I work nights and go through lots of AAA batteries that power my LED headlamps. But the AAA batteries still have plenty of power left in them,as much as 1.3 volts
So from Green Batteries http://www.greenbatteries.com/battery-adapter.html
I had purchased 4 sets of their battery Adapter/Size Converter Kits that convert AA & AAA to C & D size.
Mainly to convert some AAA's to AA's.
So I have several sets of the C  and D adapters that are not being used.

I had purchased some cheap LED flashlights at a "dollar Store" for the triple LED lights for another project.
So I had these AAA battery holders that weren't being used.
2 batteries are inserted in the same direction and 1 battery is inserted in the opposite direction.
I realized that those battery holders would fit in the D size adapters with a little modification.
So I soldered the terminals on both ends of the battery holder to make contact with all 3 post in the same polarity .
Then soldered and filed down a small tip on the "+" end of the holder to make contact with the "+" in the D adapter.
Then inserted the 3 AAA batteries into the holder in the same polarity/direction.
Then placed the AAA holders in the D adapters.

So now I can power a few "D" size gadgets with my excess of AAA's.

<p>Don't need AAA battery holder anymore. You can only keep one of this rechargable battery to replace <a href="http://www.ebay.com/itm/750-mAh-Li-ion-Rechargable-battery-to-replace-3-AAA-Flashling-Battery-Cartridge-/381655332793?ssPageName=STRK:MESE:IT" rel="nofollow">3 AAA Flashling Battery Cartridge</a>.</p>
<p>Use micro USB cable to charge this battery, very convenient.</p>
<p>just use rechargables and done.</p>
<p>yea, I've been using rechargeables for several years now the Eneloop brand of rechargeables are awesome!!!!!!</p><p>http://www.amazon.com/Panasonic-BK-3MCCA4BA-Pre-Charged-Rechargeable-Batteries/dp/B00JHKSN76/ref=sr_1_5?ie=UTF8&amp;qid=1417528454&amp;sr=8-5&amp;keywords=eneloop+aa</p>
The other day I was in a rush and needed 1 more AAA battery holder.<br>I put small pieces of aluminum foil in the top and bottom of the AAA holder and in the top (+) of the D Adapter. Worked as good as the ones I had soldered.
It's cool (3) AAA fits within a D body. <br>Now I gotta check if my AAA to A adapter <br>can fit (2) AAA in a D and if it makes sence to build them...
Yea!<br>Think you could use aluminum foil as a &quot;spacer&quot; on the &quot;+&quot; end to fill in the gap?
They have a 10 led flashlight on the market using D batteries and if you only use 1 led of the ten the batteries last very long...
This is a great use for dead batteries! Often batteries still have a fair amount of charge in them but won't power the intended device, this looks like a perfect fix.<br><br>About how much life do you get out of these 'D' cells?
Thanks! <br>I had the fan set on high speed and the six AAA batteries powered it for 4 hours.
Wow, not bad! It had not occurred to me that there was a practical way to gang semi-drained batteries in a parallel configuration. It HAD occurred to me that I could make my own custom battery pack power supply for hobby stuff, but this actually makes it useful for conventional applications!
Thanks! Yea, now I might look into getting an LED light that uses &quot;D&quot; batteries.

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