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IPFS News Link • Transportation

Weight Matters

•, By eric

Even the really little ones – like Chevy's Bolt, which is even smaller than a subcompact car like the Hyundai Accent – only go about half as far as their size-equivalents. Viz, 259 miles for the 3,589 lb. Bolt vs. 487 (on the highway) for the 2,679 lb. Accent.

That's because a gallon of gas weighs about six pounds, which means a full tank of gas (12 gallons) in the Accent weighs 72 pounds. A great deal of energy is stored in those 72 gallons of gasoline – or even just six pounds. One gallon will power a car like the Accent some 40 miles down the highway and part of the reason for that is that as you burn it, there is less of it – and so, less weight to keep moving. After a car like the Accent has used up half a tank – about six gallons – it is carrying around half the fuel weight it began the trip with.

It takes a great deal more weight – that is never shed – to power an EV the same distance. A small EV like the Bolt is weighed down by the gas tank equivalent of about 1,000 pounds of battery pack – and in fact, it's not equivalent, because the Bolt would probably need another several hundred pounds of battery pack to be capable of powering its electric motor for nearly 500 highway miles.

But for the sake of this discussion, let's assume an equivalence.

It takes 1,000 pounds of battery to propel the Bolt the same 40 miles, because whether it's fully charged or just barely, with the electric equivalent of only 40 miles of range remaining – it is always lugging around every ounce of that 1,000 pounds. An EV battery pack does not get lighter as it is discharged even though electricity is essentially weightless. But the storage medium – the battery – is not. No matter how much electricity you burn, the weight of the battery remains the same.