I wonder if this project could be applied to the X230 laptops.
Open Source Thinkpad T420 Battery Design
11–20 of 105 posts
Re: Open Source Thinkpad T420 Battery Design
#12Currently remaining battery %'s aren't exact because I'm assuming there is a linear coorelation between voltage and capacity (Which is wrong). I don't plan on fixing this, as the exact % is unimportant to me.
There are dedicated ICs which will give the remaining charge accurately, which may possibly be even cheaper than this ad-hoc solution.
Re: Open Source Thinkpad T420 Battery Design
#13Is this still needed if coreboot is installed?
Will this work to make a slice (bottom) battery too?
Re: Open Source Thinkpad T420 Battery Design
#14I wonder if this project could be applied to the X230 laptops.
Yeah it should, but the laptop's firmware would need to be modified to not check for an authentic battery
Re: Open Source Thinkpad T420 Battery Design
#15Is this still needed if coreboot is installed? Will this work to make a slice (bottom) battery too?
Yeah, this is still needed even with coreboot. The attiny isn't doing anything too complicated, it's just there to tell the laptop the status of the battery. In the testing I did, if you supply 12v without any of the SMBus stuff the laptop will shut off after a few minutes of use.
I'm actually looking in to making a slice battery, it should be possible but sourcing the docking connector seems to be much harder than getting the battery connector.
Re: Open Source Thinkpad T420 Battery Design
#16Currently remaining battery %'s aren't exact because I'm assuming there is a linear coorelation between voltage and capacity (Which is wrong). I don't plan on fixing this, as the exact % is unimportant to me. There are dedicated ICs which will give the remaining charge accurately, which may possibly be even cheaper than this ad-hoc solution.
I've read a few things about using charging circuits and battery fuel gauges but it's a bit beyond what I know how to do right now. I might look in to it more in the future, or maybe someone else who knows more than me can add a fuel gauge to the schematic :)
Re: Open Source Thinkpad T420 Battery Design
#17Apparently those Thinkpads are from 2011-2012, that's old. What do people do with such old devices that makes building a battery from scratch worthwhile?
Excellent support with Linux, the BSDs, and even other obscure operating systems like RedoxOS.
A plethora of repair, replacement, and add-on parts.
A laptop that runs great for an entire decade.
It's got a TrackPoint and is available refurbished now for ~200 dollars.
And yes, the keyboard is very high quality, far above the sorry state of laptop keyboards today.
Re: Open Source Thinkpad T420 Battery Design
#18Re: Open Source Thinkpad T420 Battery Design
#19Is this still needed if coreboot is installed? Will this work to make a slice (bottom) battery too?
Yeah, this is still needed even with coreboot. The attiny isn't doing anything too complicated, it's just there to tell the laptop the status of the battery. In the testing I did, if you supply 12v without any of the SMBus stuff the laptop will shut off after a few minutes of use. I'm actually looking in to making a slice battery, it should be possible but sourcing the docking connector seems to be much harder than g…
Would it be possible to write directly to /dev/i2c in Linux and spoof the messages? Not sure what the use case of this would be, but might be useful for something.
Re: Open Source Thinkpad T420 Battery Design
#20Earlier quoted context omitted.
Yeah, this is still needed even with coreboot. The attiny isn't doing anything too complicated, it's just there to tell the laptop the status of the battery. In the testing I did, if you supply 12v without any of the SMBus stuff the laptop will shut off after a few minutes of use. I'm actually looking in to making a slice battery, it should be possible but sourcing the docking connector seems to be much harder than g…
Would it be possible to write directly to /dev/i2c in Linux and spoof the messages? Not sure what the use case of this would be, but might be useful for something.
Yep definitely, I had this exact thought last night and found an example kernel module to spoof a battery, and one to read i2c messages. There's probably all kinds of cool things you can do with a kernel module to communicate between the laptop's i2c port and a microcontroller. The docking connector conveniently has an i2c port on it, maybe I'll look in to this in the future