What can be done to make electric cars have good high end acceleration

[whitex]

Correcting Gross Weight => Curb Weight - thanks ItsNotAboutTheMoney for pointing out the issue.

The issue is much simpler than people think, it boils down to power to weight ratio. My P85D curb weight is 4,936lb, add a driver and you're over 5000lb. Transmission doesn't add ANY power, it actually subtracts due to inefficiencies, so unless the electric motor somehow delivers less power at the high rpm, there is no need for one except to push the car to higher speeds that the max motor rpm allows. So why other cars with less hp can be faster, they are lighter.

So to answer the OP's original question, there are only 2 ways:
1. Subtract weight
2. Add more power - currently the power is limited by the battery

That said, this is a family sedan folks, over 5000lb of weight. It accelerates really well in its class. I think the perception issue is due to the fact that it basically blows most other cars out of the water 0-40, hence people expect the same at higher speeds. Unfortunately the 0-40 advantage is due to ICE inability to develop max power at low rpm, while the electric motor hp being mostly independent of the rpm. Once the car is rolling, the ICE engines can be kept at optimal RPM's (via a transmission) and then if they have a better power to weight ratio, they accelerate faster (assuming similar aerodynamic drag). Can't beat the laws of physics.

 

[brianman]

My P85D gross weight is 5,887lb

I thought it was 4936 lb?

 

[ItsNotAboutTheMoney]

I thought it was 4936 lb?

Yes, poster seems to be confusing GVWR (max rating with load) and curb weight (weight of the vehicle).

Gross vehicle weight rating - Wikipedia, the free encyclopedia
Curb weight - Wikipedia, the free encyclopedia

 

[ChadS]

It started with Hybrid batteries and rolled over to EV. 8 year, 100,000 miles Federal. Some states, like California, are even tighter.

I'm not sure whether it's a mandate, a law, or qualifier.

California does have such a rule; I don't live there but I think it's 8 years/150k miles. But it's for emissions control equipment...which on a HEV or PHEV, includes the battery. So HEVs and PHEVs do indeed have to warranty their batteries for a long time, at least in CA. That's partly why PHEVs like the Volt have such a large unusable buffer.

However, BEVs are not subject to that rule (because emissions won't rise if the battery doesn't work as well) and I am pretty sure there were some early EVs that didn't offer as high of a warranty - and that's why unusable buffers in BEV batteries are typically much smaller. But a long BEV battery warranty has become a selling point as the battery is what people fear most about BEVs.

 

[sorka]

Transmission doesn't add ANY power, it actually subtracts due to inefficiencies, so unless the electric motor somehow delivers less power at the high rpm, there is no need for one except to push the car to higher speeds that the max motor rpm allows. So why other cars with less hp can be faster, they are lighter.

The electric motor does delivery less power at higher RPMs, but only after a certain point. On the MS, the power curve is nearly flat up to about 100 MPH, starts to drop from 100 to 120 MPH, and then falls like a rock after 120 MPH.

So for normal US driving or even 1/4 mile tracks, a multispeed transmission will hurt the MS. It will help at 150 MPH on the Autobahn, but even then you'd only be able to cruiser at 170 MPH for a few minutes before the battery overheats and pulls back power.

 

[sorka]

I thought it was 4936 lb?

Curb vs GROSS. Gross is maximum cargo added to the vehicle. It's the most the vehicle can weigh carrying as much as possible. Curb weight is what it weighs without cargo or driver.

 

[sorka]

California does have such a rule; I don't live there but I think it's 8 years/150k miles. But it's for emissions control equipment...which on a HEV or PHEV, includes the battery. So HEVs and PHEVs do indeed have to warranty their batteries for a long time, at least in CA. That's partly why PHEVs like the Volt have such a large unusable buffer.

However, BEVs are not subject to that rule (because emissions won't rise if the battery doesn't work as well) and I am pretty sure there were some early EVs that didn't offer as high of a warranty - and that's why unusable buffers in BEV batteries are typically much smaller. But a long BEV battery warranty has become a selling point as the battery is what people fear most about BEVs.

I think people are confusing Hybrid power train battery warranty. In california, all Hybrid batteries are 10 years / 150 K miles. In all other states it's 8 years 100K miles.

 

[brianman]

Curb vs GROSS. Gross is maximum cargo added to the vehicle. It's the most the vehicle can weigh carrying as much as possible. Curb weight is what it weighs without cargo or driver.

Right. But read the post I quoted. His context uses these numbers incorrectly, IMO.

 

[McRat]

...
That's partly why PHEVs like the Volt have such a large unusable buffer.
...

Or at least that's the common rumor. The Volt has 4.4 kWh of extra capacity. All lithium rechargeable batteries do. Unusable is inaccurate though. When the drive battery is depleted, the 75kW generator turns on. If you floor it, the power train produces the full 120 kW. It can do this because of the buffer. If you reprogrammed the car to deplete that 4.4 kW, you would lose your passing power every time the battery ran out.

 

[ChadS]

You are correct that the power of the whole battery can be used, but I meant an unusable energy buffer. GM has said the buffer is there to ensure the battery operates as designed through the warranty period, so I think we can safely call this more than a rumor.

 

[McRat]

Isn't the Model S also 4 kWh?

 

[theboom1]

Lets also consider electric cars other than the model s. For example the next gen roadster or any other 2 door sports car. You have got to be able to accelerate past 100 strong in a 2 door sports car. Having far less weight will help, but don't you think it will need the 2 speed trans like the rimac as the power will drop off quickly as you go faster.

 

[theboom1]

OK, one more try. Yes, you can make an EV win high speed races.

No, from an engineering standpoint, it's a stupid idea for a production street car today that by law must have an 8 year battery warranty.

But if you freakin' insist, you can built one tomorrow. Do you REALLY want to race against this street legal EV? -

This is for the standing mile record:

It is faster than my 638HP ZR1 in the standing mile.

Would you look at that. It has a transmission

 

[McRat]

Would you look at that. It has a transmission

Fast and faster. Probably a Gear Vendors? I can't find the article right now, IIRC, a 45kWh battery and 750HP. LSR speed records destroy batteries pretty quick. There is an EV motorcycle about that fast also, and a 400 mph streamliner attempt coming up this summer at Bonneville by Ohio State University.

The driveline in the Vette would probably be way over $100k to replicate. All custom EV racing goodies.