Instructables
Picture of Charge AAA NiMH Batteries in an AA Charger
I had an AA NiMH charger for my digital camera. A couple of years later I had a couple of devices powered by AAA NiMH batteries. I wanted to use the charger I already had, but it was made for AA batteries only.
 
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Step 1: Make an adapter from paper and glue

Picture of Make an adapter from paper and glue
Use a piece of junk mail to roll an adapter. Cut a strip 1 7/8 inches wide from the long side of an 8 1/2 x 11 sheet of copy paper like you get everyday in your junk mail. Begin to wrap it around an AAA battery. Do not wrap it too tightly, but leave it just a little loose. Smear wood or paper glue in front of where you are rolling. The black pen line shows about where to begin. Spread the glue out very, very thin and roll forward. Apply more glue, smear, and roll until all paper in the strip is rolled around the battery. Apply some cellophane tape to hold the roll while the glue dries. The diameter of the roll will be just a little less than that of an AA battery. You could add part of another strip of paper to make the roll exactly the thickness of an AA battery, but it is not necessary.

Step 2: Finish the paper roll

Picture of Finish the paper roll
When the glue has dried, the roll of paper will be firm like cardboard. Add a wooden plug to one end of the paper roll. Use a 3/8 inch dowel for this. Cut 3/16 inch from a dowel rod. Smear it with glue and insert it into one end of the roll. Allow the glue to dry thoroughly.

Get a thin brass rod or a short piece of #10 bare copper wire. Drill a small hole in the center of the wooden plug and press the copper or brass piece into the hole.

Place the roll over an AAA battery. File the brass or copper piece until the length of the AAA battery with the paper adapter is the same length as an AA battery.
krapphace4 years ago
(removed by author or community request)
Phil B (author)  krapphace4 years ago
I was not familiar with Sculpey and Femo, but searched for them and learned they are a clay polymer substance. Wood and a drill are both very available to me, but many things would work. As long as Sculpey and Femo harden, you should be able to use them. I think a plug made from candle wax would work as long as you can get a piece of metal in place within it to make contact between the battery tip and the terminal for it in the charger. I think you could even cut a strip of paper, wind it around a metal pin gluing it up just like the paper shell around the AAA battery. Just roll it up until it is the diameter of the AAA battery.
thanks
krapphace4 years ago
Do you think it would be safe to use Sculpey instead of wood?
joinaqd5 years ago
actually Phil, the AAA batteries are shorter than AA so it wont always work..unless there are springs sticking out ot the charger..instead,why dont you get aluminum foil and stick it in there so its bigger?if you post it i promise to give you a rating,but you are posting false info so i wont rate you,sorry...
Phil B (author)  joinaqd5 years ago
You do err. Look closely at the photo in Step 2. Do you see the metallic round spot in the end of my adapter? It is a piece of brass rod. It makes up the difference in length between AA batteries and AAA batteries. Notice also the description of material to be used for this in the words, "Get a thin brass rod or a short piece of #10 bare copper wire. Drill a small hole in the center of the wooden plug and press the copper or brass piece into the hole...Place the roll over an AAA battery. File the brass or copper piece until the length of the AAA battery with the paper adapter is the same length as an AA battery." I believe I did not post any false information, but in your haste you did not read what I wrote nor observe the photos I posted. Now, about my rating from you....
joinaqd Phil B5 years ago
done...gave you 5
 this thread is priceless
lolzertank5 years ago
Whoa... don't try this on a 1 hour or shorter charger... you could rupture the AAA with all of the current. Also, wouldn't this overcharge the AAA batteries?
Phil B (author)  lolzertank5 years ago
This particular charger is a very slow charger and produces a very low level current for charging. Your point about 1 hour chargers is probably valid, but I have no experience with those. I have used this charger with AAA batteries for a number of years, although not much lately. About six years ago I had a Palm IIIxe handheld PDA and used this arrangement to charge two AAA batteries for it every week.