5 ms·

In the comments they mention about 1/4 the energy density of a lithium ion battery, so yes they don't compete on that measure. But full charging can happen in a

In the comments they mention about 1/4 the energy density of a lithium ion battery, so yes they don't compete on that measure. But full charging can happen in a minute or two, and you could top up a charge in seconds. Perhaps public areas would have inductive chargers on the wall; you'd just walk over and hold your phone or tablet up to it for a few seconds. Airline tray tables could have an inductive charger built in. Higher energy densities aren't without issues, as Boeing found out with their 787. A battery like that is basically an explosive and it can be tricky to manage.

deleted 14y ago
[deleted]
brokenparser 14y ago
Your inductive charging tray tables are terrible for my magnetic tapes and floppy disks. Also, where does it get its energy from? It's much more efficient to walk around with wearable solar panels or to embed them directly into the devices. It may not work well on the north pole half the time but batteries aren't very conductive in those environments, anyway.
- samstave 14y ago
  When was the last time you walked around with a magnetic tape or floppy disc? Now - what happens if you put your wallet full of credit cards on it?
  - Tomdarkness 14y ago
    To be honest, magnetic strips on credit cards are redundant in a fair proportion of the world as well, especially Europe, although with a notable exception of the US which seems to be seriously lagging behind in this area. I live in the UK and it has easily been over 6 years since I have been anywhere where the magnetic strip has been read rather than using chip & pin (EMV).
    - philwelch 14y ago
      I visited the UK late last year and can confirm that your card readers can still read the magnetic stripes on our outdated American credit cards if they absolutely have to.
      - lostlogin 14y ago
        Unfortunately both types die with exposure to magnetic fields - I accidentally too mine into an MRI scanner. This may not Oruro at a lower field strength with the chip type however.
        brokenparser 14y ago
        SYNTAX ERROR UNEXPECTED TO... Oh, :s/Oruro/occur/
        lostlogin 14y ago
        Wow. That was a bad one, sorry, and I can't edit it. It was supposed to say: Unfortunately both types die with exposure to magnetic fields - I accidentally took mine into an MRI scanner. This may not occur at a lower field strength with the chip-type card however.
  - danielweber 14y ago
    I'm pretty sure he was being sarcastic.
- bradleyjg 14y ago
  There isn't enough upward facing surface area on your body for solar cells to power anything non-trivial. Also floppy disks?!?
  - Gravityloss 14y ago
    Power usage is going down with every generation. A few watts is quite a bit for a machine with an e-ink display. For others, maybe nothing but charge sustaining purposes at first.
- rbanffy 14y ago
  Guess we're not going to be able to work with our SX-64 portables on planes anymore.
mbell 14y ago
I've heard this argument a few times: "It charges so fast that the density doesn't matter". What often gets missed is that for it to charge fast, you need to provide a lot of power, a lot more than any current changer and laughably more than any inductive system can provide. Lithium Ion batteries can already max out the power offered by the 10W charger that comes with the iPad and charging off computer USB is often slow (USB is current limit). See Telsa's car charge times on normal wall outlets vs superchargers for another example. To really reap the benefits of this quick charge technology you either need an infrastructure of ~1000W DC chargers throughout the world or carry something about the size of a desktop computer power supply with you at all times.
- Someone 14y ago
  Also, you would need customers brave enough to charge that tiny device they are holding in their hands at 1000W. A mobile has about the surface area of a 100W incandescent, so if charging is 90% efficient, your mobile would have to radiate about as much heat as such an incandescent would do in about 3 seconds. It won't get as hot as that lamp, because your phone has a larger heat capacity, but I doubt it would stay cool, either. Given the effect of heat on current batteries, I guess designers would want that phone to irradiate waste heat rapidly. And that's when everything goes well. You would also need companies brave enough to risk the potential lawsuits if something goes wrong (user wears a pacemaker? Has some metal in his hand, e.g. in a tattoo? Charging accident releases heat that lights clothing?)
  - ScottBurson 14y ago
    Charging capacitors is normally much more than 90% efficient. They're not like batteries, where a chemical reaction occurs during charging. Resistive losses in capacitors are normally negligible. In this case they will probably still be negligible, I'd guess, because of the high conductivity of graphene.
    - mbell 14y ago
      True but you've got to consider the numbers we're looking at here. As an example an iPhone 5 has a 5.45Wh battery, if you wanted to replace that with a super-cap and charge it to 5V in 20 seconds you'd need to provide ~1000W of power or 200A @ 5V. Even if the super cap had very low ESR, call it 1mOhm, which is extremely low compared to current super-caps, you'd still end up dissipating 40W as heat with ~96% efficiency.

deleted 14y ago

[deleted]

brokenparser 14y ago

Your inductive charging tray tables are terrible for my magnetic tapes and floppy disks. Also, where does it get its energy from? It's much more efficient to walk around with wearable solar panels or to embed them directly into the devices. It may not work well on the north pole half the time but batteries aren't very conductive in those environments, anyway.

samstave 14y ago
When was the last time you walked around with a magnetic tape or floppy disc? Now - what happens if you put your wallet full of credit cards on it?
- Tomdarkness 14y ago
  To be honest, magnetic strips on credit cards are redundant in a fair proportion of the world as well, especially Europe, although with a notable exception of the US which seems to be seriously lagging behind in this area. I live in the UK and it has easily been over 6 years since I have been anywhere where the magnetic strip has been read rather than using chip & pin (EMV).
  - philwelch 14y ago
    I visited the UK late last year and can confirm that your card readers can still read the magnetic stripes on our outdated American credit cards if they absolutely have to.
    - lostlogin 14y ago
      Unfortunately both types die with exposure to magnetic fields - I accidentally too mine into an MRI scanner. This may not Oruro at a lower field strength with the chip type however.
      - brokenparser 14y ago
        SYNTAX ERROR UNEXPECTED TO... Oh, :s/Oruro/occur/
        lostlogin 14y ago
        Wow. That was a bad one, sorry, and I can't edit it. It was supposed to say: Unfortunately both types die with exposure to magnetic fields - I accidentally took mine into an MRI scanner. This may not occur at a lower field strength with the chip-type card however.
- danielweber 14y ago
  I'm pretty sure he was being sarcastic.
bradleyjg 14y ago
There isn't enough upward facing surface area on your body for solar cells to power anything non-trivial. Also floppy disks?!?
- Gravityloss 14y ago
  Power usage is going down with every generation. A few watts is quite a bit for a machine with an e-ink display. For others, maybe nothing but charge sustaining purposes at first.
rbanffy 14y ago
Guess we're not going to be able to work with our SX-64 portables on planes anymore.

mbell 14y ago

I've heard this argument a few times: "It charges so fast that the density doesn't matter". What often gets missed is that for it to charge fast, you need to provide a lot of power, a lot more than any current changer and laughably more than any inductive system can provide. Lithium Ion batteries can already max out the power offered by the 10W charger that comes with the iPad and charging off computer USB is often slow (USB is current limit). See Telsa's car charge times on normal wall outlets vs superchargers for another example. To really reap the benefits of this quick charge technology you either need an infrastructure of ~1000W DC chargers throughout the world or carry something about the size of a desktop computer power supply with you at all times.

Someone 14y ago
Also, you would need customers brave enough to charge that tiny device they are holding in their hands at 1000W. A mobile has about the surface area of a 100W incandescent, so if charging is 90% efficient, your mobile would have to radiate about as much heat as such an incandescent would do in about 3 seconds. It won't get as hot as that lamp, because your phone has a larger heat capacity, but I doubt it would stay cool, either. Given the effect of heat on current batteries, I guess designers would want that phone to irradiate waste heat rapidly. And that's when everything goes well. You would also need companies brave enough to risk the potential lawsuits if something goes wrong (user wears a pacemaker? Has some metal in his hand, e.g. in a tattoo? Charging accident releases heat that lights clothing?)
- ScottBurson 14y ago
  Charging capacitors is normally much more than 90% efficient. They're not like batteries, where a chemical reaction occurs during charging. Resistive losses in capacitors are normally negligible. In this case they will probably still be negligible, I'd guess, because of the high conductivity of graphene.
  - mbell 14y ago
    True but you've got to consider the numbers we're looking at here. As an example an iPhone 5 has a 5.45Wh battery, if you wanted to replace that with a super-cap and charge it to 5V in 20 seconds you'd need to provide ~1000W of power or 200A @ 5V. Even if the super cap had very low ESR, call it 1mOhm, which is extremely low compared to current super-caps, you'd still end up dissipating 40W as heat with ~96% efficiency.