5 ms·

Voltage is irrelevant. You can put batteries in series.

hwillis 10y ago
It's not; it has practical consequences. Everything in a phone runs at a spectacularly low voltage compared to most electronics because the battery only has one cell. At small sizes it's simply not practical to make more cells.
- Tloewald 10y ago
  Smart phones typically run lower than 3.7V so it's still not a big deal. The weight is a possible show stopper for cars but probably not smart phones (where size trumps weight) and of course they may be able to get the weight down by some kind of chemistry or materials magic (glass foam?)
  - hwillis 10y ago
    Phones turn off automatically if the battery dips below 3 V, and this battery tops out at 2.7 V. It's totally possible to make it work, it just isn't terribly simple. As for chemistry and glass foam, the voltage of a cell is determined by the electronegativity of the reaction in the battery. With lithium, it can never be very much above 5 V- atoms just don't pull on each other that hard. This already uses lithium, and the chemistry won't be able to improve much bast 2.5 V. For any given chemistry, you can't increase the voltage without putting cells in series, because the atoms decide the voltage. Any tweaks to construction, electrolyte etc. can only increase the current, by giving it more places to flow.
    - lightedman 10y ago
      "It's totally possible to make it work, it just isn't terribly simple." Please, it's as simple as a three-component boost converter - one IC and two resistors. Same thing I use to bump 1.2V up to 3.6Vto run LEDs. It takes zero space (7x7mm total.)
      - pfooti 10y ago
        what's the efficiency of that boost converter? how much energy gets dissipated as heat in that setup, and is that likely to cause a fire?
        thesmok 10y ago
        Modern boost converters have efficiency from 80% to 95%. They also operate at high frequencies – 1MHz or even 3MHz, which allows to make inductors incredibly small. Boost converters aren't a problem for a long time now.
      - hwillis 10y ago
        Sure. You could use an SOT23 or a QFN like this: http://www.digikey.com/product-detail/en/texas-instruments/TPS61090RSAR/296-15259-2-ND/566911 http://www.digikey.com/product-detail/en/texas-instruments/T... That's 4 mm x 4 mm (more with passives, but not too bad), and hits a solid 95% efficiency at the normal load of an iphone, and is above 90% all peak loads. Heat dissipation will be fine, all parts cost about $1.20. Low EMI. However, its still a dozen new components. It's a ~10% tradeoff somewhere and while that may be totally worth it, its not simple. Phones do not have square millimeters to spare.
        Arizhel 10y ago
        >Phones do not have square millimeters to spare. Actually, they do, when you're replacing the battery with one with 3 times the energy density. Use some of the saved space for your DC-DC converter.
        hwillis 10y ago
        Its like... adding a turbocharger to a car. Yes, it is possible. There are even kits, after a fashion. But it is still not simple. Also, its not even at the stage of a hypothetical question yet. This battery would last about two weeks in an iphone under these load conditions. The only reason it "looks" possible is if you're considering a battery that is not this one.
    - pjc50 10y ago
      Sure, but you can just put the cells in series. Remember that '3.7V' nominal cells range from 4.2V down to a low voltage cutoff about 2.8V (and in practice will not be let too close to that DoD). So stacking two of these '2.5V' cells will probably give a 6-4V usable range. Remember also that the electronics is in three groups: 1.8V (most of the processor), 3.3V (peripherals), and raw battery voltage (RF front end output power amplifier). The former two will already be driven by switchmode regulators and the latter is much more flexible.
  - rocqua 10y ago
    Not just phones where volume matters, also small laptops. They simply need some weight to counterbalance the screen.
- rasz_pl 10y ago
  There is _not a single_ phone on the market running logic directly from the cell. Everything has own buck/boost converters and army of power management chips. Voltage is irrelevant!
- marcosdumay 10y ago
  Everything with a mobile CPU inside has a switching power supply that could be adjusted to use 1, 2, 7, or 40V just as easily. Really small devices do not have space for those, so ear buds may not be able to use this battery. But your phone, or watch, certainly can.

It's not; it has practical consequences. Everything in a phone runs at a spectacularly low voltage compared to most electronics because the battery only has one cell. At small sizes it's simply not practical to make more cells.

Tloewald 10y ago
Smart phones typically run lower than 3.7V so it's still not a big deal. The weight is a possible show stopper for cars but probably not smart phones (where size trumps weight) and of course they may be able to get the weight down by some kind of chemistry or materials magic (glass foam?)
- hwillis 10y ago
  Phones turn off automatically if the battery dips below 3 V, and this battery tops out at 2.7 V. It's totally possible to make it work, it just isn't terribly simple. As for chemistry and glass foam, the voltage of a cell is determined by the electronegativity of the reaction in the battery. With lithium, it can never be very much above 5 V- atoms just don't pull on each other that hard. This already uses lithium, and the chemistry won't be able to improve much bast 2.5 V. For any given chemistry, you can't increase the voltage without putting cells in series, because the atoms decide the voltage. Any tweaks to construction, electrolyte etc. can only increase the current, by giving it more places to flow.
  - lightedman 10y ago
    "It's totally possible to make it work, it just isn't terribly simple." Please, it's as simple as a three-component boost converter - one IC and two resistors. Same thing I use to bump 1.2V up to 3.6Vto run LEDs. It takes zero space (7x7mm total.)
    - pfooti 10y ago
      what's the efficiency of that boost converter? how much energy gets dissipated as heat in that setup, and is that likely to cause a fire?
      - thesmok 10y ago
        Modern boost converters have efficiency from 80% to 95%. They also operate at high frequencies – 1MHz or even 3MHz, which allows to make inductors incredibly small. Boost converters aren't a problem for a long time now.
    - hwillis 10y ago
      Sure. You could use an SOT23 or a QFN like this: http://www.digikey.com/product-detail/en/texas-instruments/TPS61090RSAR/296-15259-2-ND/566911 http://www.digikey.com/product-detail/en/texas-instruments/T... That's 4 mm x 4 mm (more with passives, but not too bad), and hits a solid 95% efficiency at the normal load of an iphone, and is above 90% all peak loads. Heat dissipation will be fine, all parts cost about $1.20. Low EMI. However, its still a dozen new components. It's a ~10% tradeoff somewhere and while that may be totally worth it, its not simple. Phones do not have square millimeters to spare.
      - Arizhel 10y ago
        >Phones do not have square millimeters to spare. Actually, they do, when you're replacing the battery with one with 3 times the energy density. Use some of the saved space for your DC-DC converter.
        hwillis 10y ago
        Its like... adding a turbocharger to a car. Yes, it is possible. There are even kits, after a fashion. But it is still not simple. Also, its not even at the stage of a hypothetical question yet. This battery would last about two weeks in an iphone under these load conditions. The only reason it "looks" possible is if you're considering a battery that is not this one.
  - pjc50 10y ago
    Sure, but you can just put the cells in series. Remember that '3.7V' nominal cells range from 4.2V down to a low voltage cutoff about 2.8V (and in practice will not be let too close to that DoD). So stacking two of these '2.5V' cells will probably give a 6-4V usable range. Remember also that the electronics is in three groups: 1.8V (most of the processor), 3.3V (peripherals), and raw battery voltage (RF front end output power amplifier). The former two will already be driven by switchmode regulators and the latter is much more flexible.
- rocqua 10y ago
  Not just phones where volume matters, also small laptops. They simply need some weight to counterbalance the screen.
rasz_pl 10y ago
There is _not a single_ phone on the market running logic directly from the cell. Everything has own buck/boost converters and army of power management chips. Voltage is irrelevant!
marcosdumay 10y ago
Everything with a mobile CPU inside has a switching power supply that could be adjusted to use 1, 2, 7, or 40V just as easily. Really small devices do not have space for those, so ear buds may not be able to use this battery. But your phone, or watch, certainly can.