#+TITLE: Ham radio battery charger mod
#+author: Svjatoslav Agejenko
#+LANGUAGE: en

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* General
+ DISCLAIMER: I DO ELECTRONICS AND 3D DESIGN SOLELY AS A HOBBY. THERE
  COULD BE ERRORS THAT CAN RESULT IN ALL KINDS OF DAMAGE. USE THESE
  DESIGNS AT YOUR OWN RISK.

+ This design is released under Creative Commons Zero (CC0) license.

+ Authors:
  - Svjatoslav Agejenko
    - Homepage: https://svjatoslav.eu
    - Email: [[mailto://svjatoslav@svjatoslav.eu][svjatoslav@svjatoslav.eu]]

  - Valeria Agejenko

+ See also:
  - [[../../index.html][Other physical projects in this repository]]
  - [[https://www.svjatoslav.eu/projects/][Other projects hosted at svjatoslav.eu]]

* Project description

Warning: this project is quite hacky. It requires breaking original
charger to get required critical charger part. Instructions are not
very detailed. Only describe the overall idea. Do not attempt to
reproduce this unless you exactly know what you are doing.

------


I have Baofeng GT-STP and Baofeng UV-82 radios. Their batteries have
slightly different geometry, so chargers are physically not
compatible. Also each changer comes with its own power adapter to plug
into wall power socket. Electrically batteries are apparently
compatible.

By building this battery charger I solved 2 issues:
+ It can charge batteries for both radios. Is physically and
  electrically compatible to both models.
+ Wall adapter is no longer needed. Now it is powered by USB connector
  from computer.

[[file:make.png]]

Body ignores small physical differences between batteries and both can
be plugged in.

[[file:body.png]]

Front side contains critical fragment of the original changer circuit
board to drive the actual battery charging.

[[file:make, 1.png]]

Back side contains voltage upstep converter that is tuned to convert
5V USB input to 10V output that is required by the charger.

[[file:make, 2.png]]

Voltage upstep converter can produce significant voltage
ripples/impulses that travel backwards to the power source and forward
to the changer. To reduce this effect, there are capacitors and
inductor.

[[file:electrical.png]]

Front and back sides are connected by wiring at the bottom. Also there
are screws to hold original Baofeng charger pins/springs that connect
to the battery.

[[file:make, 3.png]]

After assembly is complete, back, front and bottom parts are sealed
with lid: [[file:cover.png]]