I’ve been working closely with Hope and 17M19 from 51nb and jwise on fixing battery detection on the EC. The X2100 uses a new charging management chip (TI BQ24725A) that’s controlled by the EC. In short, the charging current and charge/discharge are fully fixed and all 3 batteries now are properly managed by the EC. For end-users, the battery works properly now and the laptop will be a complete mobile experience.
A laptop motherboard has many functions not managed or processed by the operating system. One of which is the embedded controller, a small microcontroller in charge of managing the many peripherals of the laptop and sends these processed information back to the OS.
The ROM of the EC in the X2100 resides in the same EEPROM as the BIOS and flashing the 16MB BIOS also updates the EC. As the X2100 motherboard has to interface with Lenovo specific hardware such as the battery, keyboard and display, these components on the new motherboard might not be perfect and involves reverse engineering to figure out how these components work.
Process & Results
The entire process was made much easier as the original X210 8th gen already had it’s EC updated by a group of talented people. The X2100 EC was easily decrypted using Ghidra and some earlier patches were ported over to the current EC. Using hardware details and information provided by 51nb, jwise was able improve the battery and charging management further.
A few problems were discovered. The charging chip did not limit high current draw and the system would exhibit ‘hiccups’ under stress-testing as the charger could not keep up with a high system-load and battery charging at the same time. It also had some issues with reading the 9-cell and 4-cell real-time capacity and did not report the battery current. The 4-cell also had issues with charging and discharging.
These were fully fixed by jwise and fully verified and tested. At present, a fully compiled BIOS can be downloaded here. The full changelog can also be found on the GitHub link. For those who wants to flash the updated EC themselves, I’ve provided a click-and-install programme in the software section for Windows. I’ll pre-install this version of the BIOS for all future X2100 shipped.
As stated in the previous update, I have already commenced shipping. I’ll be improving the speed of shipment this month and I’m expecting to clear half the backlogs. Drop me an email if you want expedited shipping and I’ll see what I can do.
I’ve also worked hard on a drop-in kit for the T480 to be converted with a T25 keyboard. The full instruction and build log can be found in mod section. I’ve put in a fair amount of work perfecting the 3D parts and process for cutting and building the parts and I’m confident the drop-in parts will be of good quality.
I’ve not decided on the pricings yet but I have managed to acquire 20 sets of drop-in mod kit. Drop me an email if you’re interested and I should be announcing a pricing pretty soon. I’ll also do a full step-by-step installation guide for this for less experienced users.