Thinkpads Forum

I have two nine cell batteries. The older one has ~300 cycles, and I did a reset with that one in the machine about six months ago. Today (for the first time), I did a reset with the newer battery (~150 cycles) in the TP. When finished, I took the newer battery out and started using the older one (without AC). If it's not my imagination, I'm noticing a difference in the "performance" of the older battery; the charge seems to "last" longer. I'm wondering, is it necessary to do the reset for each battery, or will the one reset recalibrate the guage for both? TIA for your replies.

Tõnis

Tõnis wrote:I'm wondering, is it necessary to do the reset for each battery

Yes. The batteries have individual identifiers and the "calibration" for each will be different.

Cheers,

Bill B.

bill bolton wrote:Yes. The batteries have individual identifiers and the "calibration" for each will be different.

Cheers,

Bill B.

Thanks, Bill. I kind of thought so, because I could see that it recognized the different batteries under the "Battery Information" tab of PM. Wasn't exactly sure how the gauge itself worked though, but I suppose it would make sense if the reset simply calibrates the gauge to each battery's chemistry.

Tõnis

The battery packs have a basic microprocessor built-in, and that keeps track on a number of attributes of the battery pack, including the number of full cycle equivalents it has racked up in use.

So a "calibration" is basically about aligning what Power Manager has observed is happening (which involves some degree of dead reckoning since the last calibration), with what the onboard microprocessor knows about the battery. This is achieved by Power Manager doing a full power cycle on the battery pack, and so having an accurate metric on current battery performance, then comparing that to what the on-board processor is indicating. The delta between the two views of the battery pack is then used as starting point for future power management calculations by Power Manager.

The reason that battery capacity often appears to increase after a recalibration is that the algorithm that Power Manager uses in calculating battery capacity is a bit more pesimistic than the actual usage usually turns out to be..... and over time the dead reckoning tends to indicate that the battery capcity is a bit lower than it actually is. This is a generally safe sort of behaviour in most circumstances, as it means that Power Manager is able to give you fair warning that the battery capacity is about to become exhausted rather than having a sudden surprise when it is exhausted earlier than you anticipated.

Cheers,

Bill B.

Thanks again, Bill, for the detailed explanation.

Tõnis

How cand one perform this "reset" or "calibration" of the battery?
i'm talking about a T22 battery with only 56 cycles on it and in green (original FRU) - that acts a little strange - charges ok, led flashes when done - reaching 100%, then stays on green, when unplugged Batt Max shows 2hrs plus of lifetime etc.
The first 20 minutes or so charge decreases normally (time and amps) but after that it "jumps" to 3-5%, led flashing, but strangely it works up to 40 minutes in this state, than discharges...

Is there any reset procedure that can be done?
For now i've just run the "drainer" program, that increased the time until it drops to 3%... nothing more

@ madkat, there is really not reset button for these batteries. What typically happens is one of the cells in the battery pack fails and therefore drops the percentage accordingly. When more than one of the cells fails it drops the percentage drastically. All cells have a shelf life and some outlast the others, with no specific order. What I have done is drain the pack and recharge overnight and repeat for 3 times. I say 3 times, because anymore than that mine resulted in reversing the increase of remaining capacity. The most increase I was able to achieve was 10wh.

of course there is no reset button - and i know that if one cell shoul fail the whole package will work wrong
i'll try drain the battery for the three times you've mentioned and see what happens
thanks

did the 3 cycles - and still acts weird:
sometimes it lasts for one hour and a half, sometimes not even half an hour... SAME load, brightness etc...