> When combined with their previous development of “water-in-salt electrolytes (WiSE)”, they claim that they can achieve an impressive energy density of 460 Wh/Kg.
> Some soldiers have to carry between 15-25 pounds of batteries and this technology could significantly lower that weight
What's the energy density of current batteries and how much lighter would equivalent batteries be using this technology?
> while preserving safety due to the aqueous nature of the electrolyte
What does this mean - why could the new battery be safer?
(I don't post this to be annoying contrarian in a discussion of battery tech. The externalities of burning carbon aside, it's just astonishing how effective gasoline is a relatively safe, stable means of transporting energy.)
The energy in the batteries weighs almost nothing, the batteries are just the storage mechanism, like the gas tank. To make a fair comparison between these cars, you almost need to compare not just the weight of the fuel but the entire system to convert that fuel into kinetic energy: the weight of the engine, transmission, drive shaft, gas tank, fuel pump, oil, cooling system. There is almost 500Kg of stuff in a typical passenger car to convert that gasoline into motion, the transmission alone in some cars can weigh almost 100Kg.
Right now a Tesla Model S weighs about 450Kg more than a comparable luxury car (Audi/BMW etc) and the battery pack (including cooling system etc) weights about 545Kg by itself. Another doubling of battery energy density would bring Teslas much closer in weight to a comparable gasoline car with the same range. In fact one would expect the range to go up for the Tesla by making it lighter as well. Teslas are notoriously heavy, even for an electric vehicle, an energy density of 400 Wh/Kg for batteries should bring weight parity between electric cars and gasoline cars for the same range and the same amount of cargo. That seems like the only weight number worth comparing.
Not to detract from your point since gasoline is amazingly useful, but there's a gap between energy density and usable energy density. An Otto cycle has a maximum theoretical efficiency of up to 61%, but in practice, friction and powering auxiliary system result in closer to 35% efficiency for a gasoline engine. VERY rough spitballing not to be cited: ~4500 usable Wh/kg.
Permanent magnet motors achieve upwards of 92% efficiency under optimal load, from the numbers I can find with quick googling.
Just to continue the discussion: 4,500 Wh/kg is still a 10x improvement on this new state of the art, and over a 20x improvement in current popular battery chemistries. Gas looks pretty good.
Another thing to consider is the weight of the equipment needed to convert the stored energy into "whatever." For a car, that is the weight of the drivetrain. A typical car engine+transmission weighs 300-600 lbs depending on the size and power of the car. Two Tesla model S (no transmission needed) motors weigh around 150 lbs.
This weight advantage is significant when you realize that 20 lbs of gas weighs 120 lbs. So when considering the density of a "useable system" with all necessary conversion equipment then electric is starting to catch up. Gas still looks best for most cars (also consider the convenience, and price factors), but I'm pretty sure gas will lose within our lifespans.
No, I was including it. Adding 150 lbs to a 1,200 lb battery only reduces the overall energy density by 11%. Adding 360 lbs to a 120 lb tank of gas reduces energy density by 75%. Where gas originally appeared to have a density advantage of 20x, it's now down to a 6x advantage after factoring in powertrain weight. That is what I mean when I say that batteries are catching up if you consider the total weight of the system.
Probably worth considering the efficiency of converting that stored energy to useful work. Average ICE efficiency is ~20% yielding effective storage of ~2600 Wh/kg.
Roughly an "order of magnitude" more density.
EDIT: Hadn't refreshed the page since lunch. Many have made this point already. Apologies haha
To the electric battery's advantage, electricity doesn't need to be "transported" until it reaches the car. Gasoline in the other hand needs an entire specialized and -I assume- expensive supply chain.
> What's the energy density of current batteries and how much lighter would equivalent batteries be using this technology?
Not my area, but the best info I can find around is somewhere in the region of 200-250Wh/kg at the top end for current typical lithium ion batteries. I'm not sure if that's the type they're using.
Some generals would certainly think that. To them, they are thinking of battle rattle as a knapsack problem where soldiers have demonstrated the ability to carry 80+ lbs of weight and 80+ liters of pack size. 10 more lbs of bullets means more fighting power.
Other generals are thinking that going from an 80 lb pack to a 70 lb pack means fewer injuries, so your fighting readiness increases without changing anything else. Fewer injuries means more fighting power.
The bean counter types are also considering that they can ship the same amount of electric energy to the front line with fewer shipments (assuming that they are weight constrained, but they are often volume constrained). This frees up logistics capacity for getting other things to the front lines. This means more fighting power.
No matter which lens you view it through, this thought process is what leads to military leaders salivating at the thought of new technologies. If you want your startup (or academic research team) to make big bucks, then seek out government contracts for small businesses or technology development contracts. These contracts are very favorable to your company, as you almost always get paid for your work even if you don't deliver the promised product. As long as you're willing to accept some stigma from Silicon Valley you probably have a much higher probability of success.
> When combined with their previous development of “water-in-salt electrolytes (WiSE)”, they claim that they can achieve an impressive energy density of 460 Wh/Kg.
> Some soldiers have to carry between 15-25 pounds of batteries and this technology could significantly lower that weight
What's the energy density of current batteries and how much lighter would equivalent batteries be using this technology?
> while preserving safety due to the aqueous nature of the electrolyte
What does this mean - why could the new battery be safer?