# How long until batteries are able to compete with gasoline

There are roughly 125,000 BTU in a gallon of gasoline and about 20% is turned into mechanical energy, so about 25,000 BTU of mechanical energy per gallon, a gallon of gas is about 3785 cc, so about 6.6 BTU per cc of gasoline is used for mechanical energy.

I dont know how much energy is stored in a battery, or what the efficiency of a battery is but I would assume it is much higher than 20%.

• what is the amount of energy per cc or cubic inch that a good battery holds?
• is there a standard rate of doubling of battery power per cc? Moores law shows that the number of transistors per chip doubles every 18-24 months and Ray Kurzweil has shown alot of information technology doubles every 1-3 years. So is there a rate of battery doubling? I have read that batteries have lagged far behind electronic growth and as a result we have cellphones & laptops that don’t last more than 3 hours if you actually use them so I’d guess it is close to 6-8 years per doubling.

I realize that by today’s technology it wouldn’t matter for things like greenhouse gases as only 30% of the US electricity is clean and about 60% is coal, but over the next 30 years, when batteries become able to store enough energy I expect the balance to change a bit.

Another issue is that most people don’t drive long distances at once, and people don’t refill their gas tank everyday. Much driving is under 5 miles so a car that uses electric for the first 25-50 miles, then switches to gasoline would probably work if you recharged it each night. So perhaps a storage capacity as small as the equivalent of 2 gallons of gasoline would be sufficient for an electric car, assuming it was recharged daily.

I can’t answer a whole heck of a lot on this subject, but I can at least speak of the lack of a “Battery/Moore’s Law.”

AFAIK, batter technology has been advancing at a linear rate, while transistors were advancing (and may still be) at an exponential rate. I.e. there is a set amount of time it takes for the technology in computer chips to double, but in a set amount of time, batteries only increase by a little. Compare:

``````
Chips   Batteries
1          1                 (with whatever units you feel you like)
2          2
4          3
8          4
16         5
32         6
...        ...

``````

Thus, as the computer power has been growing tremendously fast, battery technology has been lagging behind. In fact, my official prediction is that the next “major” breakthrough that hits on all facets of life will have to do with energy storage or usage.
As for batteries replacing other forms of energy storage and or transportation, I remember reading somewhere that batteries could (possibly) be as efficient as or even more efficient than power lines. There were a lot of if’s and so-long-as’s in that argument, tho.

Wesley Clark, I’m not a huge booster for electric cars, myself. They already get the equivalent of your 2-3 gallons of gas per charge on their batteries: IIRC the average electric car gets 75-80 miles per charge. Which, as you said, is quite adequate for most daily automobile uses.

The problem that has, in my mind, is that most people do buy cars anticipating that they will take the occaisional trip of longer, or much longer, duration. And the electric car just isn’t suitable for that. But, when given the choice of buying one vehicle that will be able to do both the short distance and longer distance driving, or buying one vehicle for the short distance driving, and having to make other arrangements for longer distance travel - most people would prefer the single vehicle solution.

Especially as the electric vehicle is usually more expensive than the comparable gasoline vehicle.

As for battery power - until recently I just don’t think that there’d been much reason to push for improvements in battery power. Lead-acid batteries met most of the requirements for rechargeble power applications, and were a well-understood technology. I really don’t think that it was until the creation of the Walkman, and following technologies, that the average consumer was really concerned about improving battery life, or the weight/power ratio on batteries. And with neither a mass market driven nor military reason for sophisticated battery technologies to be pushed, there wasn’t much money being spent on research.

As near as I can tell, battery technology has been essentially stagnant for 90 years: The 1913 Detroit Electric I saw in a museum in Indiana had about the same performance stats as the latest batch of electrics.

IIRC charging efficiency of a battery at 20% Depth of Discharge to 0% DoD (80% charged to fully charged) is about 20%

I think a very simple solution would be to include a onboard gas generator with basically enough power to keep the car going at average loads while keeping the battery in the 70-80 DoD (20% to 30% charged) range.

Also heard on the radio yesterday (maybe Paul Harvey) that someone is making a all electric sports car that has a 225 mile range, 0-60 time of 4 seconds.

Which, essentially, is the concept behind today’s hybrid autos.

Oh, one more point:

Gasoline internal combustion engines, IIRC, are fairly efficient at maintaining a high speed for a long distance, but much less so at changing speeds and low speeds.

Electric motors (again, IIRC) are more efficient for low speeds and changing speeds, but much less so for maintaining high speeds for long distances.

Hence, the Hybrid.

(…or, at least that’s what the ads tell you to believe)

If batteries become competitive with gasoline in the near future, it won’t be because of performance gains on the part of batteries; it’ll be because gasoline becomes more expensive.

Also, correct me if I’m wrong, but you can’t really compare the 20% efficiency of batteries to the 20% efficiency of gasoline. A 20% efficient battery means that we can get 20% of the energy we put into it back out. The 20% efficient figure for gasoline means that we can reasonably harness 20% of the energy we get by burning it. One is a fuel, and the other is energy storage.

To reasonably compare the two, you have to consider the energy cost of pumping and refining gasoline, not the energy cost that we’d have to pay to make it in a lab. By that measure, gasoline is clearly over 100% efficient, since if it weren’t a net energy gain, we wouldn’t be drilling for oil in the first place.

We need fuel from somewhere. If we don’t get gasoline for our cars we need energy from power plants to charge our batteries. I’m not really concerned about net energy, I’m concerned about how much energy per cc a battery needs to hold to have as much energy as a cc of gasoline.

My statement about 20% efficiency was just about the energy density of gasoline and trying to figure out how long until the energy density of batteries is the same as the energy density of gasoline. Since gasoline has 125,000 BTU per gallon, but only 20% is used to power the care we only need battery energy that is the equivalent of 25,000 BTU that is 3785 cc to be comparative with gasoline.