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Timson

electric car

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Hello

I am a student from belgium. I work in a group. For our thesis we have the topic "range of an electric car". My question is what you think we could test. How could we improve the range? We increased the mass of the wheels and as a result we increased the battery life a little but not much. Would you like to help me.

Thanks in advance

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19 hours ago, Timson said:

Hello

I am a student from belgium. I work in a group. For our thesis we have the topic "range of an electric car". My question is what you think we could test. How could we improve the range? We increased the mass of the wheels and as a result we increased the battery life a little but not much. Would you like to help me.

Thanks in advance

decreased?

The obvious ones....Reduce mass (except bigger and better batteries), reduce frontal area and coefficient of drag (so less drag), improved tires, regenerative braking...

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Modulate your acceleration. Harder acceleration drains batteries more quickly than gentler smoother acceleration 

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J.C.Macswell

Yes we have increased the mass. If a heavy object is spinning, it will come to a stop less quickly, so that the battery has to deliver less. (Flywheel)

 

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Did you measure already how much and where the energy is being lost in your car? If you are studying  you should have some picture how much energy is lost in batteries (charge/discharge cycle, self-discharging), how much is lost in inverter (if any), how much is lost in motor (resistance, eddy currents, hysteresis), how much is lost in transmission (if any), rolling resistance, air resistance, accessories power consumption... If you have this data then you can compare with other electric vehicles and check where you should be able to make an improvement.

If you didn't do such part-by-part measurements already, then I think you should.

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I have already done some tests. I used a flywheel and let it run for 2 hours at a speed of 17.6 km / h. The remaining battery capacity was 89%. Then I made the wheel 1kg heavier and repeated this test. The remaining capacity was then 90%. So 1% difference. This could be more because it is a completion.

I also did a test to see if the temperature has an influence on the range. I spun the wheel for 5 hours at a speed of 17.6 km / h just like I did in the previous test at 20 ° C. The remaining capacity was 76% and then I repeated the test at 2.5 ° C and the remaining capacity was 72%, so a difference of 4%. So my conclusion is the lower the temperature, the smaller the range.

I think these are good tests after all. What do you think?

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4 hours ago, Timson said:

J.C.Macswell

Yes we have increased the mass. If a heavy object is spinning, it will come to a stop less quickly, so that the battery has to deliver less. (Flywheel)

 

If it isn't spinning...it takes that much more energy to get up to speed. So you would break even, except for the extra friction losses inherent in having the extra mass, so you don't get as far.

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J.C.Macswell

Do you think a test at different temperatures is good?

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25 minutes ago, Timson said:

J.C.Macswell

Do you think a test at different temperatures is good?

Possibly. It might effect battery performance. Your test I believe is in line with what generally would be expected.

 

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I would consider a 'system' approach, instead of a 'self-contained' approach.
There is little, if any, infrastructure for electric vehicles, so why does a vehicle need to be self contained and autonomous ?
Why can it not pick up power as it moves from a distributed power system ?

Consider a very small battery used just to get the car on the road's power grid, which could be built into the road itself ( electric streetcars are an example ).
The initial outlay ( financial ) is way higher, but the rewards, such as reduced power consumption because you're not pushing around the large mass ( and volume ) of batteries, unlimited range once on the grid, and hazardous ( and limited supply ) refining and disposal of battery materials, may outweigh the financial downside.

This is a new way of doing things.
Why go with the tried and true; be bold.
The world is always ready for a new 'mousetrap'.

 

PS
The flywheel effect is only good at constant speed,; that's why it's on the engine.
If you are constantly accelerating your wheels ( like in city driving ), increasing their mass is detrimental.
Oh, and 'thinner' wheels have less rolling resistance ( think bike wheels/tires, not Formula1 rear tires )

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If you really want to improve battery life, reduce the weight.

So look at a car and ask yourself what can I remove to reduce the weight.

Look around at vehicle occupancy.

How many are full and how many have only one person ?

So would a car to seat only one person need the same size battery as a car to seat four ?

Alternatively which car would the same capacity battery take further?

So you could own several cars say a big one and a little one ?

Why is an electic bike or scooter battery smaller than an electric car battery ?

Note that the wiring in a bike is shorter than the wiring in a car (why?)

So resistive power losses in the wiring will be greater in a car unless the wiring is of greater gauge and so much heavier.

 

Another thing to consider is that a fully charged battery will take you further than a partially exhausted one as their internal resistance rises with discharge.
Good use of this fact used to be made in the days when we had daily home milk deliveries.
Dairies used to maintain a fleet of electric powered milk 'floats' and charge them every night.

In the morning the float started with a full milk payload and a full battery, but as the round proceeded the battery became discharged but the payload became less as the milk was delivered.
This partly compensatd for the lowering of the batterie's efficientcy as it discharged.
 

The floats could be seen to whiz out in the early morning, but crawl back slowly to the depot as their batteries discharged.

This of course brings me to the last major variable affecting performance.

Speed.

Over a few mph, the slower you go the longer your battery will last.
Air resistance due to speed is the most important factor in vehicle dynamics as it increases with a power somewhere between a quadratic and a cubic of the speed.
You should also investgate driving style in relation to acceleration/braking.

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