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Tethercell allows you to connect to and control AA-battery-operated devices from your mobile device.
Kellan O'Connor
Email Verified
Los Angeles, California
United States
1 Team Member


 CNET Mashable

The Verge
TechCrunch Apple Insider


What Tethercell allows you to do:

- Turn AA-battery-powered devices on and off remotely

- Be alerted when battery power is low

- Set device schedules & timers

- *NEW* Find Tethercell enabled devices with proximity function 

Tethercell Signal

Tethercell AA Battery Adapter Beside Iphone 4S

Examples of what Tethercell can be used with...

 Train Lantern Wire

Baby monitor puppy Outdoor light 



Easy Setup

Tethercell is extremely simple to install. First, remove a single AA-battery from whichever device you choose.  Next, make sure that Tethercell already has a AAA battery installed within it, then replace the removed AA battery with Tethercell. No matter how many AA batteries are required to run the device, you only need one Tethercell. After the Tethercell is snug in the battery compartment, turn on the device, fire up the Tetherboard app after downloading it free from the App store and you're ready to connect from any iOS or Android device that is Bluetooth Smart compatible.

Installation of Tethercell

The Tethercell App (for iOS and Android)

You can think of The Tethercell App as your Tethercell control center. From the Tethercell App you can easily connect to and control all active Tethercells in range straight from this intuitive interface which will be freely downloadable for supported devices. Tethercells have been tested to communicate with an iPhone 4S up to 100 feet away in an open field.


The Tethercell iOS App will be compatible with all Bluetooth Smart-enabled (i.e. Bluetooth 4.0) iOS smartphones and tablets. 


The Tethercell Android App will be compatible with all Bluetooth Smart-enabled (i.e. Bluetooth 4.0) Android smartphones and tablets running Android 4.3 or 4.4. This includes over 160 devices already in the market.

We’re designing Tethercell so that you can connect to a number of Tethercells instantaneously (we've tested up to four at once with good performance). No configuration processes, connections to maintain within your home network or other required hardware components. Once you have the app on your smartphone or tablet you’re ready to go. And since Tethercell only requires your smartphone or tablet for connectivity, connecting to Tethercell on the go is just as easy as connecting at home.

App Screens

iOS app-screen images


Intelligent Design

We believe that a lot of everyday products are begging to be re-examined and re-designed. As design engineers, we initially approached this project as a packaging problem, not too dissimilar from how you'd approach the ground up design of a new rocket engine or launch vehicle. While it may not be rocket science, our team's 20 years of collective experience in that field certainly came in handy during the conceptual and protoytpe design phase of Tethercell.

CAD Rendering of Interals of Tethercell 

CAD Rendering of Tethercell's internal workings.


The Functional Prototypes

To date, we've been through two major prototyping phases (and several design iterations within each phase). The first phase included a Windows-based application that communicated with a Tethercell that was true to the required final product dimensions. The second phase included an iOS application that executed all required control functions (except for the timer and device password functions) as well as a Tethercell that was built to the required final product dimensions.

Current Prototype Details:

  • Preliminary iOS application demonstrating attribute send & receive functionality.
  • SLS outer mechanical shell
  • Consolidated PCB assembly (produced to dimensions required for the final product)
  • Coil spring and stampings


Current prototype

Functional Tethercell prototype shown with all internal components.


We Need Your Help!

We've spent the last year designing and developing Tethercell and it's accompanying Beta App. We've been through a series of prototypes and now have functional hardware that we're really proud of. However, despite all of our successes with the prototype we now need your help to take Tethercell to the next level. In exchange for your support we want to put the first series of "Beta" Tethercell's into your hands so that you can share your Tethercell user experiences with us. With the valuable feedback we receive from supporters like yourselves, projects like Tethercell will be given the opportunity to evolve and grow in a way we simply couldn't achieve by ourselves.


What your contribution will help us do

  • Finalize the App development and electrical board layout.
  • Order parts for the first 5000 units.
  • Order tooling for the mechanical shell and stampings.
  • Obtain FCC and Bluetooth Certifications.


Who we are

Experienced engineers

Tetherboard is a passion project started by Trey Madhyastha and Kellan O'Connor, both experienced mechanical design engineers. As veterans of the aerospace industry, both Trey and Kellan drew inspiration from many of the hardware design elements developed during their respective years of service at Space Exploration Technologies (SpaceX) where they designed mechanical and fluid systems for the Falcon 9 rocket. 


Trey and Kellan


High Quality Partnerships

We of course could not have done this without the support of our friends, family and a few key partnerships. One partnership in particular was made with Brinton Engineering LLC, a premiere RF and embedded electrical systems R&D shop in Menlo Park, CA. Brinton is providing electrical design and prototyping support for the Tethercell electrical board.

Why We're Doing This

We believe in intelligent design, thinking outside the box and challenging set norms. With that said, we saw an opportunity to innovate around a commodity product that is a part of everyone's life. Yes, many are working to increase the energy density of batteries, while others are developing more efficient rechargeable batteries. With Tethercell we chose to go in a different direction. The result has been a challenging project that has landed us on IndieGoGo for support so that we may take this idea to the next level!

Production and Fulfillment Schedule

One of the many things we've learned as hardware engineers is that things take longer than expected. With this notion in mind, we've carefully thought through our production and delivery schedule and are confident that we can meet all of the project milestones listed below. Developing high-quality hardware, software, and firmware is a time-consuming venture; the milestone dates below are realistic; to suggest anything less would be dishonest, and we prefer to be as upfront about these things as we can possibly be. We will of course keep you posted on our progress.

  • January 2013 – Finalize electrical board layout and add the final set of features to the app.
  • February 2013 – Product and app testing. Order long lead electronics components as well as tooling for the plastic shell.
  • March 2013  – Further product testing and certification (FCC and Bluetooth).
  • April 2013 – Component kit delivery to PCB manufacturer and assembly house.
  • May 2013 – Complete product kits delivered to fulfillment partner for final assembly and packaging.
  • June 2013 – Start shipping the first Tethercells to our earliest backers.

Privacy and Security

Tethercell has been designed with privacy in mind. From the beginning we've included a feature to allow users to enter a personal code in order to connect to Tethercell. In the first functional prototype this feature was called "FAMILY ID." In the second functional prototype, as well as with with the final product, we are using the same underlying functionality, but are calling it "Device Password." In the final version of the app, when a Tethercell is discovered for the first time, the user will be prompted to establish a device password. From there on out no other Tetherboard user will be able to connect to that Tethercell unless they too know the established device password.

Tech Details

Tethercell is the same size and length as a typical AA-battery, which power approximately 60% of primary battery-operated devices. You’ll notice that Tethercell is powered by a AAA battery, which allows room for the embedded intelligence that we’ve packed into a really tight space. Don’t worry - your devices will still have the power they need to function when just one of the AAs is substituted with the AAA-powered Tethercell.  The electronic brains embedded within the Tethercell contains a lot of cutting-edged electronics based upon the TI CC2540 microcontroller. Packed with a current sensing OP-AMP comparator, temperature sensor, N-channel MOSFET (capable of switching up to 5A), 1.5 to 3V boost converter and embeddeded 8051 microcontroller, Tethercell represents a veritable untapped playground of potential.


Tethercell beside AA battery

Standard AA battery beside Tethercell Adapter


Tethercell will have many user-definable modes of operation. Powering the on-board Bluetooth radio consumes a very small amount of current (~20mA). However, the radio operates on a low duty cycle, meaning that it doesn't transmit for very long and ideally spends most of it's time asleep. Users will be able to tailor the behavior of their Tethercells via the Tetherboard App using simple iOS style App controls. For usage cases requiring simply turning on or off items in use and then going to sleep, the Tethercell's quiescent power consumption enables the device to run for approximately six to twelve months on a single AAA battery. In general, the device has been demonstrated to provide months of reliable use in real world testing. Needless to say, the battery life is highly dependent upon how the device is configured and how much power the host device draws.

Tethercell utilizes Bluetooth 4.0, the new low power Bluetooth protocol that will play a big part in the Internet of Things. With Bluetooth Smart Ready the range of use with Tethercell should extend to about 60 feet through one wall. As stated earlier, we have conducted some open field tests where we demonstrated connectivity at distances over 100 feet. As with any RF device, environment plays a significant role in the performance of Tethercell. We are confident in stating these range figures as we routinely exceed them in testing.

What is Bluetooth Low Energy?

Bluetooth Low Energy, as the name suggests, is the lower energy version of Bluetooth, the popular wireless radio technology. Bluetooth Low Energy was the enabling technology that made Tethercell possible; Bluetooth Low Energy, more commonly referred to as Bluetooth Smart Ready, requires significantly less power for operation than other traditional radio options. This technology will benefit a number of industries as many hardware developers are actively seeking solutions to shrink devices into increasingly smaller form-factors and power those devices for longer periods of time from equally small power sources. 

Frequently Asked Questions

Q: Tethercell uses a AAA battery in place of a AA battery.  How does this affect battery life? 

A: A good quality AAA battery has about 1/2 to 1/3 the capacity of a AA battery.  As a result, the AAA battery will run down first, at which point the app will notify you that it's time to refresh the AAA cell.  Tethercell will cut off the circuit if the AAA battery discharges to such an extent that it could otherwise reverse charge and present a hazard.  After refreshing the AAA cell, the device will continue to operate and the remaining life in the AA cells can be used until they are drained.  Approximately 1/2 of the capacity of the AAA cell is used for the Bluetooth connection for 1 year of quiescent connectivity, leaving the remaining juice for the device it is installed in.  Of course, for high drain devices, you'll probably be changing or recharging the AAA cell well before the 1 year mark. 

Q: Can I use rechargeable batteries with Tethercell?

A: Yes! Tethercell performs best with rechargable cells because of their low internal resistance, especially in high drain devices.  We have tested Tethercell with Sanyo Eneloop XX batteries with exceptional results.  In one test, a AAA cell charged to 1350 mAH capacity; paired with rechargeable AA cells, Tethercell really shines, and the life deficit is easily overcome, gaining you unprecendented functionality.  We recommend NiMH Low Self Discharge cells (like Eneloop) for maximum performance.

Q: Can I recharge my AAA cells while they are installed in Tethercell?

A: Yes!  We have successfully cycled NiMH cells on a La Crosse BC-700 charger multiple times, even at the 700 mAH setting!  Tethercell supports the typical Charge/Discharge-Test/and Charge-Refresh functions common to NiCad and NiMh style chargers.   

Q: Are you planning to make AAA, 9V, and other cell versions in the future?

A: Yes, we have been working on reducing the size of the circuitry to facilitate embedding it in a AAA battery as well as a 9V.  The larger cells are less of a challenge since the electronics present less of a percentage of the available real-estate, and we have a better power budget to work with.

Q:  How did you come up with the idea for Tethercell?

A: Trey, one of the co-founders, struggled with inconveniences associated with the many toys and battery powered devices that made their way into his life once he had kids.  Tethercell was born out of a desire to disable nuisance toys, conveniently enable parental overide for cordless mice, keyboards and the like, turn on a baby monitor without entering his son's room, and finding the TV remotes that seemed to to wander off a little too often when his toddlers took a liking to them.

Q:  Is Tethercell made in the USA?

A:  We are making every effort to manufacture the most critical components of Tethercell close to home to ease logistics.  We received many offers from US based suppliers to help us achieve that goal. 

Q:  Does Tethercell need to have an active BT connection for the timers to work?

A:  No, after setting a timing routine from the Tethercell app, the information is wirelessly communicated to the embedded micro-controler within Tethercell.  Even after a connection is terminated, the programmed timers will continue to function. 

Q:  Will Tethercell work if it's installed in a metallic enclosure device, like a Mag-Lite?

A: Yes and no.  We have tested Tethercell in an aluminum bodied AA sized flashlight.  Although the device will connect, it needs to be in very close proximity to the transmitter (ie. phone or tablet).  Once pared, it unfortunately suffers from very limited range (~ a few feet) because the aluminum impedes the RF transmissions to the antenna on-board Tethercell. 

Q: Will Tethercell work with motorized devices?

A: Yes, Tethercell can switch up to 5A of current, which is sufficient for most motorized devices.  For high drain devices of this sort, we highly recommend using rechargeable chemistry batteries (NiMH or NiCad) as they have low internal resistance and therefore will not cause a noticable drop in performance.  They also are also more economical since the AAA cell does have reduced capacity.

Q:  Does Tethercell let you know when the AA batteries (if installed) are running low?

A: No, Tethercell is only capable of monitoring and reporting the charge status of the AAA cell contained within it.


TIME: 5 Clever Gadgets from CES 2013

CNET: Tethercell magically turns AA batteries into Bluetooth devices

Mashable: Silence Annoying Electronics With This Battery Gadget

The Verge: Tethercell lets you control mostly anything with Bluetooth (hands-on)

Golem.de: Die Bluetooth-Batterie-Macher zeigen Tethercell


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