Thursday, January 19, 2012

Challenges with Electric Cars



I have closely watched the developments of electric cars for last 5 years. I own a Reva electric car for four years and as an electrical engineer, I am interested in electric cars. As a owner of electric car, I get questions on viability of electric cars and people are curious to know why there is not much choice of electric cars in the market despite the huge buzz and hype in the media.

Every year, in every auto expo, all the major car manufacturers display their concept electric cars, but almost none of them have made it to the market - except for Nissan Leaf & Chevrolet Volt. And there is a good reason for this absymal record. There are several challenges - both technical and economic challenges which are stopping the electric cars from becoming an everyday reality.

The main challenge with electric cars is economics: COST

Today a Reva car costs (on road) about Rs 4 Lakhs (~$8,000) in Bangalore. The operating cost of Reva is ~Rs4.5/Km. (The battery cost os Rs 75000 - which lasts for 25000 Kms - under ideal conditions + Electric charges + Maintanence).

This does not compare favorably with Diesel cars - such as Maruti Swift or Ritz - which costs Rs 6.5 lakhs (approx US $13,000) and with a running cost of ~Rs5/Km. Yes mathematically Electric car Reva is cheaper to buy and run, but Reva can seat only 2 adults. While Ritz/Swift can easily accommodate 4-5 adults. So the cost/seat advantage lies with the diesel cars.

The same economics work with Nissan Leaf or Chevy Volt. The electric cars always cost more!

Auto maker, environmental activists and host of influential forward thinkers have lobbied with governments to give tax breaks and subsidies for electric cars. In Europe, governments have exempted electric cars from various charges - such as congestion charge, parking charge, plus free charging points - all this in addition to subsidies. This has led to some level of user acceptance of electric cars in London, Paris & Amsterdam.

Subsidies and user incentives can solve the cost problem for the user, but the basic economic problem of higher cost of battery is a technical challenge that needs to be addressed.

Technical Challenges

Even if one were to overlook the cost disadvantages of an electric car, there is another major disadvantage of range: An electric car has a limited driving range, i.e., the distance one can travel per charge, after which the car battries must be recharged. With lead-acid battries, the recharge time is quite long 8 hours for a full charge. The range essentially limits the usage of electric cars for urban office commute.

I love electic cars for urban commute - as often times, only one or two persons travel in the car and the range of 80 Kms is more than adequate for urban office commute. But I cannot take the electric car for longer distances.

Electric cars have three main components: Battery, Electric power train (motor + controller + gearbox) and the car body (chassis + Passenger cabin). Today we have mastered the technology needed for the car body and the electric power train, but battery remains a stubborn obstacle. Even after several decades of research - reliable, low cost, environment friendly battery technology has remained elusive.

There are four technical challenges with battery for electrical cars.

1. Time for charging the battery
2. Life of the battery
3. Cost of battery

All the four challenges will have to be solved in tandem - and only then electric cars can become viable.

Time for charging the battery

Today there are two main technologies available automotive battery: Lead-Acid battery, Li-Ion battery. Li-Ion battery has a recharge time for 30 minutes to 2 hours, while Lead-Acid battery needs about 8 hours for full charge.

When it comes to charging the battery, there are three possible options:

1. Over night recharge via a wall socket at home.
2. Rapid recharge using 440V charging station - possibly a commercial recharging station.
3. Swapping a fully charged battery for a drained one.

Over night recharge is currently the preferred option - but it is not a comparabe solution to gasoline driven cars.

Even with today's best recharging technology, the charging time of 30 minutes is unacceptable. Adding to the fact that rapid recharge damages the battery reducing the life-span of the battery.

Swapping batteries works only in a controlled environment. Here the problem of battery life span comes into the picture. A fully charged "old" battery is not the same as a "new" battery as we see in the next section.

Life of the battery

Electric batteries have a defnite life span. Li-Ion battery, which is now the preferred battery for electric cars, has a life span of 1000 charge-recharge cycles - which roughly translates to about 3 years of useful life.

Over this life span, the charging and discharging of battery forms deposites inside the electrolyte that diminishes its energy storing capacity and also increases the internal resistance of the battery - which limits the current delivered by the battery. All this implies that the older battery provide lesser range than a new battery. Older battery has higher internal resistance and this translates to a longer time for charging.

Newer Li-Poly batteries have a lifespan of 5000 cycles - but these batteries are yet to reach mass production.

Older battery consumes more power to recharge, stores lesser amount of energy and gives lesser power than new battery. After the rated life span - the battery has to be disposed. Disposing an old battery - both Lead-acid and Li-Ion has huge environmental consequences.

Cost Of Battery

One of the biggest challenge with electric cars is the cost of battery. Li-Ion battery usees rare materials - which are expensive, and thus the overall cost of car is high. For electric cars to succeed in the market, the total cost of ownership (over a period of 5 years) must come down to match that of gasoline or diesel powered cars.

Today, in India, the Total cost of ownership on Reva cars is same as Maruthi Swift VDI (diesel powered). For the average user, Reva sounds expensive - because he gets a much smaller car and with several limitations, while Maruthi Ritz or Swift costs the same and is a bigger car and without limitations.

The same economics is applicable to Nissan Leaf or any other electric cars. Subsidies and other incentives are temporary and can artificially lower costs. For electric cars to be successful, the overall cost must come down drastically and atleast match that of the fossil fuel based cars.

Closing Thoughts

Electric cars still have several challenges to overcome before it becomes accepted by mass market. Today, only the 'early adaptors' and green activists are using electric cars, and this is a niche market. Only when the challenges are overcome, electric cars can hope to become the main stay for the market.

20 comments:

Anuradha Goyal said...

Excellent Analysis Arun...

D.K said...

nice writing arun keep it up friend the cheapest new car

Dwayne Charles said...

There is no doubt that the newly invented electric cars have to pass through a lot of problems and tests before coming to the roads.
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Marjorie Bakre said...

The comparison crucially omits the fact that after Mahindra and Mahindra took over the Reva Co., it doubled the price of the car. Was it done just to satisfy its shareholders?( Why should the user now have to pay a high price just for a big brand name of M&M?) It also omits the fact the unconscionable waste of fossil fuel used (and hence its fast rising cost due to frequent hikes) while there are just one or two cars including the driver (self driving, virtually in all cars) but argues so much about the total capacity of fuel driven cars as such a big point visavis the electric car. Rather, the electric cars provide such an inexpensive commute unlike oil driven cars. The major disadvantage with electric car as mentioned in the blog, is lack of technology to increase battery life and price through mass production which is bound up with lowering of car prices.

syed jameel ahmed said...

Good info

arunssthoali said...

Very good analysis

arunssthoali said...

Very good analysis

Stefano De Bernardi said...

I am an italian 64 y.o. engineer, with a home photovoltaic plant of 16 kWp since 2002.
I got my first REVA in 2005, than I got another new REVA-i in 2008.
In 2009 replaced the power pack of REVA-i with litium Thunder Sky LiFePO4 battery (no. 16 cells of 200 Ah each).
Today, 2016, I've run it for more than 40.000 km, with no problem (excluding tire inflating).
Now I'm planning to install four BLDC hub motor in the first car and a bigger (400 Ah) litium battery pack, so to have a better car.
In my impression, REVA is a really great car, but the petrol masters do not allow normal people to move 'tax-free' (and pollution free): they have to profit, on us!

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Dhanunjay said...

Excellent analysis which can be understand by a person who is not familiar with electronics.
Thank you very much

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This post was knowledgeable as I am also thinking to purchase an EC. I just read Electric car buyers guide and it was helpful. They had included many options that were quite good and didn’t have such issues you have mentioned here.

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