Ok, where do I purchase a "dummy AA Cell"

[Xrunner]

Re: Ok, where do I purchase a \"dummy AA Cell\"

Any idea where shrink wrap would be located in Home Depot or Lowes? Thanks

-Mike

 

[gadget_lover]

Re: Ok, where do I purchase a \"dummy AA Cell\"

Home depot usually has it near the 'electrical tools' section.

You can also get some at tap plastics.

Daniel

 

[Hookd_On_Photons]

Re: Ok, where do I purchase a \"dummy AA Cell\"

First of all, maybe this thread should be moved to the "Batteries" forum?

Here are a couple links to related threads:

Making dummy AA & AAA batteries

Where to find Dummy batteries?

I've made AA dummy batteries with the following ingredients, easily found at Lowe's, Ace Hardware, and Sears Hardware (all three stores I visited had all of the necessary components):

One 10-32 x 2" brass flat head machine screw (40 cents)
Three 1/2" OD x 0.194 ID nylon spacers: 1" + 1/2" + 1/8" (25 cents + 17 cents + 17 cents)
One 10-24 nylon lock nut (30 cents)

Thread the screw through the spacers and loosely apply the lock nut. Grasp the lock nut with pliers, and tighten the screw. I tightened it enough to countersink the head into the spacer a bit. The spacers will tend to displace laterally under axial load - I put the assembly into a vise clamp to prevent the spacers from misaligning while tightening.

You may have to file down the tip of the screw just a bit to get it to fit properly.

The end result looks something like this:

|\|¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯|¯¯¯¯¯¯¯¯¯|¯¯¯|__
| |––––––––––––––––––|–––––––––|–––|––|__
| |––––––––––––––––––|–––––––––|–––|––|__|
| |––––––––––––––––––|–––––––––|–––|__|
|/|__________________|_________|___|

The ASCII art is a little misleading, as there is a little more than 1 mm of clearance between the edge of the screw head and the rim of the spacer.

Alternatively, you can assemble the following ingredients:

One aluminum 8/32 x 1.5" binding post (65 cents)
One aluminum 8/32 x 9/16 knurled thumb screw (45 cents)
(Both can be found in the "screen and storm door fasteners" tray)
Two 1/2" OD x 0.257" ID nylon spacers 1" + 3/4" (25 cents each)

The spacers are loose around the binding post, but the neck of the thumb screw matches the inner diameter of the nylon spacer. When the assembly is tightened down, friction prevents the spacer from wiggling around the binding post, and the length almost perfectly matches an Energizer or Rayovac AA battery.

::
::____________________________
::––––––––––––––––––––––––––––| <--Binding post-flat head
::¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
::

|¯¯¯|__
|––––––//////////// <-- Thumb screw
|___|¯¯

::|¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯|¯¯¯¯¯¯¯¯¯¯¯¯¯¯|
::|–––––––––––––––––––|––––––––––––––|¯¯¯|
::|–––––––––––––––––––|––––––––––––––|–––|
::|–––––––––––––––––––|––––––––––––––|___|
::|___________________|______________|

Once again, the ASCII art is a bit misleading, as there is about 1 mm of clearance between the rim of the binding post base and the rim of the spacer. The head of the thumb screw makes a rather fat and knobby positive terminal. I don't think it poses a short hazard, as there is plenty of clearance between the rim of the head and the rim of the spacer. If you're paranoid, you could wrap the edge with electrical tape. You could potentially adjust the length of the dummy by loosening or tightening the thumb screw, but there are obviously limits to how much this can be done.

Aluminum has low resistivity, but the cross-sectional area of the binding post + screw is somewhat small when you consider the binding post is partially hollow (the post appears to be solid for half of its length, and hollow at the tip to accept the screw). I stuffed a bit of aluminum foil down the shaft of the binding post, and also filled the empty space around the binding post in the spacer. This might improve conductivity, and helps to prevent toggling of the spacer around the binding post (though friction seems adequate when the screw is tightened sufficiently; a drop of glue between the spacers would accomplish the same thing).

I have also used the "brute force" approach, threading a large brass flathead machine screw into two 1/2" OD x 0.194 ID x 1" long nylon spacers (I cut down one of them, as 1+3/4" seemed too short and 2" was definitely too long). This yields a very stout, heavy dummy battery. However, it takes quite a bit of effort to modify the stock materials. To prevent a potential short at the base, I filed down the rim of the head to reduce the diameter, and reamed out one of the spacers to countersink the head with a power drill. I split a few spacers while reaming the ends, and also while threading the screw (ream out enough of a channel to countersink the head, and don't overtighten).

ALWAYS WEAR EYE PROTECTION WHILE PLAYING WITH POWER TOOLS!

Does anybody know if corrosion of the brass or aluminum screws will significantly alter the electrical conductive properties of these dummy batteries over time? If so, would a large stainless steel screw or bolt suffice? I know the resistivity of steel is much higher, but wouldn't the cross-sectional area of a #10 stainless steel screw compensate for this?

 

[wquiles]

Re: Ok, where do I purchase a \"dummy AA Cell\"

Very cool ideas - thanks /ubbthreads/images/graemlins/grin.gif

Will

 

[twentysixtwo]

Re: Ok, where do I purchase a \"dummy AA Cell\"

I make them out of wood dowels cut to length, copper wire, and shrinkwrap. The positive side is a copper tack.