Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

New lithium-ion battery design – 2,000x more powerful, recharges 1,000x faster

extremetech.com

Post reply on HN
Print view View original

61–70 of 89 posts

Re: New lithium-ion battery design – 2,000x more powerful, recharges 1,000x faster

#61

Post by mbell »

lutusp wrote: post #59
talmand wrote: post #58

Earlier quoted context omitted.

For those of us that didn't study thermodynamics, what is the answer that's so stunning?

The OP didn't give enough information to produce a specific answer. For a higher voltage and lower current (same power), the wire could be thinner with the same outcome. The reason electricity utilities string million-volt lines between cities is to minimize the heating losses in the conductors, not to impress the civilians. It's the same reason electric car designs favor putting a lot of cells in series -- a high-vo…

You still need to convert this high supply voltage to a lower voltage to match the cell voltage for charging. The currents involved mean this converter is still likely to dissipate a lot of heat, even if it is extremely efficient.

Re: New lithium-ion battery design – 2,000x more powerful, recharges 1,000x faster

#62

Post by lutusp »

mbell wrote: post #61
lutusp wrote: post #59

Earlier quoted context omitted.

The OP didn't give enough information to produce a specific answer. For a higher voltage and lower current (same power), the wire could be thinner with the same outcome. The reason electricity utilities string million-volt lines between cities is to minimize the heating losses in the conductors, not to impress the civilians. It's the same reason electric car designs favor putting a lot of cells in series -- a high-vo…

You still need to convert this high supply voltage to a lower voltage to match the cell voltage for charging. The currents involved mean this converter is still likely to dissipate a lot of heat, even if it is extremely efficient.

> You still need to convert this high supply voltage to a lower voltage to match the cell voltage for charging.

No, instead you charge the cells in series. That delivers the same power while avoiding the problem of having to produce overly high currents.

> The currents involved mean this converter is still likely to dissipate a lot of heat, even if it is extremely efficient.

Yes, but there are ways to minimize this loss factor. Obviously a fast-charging scheme for a car is going to involve a lot of current, but the system designers do all they can to minimize that current. The primary way they do that is by both charging and discharging the cells arranged as much in series as is practical.

In the Tesla design, there are 11 modules connected in series and delivering 375 volts nominal (and requiring 375 volts to produce an optimal charging current). So there's no issue of changing individual cells at their normal cell voltage, instead the system charges modules consisting of 621 cells in an optimized series-parallel scheme:

http://en.wikipedia.org/wiki/Tesla_Roadster#Battery_system

Quote: "Tesla Motors refers to the Roadster's battery pack as the Energy Storage System or ESS. The ESS contains 6,831 lithium ion cells arranged into 11 "sheets" connected in series; each sheet contains 9 "bricks" connected in series; each "brick" contains 69 cells connected in parallel (11S 9S 69P)"

Re: New lithium-ion battery design – 2,000x more powerful, recharges 1,000x faster

#63

Post by Lagged2Death »

talmand wrote: post #58
VLM wrote: post #53

Earlier quoted context omitted.

Minor nitpick is charge time at a supercharger would remain 45 minutes. You'd need some kind of miracle superduper charger to deliver that kind of current. A cable that can handle that kind of current would be kind of unimaginable for the average civilian. It would resemble a telephone pole. Not the wires on the pole, but the pole itself. A stereotypical thermodynamics class assignment was something along the lines o…

For those of us that didn't study thermodynamics, what is the answer that's so stunning?

10 gal = 37.85L

37.85L x 36MJ/L = 1,362 MJ in the tank.

1,362 MJ / 60s = 22MJ/s from the hose.

J/s is Watts, so that's 22 megawatts. A cable that carried 200A at 110KV would do it. I think 000 gauge would handle 200A, it's just under 11mm in diameter.

Re: New lithium-ion battery design – 2,000x more powerful, recharges 1,000x faster

#64

Post by Aardwolf »

Uh, let's combine this with the other 3 articles claiming a 10x more long lasting battery, and we'll have a 1000x longer lasting, 2000x more powerful, 1000x faster recharging battery.

I really love progress, but I've seen too many of these "N times better" articles and no actual consumption products by now.

Same with these memristors, MRAM and feRAM, and 1000x faster internet.

Re: New lithium-ion battery design – 2,000x more powerful, recharges 1,000x faster

#66

Post by lutorm »

Lagged2Death wrote: post #63
talmand wrote: post #58

Earlier quoted context omitted.

For those of us that didn't study thermodynamics, what is the answer that's so stunning?

10 gal = 37.85L 37.85L x 36MJ/L = 1,362 MJ in the tank. 1,362 MJ / 60s = 22MJ/s from the hose. J/s is Watts, so that's 22 megawatts. A cable that carried 200A at 110KV would do it. I think 000 gauge would handle 200A, it's just under 11mm in diameter.

But 110kV into the car is totally out of the question. At a more reasonable battery voltage of 1kV, you'd need 20kA. That'd be a fat cable indeed.

Re: New lithium-ion battery design – 2,000x more powerful, recharges 1,000x faster

#67

Post by mbell »

lutusp wrote: post #62
mbell wrote: post #61

Earlier quoted context omitted.

You still need to convert this high supply voltage to a lower voltage to match the cell voltage for charging. The currents involved mean this converter is still likely to dissipate a lot of heat, even if it is extremely efficient.

> You still need to convert this high supply voltage to a lower voltage to match the cell voltage for charging. No, instead you charge the cells in series. That delivers the same power while avoiding the problem of having to produce overly high currents. > The currents involved mean this converter is still likely to dissipate a lot of heat, even if it is extremely efficient. Yes, but there are ways to minimize this l…

By 'cell' I meant the overall pack, not the individual unit within the pack.

From your link: "A full recharge of the battery system requires 3½ hours using the High Power Connector which supplies 70 amp, 240 volt electricity"

Multiply that current by 10-100 to 'charge it faster' and you have a huge problem with thermal dissipation, not to mention using truly massive cables.

Re: New lithium-ion battery design – 2,000x more powerful, recharges 1,000x faster

#69

Post by Lagged2Death »

lutorm wrote: post #66
Lagged2Death wrote: post #63

Earlier quoted context omitted.

10 gal = 37.85L 37.85L x 36MJ/L = 1,362 MJ in the tank. 1,362 MJ / 60s = 22MJ/s from the hose. J/s is Watts, so that's 22 megawatts. A cable that carried 200A at 110KV would do it. I think 000 gauge would handle 200A, it's just under 11mm in diameter.

But 110kV into the car is totally out of the question. At a more reasonable battery voltage of 1kV, you'd need 20kA. That'd be a fat cable indeed.

But 110kV into the car is totally out of the question.

It would be pretty unreasonable. But burning gas at 100% efficiency is actually impossible, so it's sort of a silly scenario anyway.

...you'd need 20kA. That'd be a fat cable indeed.

Maybe not as fat as you'd think; this guy figures 50KA here, and you wouldn't want to work with an extension cord like that every day, but it's not like you'd need a crane to lift it, either:

http://youtu.be/uXEPy6Za6cI

Post reply on HN