BMW i3 REx vs. Chevrolet Volt: two different approaches to plug-in hybrids - Chevy Volt Forum - Forums and Owners Club!
Chevy Volt Forum - Forums and Owners Club!  

Go Back   Chevy Volt Forum - Forums and Owners Club! > Chevy Volt Forum - News Desk > Automotive Industry News and Chevy Press Releases
Notices

Automotive Industry News and Chevy Press Releases News regarding the Chevy Volt and other industry info. Post it here!


Reply
 
Thread Tools
  #1  
Old 06-19-2014, 08:28 PM
TorqueNews TorqueNews is offline
Chevy Volt Forum Junior Member
 
Join Date: Jan 2014
Location: North Carolina
Posts: 38
TorqueNews is on a distinguished road
Default BMW i3 REx vs. Chevrolet Volt: two different approaches to plug-in hybrids

       

Aside from general misunderstanding of how plug-in hybrids work, an even less understood nuance is how the range-extended version of the BMW i3 is different from the most well known plug-in hybrid, the Chevrolet Volt. Torque News breaks it down.

This story discussing Chevy Volt vs BMW i3 REx, is reprinted from TorqueNews.com and written by Luke Ottaway.

The Chevrolet Volt and the BMW i3 REx are two electric vehicles that rely on gasoline backup to alleviate range anxiety. How the two vehicles go about it, though, is what distinguishes one from the other.

Chevrolet Volt: how it works

When it was first unveiled, GM tried to tell everyone that the Volt was a pure series hybrid; that is, the battery supplied electricity to the motor until it ran out, at which point the gasoline engine would rumble to life and generate electricity to feed to the motor. We eventually found out that GM wasn’t being entirely truthful and the real system is actually far more complex.

In reality the Volt is technically a series-parallel plug-in hybrid, meaning the engine is also capable of powering the wheels when necessary. The 16 kWh battery pack allows for approximately 38 miles of all electric range powered by a 149-hp electric motor. When the battery depletes to a certain level, the 1.4 liter 84-hp gasoline engine kicks on in a smooth transition. It functions as a generator to produce electricity for the drive motor.

Interestingly, though, the Volt doesn’t have just a single-speed direct drive transmission as you might expect for what is effectively an EV. It actually uses a planetary gearset with a second electric machine; the 149-hp traction motor is connected to the central sun gear, while the planetary carrier provides the output to the differential. The 72-hp generator motor can be fixed to the outer ring gear, the gasoline engine, or both at once using clutches.

Volt drive modes

This configuration allows for four different “drive modes” with the Volt, as described by Edmunds:

1 – Low speed EV mode. Up to 70 mph, the larger traction motor provides the necessary torque while the engine and smaller motor-generator are disconnected from the transmission and the outer ring gear is locked in place.

2 – High speed EV mode. Up to 100 mph, the Volt is still capable of running without using the gasoline engine. However, the configuration changes to improve efficiency above 70 mph. In this mode, the ring gear is fixed to the smaller motor while the larger motor turns the sun gear. Both motors turning in the same direction allows the planetary carrier to rotate faster and reach high speeds while keeping the speed of both electric machines closer to the optimal efficiency band. If the larger traction motor were to provide sole motive power at high speeds, electric range would be compromised as motors lose efficiency at excessive RPM.

3 – Low speed series hybrid mode. Up to 70 mph after the battery has depleted to a certain level, the engine fires up and is connected to the smaller motor that acts as a generator to provide electricity for the larger traction motor.

4 – High speed series-parallel hybrid mode. Above 70 mph with the battery depleted the engine will be connected to the outer ring gear to assist in providing power the wheels. It also is fixed to the smaller motor-generator to simultaneously recharge the battery, which forces the engine to work harder. In this mode the larger traction motor is still driving the sun gear; the vehicle cannot move unless the traction motor is operating.

Note: A previous version of this story contained inaccuracies in the drive mode descriptions, pointed out by alert readers. We regret the confusion.

So it is clear that the Volt is more complex than you might think. After the electric-only mode is exhausted, the vehicle gets somewhere between 35 and 40 miles per gallon, not great for a hybrid. But it is capable of driving about 350 miles on a tank, which makes it an EV that is practical for long trips.

BMW i3 REx: a different approach

BMW went a different route with the all-new BMW i3. The vehicle is offered as either a battery electric or a plug-in hybrid REx model, and the buyer can choose which he prefers. The optional range extender gasoline engine costs about $4,000 extra, and lengthens the vehicle’s effective range from 72 miles to 150 miles. The unladen battery electric version without the range extender achieves 81 miles of range per charge.

The gasoline engine in the i3 REx is very small and serves only to increase driver confidence, and the 1.9 gallon fuel tank only provides enough juice for an additional 80 miles after the battery is depleted. The two-cylinder engine is pitifully small at 0.68 liters; once it switches on the vehicle’s performance is negatively affected. The 170-hp motor cannot call the same power from the battery that it can in EV mode, as it is relying on the tiny engine to spin a generator that provides electricity for the motor.

The most interesting aspect of the i3 REx is simply that it is optional. BMW obviously reasoned that allowing customers a choice would help the vehicle sell to more drivers concerned about the limitations of an 80-mile electric range. Although it makes the i3 viable for trips up to 150 miles, the vehicle is without a doubt compromised by the addition of the range extender and should be driven with only the battery as much as possible.

Which should you choose?

Both vehicles serve their intended purpose, but that purpose is not the same for each. The Volt is the car that is ideal for shorter commutes in EV mode and the occasional long road trip when necessary, and eliminates any shadow of range anxiety. The i3 REx is primarily a pure electric car that just happens to have an emergency backup engine that reduces performance when it is needed. The REx can commute twice as far as the Volt in EV mode but is not viable for long trips.

Both vehicles are not cheap, although the Volt has come down in price and will drop further with the next generation in 2015. The Volt starts at $34,185 while the BMW i3 REx will set you back a cool $45,200. If you’ve got the cash, both are excellent vehicles that go about their different tasks in different ways.
   
Attached Images
File Type: jpg i3_vs_volt.jpg (61.1 KB, 19 views)
__________________
VoltForumz.com | Chevy Volt Forum | Chevy Volt Forums
Reply With Quote Quick reply to this message
Reply

Tags
chevrolet, chevy volt

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Chevy Volt Forum - Forums and Owners Club! forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Member names may only be composed of alpha-numeric characters. (A-Z and 0-9)
!!ATTENTION ADVERTISERS!! If you intend on advertising anything on this forum, whatsoever, you are required to first read THIS INFORMATION!! Additionaly, we do NOT allow BUSINESS NAMES in your user name. If you own a business, once you have been set up as a "Supporting Vendor", you will be permitted to enter your business name in your "User Title" which appears directly below your name.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address

Please enter a valid email address for yourself.

Note: If your email address requires someone to click a link before they can send you email, DO NOT REGISTER WITH IT as no one is here to click the link and you will never get your activation email!
We have banned MANY Free email providers.
If you get notice that your email address is banned when you try to sign up, it is because its been banned due to spammers using the provider, or too many members bouncing emails we send back to us via the free provider! If this happens to you, you will need to use a different email. If you do not provide a valid email address you will not receive your activation email. We recommend that you register with an email address which is attached to your ISP! Not a free service! We have found that using free accounts causes you to not receive your registration email. In any case, you should add VoltForumZ.com to your spam filter whether using a free account or your ISP account. If you bounce email to us, you will have your account deleted and your IP address banned!

Email Address:
Location
Where you live
SEX?
Enter your Sex!
Insurance
Please select your insurance company (Optional)
Date of Birth
Your date of birth and age are displayed in several places on the forum. Only the administrator will have access to your date of birth should you choose to hide it via the privacy option below.
Month Day Year
     
Privacy

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Here is the better range and new look of the new Chevy Volt TorqueNews Automotive Industry News and Chevy Press Releases 1 05-29-2017 09:20 AM
VOLT: The Best EV in America Keeps Getting Better TorqueNews Chevy Volt General Discussion 1 04-13-2014 10:55 PM
Chevrolet Volt to receive much-needed upgrade for 2016 TorqueNews Automotive Industry News and Chevy Press Releases 0 03-17-2014 08:45 PM
Chevy Volt Owner's Tips for Winter Driving TorqueNews Chevy Volt General Discussion 0 02-04-2014 09:41 AM
The Cadillac ELR Should Lead to a Chevrolet Volt Coupe TorqueNews Automotive Industry News and Chevy Press Releases 0 01-30-2014 11:18 AM


» Advertisement




All times are GMT -5. The time now is 11:04 AM.


Powered by vBulletin® Version 3.8.10 Beta 2
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
vB.Sponsors
Copyright © VerticalScope Inc. All rights reserved.