Why aren't AA batteries square?

"Legacy" is also why all cylindrical cells have a nipple at the top for the positive connection, originally a brass cap on the top of the carbon electrode, with the zinc case the negative. In alkaline cells the case is actually positive - steel - and there is a brass rod which is negative, but they have to have the same form factor as zinc/carbon cells for compatibility.

James Wilkinson Sword posted for all of us...

Because your head is square. Commonly called a blockhead. Next...

It takes less material to create the same volume using circular cross section versus square cross section. Think of a rectangle formed by a piece of string, and observe that you can increase its area by deforming it (alternately, do the math).

Please explain better about creating volume. It takes less material to get say, a 1" cross section. A cylinder will touch at 4 points in a rectangular opening battery pack. A 1" square bottle or can holds more volume than a 1" dia. cylinder. 1 x 1 = 1 sq, inch pi r2 (0.05 x

First, when you are measuring the area of a cross-section, notice that you get inches^2, rather than inches. I use "in" below. If we have a string of length L forming a circle (of unknown radius r). Then L =

The area of a rectangle having perimeter L is maximized when the rectangle is a square (that's a separate problem I won't go into now). However, in this case, where we have a square cross section, we we get side length s = L/4, so A_2 = (L/4)^2 = L^2/16 in^2.

We conclude that A_1/A_2 is about L^2/(4*PI) /(L^2/16)= 16/(4*PI) = 4/PI is about 1.27.

So A_1 is about 1.27 times the area of A_2.

Note that the result, does not depend on the value of L. Let me know if you have any questions or if you find an error (they happen!) : )

Bill

WTF does your square have to do with volume?

So in conclusion:   A 1" square bottle or can hold more volume than a 1" dia.

Rectangular packaging is more efficient use of space than cylindrical.

He's showing that you get maximum area with a given length bit of string if you arrange it in a circle rather than a square. This also means that if you battery is constant cross-section, as an AA is, the best shape for it to have to minimise the amount of case-material used to make it, is a cylinder.

That makes some sense. I don't know if batteries need a constant cross section but they may to have the best chemical reaction.

Because batteries and cells are universally prisms - a area extended along a length, such as a cylinder. To refute, please link to a spherical battery.

Well there was the one held by Inspecteur Clue-zo, which had "berm" written on the side. Or was that just a giant sparkler?

From the point of view of minimizing the use of materials for an enclosure, the *sphere* does best. And, I can't think of any reason why this wouldn't be a great design (ha!) ; )

Yes.

Spherical batteries would waste a lot of space between them. You'd need larger flashlights.

What do you mean, "them". You would only need one appropriately-sized battery (using more than one would be a waste of materials!) : )

Why not say "torches"? they don't flash, most people turn them on, not on and off and on and off.

On Fri, 22 Sep 2017 20:22:18 +0100, Tekkie=AE wrote= :

re square in crosssection, they wouldn't roll off the desk.

At least I don't roll away. Place an AA on your desk, attempt to touch = the ends with a multimeter. Chase battery around the desk, pick it up o= ff the floor, then try again.

-- =

"Beam me aboard, Scotty!" [-] "Will a 2 X 4 do, Captain?"

What annoys me is rechargeable AAs. The casing is negative, covered by a very flimsy plastic sheath, which often gets damaged (they are kept for a decade instead of a year like with alkaline), hence you get positive and negative right next to each other at one end, which gets shorted, and all hell breaks loose since rechargeables have a very low internal resistance.

Try refilling a lemonade bottle. The bloody thing tips.

I thank you for your useful input to the discussion. Grow up.

Round is hard enough!