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Battery Less Phones

Published on Aug 14, 2018


If we just date back to January 9, 2007, it’s the date when the world first witnessed a smart phone, and in fact, the first ‘Touch screen phone’. Mr. Jobs, the owner of Apple Inclusive launched the “I-phone” aiming to turn everyone’s life uncomplicated. And then, it has been ten years since the launch of the smart phone, and in these 10 years, the world has observed a revolutionary change in the era of smart phones. One of the most drastic changes was witnessed in the batteries of these smart phones, ranging from 1000mAh to 5000mAh on an average. In the past couple of years, intense usage of smart phones for various purposes has resulted in battery draining at a rapid rate.

Many types of research have been done in order to find the exact reason for the battery drain at a rapid rate and its solutions, although none of them were able to accomplish anything special, and hence, rather than to find a solution to battery’s long life, a different solution was established, and it was to construct phones, which can be operated without batteries. This research paper focuses on the implementations of “Battery Less Smart phones”, and on its pros and cons. It will also state some of the economic and possible changes that can be made as per our research.


The smart phones we are using these days are indeed smart, however, are they really that smart as the companies claim? The answer to this question is yes, but aren’t those really dumb if discussed in terms of battery life? Yes, they are. Even the companies that sell smart phones at phenomenal rates have the issue of battery’s performance [1]. The performance is better as compared to others, but it is still a mystery if discussed in terms of long life. The idea of battery less smart phones was initiated by a group of researchers from “The University of Washington”, who invented the phone with a dial pad, and to the next level of astonishment, the phone was designed so that it could harvest energy from “Radio Signals”. The phone developed, features a dial pad, a small led light, and will also include an E-ink display.

Battery Less Phones

A. Perspective for Battery Less Phones

A lot of discrepancies about the battery’s performance were going on around the world. The issue about the battery’s anomalous drain lead to the research of innovative stuff, which furthermore lead to the invention of these Battery Less Mobiles. Smart Phones these days are a real help for the human race, the way they are used to reduce our burden and anxiety by saving our time is just unexplainable, And to the fact that everyone knows about the battery affair, people still purchase phones to stay connected to the world, and hence, these battery less phones were created to replace the battery’s draining issue and to offer an effective method of staying connected to the world.

B. Battery Less Smart Phones Vs Battery Saving Applications

The multi task calculating apps can increase your battery’s life, but to a very small extent. These apps maintain your phone’s battery life by clearing other apps from the background and by suggesting you the precautions about how to use your phones effectively, but battery less phones are way different as the battery doesn’t exist and hence they will be greatly helpful in the future, especially for upcoming generations [3]. So, this paper will completely focus on the methods about how to implement the technology as soon as possible and what could be the effective changes in it.

Framework for Battery Free Phones

ambient sources, and surprisingly those ambient sources are “Radio Signals or Radio Waves”, and the device uses a minute photo diode to harvest energy from the ambient light or RF sources. It consumes only 3.5 microwatts of power from these energy sources. The device has a limited range of just 31 feet from the base station and the range can be expanded to 50 feet with the help of a small “Solar Cell".

A. Procedure for Fetching Energy from Ambient Sources

1. Harnessing Energy

In order to harness energy from the ambient sources, a base station is required and the base station is placed as per the range specified(31feet-50feet), RF energy can be transmitted in unlicensed bands or grids ranging from 868MHz to 5.4GHz from their respective base stations. It is then, that this RF energy is transfigured into DC power through some energy harnessing devices such as “Powercast’s Powerharvester Receivers”, these receivers also contain criterion or conventional antennas having an average resistance of 40-50 ohms.

Battery Less Phones

The main feature of these harvesters is to maintain the effectiveness while maintaining the disparities of RF to DC transfiguration in order to make the output stable, Although heading with the new technology of battery free phones, the procedure was way different as compared to the described one. In the phone, a “photo diode” was used to convert the ambient light into current or DC power. These photo diodes can also produce energy in absence of light as they contain optical filters and in-built lenses to perform better in dark conditions.

2. Conversion of Ambient Signals to Power with the Photo Diode

The researchers at the University easily found the fact that using a photo diode for converting ambient signals and light into current is much efficient and economical than installing a power harvester since the amount of power required for the functioning of the prototype was very less. A Photodiode is a semiconductor, with p-n junction diode and an intrinsic layer between two junctions [8]. The photocurrent is provoked by the electron hole pair because of the assimilation of light between depletion region. When photons of energy greater than 1.1 electron volt (eV) strike the diode, electron-hole pairs are originated. The potency of photon absorption depends on the energy of photons – the lower the energy of photons, the deeper the assimilation is. If the absorption occurs in the depleted region of the p-n junction, these hole pairs are wiped from the junction - due to the inbuilt electric field of the depletion region. Hence, the holes proceed toward the anode and the electrons move toward the cathode, thereby generating photocurrent. The sum of photocurrents and dark currents, which flow with or without light, is the amount of current progressing through the photodiode, And this is how a small amount of power is generated in the battery less phone with the assistance of a tiny photo diode

Prototype & Working of Battery Less Smart Phones

In the given model, the user undertakes a button to twig in between the two transmitting and listening notes. The team of researchers utilized the shell components on a printed circuit board and the team corroborated and ensured that the battery free prototype can perform basic functions like calling someone up and then hanging up the call without any inadequate call drops. A custom base station collects the data in form of digital packages with the help of a “Backscatter” and connects our call through “Skype” and the person at the other end answers the call and responds. The device inherits the signals with a technology referred as “Zero Power Amplitude Modulation” and plants the audio onto the earphones. For making a call, the user has to dial the number on the dial pad and has to speak into the microphone. For attending the call at receiver’s end, the user has to pick up the call and respond, the call is transported to a long distance with a backscatter, which helps in the cycling of data packages.

A. Shell Component and its Working

The Shell, which is used with the Kernel (part of operating system), is a part of the operating system of the battery free device that is utilized for recasting the Human made programming into the machine language. When the user enters the command for executing any sort of operation, the request proceeds to the shell parts, also known as Interpreter which then translates the code and transfers it to the Kernel [11], the kernel then receives and accepts the request and exhibits it on to the display area or screen. The kernel also provides memory for the running processes on the prototype.

Battery Less Phone

B. How is Power Saved?

If we head back again towards the mobiles and devices of today’s generation, the phenomenon behind the battery’s hunger for power is the process of converting analog signals into digital data packages that a phone can interpret. This process consumed the highest amount of power in smart phones that we are operating at present, however that’s not the case with battery free cell phones as the battery free prototype takes the dominance of minute vibrations that occur in the phone’s microphone and speaker when the user speaks into the microphone or listens to an incoming call. An antenna connected to the shell and speaker components receives the analog radio signals, which are emitted by the cellular base station and then these signals are transmitted back to the cellular base station by the use of a “backscatter” in order to maintain a cycle of transferring digital packages that furthermore helps in retaining signal strength so that the call doesn’t hang up in an insufficient manner.

Backscatter-Working and Performance

A backscatter is a device that reflects or deviates any particle through an angle measure of approximately 180 degrees. RFID (Radio Frequency Identification) backscattering is a technology which uses the RF power transmitter in accordance to the tag reader to vitalize the tag(objects that are to be identified). Necessarily, they “deviate” part of the power conveyed by the reader, although it affects some of the properties, and in this manner, it sends backs information to the reader. With the help of RFID backscatter, some tags obtain their data transmission by converting the properties of the tags themselves, where as the rest twig between a load resistor in and out of the antenna circuit [13]. RFID backscatter conversion controls outside the field region, and the radio signal proliferates away from the RFID reader. When the signal approaches the RFID tag, this inter communicates with the ongoing signal and some energy is deviated towards the RFID reader [14]. Over momentary ranges, the quantity of power outstretching the tag from the reader is quite enough to allow operation of low current circuits inside the tag, and so even with these low currents, the battery less device was able to reflect digital data packages.

Battery Less Phones

How do solar cell work and increases range by saving energy?

Solar cell constitutes of P-N junction diode, which is assembled from Silicon and Germanium. With the help of vapor deposition, P type layer is diffused over N type semiconductor with p type having some electrodes. This process constructs open space for light to fall on P layer and hence underlying the P-N junction [22]. The bottom of N layer comprises of current assembling electrode. When a light photon arrives at the junction, they exhilarate electrons from valence band to conduction band, discarding behind an equal number of holes in the valence band.

Battery Less Phones

This electron hole generated in the depletion region accelerates in opposite direction because of the barrier field. Photo generated electrons accelerate in direction of n type and electrons directed towards p side. The hoard of these charges carriers formulates p side, a positive electrode, and N side, a negative electrode. Hence photo voltage is set up across the junction. When load resistance is connected in the circuit, the current flows through the solar cell [23]. This current from the solar cell is greater than that produced by the RF signals and hence a reason ,the capacity of backscatter increases in order to send digital packages back to the base station, and finally the range increases


The advantages of this battery-less phones are exceptional, though the implementation of these phones completely, is still a mystery. From saving energy to utilizing new technology, this outstanding prototype stands rigidly in every part of the platform, when it comes to energy saving.

A. Conserves Electricity

Since the phone doesn’t consist of a battery, it saves electricity to a great amount. As per a survey, it approximately costs a person around 5$ a year to charge a phone. The amount may not seem that big, but it increases to 500 $ for 10 years and around 5000$ in a century. So now it can be easily figured that battery less phone can save electricity and money by large amounts.

B. Saves Time

From some of the latest facts and figures, it was estimated that a person usually spends approximately 2.5 hours in a day while waiting for the phone to charge. The amount of time increases to around 1000 hours in a year.

C. Low Power Consumption

As explained earlier, the battery free cell-phone consumes only 3.5 microwatts of power, which is captured from ambient power sources. On an average, it was found that charging your phone consumes 1kWh of power in a year. The power is quite low as compared to the time period of one year, Although if we imagine that if a normal mobile with battery consumes this much power, then how many years would it take for a battery less cell phone to use 1kWh of power? The answer goes even beyond hundred thousand years, so it saves power by a huge amount.

D. No Charging Issues

The fact is not hidden that charging a phone, again and again, annoys a person, the most. Charging a phone completely and plugging it once more after using it for some hours, displeases the user in emergency and crucial situations. With the battery less phone, anyone can operate the phone anytime and anywhere without worrying about the sudden drain of the battery


It was extremely astonishing to witness that a group of researchers have finally developed a phone that uses no power, which means the phone has no battery and harnesses energy from ambient signals and light sources. Even Mr. Jobs, who designed the first ever smart phone, might have never thought that smart phones would be that smart that someday we would be able to use it without a rechargeable option, that is without a battery. The phone just consumes 3.5 microwatts of power and harvests energy from ambient radio and light sources with the help of minute diodes that convert light and signal strength into a current which is furthermore converted into few microwatts of power. With the phone, we can just dial a number and call to another person.

The phone possesses a backscatter that sends the digital packages back to the cellular base station. The base station then receives the signals and connects the call through Skype. The battery less phone obtains signals with the help of zero power amplitude modulation and transfers audio onto our earphones. To respond, the user has to press a button and speak into the microphone. Even after combining these amazing technologies, the phone has multiple disadvantages, Range being the biggest one. As per the rate of growing technology, these limitations will be fixed soon with all the Wifi routers having RF emission sources, and we would soon witness an ‘Advance Battery less Phone’ with multiple features.

Paper Submitted by Sparsh Rawlani, Purvesh Biyani, Apoorv Joshi


[1] Shin, Choonsung, Jin-Hyuk Hong, Anind K. Dey, "Understanding and prediction of mobile application usage for smart phones", In Proceedings of the 2012 ACM Conference on Ubiquitous Computing, pp. 173-182. ACM, 2012.

[2] Goodenough, John B., Kyu-Sung Park,"The Li-ion rechargeable battery: A perspective." Journal of the American Chemical Society 135, No. 4, pp. 1167-1176, 2013.

[3] Cuervo, Eduardo, Aruna Balasubramanian, Dae-ki Cho, Alec Wolman, Stefan Saroiu, Ranveer Chandra, Paramvir Bahl. "MAUI: Making smartphones last longer with code offload." In Proceedings of the 8th international conference on Mobile systems, applications and services, pp. 49-62. ACM, 2010.

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