another range/efficiency discussion

[SByer]

What's all this talk of full charges? That's going to be rare; most days you just have to replace the mileage used. That can happen on quite a slow charge and still take less than 6 hours. And you rarely want to charge the battery to full, either.

Maybe we need the charger to have daily schedules like thermostats? One charging program for "school nights", another prepping for that weekend outing to Napa.

 

[graham]

Maybe we need the charger to have daily schedules like thermostats? One charging program for "school nights", another prepping for that weekend outing to Napa.

This is a really good idea.

Additionally, does anyone have an idea of the amount of charge lost while sitting? If I get roughly 200 miles per charge, drive 100 miles and let the car sit for 8 hours will I be able to drive 100 miles home? What if it sits for 72 hours?

 

[Kevin Harney]

I am hoping that we will see something from Martin soon on his actual range. I read his blog on it and it was good but did not quite answer my questions. I want to know if I can realistically expect to be able to take a 175-200 mile trip on the highway at highway speeds (say around 70 mph) - OK so I speed a little bit but if I had a Roadster that CERTAINLY would NOT change .... :biggrin: My sense from your blog Martin is that this is not a realistic expectation. If it isn't then I will have to wait for one that is realistic for me or make the decision to settle for a hybrid instead.

 

[WarpedOne]

There were reports on 160 miles range of spirited highway driving.
How exactly does that spirited driving looks like is anybody's guess .

 

[deenko]

The unfortunate thing is that freeway diving at constant high speeds is the least efficient thing for the roadster, due to the fact that it take so much energy to maintain high speed while there are very little regen opportunities. I do know that one of the highest ranges for freeway driving was easily over 200 miles. This was set with a long drive in mind, so the driver drove the car for max range (no spirited driving here). Probably set the car in max range mode (torque limiting) and kept the max speed below or at the speed limit.

 

[Kevin Harney]

The unfortunate thing here is that all of the reports are from TM sources and none of them specify anything about "spirited driving" or speed limits or other such things. I realize that this is the worst case senerio for range that is why I am specifically interested in it. Daily driving is no problem for me as it is usually a max of 50 -75 miles. Every other week I take a 200 mile trip and that is what I am hoping to be able to satisfy. I really don't care to maintain 2 cars but it will either be 1 suffices, a hybrid or 2 will have to suffice.

 

[vfx]

There were reports on 160 miles range of spirited highway driving.

How exactly does that spirited driving looks like is anybody's guess .

This is the number that I have been working with as well.

That's why the 73 number hit so hard.

My thinking:
"hypermiling" a Tesla 260 miles per charge.
EPA 225 miles per charge
Spirited driving 160 miles
My extrapolation:
Really spirited driving 140 miles per charge
Super really crazy spirited driving 100 miles per charge but never really below that. 73 sounds like it would be on the charger every second that the car is not moving and indeed it would not move very far.

73 miles would not get you very far out of SF on the way to LA.

 

[Joseph]

"Additionally, does anyone have an idea of the amount of charge lost while sitting?"

For lead-acid batteries, I it takes many, many weeks for the voltage of the batteies to measurably drop. However, that doesn't take into account parasitic losses.

I know there are a bunch of "computers" (that's probably the wrong word, but it's the only thing I can think of) on the Roadster which, according to one of Tesla's blogs, consume as much power as a laptop. Does anyone know if these are on even when the car is off?

 

[DaveD]

I know there are a bunch of "computers" (that's probably the wrong word, but it's the only thing I can think of) on the Roadster which, according to one of Tesla's blogs, consume as much power as a laptop. Does anyone know if these are on even when the car is off?

It's my understanding that the thermal management of the ESS is active at all times, even when the Roadster is "off". That implies that significant parts of the electronics are always on or are in a standby mode.

 

[WarpedOne]

This is the number that I have been working with as well.
That's why the 73 number hit so hard.

I guess they were doing LOTS of 0-60 runs with previous charge. In this view 73 miles is not so little.

A "normal car" needs about 20kW of power to sustain 80mph. If that number holds for Tesla also that would mean 53kWh / 20 kW = 2,6 hours of driving with 80mph = 212 miles of range. If it only needs 15kW to sustain 80mph then range would rise to 280 miles. With 25kW needed for constant 80 mph the range would drop to 170 miles. I'd bet the reality is somwhere in between.

I'd recommend putting hardtop on though as this likely improves the aerodynamics and decreases needed power hence increases range.

 

[malcolm]

What's all this talk of full charges? That's going to be rare; most days you just have to replace the mileage used.

Which might explain the mysterious "Top Off" button (?) seen in the photo at the start of the thread.

I know that the Roadster has a "Timing" option on one of the VDS screens, but I don't know if this allows you to set charging rate as well as (presumably) start or stop times.

Maybe you have to use the mobile charger to force the car into charging more slowly???

 

[Kevin Harney]

Warped,

Thanks for the math. That makes things better for me. Now I am just wondering if reality matches that

 

[doug]

Another shot of the VDS:



Looks like it shows two range numbers: one based on recent driving habits, the other based on the EPA cycle.

 

[doug]

Looks like this keeps evolving:
Tesla Motors Seattle Road Show - Tom's Blog

Tesla is continuing to improve the firmware and the range estimate. Newer firmware will show three range estimates based on (1) your current instantaneous power usage, (2) average power usage over the past 30 miles, and (3) expected power usage by the EPA highway cycle.

 

[power]

Has anyone ever seen how long the Tesla Roadster can last at near full power? (i.e. Track use?)
I would think that it possibly could be use on the race track at near full power for about 20-30min, but I wonder if the eletronics and batteries could survive.

 

[graham]

There were reviews from Germany earlier this year which took the current Roadster on the Autobahn. After only about 4 or 5 minutes at top speed, the powertrain begins to overheat and reduces the maximum speed to around 100 mph to compensate. The Roadster can do over 120, but not for sustained periods today.

They have talked about the idea of making a track-specific version of the car in the future to work around these issues, but the consumer version available today has limitations as a track car.