like the LEAF or a Prius. So, on a downhill slope where a bicyclist reaches energy equilibrium at a given speed, a LEAF or Prius should be able to travel at that same rate of speed and still capture energy from regenerative braking. Traveling the same roads, I'm able to do a lot more coasting in our Prius than on my racing bike.

 

[JimSouCal]

The difference is that a bicyclist has a much higher coefficient of drag than a car, especially an aerodynamic vehicle like the LEAF or a Prius. ... Traveling the same roads, I'm able to do a lot more coasting in our Prius than on my racing bike.

Indeed. The mental model isn't a precise analogue--but is a visceral example of why a hill climb isn't likely to fully recharge the battery on the way down--cars, and even personalities at my work, manifest friction and waste effort...

 

[tbleakne]

Thank you for setting my thinking straight. In that light, let's re-think the descent from Baldy village to Baseline Rd. in Claremont (2720' over 9.2 miles). Total potential energy is just over 3.5 kWh. Assuming a moderate average speed, that descent also requires roughly 9.2 "flatland" miles of energy, or 2.2 kWh, to overcome wind/friction losses. The remaining potential energy available for regen is 1.3 kWh. 90% of that is just under 1.2 kWh back into the pack. That could easily explain why Sparky didn't light the 4th bar of charge.

I concur. This calculation for downhill now looks right.

For uphill, I believe there will be some combination of grade and speed where the total KW power being drawn from the battery begins to strain its chemistry. At this point the battery will introduce an additional efficiency penalty beyond normal friction and air resistance. All EV batteries exhibit this limitation, but we don't know its magnitude for the Leaf. When I get my car, I plan to test this on the Cajon grade leaving Devore, which is a rather even and steep grade, straight and fast.

For anyone who wants to do the Baldy drive, you are welcome to top-off your charge at my AV EVSE. I live only .6 mi S. of the 210, and about 4.5 mi from the base of the Baldy grade. Just PM me a day or two before to setup a time.

 

[SanDust]

The numbers being thrown out for regen efficiency are too high. Regen efficiency for the Prius is 20%. Regen efficiency for the RAV-4 is maybe 25%. GM says the regen efficiency for the Volt is 30% -35%. That's for a roundtrip of course. Assuming the trip out is more efficient than the trip back, which would seem a given, and you're looking at 30% or 35%.

The numbers aren't hard to figure. Energy released when going downhill is just mgh. You have to assume the Leaf loaded is at least 1800 Kg. If you drop 2700 fee you're looking at 4000 wh or 4 kWh. ((1800 X 9.8 X 825) / 3600) Slightly more than 3.5 kWh. Driving in the mountains is also challenging. You have curves, uphills, and steep downhills, all of which may require acceleration or conventional breaking. The brakes will be warm or hot at the bottom and the wh/mile may be higher than 300 wh/mile.

Bottom line is that, given the precision of the display, it will be hard to add bars unless you're doing something like Pike's Peak which is about twice as steep and twice as long unless you're a few watts away from the next bar.

 

[abasile]

1800kg is about 4000 pounds, i.e., 600 lbs. of people/gear. While realistic for many families making trips to the mountains, I am assuming Sparky's LEAF was not that heavily loaded on his Baldy climb.

If Sparky's potential energy was 3.5 kWh and we are theorizing that he picked up 1.2 kWh in regen, then that would be a regen "efficiency" of 34% if one desires to more simplistically look at the overall picture.

With decent regen capabilities, knowledge of the road, and anticipatory use of braking, the friction brakes should not even have a chance to warm up. This has been my experience driving our 2010 Prius around the San Bernardino Mountains communities, even where the grades are on the steeper side (i.e., Kuffel Canyon above Lake Arrowhead).

Also, Randy3 did add one bar on his longer descent from Shaver Lake: http://www.mynissanleaf.com/viewtopic.php?f=24&t=2753

Finally, I think tbleakne is wise to consider uphill testing on I-15 leading to Cajon Pass, given the relative uniformity of the ascent and the potential for greater speed.

 

[AndY1]

Hello from a Vectrix owner

We, Vectrix drivers also have a SOC representation with battery bars:


That dashboard was me, passing the 10.000km mark.

Our forum's record driver passed 50.000km:

Back on topic. The best way to see if you get battery bars back when using regen is to use regen immediately or as soon as possible after you lost a bar.

We, Vectrix drivers have 17 battery bars, each representing aprox. 5km at 50km/h, so it's also a very rare occasion to see getting a battery bar back. However, it happens.

I may assume, that when you got to the top of the mountain, you were about to lose a bar or you were close to losing a bar. That's why you didn't get another bar back on your way down. It happened to me too, when I went on my journey over a high hill. But when the descent ended, that 9th bar lasted for another 4-5km. That means, that I was about to lose the 9th bar and on the way down regened it the whole back, which gave me power for further 4-5 km.

If you want to trigger getting the bar back, do the what I said above.

Best regards.

P.S.: We named an Estimated Range figure a Random Number Generator. :lol: I see Leaf owner are getting there too :lol:

 

[Glenn]

We named an Estimated Range figure a Random Number Generator. :lol: I see Leaf owner are getting there too :lol:

Best post of the day!!