Battery care

[richarddd]

Lenovo toolbox reported that the battery in my x220 is in poor condition and I'm getting a warranty replacement.

The phone rep suggested:

1) Do the initial charge overnight, not when using the notebook

2) Run the battery reset function in battery maintenance in power management (which charges, discharges and recharges the battery) every six months.

Do you agree?

I usually run the notebook on AC power, only using the battery for brief periods. I was thinking of using the existing battery for these purposes and only use the new battery when travelling. What's the best way to store the new battery when not in use? Full charge in a cool dry place? Something else?

[EOMtp]

Nothing wrong with the rep's advice above. Additionally,
-- Set Thinkpad to start charging at 75% (anywhere between 40% and 80% is fine), stop at 98% ... (compared to Lenovo's defaults of start at 98%, stop at 100%).
-- Do not discharge often "too low", e.g., below 10%, if avoidable.
-- Store in refrigerator (not freezer) with 40% charge.
-- Periodically, i.e., every few months, recharge to 40%, as the previous charge will decay with time.

[richarddd]

I see that thinkwiki has similar recommendations:

- avoid charging if battery is nearly full, unless you will need its full capacity soon; keep it on the 30%-85% charged range

--> What's the basis for 75-98% or 30-85%?

- fully discharge, then fully charge battery when needed to recalibrate fuel gauge; newer battery pack models require this less often, old ones might need it as often as every 30 cycles

--> phone rep suggested every six months

- never fully charged or discharged, ideally at about 40%. cool and dry, but do not freeze them: 10-15C is recommended.

--> Refrigerators are typically about 4c, but I suppose that's close enough?

http://www.thinkwiki.org/wiki/Maintenance

[EOMtp]

--> What's the basis for 75-98% or 30-85%?

Chemistry! More details below:
http://batteryuniversity.com/learn/arti ... _batteries

[richarddd]

Chemistry! More details below:
http://batteryuniversity.com/learn/arti ... _batteries

What's the basis for choosing 75-98% rather than 30-85%?

Andre Gardner, in the comments at June 12, 2012 at 1:25am, suggests letting the battery discharge to 35-50%, then charging to 90-95%.

[EOMtp]

What's the basis for choosing 75-98% rather than 30-85%?

The battery does not "care" in any way if you start charging at 30% or 75% ... but you might, i.e., you may prefer to have a relatively full battery most of the time, just in case ...

The battery also does not care if you stop at 85% or 96% ... the "damage" curve is relatively flat and minimal up to that point, but increases exponentially beyond that, as one approaches 100% ... and since one might prefer a relatively full battery to a relatively less full one, might as well take it up to the high 90s ... stopping just short of 100.

[richarddd]

That makes sense.

Regarding the new battery, if I want to store it until needed, when I get it should I first charge to 100%, then discharge it to 40% and put it in a sealed container in the refrigerator? Or not charge it until closer to when I'll need it?

[EOMtp]

Won't matter either way. Even if you charge to 100% before storing, the charge will bleed off soon enough. Just make certain it is not totally discharged before storing. Li-Ion battery cells, depending on manufacturer, have subtle varying tolerances/"preferences", but for all of them the "activity" of any concern happens at the margins. Consequently, whether you charge to 80% and store or charge to 40% and store will not make any measurable difference whatsoever.