#+TITLE: 12V Lead-Acid battery changer and terminal
#+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.

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

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

* Project description
[[file:make.png]]

[[file:make,%202.png]]

Simple charger and terminal (front-end) for 12V lead-acid battery.

Idea is to distribute power from rechargeable 12V battery to various
appliances (soldering iron, radio transmitters, etc..) while also
providing use-charging in the background.

Single on/off button disconnects battery and up-step voltage source
from front panel terminal connectors.

[[https://www.amazon.de/gp/product/B07G4KWV6S/ref=ppx_yo_dt_b_asin_title_o08_s01?ie=UTF8&psc=1][Tecnoiot MT3608]] voltage up-step is used. 3V DC external power supply
is used to feed voltage up-step. Up-step is tuned to ~14.4 V.

[[file:schematic.png]]

Current design is rather of blog (experience sharing) value. It has
quite some drawbacks:

- Warning: Circuit has dangerous instability. Requires low voltage
  ~3V but relatively high current external power supply. Using
  higher voltage but low current power supply could easily lead to
  situation where step-up generated load pushes power supply output
  voltage down too much. This leads to too much power being lost
  within power supply and easily leads to power supply overheating!

- There is no dedicated current limiter. 3V external power supply
  and up-step are acting as current limiters.

- While RCA connectors do work as DC power connectors, but are not
  intended to be used this way and are not very reliable.

- Voltage up-step provided output is not very clean. Extra capacitors
  and induction coils could be added to remove high frequency noise in
  the voltage.

- Metallic and shielded body would be helpful to reduce
  electromagnetic/radio noise generated by step-up.

* Body

[[file:body.png]]

[[file:cover.png]]


+ Download:
  + [[file:body%20and%20cover.FCStd][body and cover FreeCAD file]]
  + [[file:body.stl][body in STL format]]
  + [[file:cover.stl][cover in STL format]]