Electric cars cost equivalent to a gasoline car going 4 to 6.5 miles per gallon - on battery costs

Here is a little calculation I did to work out the cost of electric cars in miles per gallon equivalent - based on the cost of the batteries and how long they last for - I worked out that its about 4 miles per gallon (for a Tesla in the US) to 6.5 miles per gallon (for a G-Wiz in the UK).

It is probably fair to say that if electric cars can work viably, then there isn't much point for a hydrogen economy - apart from as an expensive large scale electricity storage option.

I'm trying to work out how viable electric cars are compared to hydrogen - taking into consideration battery life and cost, effort to look after the battery, and charging time.

(Hydrogen cars, assuming hydrogen is available from a nearby station, should beat electric cars on these features - if they can be fuelled in a few minutes, the fuel cell lasts for the lifetime of the car, and the fuel cell is inexpensive, and you don't have to worry about the hydrogen in the car apart from filling it up when its empty. None of these factors are entirely true but probably they get it closer than electric cars do).

Lithium-ion batteries, being used in electric cars which (unlike the Prius) use a battery as the main source of power, have a lifespan of 300-500 discharge cycles (click here for source - Battery University article.).

Today's Guardian has an interesting review of electric cars currently available.

The Tesla has batteries which the manufacturer claims can go 244 miles on one charge (Top Gear says 54 miles on their test track but never mind about that) - according to the Wikipedia page. So with a lifespan of 400 cycles (take an average number) the batteries can go 100,000 miles. Tesla actually estimates that the battery will have 70 per cent of its capacity after 50,000 miles of driving and total lifespan will be 100,000 miles (according to the Wikipedia).

Bear in mind the cost of $98,000 for a Tesla and a cost of $36,000 to replace the battery pack. Assuming you run the battery to death (100,000 miles), that means you pay 36 cents a mile for the battery cost. So for $2.00, the cost of a gallon of gasoline in the US, you would get 6 miles. The Tesla's cost are equivalent to a 6 mile per gallon car. Is there something wrong with my maths here?

At the other end of the electric car market you have the G-Wiz. According to Wikipedia the lithium-ion battery model has a range of 75 miles.

According to this vendor website battery replacement cost is £1395 (tax included) - which I think means for the lead acid version of the car (cost of car £8,000). The UK retail cost of a lithium ion car is £16,000. If the rest of the car costs the same whether it is lead acid or lithium batteries, then the cost of a G-Wiz lithium ion battery pack must be £9395 ($14,000).

This all fits roughly together - you can have $14,000 battery which goes 75 miles on one charge in a G-Wiz, or a $38,000 battery which goes 244 miles in one charge in a Tesla.

But coming back to the Tesla's cost per mile in batteries - a $14,000 battery will go 30,000 miles - a cost of $0.46c a mile. If you're paying $2 a gallon of fuel, that's equivalent to a 4 miles per gallon car. (Of course in the UK, if you're paying £4.72 a gallon of fuel as we are in the UK ($7) then its equivalent to 6.5 miles per gallon.

There's plenty more electric car owners have to worry about as well. Coming back to the Battery University article - electric car owners will want to ideally recharge when the battery is 40 per cent full (ie when the car has only travelled 60 per cent of its full range). The article doesn't say how the battery life is impacted by how full the battery is when recharged - perhaps the maximum 500 recharging cycles is when you only drop it to 40 per cent each time.

Car drivers can't stop using their cars for 6 hours to recharge every time the charge gets to a certain level - they have to somehow map the battery management against their usage requirements. Although if they drive the UK's average daily commute of 8.7 miles (or 17 miles a day), with a car with a range of 75 miles, they can probably comfortably recharge it every 3 days (51 miles).

At 46 cents a mile, a 17 mile a day commuter would be paying $8 a day for batteries in a G-Wiz - equivalent to what they might pay to travel to work and back on the London Underground, but much more than with gasoline.

Comparing to hydrogen costs - the current target for US Department of Energy .is for roadside hydrogen to cost $2 to $3 per gasoline gallon equivalent.

An average US mid-sized car travels 21 miles per gallon in the city according to Wikipedia..

A Tesla, at $0.46 per mile, has a cost of $9.66 per gasoline gallon equivalent.

My conclusion - right now - between electric cars and hydrogen - there is everything to play for. Will hydrogen costs get down to $2-$3 per gasoline gallon equivalent (with hydrogen readily available, costs of fuel cell cars competitive and fuel cells lasting for the lifetime of the car)? How much will battery technology improve? Since no-one can answer these questions, it is much to early to make a decision about whether battery or hydrogen is the right fuel for electric cars of the future.