The Itch

Phil bought himself a replacement high-capacity battery for his Lenovo T430 laptop recently. It was from a reputable supplier in Germany, clearly listed the T430 as ‘compatible’ on the product description and was half the price of an official Lenovo battery. What could possibly go wrong…

Upon insertion all looked well, the T430 worked fine, Ubuntu was able to read the capacity and charge level (68%), but after an hour of use while plugged into the AC power it didn’t seem to have charged up (still 68%). Hmmn. Rebooting displayed a warning message:

The battery installed is not supported by this system and will not charge.
Please replace the battery with the correct Lenovo battery for this system.
Press the ESC key to continue.

WTF!

I contacted the seller who promptly offered a return of the item, and a postage refund once I had a receipt for posting. So I repacked the battery and popped down to the post office, who told me that Royal Mail won’t handle a battery pack without it’s associated ‘device’ aka my laptop. Great, so back on the ’net to find a delivery company who will ship a battery to Germany. No one. Nowt. Zilch. At least, not for less than the cost of the thing (£40)!

Research

Searching the ’net for the displayed error message it becomes clear that Lenovo laptops have a ‘Smart Battery’, and that from the T430 onwards, they implemented a challenge/response authentication mechanism to lock users into buying Lenovo supplied parts, ostensibly to protect systems from battery fires when ‘fast charging’ the pack. Seems like 3rd party manufacturers are unable to replicate this behaviour properly, and some (thanks INTENSILO) mis-label their batteries as compatible when they are not.

It also turns up the splendid work of zmatt http://www.zmatt.net/unlocking-my-lenovo-laptop-part-1/, who had the exact same problem on his X230, but chose to reverse engineer the problem rather than return the battery - good man!

A little later I come across more good work by Hamish Coleman https://github.com/hamishcoleman/thinkpad-ec, who has automated the earlier work of zmatt and added other patches to support different keyboards on multiple IBM/Lenovo laptops, including the original battery fix for the X230.

The Scratch

Since I have no sane way to return my 3rd party battery, and prior work exists which is /almost there/ to fix my problem I decide to go for it (what’s the worst that can happen? I’ll brick my laptop):

Step 1: Replace the original battery and check all is well (apart from the rubbish capacity).

Step 2: Carefully work through zmatt’s BIOS unpacking and editing descriptions, double checking with Hamish’s Makefile and tooling, and teaching myself to drive radare2 (also awesome), I arrive at a point of no return: I /think/ I have a correctly patched BIOS file, there is only one way to test it: flash my laptop and hope for the best… I’m good: it starts up :)

Step 3: Swap to the 3rd party battery and see if it charges.. yep! Relief!

The Payback

It’s how open source works: I’ve got a new capability in front of me - one that can fix battery charging issues on T430 laptops with a specific BIOS version (2.57 if you’re interested). I have to do the decent thing and work that into Hamish’s tools to give back to the community.

[edit: pull request accepted] Go get it from Hamish’s Github above!