AA battery with voltage regulator inside

This is a dummy AA battery, with a soon-to-be switching regulator inside, allowing one to replace regular AA's with 14500 lithium cells.

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This started as way to possibly extend the battery life of my DeWalt crossline laser. The laser takes 3 AA batteries in series, for a total of 4.5 volts. I replaced two of the AA's with 14500 cells. In the third space, I put an LM7805 (to be replaced with a switching regulator when it arrives) inside of an AAA to AA adaptor shell. I soldered the output of the regulator to the positive of the dummy cell, the input to the negative, and a wire from the bottom to the negative of the tool that is attached to the ground of the regulator. Certainly not the cleanest, but It works, inspite of being a half volt above nominal. With no heatsink or airflow, the linear regulator gets pretty warm (33º C) after 10 mins of continuous use, so I'm looking forward to getting a mini switching regulator. This will increase the efficiency, and ultimately the runtime of the tool.
  • 1 × AAA to AA battery adaptor It's basically a plastic shell that allows you to use an AAA battery in place of an AA in a pinch
  • 1 × LM7805 Power Management ICs / Linear Voltage Regulators and LDOs
  • 1 × wire
  • 2 × 14500 lithium cells 3.7v Lithium cells that are the same size as AA batteries
  • 1 × 5v switching regulator

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rafununu wrote 03/05/2018 at 14:12 point

Linear regulators, such as 7805, to be efficient and precise need 1.5V more at the input than the output, this is a lost voltage and energy as well. I think one 14500 battery would be enough  using a converter to give the 4.5V asked by the device.

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milesdecourcy wrote 03/05/2018 at 14:38 point

I don't understand, one 14500 cell is only 4.2v max. The linear regulator was for proof of concept, the excess voltage is coverted into heat essentially. A switching regulator will not have the same issues, and will be far more efficient while achieving the same goal. 

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