Featured Tesla's latest competition in making efficient truck to crisscross country: Big Oil

I still think that a hybrid plug-in system is the way to go for trucks and buses for a long time.
The engine is not really that efficient for driving around dense city traffic. Plus you don't need the engine on to power a truck down a long hill.
But a battery is not efficient to power a truck up a hill, so then you switch to diesel.

 

After the second click-through, the Shell flyer says "DEMONSTRATING WHAT IS POSSIBLE".

Tesla announces an EV semi truck and suddenly out of the woodwork comes the 'fool cell' truck and now the Shell 'demo.' To me this stinks of 'patent sitters.'

Bob Wilson

 

Why can't a battery be efficient at powering a truck up a hill?

 

Well it's not as efficient as it is in low-power applications.

 

It depends on the battery technology:


Just add a truck:


Notice, no fire risk except for the vat of hot oil:


Bob Wilson

 

Are you simply thinking that just because an ICE is most efficient at higher power loads that that makes it more efficient than a BEV doing the same thing?

 

In Alabama, hills have an equal number of nearly identical up and down grades. The battery truck regenerates a significant amount of energy on the down grade. Diesel and gas truck don't.

Bob Wilson

 

Actually this is totally false.
diesel is most efficient at moderate loads. Electricity is efficient at all loads. After you use a lot of power going up that hill, the battery adds to efficiency, because not only is it more efficient going up, it can regenerate braking charge going down ;-)

What should be said is for a given range, if it is big, a battery will be heavier than an engine and fuel. The battery must supply power to lift the truck and itself up the hill, which means more power is required than of the diesel. Not really a big deal.

The only things a diesel truck is more efficient at than a bev truck is up front costs, and speed and convenience of refueling. If total cost of ownership, instead of up front cost is the important thing, a phev truck will beat diesel in that while being as fast to refuel and even more convenient (many times it can just refuel at the plug when not in use).

So I agree with skylis A on the concept that phev is better, but not in the reasoning.

Compare Side-by-Side


123 mpge on the highway for the model 3 long range versus 43 mpg diesel on highway for the less powerful bmw 3 series diesel or 53 mpg highway gasoline for the camry hybrid. Those batteries are a lot more efficient ;-) Of course you may discount the electricity to gasoline because of the grid, etc, but normally the worst you would get is half, or 61 mpge highway for the bev.

 

I could be wrong but I read the efficiency statement in terms of a PHEV/HEV not a BEV.

In systems where the primary fuel is dino (like a Prius) it is less efficient to burn dino charging up the battery just to spend it going forwards again later. The greatest efficiency comes from allowing the battery to act as a buffer to shut the engine off completely and just keep on trucking. Either downhill or coasting in situations that would otherwise be a power failure scenario. And the next biggest gain is the ability to supplement power to run the dino engine in the most efficient band possible.

In something like a cross-country truck, the long stretches of open road with gentle ups and downs are perfect for the dino power up, battery power down.

If the truck is mostly battery powered, then it isn't a thing. But for the near term, most trucks will be primarily dino powered. Adding in a hybrid system will be a huge benefit. The big redneck truck people are starting to realize it after this year's unveil of "new" hybrid trucks that can keep your beer cold with the engine off and provide better torque. Things us Prius drivers have been saying for two decades now. The locomotive industry gets it. Trucking will come next.

 

Yes. Isn't that what we keep telling here?

Also, what about battery overheating problems up long hills?

 

Liquid cooling is your friend. Don't do this in a Leaf.

Bob Wilson

 

This is also pretty false.

The bigger the battery, the higher the possible load without causing as much heat. The Prius battery is puny, so it heats up (and cools down) really quickly.

A Leaf can go up and down mountains all day and not get too hot to use and it has zero thermal management. A big truck with HUUUUUUUUGE batteries and a full load, the batteries would be fine.

 

this is a tesla buy signal for wall street, keep the competition coming, someone is worried.

 

True enough, I don't have a Leaf to experiment with. However, I have both a BMW i3-REx, liquid cooled, and Prius Prime, air cooled. I don't have battery temperature metrics, yet. But I realized I haven't done a well designed, head-to-head comparison although I have some metrics:

1. Why the BMW i3-REx | Page 3 | PriusChat
   
2. Prius Prime Plus in my hands | Page 5 | PriusChat

PROPOSED PROTOCOL

• Use Brindley Mountain hill climb route:
  • 525 ft (160 m)
  • 1.1 mile (1.76 km) run
  • 8% grade
  • 60 mph (96 kph) ascend speed, replicating typical truck performance
  • 75 mph (120 kph) descent speed, replicating typical truck performance
  • includes acceleration at base; turn around at top, and; deceleration to stop
• Reset trip meter at start and record:
  • round trip distance
  • mi/kWh (may be a problem for Prime as I need to find the trip value display)
• Metrics
  • Use dash cam to record trips
  • Use GPS to track speed and route

ANALYSIS

• Use measured battery capacity and indicated % for kWh
  • 18.5 kWh BMW i3-REx
  • 5.6 kWh Prius Prime

We won't be at Standard Day temperatures until after midnight when I'll tell my wife, "Time to walk the dogs."

Bob Wilson

 

ACTUAL PROTOCOL

• Use Brindley Mountain hill climb route:
  • 525 ft (160 m)
  • 1.1 mile (1.76 km) run
  • 8% grade
  • 55 mph (88 kph) ascend speed, replicating typical truck performance
  • 65 mph (104 kph) descent speed, replicating typical truck performance
  • includes acceleration at base; turn around at top, and; deceleration to stop
• Reset trip meter at start and record:
  • round trip distance
  • mi/kWh (may be a problem for Prime as I need to find the trip value display)
• Metrics
  • Use dash cam to record trips
  • Use GPS to track speed and route

DATA

2017 Prius Prime in EV mode:

	longitude	latitude	miles	kWh	speed
1	34.65289	-86.57163	0.0	0.00	0 mph
2	34.53006	-86.58991	9.0	2.14	55 mph
3	34.50485	-86.60262	2.4	1.42	55 mph
4	34.53334	-86.58965	2.2	-0.25	65 mph
5	34.59196	-86.56261	4.4	0.60	55 mph

• Going up the hill, 2.4 mi, the efficient EV used 1.42 kWh
• Descending the hill, 2.2 mi, the efficient EV gained 0.25 kWh

CONCLUSION

The same works with any electric truck because regeneration keeps the brakes cool and speeds moderate. In contrast a diesel, fuel cell, or small hybrid truck just heats the brake pads descending a hill it just climbed.

Bob Wilson

 

In a properly designed Fuel Cell or hybrid, why would brakes be heated?

A Fuel Cell is really a hybrid with different power source than gas. It still has a small battery pack needed for smooth power delivery. And needed battery power during fuel cell warmup time.