Electric Differences
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- Last Updated: Wednesday, 26 February 2025 14:57
The Features - General EV and Tesla
About Instant Torque
This is the first thing one notices when driving an EV, and especially for a Tesla performance model, which is stunning, very addictive, and hard on the neck muscles.
Petrol or diesel Internal Combustion Engines (ICE) just cannot compete here. When pressing the accelerator pedal, the butterfly valve controlling the intake of air is opens allowing the engine to breath. As the volume and speed of air increases it draws in fuel, either via a carburetor or by injectors designed to maintain the optimum oxygen/fuel ratio. This mixture is compressed and ignited, causing expansion producing power that increases engine revolutions, which in turn draw in more air and fuel and the process repeats, further increasing the torque and power. If the engine has a turbo, which is driven by the increasing exhaust gasses, it further boosts the air fuel mix giving more power and acceleration, until the peak torque point is reached. The point is that the above process takes some time to reach a maximum and thus the occupants feel one of building acceleration up to the next gear change.
Electric motors are different. Torque is directly proportional to the current applied, even when not rotating, as its just a magnet pulling on another magnetic object. At this instant electric motors are the least efficient, as, until rotation begins, no work is being done for the energy being applied. Its all sudden torque with no rotation and the reverse of a combustion engine where torque builds with increasing rotation. An electric motor produces near constant torque with increasing power as rotation increases, up to the point when torque falls off. Because they are perfectly balanced, the rotations per minute can become extremely high. The torque actually produced at any time is directly proportional to the current applied and hence instant when a switch controlling this is closed.
Typically combustion engines max out at about 6000 rotations per minute. (RPM) This is limited entirely by the speed of the pistons against the cylinder walls, which in turn is governed by the ratio of bore diameter to stroke length, which, when multiplied by the number of cylinders decides the swept volume or capacity of the engine. The shorter the stroke length the faster it can rotate, but with less low speed torque. Electric motors max out at around 20,000 RPM and this limit is governed by the increasing centrifugal forces which eventually forces the rotating parts to fly apart, much like a jet engine.
This difference is why combustion engines need gears and electric motors don't. Most ICE vehicles have a maximum speed of around 100 Kph in second gear which usually gives the best acceleration. EV's are fixed geared through their differentials to a similar ratio. An ICE at 18,000 RPM in second gear would be near 250 kph. Thus the experience of driving an EV is like an ICE car in second gear at around 3000 RPM, but at all speeds. The maximum RPM and Current allowed is controlled by the software.
Actual torque (acceleration) at some point decreases as RPM increases. With most Tesla 3 models this happens at about 140 Kph. The acceleration differences between a dual motor performance, and a regular dual motor at over 140 Kph are small. The performance model software just applies a much greater current to the motor from the start, greatly increasing initial torque and therefore acceleration. The maximum speed for the performance model is also set higher in the software. Owners of some other models can purchase a partial boost option. All have a switchable Chill Mode available for drivers who prefer a more ICE like performance.
Regular single motor rear wheel drive models, while still very quick, are not that neck snapping. (Partially due to the type of motor fitted. Latest versions have about 20% more power.)
Efficiency and Regeneration.
Electric motors are over 95% efficient compared to an ICE where over 20% is considered good. This is the main reason why EV's are cheaper to run. They also have a huge advantage, that when power is removed, the car movement continues rotating the motor, (no clutch to freewheel) and power is generated instead. Thus when going down hill, or slowing to a stop for traffic lights, power generated under these conditions is fed back into the batteries, charging them up. The load of charging makes the motor harder to rotate and thus slows the car like a brake. This process is known as regenerative braking and can recover up to 80% of the energy used in accelerating to cruse speed. Depending on the software settings this can be quite considerable. After climbing a hill much energy can be recovered when descending. The recovery rate varies depending on the total mass or car weight, plus the speed maintained during the descent. A Steeper decent at a lower speed has less wind resistance and recovers more power in maintaining that speed. When following an EV in an ICE you may notice this by having to brake harder than usual, as its speed usually decreases going downhill.
Smaller electric motors are less efficient - the reverse of an ICE. We all know a V8 uses more gas than a four cylinder engine when driven in the same manor. The efficiency of an electric motor depends on two things - friction and wiring losses. Friction is from bearings supporting the motor and associated gears and is low due to few moving parts.
Wiring losses produce heat directly proportional to the current being applied. It is calculated as I2R, where I is the current squared and R the resistance of the wiring involved. Losses also occur in the electronics controlling the motor and are considered as part of the wiring. Resistance (R) is governed by the type of metal in the conductors and the cross sectional area. Gold, Silver, Copper, Aluminum and Steel are all good conductors, with gold having the lowest resistance. A bigger motor has thicker wiring and lower losses for the same applied current in producing the same power. This is one reason why Tesla's have good economy and performance. The newer Models have a heat pump that can recover the heat generated in many places and re-direct it to the cabin or where needed, such as pre-heating the battery prior to fast charging. (A cold battery charges more slowly.)
It typically takes 0.5 amps from a 400 volt battery to maintain a constant 100 kph on level ground, or under 200 watt hours per Km traveled, therefore:-
A 160 horse power motor (about 120 Kw) needs 300 amps at 400 volts for that power and will be built with wire thick enough to handle that without over-heating (R=400/300=1.33).
A much smaller 20 h.p motor (15Kw) will have wiring sized to handle just 37 amps at 400 Volts, and its resistance is (R=400/37=10.8).
Thus when cruising at 0.5 amps as above, the large motor uses = 0.5 x 0.5 x 1.33 = 0.33 watts and the smaller motor = 0.5 x 0.5 x 10.8 = 2.7 watts or 8 times more. So bigger is definitely better!
There are many other variables of course, the bigger motor will be heavier and need more power to move, but conversely gets more back on regeneration. However, as a general rule, having an EV with higher powered motor is more efficient with a minimal penalty upon its economy for the same usage.
The effect is even greater when under load. Resistive losses in an electric motor typically waste about 3%. (There are other losses.) When climbing a hill, the small motor might run at max power, and at 37 amps the power wasted is then 450 watts. The same 37 amps on the bigger motor wastes 54 watts in producing the same 15kW. (The bigger motor gives a lot more power and able to accelerate, but the smaller might struggle and even slow down.)
One can see this from the smaller sized E.V's on the market. They have lower powered motors and smaller batteries in proportion, but fail to get the range of the Tesla's which seem to hit a sweet spot. It will be interesting to see how the next smaller Tesla model 2? performs.
Weight and Centre of Gravity.
There is no argument that E.V's are heavier than ICE vehicles due to their batteries. However, it does provide some benefits. With the batteries under the floor and at a bit over half the wheel diameter above the ground, such cars are very difficult to roll over. The extra mass also lowers the effect of road bumps giving a smoother ride although with slightly more road noise.
A greater mass is also beneficial in an accident. While the crumple zones must absorb more energy, the deceleration of the occupants is less and more of the energy dissipated is transferred to the other lighter vehicle. (In a car versus truck accident the truck always wins.)
Note the difference between mass and weight. Mass never changes, but weight depends on gravity, meaning once moving on a flat surface, weight has little effect on economy, other than a little more friction, mainly in the tires which benefit from a higher pressure. (Ignore wind resistance which depends on speed and shape.)
Safety
Because the motors are lower and between the wheels with nothing in front, the crash crumple zones can be longer and designed to be progressive and more effective. Tesla's have stronger structure by being made from aluminum which is strong and lighter than steel. Some parts protecting the cabin also use special high strength steel. This and their low center of gravity, plus their many electronic safety features, have given Tesla vehicles one of the highest safety ratings in independent accident testing.
One controversial feature is Auto Pilot and Full Self Drive. Both these features currently require the driver to monitor and interact with them and he is always responsible for controlling the vehicle. All newer Tesla's have hardware considered capable of self driving and come with basic Auto Pilot. This has two stages, the first being cruse control and the second self steering (Enhanced Auto Pilot). Once enabled, it will stop and start for lights, maintain a safe distance from the car in front, and adjust to the speed limit within a set tolerance according to the data available. The second stage (self steer) enables the car to follow the road within the lane markings. With no auto pilot enabled there are still settings to avoid obstacles, warn of (or prevent) lane departure without signalling, or from other vehicles drifting into or stopping in your lane. It will self brake if a collision seems likely. These features continue to improve with software updates.
Enhanced auto-pilot adds, lane changing to pass slower traffic or when indicating, navigation to destination with off ramps, summon, smart summon (finds the driver), self park and more.
Full Self Drive or F.S.D enables all of the above and adds the promise of the car driving itself to a destination, even in city traffic. Versions of this are being rolled out in the USA, initially to selected testers, then purchasers, and eventually to all as a free monthly trial. Many You-tube videos show US owners successfully using it to drive great distances through cities with none or few interventions. No time-line for it arriving in N.Z yet but we believe its now being tested.
Hopefully it will arrive here in 2025. Testers are raving about the latest V13 which has successfully navigated Manhattan in New York city at night during rush hour totally unassisted for an hour.
As an F.S.D purchaser, I do have the enhanced auto-pilot features and apart from not making turns at intersections, which must be done by the driver, I have been able to let it drive the motorway to Cambridge, Highway 29, and over the Kaimai ranges to Tauranga. It always enforces the user to remain in control (and awake) by maintaining contact with the steering wheel, at least every 30 seconds or so depending on speed.
While this does seem to offer little, once one gains confidence, the drive is far more relaxing allowing one to enjoy the scenery and the fantastic sound system, all without fear of missing unexpected forward events. Taking a phone call is no problem, which is built-in, and one can answer from the screen, steering wheel button, or voice command. It can read-out text messages and one can dictate and send a reply.
Surprisingly basic autopilot is also very useful in heavy or grid locked traffic. It just follows the car in front at a safe distance, and only requests confirmation every few minutes while stationary or creeping.
Connectivity
This is either via WiFi or LTE (mobile). Premium LTE connectivity is initially free, but about $100 P.A. Premium LTE is well worth the cost as it provides many other features for navigation, showing live traffic volume on the map, as well as media streaming. At various times offers of, premium for life, a 1 year trial, or via referral rewards, have been available. Be sure to fully check-out premium features during your trial.
Standard LTE connectivity includes Navigation and remote access to the car via the phone app with notifications.
Premium adds extra features: like a Web browser, Live Traffic Visualization, Sentry Mode live Camera view, Satellite Maps, and media Streaming. At $10 a month its very cheap for an unlimited LTE connection in N.Z. One could instead tether the car to your phone via WiFi and get some of the extra features.
While the phone remains Bluetooth connected to about 10 metres away, the car will only unlock when the phone is within 2 metres.
Security
Having no keys enhances this as a car-jacking or theft cannot proceed without the phone or card. Additionally one can set a pin to enable driving and for access to the glove box. Once a door has been opened and the drivers seat evacuated, this must be re-entered. The phone should always be removed as it allows one to remotely set car speed and performance, view it's occupants, surroundings, and report its location.
The car has eight cameras used for autopilot. Three appear on the screen when reversing or on demand. Sentry mode uses these, plus one front camera to always be recording, unless specifically turned off when parked at home or work. (It knows these locations by GPS.) Any detected events will have the previous 10 minutes separately saved for later viewing. This feature has saved me some $2000 insurance excess costs when it captured the car next to me denting my door while away shopping. I was later able to identify the registration of the offending vehicle and its occupants, allowing my insurance company to eventually track it down.
Another feature is Dog-Mode. Enabling this keeps the air conditioning running while stationary with a public message in large letters on the screen showing the current inside temperature and that the occupants are quite comfortable. If this was to fail the driver would get a phone message in short order and can immediately view the car cameras. A notification happens if one has left a window down, or a door not shut properly.
Internal Space
As there is no engine or transmission the space between seats is greater and both the front and back have extra space. There is a small front trunk where an ICE engine would be, and extra boot space in place of the fuel tank. In all models the rear seats fold down joining the boot space into the cabin. For the model 3 saloon a limiting factor is the small height of the boot opening. Despite this, mine has carried four international travelers with their luggage. The model Y (SUV style) rear hatch provides more with top height when open close to that of the car roof.
Entertainment
Probably the best car ever in this respect. Tesla hired sound engineers from Bang & Olufsen who arguably produce the best sound systems in luxury cars including Mercedes, Porsche and BMW. Many experts consider the sound of systems fitted to Tesla's are even better. However, be aware there are two versions. A standard RWD model has only 8 speakers:- 4 full range - 1 in each door and 3 in the front plus one tweeter. The premium version is included with the dual motor models and some long range plus models. These have 15 speakers - additionally two in the rear plus a sub-woofer, and in the front 2 on each side for the immersive system. (1 in each front door quarter light and 1 at the top of each A pillar.) The difference is quite dramatic, and as such I would always choose the premium. (Surprisingly most do have the speakers, but not the wiring fitted. Some third-parties have this available for purchase and D.I.Y fitting.)
Sources of music include Spotify, Tune-in, Apple Music, TIDAL, Karaoke, plus FM Radio, from phone via Bluetooth or a USB thumb drive.
Video can be streamed while in park, from Netflix, You-Tube, Disney+, Twitch and Tesla instructional videos. A Toy-box offeres some 20 games, including Luna Lander, Cat Quest, Sudoku, Backgammon, Solitaire, Mahjong. Of course many streaming services also need an independent subscription, and some games need a USB controller. The actual streaming services available vary by country and some games depend on the CPU fitted.
Software Updates
These happen every month or so depending on bug fixes, new features, and factory recalls. Its very rare to take a Tesla to a service centre for physical recalls as virtually everything is controlled by software.
Since about 2005 most other cars use software written by different third party manufactures who provide many electronic bits, such as engine computer, anti lock brakes, accelerator pedal, instrument cluster, entertainment modules, alternator and charging, seat position memory, and locking security systems. These cars are built like Lego and have little control over the software in each part and its not surprising that the auto industry has evolved slowly with 3 or more yearly release cycles. Because Tesla was primarily a software company, once they learned about manufacturing hardware and writing their own software, the whole auto industry changed leaving many other manufactures up to seven years behind in technology and no software engineers.
For a Tesla, the changes to features and safety over the last 3+ years have been considerable, to the point of it being a different car. Apart from active safety changes, such as improving seat belt accident pre-tensioning time, improved repeated braking distances and other safety things, that one hopefully will never need, I can count over 20 features that have been added. These range from Auto stop with hand brake at intersections, Orange/Red traffic light stop, green light chime, auto high beam, dog mode, sentry mode cameras, and blind spot camera on indicate. There have also been numerous additions to entertainment sources and games.
Maintenance
An EV still needs regular user maintenance as an ICE car. Tyre's - pressures, rotation & replacement, washer fluid top-up, brake fluid moisture check, W.O.F, and general cleaning, etc. As there is no engine, oil & filter, radiator, spark plugs, turbo, no service or tune-ups are needed. Tesla don't actually require a service for warranty purposes. One may only be recommended after 3 years or so depending on distance driven and the environment. If in a salty environment the brake calipers may need more frequent attention, as due infrequent use of the brakes cleaning and lubrication may be advisable. Otherwise a brake fluid moisture check, cabin air filters, and 12 Volt battery replacement are basically the only maintenance items. The software will notify of issues and if a service visit is needed.
Much of the above can be done by the owner if so inclined. Parts and servicing are likely available through the phone app purchase or website.
Now at four years and while still under warranty I decided to get mine serviced. A couple of minor issues need checking along with a recall to check the rear seat belt mounting. It included a WOF, tyre rotation, brake fluid replacement, new wiper blades, plus a new boot lid wiring harness. (Non requested warranty item.) Total cost: $514 inc GST. That's less than $130 per year and about 1/4 of an ICE car.
Model Y Sales
At the end of the 1st quarter of 2023 it was announced that world-wide its now the highest selling car of any type, displacing the Toyota Corolla into second place. When it's cost with rebates, features, and performance are considered, many now consider it represents the best value of any car ever. While many brands may have similar or better features, none come close to providing all of them at its current price.