I recently found a great appreciation for the long battery life of my newly acquired mac book pro and was thinking how I can scale that up even more (since I travel and work on site a lot), by building DIY "Power Bank" for the mac. So I have some very basic knowledge of electrical engineering (built a few small home Raspberry Pi Projects), and now just need some guidance with taking on this project. I'll keep it to a strict question-answer format for the things I am unclear about.
The plan is to take a 12V 7ah Lead Acid Battery and build the nessecary transformer/step-up module to get a USB-C output delivering 20.3 V @ 3A or 9V @3A (both work for my mac).
To get from the 12V to 20.3V, I'd thought I'd use this step-up module. Will this be able to do the job? Also, how do I specify on the step-up module the exact voltage that I want (In & Out).
Then I read here that one needs a pull-down resitor in order for the USB-C connection to be recognised and enable VBus, the post suggests that you
"use a regular USB A male cable with an A to C adapter..." to achieve this - that makes sense, but how to I get power from the step-up module to the regular USB head?