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# Plus-sized Batteries

Batteries that use the extra space in many battery compartments
 (+3, -2) [vote for, against]

Sure, AA batteries have a round cross-section, but have you ever really looked at the battery compartment in your assorted portable devices? I have, and there's often a lot of space in there.

My idea is to use the space typically found in a battery compartment to boost the capacity of a AA battery. They won't fit in everything, but for those things they do fit in, the extra capacity will undoubtedly be handy.

It's hard to describe, but a normal battery has a circular cross-section, while my two designs have either a square cross-section (AA++) or a compromise of half a square cross-section and half a circular cross section (AA+).

AA+ is designed based on the premise that many battery compartments only require a curve on one side of the battery. The AA++ design is based on compartments with no guides beyond where the circular cross-section of a normal battery would meet the inside of a square.

Typical battery compartments only have a curved guide on one side of the compartment, or both ends but not the middle. Some battery compartments are just a simple square or rectangle.

I've had this idea bouncing around in my head for a while, but when Moixa Energy came out with the "USB Cell", I thought it was worth putting together an explaination of my idea in case the room could be used for the charging circuitry, even if current battery cell technology still favours a circular cross-section.

 — Krisjohn, Sep 21 2006

Illustrated version http://www.krisjohn.net/batteries.html
I have an illustrated version of this explaination at this link. [Krisjohn, Sep 21 2006]

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Annotation:

 Also electrons don't paticularly like corners.

 Battery cells are made in two basic styles.

 Your basic cylindrical battery has a carbon rod in the center for a cathode, a metal can on the outside for an anode. The space in between is felt dampened with electrolite. The cell works best when the distance between the anode and cathode is constant. So cylinders work very well and are very simple.

 The second type of cell has cathode and anode plates separated by electrolite (either as a liquid, or a saturated solid). These cells are typically rectangular, and stacked in banks to make more powerful batteries. Car batteries are this type, as are many small electronic batteries. This type is more expensive and complex to manufacture. But can be of arbitrary shape.

So, sure, you can do this, but they are going to cost more.
 — Galbinus_Caeli, Sep 21 2006

I gave you a bun for a good idea, but i think this is baked. I used to have a sony walkman that could run on two AA batts, or on its own special rechargeable battery. The rechargeable battery was a single unit with a flattened oval cross section that took up the space of the two side-by side AA's (and filled in some of the wasted space that woudl have surrounded the AA). I found that I could use the battery in several other various devices that also required two AA's
 — ServoMan314, Jun 21 2008

 [ServoMan], many camcorders use the battery you describe. I forget what it's called though.

Ansmann also has a 2800mAh AA which is a little bigger than spec, yet still cylindrical. And it doesn't fit everything.
 — Spacecoyote, Jun 21 2008

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