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iBook battery -- how to rejuvenate it, maybe

Message #1 - Posted 2003/10/14 - Peter Renzland

Recently my iBook's battery gave out after only about 30 minutes. It's two years old, and I had used the battery infrequently, and rarely for long. With the help of good answers to my question here, for which I'm grateful, I did some measuring and experimenting.

ioreg -p IODeviceTree -n battery -w0 | grep Bat

(In Terninal) will tell you your battery's capacity.
A new one is about 4000 mAh. Mine was 1500. One calibration brought it down to 1300, and the next to 1100. At that point I thought "better stop these calibrations -- they are killing my battery". The Apple store said "you need a new battery, $200". So I made a nice little logging script and came up with the following, which after a couple of iterations brought by capacity to 2100, which is over 3 hours of minimal use.

Apple recommends a calibration cycle every 3 months or so. What really helped my batter was minimizing use while discharging:

"Trickle" Calibration:

1. start fully charged
run ioreg to query Capacity
Set "Energy Saver" to never sleep, display off after 1 min, spindown disk. no programs running. airport off. turn display down to lowest.

2. unplug, and let it discharge to deep-sleep (could take 5 hours)

3. plug in and charge fully
run ioreg to query Capacity (it will have been adjusted within 3 minutes of being plugged in)

If this increases the capacity significantly, a second cycle may increase it further.

(Don't forget to reset sleep trigger back from "never" to something closer to 5 minutes of inactivity.)

When using the computer on battery, try to keep display on lowest, and airport off. A surge in power use may trigger premature deep-sleep.)

What I found was that after the predicted "empty", it would continue running on "empty" for as long as 20 or 45 minutes, and the firmware would then add this to its estimate of the battery's capacity, once plugged in again.

Perhaps the above is helpful to others.

=============================================================== What follows is not necessary for those who just want to rejuvenate their battery. It's technical notes and questions that may be of interest to some. I'd appreciate any answers, of course.

calibration:

1. start fully charged
2. unplug and use until force-sleep
3. plug in and charge until charged fully

Q1: I strongly suspect that the lightest possible load should be used. I suspect that for optimal calibration it would be best to
* set power mgt: never sleep; spin down disk when possible [Q4] * have no programs running
* turn airport off
* turn display down

Q2: When charging, is it best not to use the computer? (shouldn't matter?)

Q3: Battery firmware recalculates "capacity" within 2-3 minutes after being plugged in. Is it necessary to charge it fully after that?

Q4: Disk does not seem to spin down when on battery. Only on plug. "Put the hard disk to sleep when possible" is a little vague. [Does this work for others?]

Q5: ioreg provides 5 values from battery firmware:
Voltage, Current, Capacity, Charge-Level (, and Flags). Voltage appears to be measured more or less directly. Current appears to be measured, perhaps averaged?
Charging current appears constant at 1200mA?
Capacity appears to be recalculated after discharge-to-sleep? How is Charge-Level determined?
[Apparently by integrating discharge-current over discharge-time] [Capacity appears to be upgraded by adding empty-running-time * discharge-current]

Q6: When discharging, forced-sleep appears to be triggered by low Voltage, which can be precipitated by (even a temporary) heavy load. This can happen when battery is 75% "full". [Perhaps this is the only problem with the firmware? After this happens, the firmware reduces its capacity estimate.]

Q7: When charging, after pre-mature force-sleep, the charge-level can jump from "30%" to "full". (See Q6)

Q7: Is there a risk of over-deep-discharging the battery by running "on empty"? [Don't think so, since it sleeps fine]

-- Pete

Message #2 - Posted 2003/10/16 - kmc

thanks Peter, it sounds promising!

Previously, Peter Renzland wrote:

Recently my iBook's battery gave out after only about 30 minutes. It's two years old, and I had used the battery infrequently, and rarely for long. With the help of good answers to my question here, for which I'm grateful, I did some measuring and experimenting.

ioreg -p IODeviceTree -n battery -w0 | grep Bat

(In Terninal) will tell you your battery's capacity.
A new one is about 4000 mAh. Mine was 1500. One calibration brought it down to 1300, and the next to 1100. At that point I thought "better stop these calibrations -- they are killing my battery". The Apple store said "you need a new battery, $200". So I made a nice little logging script and came up with the following, which after a couple of iterations brought by capacity to 2100, which is over 3 hours of minimal use.

Apple recommends a calibration cycle every 3 months or so. What really helped my batter was minimizing use while discharging:

"Trickle" Calibration:

1. start fully charged
run ioreg to query Capacity
Set "Energy Saver" to never sleep, display off after 1 min, spindown disk. no programs running. airport off. turn display down to lowest.

2. unplug, and let it discharge to deep-sleep (could take 5 hours)

3. plug in and charge fully
run ioreg to query Capacity (it will have been adjusted within 3 minutes of being plugged in)

If this increases the capacity significantly, a second cycle may increase it further.

(Don't forget to reset sleep trigger back from "never" to something closer to 5 minutes of inactivity.)

When using the computer on battery, try to keep display on lowest, and airport off. A surge in power use may trigger premature deep-sleep.)

What I found was that after the predicted "empty", it would continue running on "empty" for as long as 20 or 45 minutes, and the firmware would then add this to its estimate of the battery's capacity, once plugged in again.

Perhaps the above is helpful to others.

=============================================================== What follows is not necessary for those who just want to rejuvenate their battery. It's technical notes and questions that may be of interest to some. I'd appreciate any answers, of course.

calibration:

1. start fully charged
2. unplug and use until force-sleep
3. plug in and charge until charged fully

Q1: I strongly suspect that the lightest possible load should be used. I suspect that for optimal calibration it would be best to
* set power mgt: never sleep; spin down disk when possible [Q4] * have no programs running
* turn airport off
* turn display down

Q2: When charging, is it best not to use the computer? (shouldn't matter?)

Q3: Battery firmware recalculates "capacity" within 2-3 minutes after being plugged in. Is it necessary to charge it fully after that?

Q4: Disk does not seem to spin down when on battery. Only on plug. "Put the hard disk to sleep when possible" is a little vague. [Does this work for others?]

Q5: ioreg provides 5 values from battery firmware:
Voltage, Current, Capacity, Charge-Level (, and Flags). Voltage appears to be measured more or less directly. Current appears to be measured, perhaps averaged?
Charging current appears constant at 1200mA?
Capacity appears to be recalculated after discharge-to-sleep? How is Charge-Level determined?
[Apparently by integrating discharge-current over discharge-time] [Capacity appears to be upgraded by adding empty-running-time * discharge-current]

Q6: When discharging, forced-sleep appears to be triggered by low Voltage, which can be precipitated by (even a temporary) heavy load. This can happen when battery is 75% "full". [Perhaps this is the only problem with the firmware? After this happens, the firmware reduces its capacity estimate.]

Q7: When charging, after pre-mature force-sleep, the charge-level can jump from "30%" to "full". (See Q6)

Q7: Is there a risk of over-deep-discharging the battery by running "on empty"? [Don't think so, since it sleeps fine]

-- Pete

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