Energy density of gasoline vs. Lipo batteries

[Antonio Zanardo]

I have a bike with 6 lipo batteries each one supplying 28.5V11Ah. I connect them to various ways, according to my speed or range needs. They cost me a small fortune but, in spite of that, I myself am continuing doing those costly experiments, therefore I hope to not be regarded as the guy who nastily enjoys frustrating other people.

However I can't help thinking to the enormous difference of power density contained in one Kg. of gasoline vs. one Kg. of lithium batteries: the ratio is about 100 / 1. In case of Lead-acid batteries, the ratio is about 400 / 1.
In simple words, we need 400 Kg of lead batteries to supply the same energy as 1 Kg. gasoline!

I realize that the electric motor efficency is much higher than the combustion engine, but even if we take into account this fact, still the the difference of energy content is much much much in favour of gasoline.

http://xtronics.com/reference/energy_density.htm
http://en.wikipedia.org/wiki/Energy_density#Energy_storage

I feel like we are toying with E-Vehicles which cannot have any large diffusion, until (and IF!) this huge energy gap could be filled up.

Am I right in my reasoning or what?

Antonio Zanardo

 

[xyster]

You make an excellent point about the comparatively low energy density of even the best batteries. On the plus side for automobiles and other large vehicles, going electric allows the removal of hundreds of pounds of comparatively much less reliable engine and transmission. The weight reduction of engine and transmission compensates for the increased battery weight necessary to achieve normal range.

One member here converted a car using ~550lbs (3,600 cells) of 70 gram a123 cells.

http://endless-sphere.com/forums/viewtopic.php?t=1948&highlight=3600+a123

He describes the vehicle as having a 2100lb dry curb weight, 3.4 sec 0-60mph time, and 80-120 mile range.

http://www.attackforums.com/showthread.php?t=2419

I'm struggling to stay under 2100 lbs dry curb weight. I originally was optimistic at 2000 lbs, but I failed to factor in numerous structural reinforcements, and the extensive amount of copper needed to pass 150kw to the drive system without losing some it as waste heat.

Q-What is your estimated performance 0-60, 60+, range, etc.?

A-Based on weight, I'm estimating 0-60 in under 3.4 seconds. Top speed is 82 MPH (fixed gear speed at 12k motor RPM). I don't expect anything better than 80 miles per charge -considering the way I will be driving. Normal range, driven like an average car would deliver around 120+ miles. The true available pack capacity is 27kwh, and cruise at freeway speed will consume energy at 15kw.

 

[Lowell]

For a good real world comparison, check out some of the popular bicycle motor kits, and the gas mileage they get. Fuel vs. lithium batteries is probably around 10:1 in favor of fuel.

 

[patrick_mahoney]

Definitely the whole problem with electric vehicles is the difference in energy density between batteries and gasoline. If this weren't the case... we'd all be driving around in electrics. They are quieter, cleaner, require less maintenance and generally are more reliable... clearly the downside to them is the capacity and cost of batteries.

As mentioned, though, the efficiency of an good electric motor is 85-90%, and an internal combustion engine is more like 20% ( http://en.wikipedia.org/wiki/Internal_combustion_engine ).

So for a typical gasoline motor, you get 12200Wh/kg * 20% = 2.4kW/kg energy utilized vs. for a good electric motor and lithium battery combination you get something like 130Wh/kg * 90% = 117Wh/kg energy used. So rather than a ratio of close to 100:1 in favor of gasoline, it's more like 20:1. Which is still really bad but not as bad as first glance.

I personally think plug-in hybrids are the best way to go right now - use batteries and electricity for short-range driving, and gasoline for longer range trips. You get the higher efficiency of electrics for the majority of trips, and the higher energy density of gasoline for longer ones... up until someone figures out how to make a really good methanol fuel cell.

 

[Lowell]

Yes, I was beeing rather generous to electrics at only 10:1

I wonder if a 2400Wh/Kg battery is even possible?

 

[knightmb]

Don't forget the large amount of energy it takes to refine Gasoline. That further reduces how useful it is because it doesn't come out of the ground as pure "Gas" to begin with. The local food store has vegetable oil that's an even higher energy density, yet all it is was the oil left over from squeezing a certain vegetable in a press.

The technology is already here, we could have vegetable powered engines to produce electricity in the same hybrid as the "gas" hybrid. Some people have done it already. It's just a matter of where you want the money to go. Vegetable farmers are finally getting into the fuel game, hopefully they have it what it takes to complete with the big gas companies. Veggie engines being carbon neutral and you can grow more would be a much better alternative for this planet for certain, as any country could "grow" it's own fuel then.

 

[xyster]

Yes, I was beeing rather generous to electrics at only 10:1

I wonder if a 2400Wh/Kg battery is even possible?

Based on what I remember of electrochemistry in college, I don't think so -- not for chemical batteries. Lithium is already the metal most readily providing of electrons. But fuel cells are already approaching, if not surpassing that gravimetric energy density, and may be the best vehicle for vehicular energy (in concert with chemical batteries or supercapacitors for high amp loads) if political, economic, or environmental issues dictate we must completely dump large-scale combustible fuel use ASAP.

http://www.millenniumcell.com/fw/main/Technology_Advantages-28.html

 

[monster]

check this out. the solution to all your energy needs...

the fuel cell bike!

...coming soon to a site near you.

 

[vanilla ice]

I want an ebike that uses those little blue propane tanks you can get at home depot for $2.50 each. That would be sweet.

 

[monster]

this one uses comercial grade hydrogen which is only 99.95% pure and only £6 for a massive tall cyclinder.

these FC's putt out 200watts and are lighter than my nimh cells even with the h2 tanks attached.

its a really nice power unit. shame the bike is so fugly.

 

[xyster]

this one uses comercial grade hydrogen which is only 99.95% pure and only £6 for a massive tall cyclinder.

these FC's putt out 200watts and are lighter than my nimh cells even with the h2 tanks attached.

its a really nice power unit. shame the bike is so fugly.

Oh but this is definitely heading the right direction. It shouldn't be long before fuel-cell prices come down and options go up.

 

[Lock]

Definitely the whole problem with electric vehicles is the difference in energy density between batteries and gasoline.

No, the whole problem with electric vehicles is that folks "need" a vehicle that weights several thousand pounds and a top speed that is 2-3 times the speed limits. The problems are social and not technical.

tks

Lock

 

[TylerDurden]

No, the whole problem with electric vehicles is that folks "need" a vehicle that weights several thousand pounds and a top speed that is 2-3 times the speed limits. The problems are social and not technical.

Kinda hard to separate the two. All technologies have evolved in relationship to social dynamics; for better and for worse.

 

[vanilla ice]

folks "need" a vehicle that weights several thousand pounds and a top speed that is 2-3 times the speed limits

When I went to Japan seemed like half the cars on the road were of the little Kei car 600cc variety. Those can't be too heavy. I wonder when, if ever, those will make it over here. That would at least get the ~5% of vehicle operator-weight figure up a little.

 

[Antonio Zanardo]

By doing some maths on energy density, I believe the content of those two small H2 tanks (supposed to have a 0.25 liter capacity each pumped to 200 bar) should be energy wise equivalent to about a 2kg lithium battery.

Not a big deal, considering that the fuel cell will surely cost (and probably weigh, tanks included) much more than a 300Wh lithium battery, wich costs about 220 euro.

Am I right?

Antonio Zanardo

 

[Lowell]

Definitely the whole problem with electric vehicles is the difference in energy density between batteries and gasoline.

No, the whole problem with electric vehicles is that folks "need" a vehicle that weights several thousand pounds and a top speed that is 2-3 times the speed limits. The problems are social and not technical.

tks

Lock

I prefer at least 3-4 times the speed limit.

As for the weight, some people need to haul things other than their own asses.

 

[monster]

they are actualy metal hydride stores not presurised cylinders (low pressure but has a special H2 adsorbent) i dont know what the range is yet, that was my first question too.

the fuel cells are about £1000 each and are just coming on to the market in china, they are not yet mass produced.

i supose the idea is that you can refil it quicker than you can charge a battery.

i still like batteries because they are greener but for the odd time you want to do more than 10 miles it would be good to have H2 and (possible future) refils at gas stations

 

[Lowell]

My ultimate ebike battery pack would be Thunder Power Prolite cells @ 190Wh/Kg. No need for a BMS as the pack would be capable of 100's of amps, and a ~15kg pack could have 2500+Wh capacity including packaging etc. 88.8v and 30Ah sounds pretty good... now if only they could cut the cost a few fold.