Tethercell battery could redefine smartphone control

January 11, 2013 by Nancy Owano report

(Phys.org)—An Indiegogo project by Tetherboard drew interest at CES in Las Vegas this week where a novel concept of phone battery was demonstrated. The prototype on show was Tethercell, an adapter which the user can control from a smartphone or tablet, The adapter, powered by a AAA-battery, embeds Bluetooth into a traditional AA battery form. A Tethercell holds an AAA battery inside its little case.

Tethercell comes with an app, and once the device is -operated with the product, one can time activities, get alerts when batteries are running low, and other tasks. The user can set hours when a device can be used; AA battery-powered devices can be turned on and off remotely; Tethercell can help to set device schedules to save ; and set simple timers. Instead of a phone running on batteries, in a sense, the batteries are helping to run the phone, as the Tethercell turns phone batteries into .

It works by the user taking out one AA battery and replacing it with a Tethercell with an AAA battery within it. No matter how many AA batteries are required to run the device, only one Tethercell would be needed. Then a Tetherboard app downloaded from the App store would be started up and the user would connect to an iOS device that is Bluetooth Smart compatible.

The design is a plastic enclosure with wireless the size of an . According to the product creators, Trey Madhyastha and Kellan O'Connor, mechanical design engineers, "The electronic brains embedded within the Tethercell contains a lot of cutting-edged electronics based upon the TI CC2540 microcontroller." They said it is packed with a current sensing OP-AMP comparator, , N-channel MOSFET (capable of switching up to 5A), 1.5 to 3V and embedded 8051 microcontroller."

Tethercell uses Bluetooth 4.0, a low-power Bluetooth protocol. "With Bluetooth Smart Ready the range of use with Tethercell should extend to about 60 feet through one wall," the creators said on their campaign site. They also said that they conducted some open field tests where they 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."

For the present, Tethercell will support AA-batteries and iOS. The goal is for the product to start shipping in June.

The creators are offering the product as an Early Bird Special at $29 as part of its indiegogo campaign. Funds obtained from the campaign will be applied to such activities as finalizing the app design and electrical board layout, ordering parts and tooling for the shell and stampings, and obtaining certifications. Their goal is to raise $59,000. At the time of this writing, with 43 days left, they raised $11,335.

Explore further: IPhone 4S first phone for low-power Bluetooth

More information: www.indiegogo.com/tethercell

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1 / 5 (3) Jan 11, 2013
Another gadget that will have very few actual practical uses but I guess if you need something like this...... It's far too expensive though for what it is.
2 / 5 (4) Jan 12, 2013
Ever read the user manual of _any_ battery operated gadget? Each and every one of them says: Do not mix different batteries!

Usually that means not mixing rechargeable with regular batteries, or alkalines with zinc-carbon batteries. But taken a little more seriously, you shouldn't even mix the same type of batteries from different brands, or fresh and half-used batteries. There are many reasons, but the most obvious one is a leakage that destroys your gadget.

For the same reason, you should not mix different sizes of even the same batteries.

What happens is, when the weakest (or smallest, or one that wasn't fresh) runs out before the others, the other batteries start force-feeding current through the weak one. This is what makes it leak.

These guys haven't done their home work, at all. Anyone with, say, a spare flashlight you can afford to throw away, can test this at home.

Customers won't like it when it's always the little battery within the Tethercell that leaks.
3.7 / 5 (3) Jan 12, 2013
I'd guess that the Tethercell designers are aware of this. And that the smaller AAA cell in the Tethercell will be the first in the series to become discharged. And include provisions for exactly that in the Tethercell's firmware. I.E. when the Tethercell's battery charge is low, remain off - perhaps even default to "off" when there is no charge.

As I was writing this, it occurred that it might not be difficult to have the Tethercell detect such a discharge condition and use the available reverse voltage to power up its bluetooth enough to alert that it is discharged
not rated yet Jan 12, 2013
To clarify - when I said "off" I meant: remove the battery from the circuit.
2.3 / 5 (3) Jan 12, 2013
The smallest cell in a series limits the capacity of all cells, because every cell has the same current going through it.

If the capacity of the AAA cell is 600 mAh and the regular AAs have 1800 mAh then you just effectively cut the battery capacity by 2/3. You can't use the remaining capacity without reversing the potential of the smallest cell, which would be destroyed, and you can't bypass the smallest cell because the series voltage would drop significantly and the device would think it's out of charge.

I think they really didn't see it coming. Otherwise they wouldn't have even suggested it.
5 / 5 (1) Jan 12, 2013
Great. A bluetooth detonator.
2.3 / 5 (3) Jan 12, 2013
The power requirements of a cell phone, more than any other consumer device, varies with task - from a stand-by current of a few hundred milliamps to a full-load demand of 1 to 3 amperes, a change of up to a 1000%. Output impedance varies with changing load. It doesn't matter, in the case of a cell phone, that one of the AA slots is taken up by an AAA battery with control circuitry.
5 / 5 (1) Jan 12, 2013
It doesn't matter, in the case of a cell phone, that one of the AA slots is taken up by an AAA battery with control circuitry.

Cellphones vary from a few microamps to a few hundred milliamps.

And cellphones don't use AA batteries.

And it still matters that one cell in a series is of lower capacity, because it limits how much energy you can get out of the entire pack. When the smallest one is empty, the entire battery is "empty" because drawing current through an empty cell will destroy it, making it bulge or leak, or vent.

AA cells are always in series, because most chips don't work all the way down to 1 volt. In fact most need at least 3 volts to operate, which is what you get when you have 3xAA in a series about to go empty.
not rated yet Jan 17, 2013
So? You replace the AAA batter 3x more often and keep the AA cells in place. They say it monitors the battery life. It will know when the AAA is depleted and stop using it. It will know when the AA's are depleted and stop using them.

And by stop using them I mean turn off the device. Yes you'll be replacing batteries more often, but what devices use a AA battery that you really want cell phone control of anyway??
5 / 5 (1) Jan 17, 2013
I have a very similar device in my TV remote control. You install a small rechargeable lithium battery into a holder very similar to this and install that as a AA battery. It detects the IR signal sent to the TV and transmits it using RF to a waiting receiver that then makes an IR signal. You put the new IR transmitter on a little wire in front of your TV.

What this does is allow you to use your remote from any room, anywhere, any time.

Works like a dream. I've only had to change the battery twice/year instead of once/year.

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