12V Lead-Acid battery changer and terminal

• 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: svjatoslav@svjatoslav.eu
• See also:
  • Other physical projects in this repository
  • Other projects hosted at svjatoslav.eu

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.

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.

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.

• Download:
  • body and cover FreeCAD file
  • body in STL format
  • cover in STL format