How can I limit battery charging to 80% capacity?

Question

I just learned that some Lenovo laptops include a utility that offers to limit battery charging capacity to within 0–80% in order to slow the attenuation of the battery lifespan:

How can I do this in Ubuntu?

Answer 1

The charging thresholds are, very unfortunately, firmware and vendor specific.

The Lenovo user is luckily provided with a solution outlined on ThinkWiki.

It basically says that you would have to install and load the tp_smapi kernel module:

sudo apt-get install tp-smapi-dkms
sudo modprobe tp_smapi

and write the desired charging thresholds to virtual files in /sys/devices/platform/smapi:

echo 40 | sudo tee /sys/devices/platform/smapi/BAT0/start_charge_thresh
echo 80 | sudo tee /sys/devices/platform/smapi/BAT0/stop_charge_thresh

Then it will stop charging once it reached 80% and only start charging when it drops below 40%.

Toshiba and others might have a similar kernel module that exposes firmware functionality to the /sys or /proc space, but it is very unlikely for patent issues. For the same reasons, an application that could handle this would be either Thinkpad- specific or only address a few select vendors.

Answer 2

If you would like to extend the lifetime of your battery, I would suggest no single application, but some more measures:

1. Remove your batteries when not needed: If you do lots of desktop work without moving your laptop, remove your batteries. Usually this will save a lot of lifetime, because they are not (un)loaded. However you should remember that the batteries are not inside the laptop. I lay them near my keyboard. So I always remember that they are not inside.
2. Load your battery at low temperature: Usually it is recommended that you load the battery when the temperature of your laptop is low (10-30°C, 50-86°F). Higher temperatures shorten the lifespan.
3. Keep your laptop cool: High temperature is in general not a good idea. So you should always have an eye on the temperature. Make sure that enough air flows around your computer and keeps it cool.
4. Avoid short loading: If you load your battery for five minutes, switch off power and load again, you can also shorten the lifetime. It is better to use have longer loading times (Load until battery is full).

However often it is claimed that batteries have some memory effect. This is not true. There were several studies which showed that the memory effect is a false claim. See also Repairfaq: NiCd Batteries do NOT have "memory".

I treat my batteries this way and they usually keep their abalities for years. My colleagues often wonder why my batteries don't get broken.

Answer 3

Did you check to see whether there is a BIOS setting on your laptop for this? My laptop had a Windows Application as well as a "Battery Life Extender" setting in the BIOS for this exact feature.