Brammofan

07 December 2010, 0852

I'm pretty clueless about electricity, so I need some help. I was over on a gas bike forum and they were talking about Brammo bikes specifically and electric bikes in general and, as usual, dissing the range.

I mentioned the Enertia (40 mile range) and the Enertia Plus (80 mile range) and noted that the bikes, as reported, weighed the same. Sure, some components might have changed weight, but I made the assumption that the energy density of the batteries had doubled and this was not unlike Moore's law (transistor # per card doubling every two years).

One guy said:

unlike Moore's law, the energy density in commercially viable batteries hasn't gone up by even a single order of magnitude in 100 years. There are physical constraints that have proved challenging for as long as people have been at this, and while there is always hope for improvement, huge improvements have proved to be much harder than just about anyone would have imagined 5, 15, or even 50 years ago.

So I said,

It might depend on your definition of "commercially viable" but are you saying that a Lithium Ion battery from 2010 doesn't have at least twice the energy density of a lead acid battery of the same size from 1910?

and he replied,

To be raised an order of magnitude higher it must be at least the same amount squared... not just doubled. "Amount of what?" I dunno, some smaller capacity measurement that doesn't total to "1" or "2" in said LA battery.

It's just a friendly debate - but I'm out of my league here and wondered if anyone had any facts/figures that disputed his hypothesis.

I mentioned the Enertia (40 mile range) and the Enertia Plus (80 mile range) and noted that the bikes, as reported, weighed the same. Sure, some components might have changed weight, but I made the assumption that the energy density of the batteries had doubled and this was not unlike Moore's law (transistor # per card doubling every two years).

One guy said:

unlike Moore's law, the energy density in commercially viable batteries hasn't gone up by even a single order of magnitude in 100 years. There are physical constraints that have proved challenging for as long as people have been at this, and while there is always hope for improvement, huge improvements have proved to be much harder than just about anyone would have imagined 5, 15, or even 50 years ago.

So I said,

It might depend on your definition of "commercially viable" but are you saying that a Lithium Ion battery from 2010 doesn't have at least twice the energy density of a lead acid battery of the same size from 1910?

and he replied,

To be raised an order of magnitude higher it must be at least the same amount squared... not just doubled. "Amount of what?" I dunno, some smaller capacity measurement that doesn't total to "1" or "2" in said LA battery.

It's just a friendly debate - but I'm out of my league here and wondered if anyone had any facts/figures that disputed his hypothesis.