Edgar landivar 
It happened to me that I got to the office and realized that I left the forgotten charger at home. So after trying for a while I managed to charge my laptop and share what I did. After all, I like the topic of researching charger designs for types of devices, especially cell phones and computers. In a previous article I explained how to make a USB type cell phone charger.
Before I begin I will note that I have relied on experimentation, so everything shown here should be used with great care and at your own risk. I have practically experimented blindly.
Macbook charger provides voltage steps
The first thing is that the Macbook Pro charging procedure (I don't know if it applies to other models) is quite tricky. According to the charger that comes in Mac there are 4 voltages that can be provided: 5V, 9V, 12V and 20V. Obviously I started testing with the lower voltage and it did not charge at all.
The same is also true if you test with the other voltages. The TRICK was to gradually increase voltages: first 5V, then 9V, then 12V and finally 20V. With the last voltage a power of almost 60W is reached, which is very similar to the power that is marked on the source.
To better explain I used a configurable power source, from the SIGLENT brand, and I increased the voltage to the desired values. I share a video that I made with the details.
Building a compatible charger for Macbook Pro
I am in this task now. The one to build a compatible open-design charger, let's see how I do. I hope to publish more information in the next few days.
