Re: Semi-OT: Laptop battery calibrations

Mar 25, 2007 2 Replies

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joseph2k 19 years ago

whit3rd wrote:

>
>> >>
>>>Mart>>
>>
>>>>>...is calibration really
>>>>>needed?
>>
>>
>> A lot of dissatisfied customers complain about battery life issues,
>> so the warranty service folk will ask (require) a full charge/
>> discharge
>> cycle if you call in with a complaint. It takes all day to do that.
>>
>> The internal charging circuitry will fail to fully charge the battery
>> in some out-of-calibration scenarios, so the calibration IS important.
>> Apple had some firmware updates, some calibration software
>> (Powerbook Battery Reset), and on recent models, a recommendation
>> to let it fully discharge once in a while. All these things were
>> just
>> to get the calibration correct, and (when I was doing warranty
>> service) I saw each of 'em work successfully. If the
>> alternative is buying another $90 battery, do the calibration.
>>
>
> Well, I would. But it doesn't work :-(
>
> Could it be that calibration should better be started when the battery
> is somewhat empty?
>

A google or two could reveal much, try:

"li-ion battery conditioning"

which produces:

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and somewhat indirictly this:

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JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller

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Joerg 19 years ago

I had tried that before posting (and read BatteryUniversity) but got three conflicting opinions on numerous web sites:

a. It doesn't matter much. b. The occasional drain to where the laptop shuts down suffices. c. Only BIOS recalibration really works.

Regards, Joerg http://www.analogconsultants.com

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Joop 19 years ago

What I understand is that in a laptop battery pack the "battery gauge" is supposed to have best knowledge of the state of the cells. It monitors voltage, current etc and reports to the main computer via I2C (SMBus) low level status or on request stuff like the charge level.

What the BIOS has to do with it I would not know.

I can imagine that to be able to give a reaonable estimate of charge left, it needs to go from full charge (laptop powered down to make sure it really reaches 100%) to low level once and a while to re-adjust itself. Re-adjusting is necessary, especially when the pack ages. Otherwise it can go from 40% reading to "red alert" in a matter of minutes.

From my investigation of a dumped "bad" pack the capacity of the cells is still reasonable, but the internal resistance has increased. And with the high current peaks of the laptop this means the gauge has to mark it empty, eventhough plenty power is left inside. I use old cells in homemade portable gear that I switch on a few times per year but want it to work always. Li-ions do really well on low self-discharge, even the dumped stuff.

But again, all of this calibration takes place inside the battery pack. The laptop does not need to know. Taking a pack from one laptop to another should show "charge level" the same.

Unless things have changed...

Joop

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