5 ms·

Electric cars?

Retric 14y ago
Weight, Energy density. and cost are what's most important for general Electric car energy storage. So if this cost's more or weights significantly more it's next to useless for that. However, they might have some use as part of a more efficient regenerative breaking system. PS: As to faster charging, issues are going to Limit that. A 99% efficient battery charging 100x as fast as Li-Ion is going to dump a lot of heat vary quickly. Duping heat is not really an issue for small battery's but scale this up into the 50+kwh range for an electric car or even just a cellphone battery and you will have significant issues.
- userulluipeste 14y ago
  About charging speed, you're invoking another problem, that of (over)heating. That however, deserves a separate context of its own to be addressed in. I think it's safe to assume that a lot of efficiency can be safely salvaged from that 100x improvement.
icegreentea 14y ago
Well... it's tricky. If you assume that current electric cars have the performance of that A123 battery from the graph, and then pick something in the middle of the spread of the colourful dots, you get a roughly 1 order decrease in energy density, and a 1 order increase in power density. So, taking the Model S as an example, you have a 300 mile range, and a charge time of like 45 minutes at a super charger. So... now you end up with like a 30-60 mile range range, and can charge up fully in like 3-5 minutes. So we've brought charge times into the realm of filly up gas, but you're doing it waaay more often. If this is a useful advancement or not depends completely on what type of infrastructure we want to envision. I would certainly love a world where this was possible/feasible, but it's certainly not a grand slam.
- colanderman 14y ago
  Don't you mean a charge in 24-30 seconds? Otherwise your example is just that of a 10x smaller A123 battery.
  - meepmorp 14y ago
    45 min is 2700 seconds, so 10x faster charging is 270 seconds or 4 1/2 minutes.
    - flakmonkey 14y ago
      The rate that the battery charges is independent from the capacity of the battery. Assuming the new tech is 10x less energy dense and has a 10x faster charge rate, if you compare one of these new batteries with capacity equal to that of the Model S battery, the new battery will charge 10x faster but occupy 10x the volume, since it is less energy dense. A new battery of this kind that occupied the same volume as a Model S would contain 10x less energy than the Model S battery, but it would charge to full capacity 100x faster than the Model S.
    - cdash 14y ago
      There should be two multipliers though right? If it charges 10x faster and you are charging to a 10x less total energy it should charge 100x faster right?
- jguimont 14y ago
  Could electric car battery use a dual type battery pack to optimize charging and range?
  - bradleyland 14y ago
    You could do that, but energy density is the key metric here. Energy density determines the size of the battery required to store a specific amount of energy. There's only so much space in the car, and you also have to factor in that any battery that will be moved by its own power loses efficiency with lower energy density. You've got a huge battery to move, and physics dictate that accelerating this battery is going to use more energy. So, let's say you split this hybrid battery 50/50, your quick charge-discharge battery quickly becomes too small to deliver meaningful range, and you've given up space that could be used for the traditional battery.
  - chongli 14y ago
    The Tesla Model S already uses 7000 individual battery cells. This is how it's able to charge as quickly as it does with the supercharger. The main limitation of household charging is lack of power.
    - reportingsjr 14y ago
      That isn't necessarily true. Them using small batteries to make a larger battery is what allows them to make their car sized batteries cheaper, since the smaller sized batteries are already mass produced for things like laptops. For charging time it depends on how those batteries are connected.
- VLM 14y ago
  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 of assume your 10 gallon gas tank is filled in a minute at the gas pump through a little half inch gas nozzle. Now calculate the thermal energy of that nozzle assuming perfect combustion in megawatts. Then given that the gas nozzle is about half an inch, look up what diameter copper wire would be required to transfer that kind of energy if it was electricity. The answer was pretty stunning.
  - talmand 14y ago
    For those of us that didn't study thermodynamics, what is the answer that's so stunning?
    - lutusp 14y ago
      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-voltage electric motor gets more of the power delivered by the batteries, less of it is wasted in the connecting wires. Also, in the car's charging circuit, the high voltage choice maximizes power transfer for a given connecting wire size.
      - mbell 14y ago
        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.
- rdtsc 14y ago
  Imagine shorting this capacitor.
VLM 14y ago
One parameter not discussed so far is self discharge rates. Maybe a problem maybe not, either way that parameter is going to be important. For simple regenerative braking its not so big of a deal but if you're hoping to use it as a primary energy source its a big deal.

Electric cars?

Weight, Energy density. and cost are what's most important for general Electric car energy storage. So if this cost's more or weights significantly more it's next to useless for that. However, they might have some use as part of a more efficient regenerative breaking system. PS: As to faster charging, issues are going to Limit that. A 99% efficient battery charging 100x as fast as Li-Ion is going to dump a lot of heat vary quickly. Duping heat is not really an issue for small battery's but scale this up into the 50+kwh range for an electric car or even just a cellphone battery and you will have significant issues.

userulluipeste 14y ago
About charging speed, you're invoking another problem, that of (over)heating. That however, deserves a separate context of its own to be addressed in. I think it's safe to assume that a lot of efficiency can be safely salvaged from that 100x improvement.

icegreentea 14y ago

Well... it's tricky. If you assume that current electric cars have the performance of that A123 battery from the graph, and then pick something in the middle of the spread of the colourful dots, you get a roughly 1 order decrease in energy density, and a 1 order increase in power density. So, taking the Model S as an example, you have a 300 mile range, and a charge time of like 45 minutes at a super charger. So... now you end up with like a 30-60 mile range range, and can charge up fully in like 3-5 minutes. So we've brought charge times into the realm of filly up gas, but you're doing it waaay more often. If this is a useful advancement or not depends completely on what type of infrastructure we want to envision. I would certainly love a world where this was possible/feasible, but it's certainly not a grand slam.

colanderman 14y ago
Don't you mean a charge in 24-30 seconds? Otherwise your example is just that of a 10x smaller A123 battery.
- meepmorp 14y ago
  45 min is 2700 seconds, so 10x faster charging is 270 seconds or 4 1/2 minutes.
  - flakmonkey 14y ago
    The rate that the battery charges is independent from the capacity of the battery. Assuming the new tech is 10x less energy dense and has a 10x faster charge rate, if you compare one of these new batteries with capacity equal to that of the Model S battery, the new battery will charge 10x faster but occupy 10x the volume, since it is less energy dense. A new battery of this kind that occupied the same volume as a Model S would contain 10x less energy than the Model S battery, but it would charge to full capacity 100x faster than the Model S.
  - cdash 14y ago
    There should be two multipliers though right? If it charges 10x faster and you are charging to a 10x less total energy it should charge 100x faster right?
jguimont 14y ago
Could electric car battery use a dual type battery pack to optimize charging and range?
- bradleyland 14y ago
  You could do that, but energy density is the key metric here. Energy density determines the size of the battery required to store a specific amount of energy. There's only so much space in the car, and you also have to factor in that any battery that will be moved by its own power loses efficiency with lower energy density. You've got a huge battery to move, and physics dictate that accelerating this battery is going to use more energy. So, let's say you split this hybrid battery 50/50, your quick charge-discharge battery quickly becomes too small to deliver meaningful range, and you've given up space that could be used for the traditional battery.
- chongli 14y ago
  The Tesla Model S already uses 7000 individual battery cells. This is how it's able to charge as quickly as it does with the supercharger. The main limitation of household charging is lack of power.
  - reportingsjr 14y ago
    That isn't necessarily true. Them using small batteries to make a larger battery is what allows them to make their car sized batteries cheaper, since the smaller sized batteries are already mass produced for things like laptops. For charging time it depends on how those batteries are connected.
VLM 14y ago
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 of assume your 10 gallon gas tank is filled in a minute at the gas pump through a little half inch gas nozzle. Now calculate the thermal energy of that nozzle assuming perfect combustion in megawatts. Then given that the gas nozzle is about half an inch, look up what diameter copper wire would be required to transfer that kind of energy if it was electricity. The answer was pretty stunning.
- talmand 14y ago
  For those of us that didn't study thermodynamics, what is the answer that's so stunning?
  - lutusp 14y ago
    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-voltage electric motor gets more of the power delivered by the batteries, less of it is wasted in the connecting wires. Also, in the car's charging circuit, the high voltage choice maximizes power transfer for a given connecting wire size.
    - mbell 14y ago
      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.
rdtsc 14y ago
Imagine shorting this capacitor.

VLM 14y ago

One parameter not discussed so far is self discharge rates. Maybe a problem maybe not, either way that parameter is going to be important. For simple regenerative braking its not so big of a deal but if you're hoping to use it as a primary energy source its a big deal.