[ltp] Battery options for X240

Tamas Papp linux-thinkpad@linux-thinkpad.org
Wed, 05 Mar 2014 15:46:38 +0100

On Wed, Mar 05 2014, Leon Weber <leon@leonweber.de> wrote:

> On 05.03.2014 15:13:57, Tamas Papp wrote:
>> I can't help you with the particular question, but if you are looking
>> for battery balancing, AFAIK it is not supported since Ivy Bridge. I
>> don't know about the X240 in particular, but unless the BIOS implements
>> battery balancing, the second battery might be drained to 0% before the
>> machine starts using the main one. I find this inconvenient on my T430s,
>> and in retrospect I would have been better off with another laptop (with
>> a single, larger battery).
> My X240 drains the external battery to 5% and then switches to the
> internal battery.  When charging, the internal battery is charged first
> until it reaches 80%, then the external battery is charged, and after
> that, the internal battery is charged the remaining 20%.
> So I’m not sure what you mean by “battery balancing”, but my X240
> doesn’t drain the external battery down to 0%.  I’m actually quite
> pleased with the way it drains and charges the batteries.

When Thinkpads were controlled with tp_smapi, there were scripts around
to discharge the batteries in a more or less balanced manner (eg so that
the difference in charges was always kept below a given limit --- this
was achieved by a script checking charge levels and switching batteries
when needed). See

The claim is that frequently discharging the battery to near 0 is bad
for battery health in the long run. 5% is marginally better (the 0 is
not truly 0 in practice anyway). I am not sure how present-day batteries
are affected by this, but historically this was important for Thinkpad
owners in the past.