# Tag Info

## Hot answers tagged electric-vehicles

31

It depends on how steep the hill is. On a slight hill, the energy added by gravity is still not enough to overcome rolling friction and air resistance, so the car still needs power to maintain speed. On a steeper hill, the two may balance out, so no power is used, and no power is generated. On a hill that's steep enough to require braking to control the ...

6

Yes, it can certainly happen. To recharge the battery when going down hill, the free roll speed needs to be greater than the speed you are trying to go. That means going down the same hill may result in a different outcome depending on speed. For example, let's say you put the car in neutral and coast down a particular hill. For most of the hill, the car ...

5

Maximum speed in a straight line is largely determined by the vehicles maximum power output compared to its drag although once you get past about 200 mph dynamic stability can start to become a serious issue as well. The current Land speed Record is held by Thrust SSC which was powered by two jet engines, reached supersonic speeds and has as much in common ...

5

One problem with generating electrical energy from a car engine is that the RPMs are constantly changing, and consequently the power output of an electrical generator would vary with engine speed. An alternator is very good at responding to these variations; the current in the rotor can be quickly adjusted to change the power output at a given RPM. I don't ...

5

This cannot be answered as is because almost all the critical information is missing. Mechanical Power required to move to the go kart is determined by the force and speed required Motor Power can converted from mechanical power and be put in terms of motor torque and motor RPM. Battery power can be converted from motor power and put in terms of voltage and ...

5

As an owner of an Airwheel S8™ self balancing scooter (with a seat) that operates similarly to a Segway™, I can offer insight and my own experience. There is an upper limit, which is primarily based on the maximum power available to be transmitted to the wheels. When in a "stopped" attitude, some motion is required to keep the primary mass (...

4

The basic equations governing an electric car are reversible, so a simple analysis would say that the battery is getting charged. In the real world, there are more complications. In the case of an electric bike, there is a ratchet that disengages the engine from the wheel when the wheel is going faster from the engine (just like how on a regular bike -- ...

4

ABB train regenerative braking. Some Swiss trains give back energy to the grid upon descending the mountain pass that they previously climbed. The article claims as much of 70% is recovered. I rode the Jungfraujoch and the personnel mentioned for every 3 trips down the mountain enough electricity was recovered for a "free" trip up.

3

The additional equipment is onboard the EV in today's crop of electric cars. The charger is part of the vehicle, while the station, formally known as EVSE, Electric Vehicle Service Equipment, negotiates with the charger, "letting it know" the source voltage and confirming that no one will be electrocuted once the power is turned on. My 220v EVSE is ...

3

It is certainly possible as each cylinder could effectively be a solenoid (i'm actually pretty sure I have seen exactly this but can't remember where atm) ....however the reciprocating nature of IC engines is one of their big disadvantages as it introduces inherent vibration and puts big transient loads on certain parts (especially connecting rods). In ...

3

Answers to your specific questions: No, voltage converters won't help, at best they will waste 10% of your power. Think about this : they involve transformers. two different windings on a magnetic core to translate one voltage to another. That might help you understand that any given motor (which is just a winding on a magnetic core to translate voltage ...

3

Yes, but it would probably be a very poor engine. As you noted in your question, there are huge practical issues with using the arc alone as your power source, compared to using it to ignite the fuel mixture in a conventional spark-ignition engine. But you are correct to observe that both the electric arc and the combustion process cause a rapid expansion ...

3

While DKNguyen's answer is accurate. I believe you're looking for a more holistic answer. Will it move? Absolutely it will move if you give it enough gear reduction. You could move the cart with a minuscule motor and a worm drive if you don't mind it creeping along. So the question is, how fast will it go? Or more accurately, how hard can it accelerate? and ...

3

Different electric assist bikes will present different circumstances. For instance, a standard hub motor (front or rear wheel) will have permanent magnets which react with the iron in the stator. You can feel what is called cogging when rotating the wheel by hand, without power. This is energy expended by hand, but also applies when pedaling without applying ...

2

The answer to the first part of question is, you're right, you don't concern yourself with the other carriages friction or weight. The second part, you have to consider static friction force on the wheels for traction. In steel on steel it is approximately 0.60. So the approximate traction your locomotive can provide is 60% of its weight tributary to its ...

2

You get more free gearing with the hydrostat, and much smaller package and less weight. Take a 60hp diesel and hook it to a hydraulic drive servo. It makes up to 4500 psi peak pressure, or 8 gpm peak flow. It gives infinite gearing from max reverse to max forward speed. The servo weighs about 30 pounds and is the size of a loaf of bread. The wheel motors are ...

2

you will find that a generator capable of delivering, say, 10HP (electrical equivalent, 750 watts = 1HP) is very big and heavy and a hydraulic pump with a 10HP rating is smaller and lighter. Similarly, an electric motor good for 5HP will be much heavier than a hydraulic motor with the same rating. So if hydraulic power is available, it makes sense to use ...

2

I think you're on the right track to not use a solid driven axle, as it will give you problems as you describe. I don't believe that a single wheel drive would be too much of a problem, unless you're on slippery surfaces like ice or mud, but you do have to deal with the counter torque. For hub motors, there's usually a means to secure the hub assembly, often ...

2

This isn't a complete answer but may give you some ideas. I think you are correct not to drive only one wheel. The cart looks rather rigid and I can imagine that on rough terrain that one wheel will often be lightly loaded and if that's the driving wheel then you'll have no traction. I suggest that you motorise two wheels. This way they can balance each ...

2

This is not an answer, it is just pointing out an error in calculations. DC motor torque discrepancy A DC motor at 2750[rpm] and 250[W], outputs $$M=\frac{P}{\omega} = \frac{P}{\frac{2\cdot\pi\cdot n}{60}} = 60\frac{P}{2\cdot\pi\cdot n} =0.8681 Nm$$ So your torque after the sprockets (if you are increasing the speed) is even less, probablyt around .5Nm. ...

1

It would be very unusual to have a wind turbine power a charging station without having a buffering device for energy storage such as an electrolyser or a battery of its own. But if it's a textbook calculation and these things are not there, then one approach is given below. The limiting factor for battery charging is the current. If it takes 21 min at the ...

1

There isn't enough information in the question to give a reliable answer. But here are some possible crude answers, just in case you are being tested on basic arithmetic and the relationship between power and energy. 1 kWh is an amount of energy equivalent to 1 kW for 1 hour. It's also the amount of energy equivalent to 10 kW for 0.1 hour, or 0.01 kW for ...

1

They are not the same, even while they meet the exact same standards minimum. Basically level 1/2 chargers are actually not charging, they just deliver AC power safely to the onboard charger of the car. That's why some call them smart cable. Level 3 chargers deliver very high amp DC directly to the battery and talk with the EV to control and modulate power ...

1

The essential question here is why or why not use a transmission in an electric car. Here are the underlying issues. It is commonly asserted that a DC electric motor is a constant-torque device, developing the same torque at standstill (0 RPM) that it does at its rated RPM (in this case, 3000). Advocates of the "no-transmission" position cite this as a ...

1

As a first approximation. Those batteries are rated at 5Ah (more on this later). At full power a 12V 250W motor will draw about 21A so on the face of it one battery will give you about 15 minutes of operation at full power. However standard lead acid vehicle batteries don't really like being used by this, they are designed to give short bursts of high ...

1

One thing about using overhead trolley wires to power vehicles is traffic congestion. I can remember riding on trolley buses when I was very young & if a trolley bus had to pull over at a bus stop to drop off or pick up passengers it blocked the vehicles behind it. All vehicles behind it had to wait until the bus moved again. Any vehicle connected to ...

1

The main problem is the extremely peaky load. Your gas tank stores power for a week, batteries store power for days, and can be charged off peak. OLEs deliver on demand, and that sort of power is expensive to dispatch compared to more balanced loads. You really need to look at what this sort of recharging infrastructure consists of. How many combined cycle ...

1

This idea has been suggested often, but there's way more to it than you'd think. One big problem is that batteries are heavy, and there are multiple problems arising because of this. The main thing being the packaging in the car. You want a decent range in a car, so the battery will be large and heavy. If you put it in the front, the car will be front heavy,...

1

Short answer: neither BLDC nor PMSM requires a hall sensor, and both may need need it for some applications. BLDC (brush-Less Direct Current) motors and PMSM (Permanent Magnet Synchronous Motor) are basically the same type of motor: three-phase synchronous motors, with permanent magnets to generate the rotor's magnetic field (it would work with other ...

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