Add slow-charging mode / change one detected type to only use 45W?

[ce-4]

Is it possible that the EC tells the charging IC to draw less than 65W (eg. 15W or 45W)?
Could this be explored or would this totally not be feasible?

Use case:
With the advent of USB-PD charging I have a collection of Type-C chargers and it would be nice to use them with my TP. Now there's Type-C-to-Barrel adapters available that act as a USB-PD trigger and it then carries a fixed resistor value on the barrel to signal the 65W or 90W models. They don't work with 30W/45W/etc though because the overcurrent protection for these chargers kicks in and shuts them down. Would be nice to have some way of enabling slow charging to make use of the lower wattage charger (especially powerbanks and car-usb-pd adapters rarely offer 20V/65W), maybe change the 0Ω mode (135W) to 45W and the 170W mode to something else?

65 W | 10 kΩ
90 W | not connected
135 W | 0 Ω
170 W | 1.5 kΩ

There's also a charging mod available that completely changes the port to Type-C:
https://www.tindie.com/products/mikepdiy/lenovo-charging-port-type-c-pd-x220-x230/

[hamishcoleman]

While the EC does control the charging system, the charge circuit might not be able to adjusted lower than the minimum size that Lenovo sold (did they sell a 45W version?). So, I would first look at the schematics for the design of the charger.

Once you have proved that it is possible, you would need to start using the tools and reverse engineering documents from this repo to look for the right part of code. It is not a quick and simple task, but it is certainly possible.