One of the challenges for smart phone users is limited battery life. While there are external batteries available to allow for on the go phone charging, these external chargers have two flaws aesthetic and clutter. An external battery system is difficult to make aesthetically pleasing. Beyond the aesthetic consideration many consumers are left with the challenge of finding space for another device to keep track of. Personally as a male consumer, who isn't interested in getting a men's purse and has been told that cargo pants are no longer acceptable attire, I would rather limit the number of things I bring with me for a night (please note that I am simply referring to my personal experience, I feel that both men and women would appreciate a new solution).
To solve the concern of sufficient battery life in a convenient package, I would like to propose the "Power Wallet" The Power Wallet aims to be a smart wallet for modern consumer, shaped like a standard bi-fold wallet, it would users to recharge their smart phone via an inbuilt USB power connector, all while still serving as a traditional wallet.
For the Power Wallet to make sense it must achieve these design parameters, the volume should not exceed that of a standard wallet, it should be able to contain an assortment of currency and credit cards, all wiring elements should be able to be stored conveniently, and the wallet should be robust enough to survive regular daily use. Ideally the design would provide minimal interference with RFID/NFC based communication standards used in many card systems. Additional features might include, solar panels on the back of the wallet, a mini-flashlight, e-ink display (for reasons), the ability for wireless charging, and outlet prongs for the internal DC adapter(this might be pushing things).
The hard science limit of the design is the energy density of battery technology, for Li-Ion batteries this value currently ranges between 250 Wh/L to 730 Wh/L. If we assume a middle value of 500 Wh/L= 500mAh/cm^3 we can then start to estimate how large of a battery we can add into the wallet. For reasons of safety I am also going to imagine that the battery requires 2 mm of some kind of external protection, before the material of the wallet is considered.
Credit Cards have the dimension of 53.98 mm x 85.6 mm x 0.76 mm
Starting from these baselines and a quick test of simply placing my cellphone's battery in my wallet we can assume that the Smart Wallet's internal battery could have the external dimensions of 6.4cm x 9.4 cm x 0.6 cm, making the actual battery volume 6.0cm x 9.0cm x 0.2 cm or 10.8 cm^3 continuing with the energy density assumption of 500mAh/cm^3 we can estimate the ability to store up to 5400mAh of power, or enough to fully charge a smart phone one and a half times (there are some efficiency issues to consider).
While these numbers do sound appealing they should be taken with a grain of salt, to the best of my knowledge Li-Ion battery manufacture doesn't generally allow for company's to order batteries to volume, most of the sub-elements of the battery, referred to as cells, are cylindrical in nature, consequently the actual storage capacity of the battery system will be less.
April 17 2014 It turns out someone was already looking into this idea, here is an article on gizmag that highlights a credit card sized back up battery.
To solve the concern of sufficient battery life in a convenient package, I would like to propose the "Power Wallet" The Power Wallet aims to be a smart wallet for modern consumer, shaped like a standard bi-fold wallet, it would users to recharge their smart phone via an inbuilt USB power connector, all while still serving as a traditional wallet.
For the Power Wallet to make sense it must achieve these design parameters, the volume should not exceed that of a standard wallet, it should be able to contain an assortment of currency and credit cards, all wiring elements should be able to be stored conveniently, and the wallet should be robust enough to survive regular daily use. Ideally the design would provide minimal interference with RFID/NFC based communication standards used in many card systems. Additional features might include, solar panels on the back of the wallet, a mini-flashlight, e-ink display (for reasons), the ability for wireless charging, and outlet prongs for the internal DC adapter(this might be pushing things).
The hard science limit of the design is the energy density of battery technology, for Li-Ion batteries this value currently ranges between 250 Wh/L to 730 Wh/L. If we assume a middle value of 500 Wh/L= 500mAh/cm^3 we can then start to estimate how large of a battery we can add into the wallet. For reasons of safety I am also going to imagine that the battery requires 2 mm of some kind of external protection, before the material of the wallet is considered.
Credit Cards have the dimension of 53.98 mm x 85.6 mm x 0.76 mm
Starting from these baselines and a quick test of simply placing my cellphone's battery in my wallet we can assume that the Smart Wallet's internal battery could have the external dimensions of 6.4cm x 9.4 cm x 0.6 cm, making the actual battery volume 6.0cm x 9.0cm x 0.2 cm or 10.8 cm^3 continuing with the energy density assumption of 500mAh/cm^3 we can estimate the ability to store up to 5400mAh of power, or enough to fully charge a smart phone one and a half times (there are some efficiency issues to consider).
While these numbers do sound appealing they should be taken with a grain of salt, to the best of my knowledge Li-Ion battery manufacture doesn't generally allow for company's to order batteries to volume, most of the sub-elements of the battery, referred to as cells, are cylindrical in nature, consequently the actual storage capacity of the battery system will be less.
April 17 2014 It turns out someone was already looking into this idea, here is an article on gizmag that highlights a credit card sized back up battery.
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