CF-18 rapidly changing battery numbers

I recently accquired a couple of CF-18's: N model, low hours, in beautiful condition, with apparantly new software restorations. Last night I put two of them through a battery recalibration per the Reference Manual. This morning, when I turned the first one on and checked the expected battery life, I was told 6:13. A few seconds later I clicked the battery icon again and this time was told 4:17. I then clicked the icon about every 5 seconds and got the following series of battery life predictions; 4:46, 5:55, 4:41, 4:25, 6:05, 4:16 -- these all in less than one minute. I then tried the othr CF-18; 5:44, 6:02, 5:09, 5:40, 6:24, 5:58, 6:29 -- again, all in less than a minute. No programs running on either, no indications of hard drive activity, neither hooked up to the AC adapter. I continued to use one of the units throughout the afternoon and the battery is working fine and giving hours of power - but still with the constantly changing battery life predictions. Thoughts?

 

The Windows Battery Monitor is based on several conditions, the Battery Calibration being only one of them. Give them a good couple days to a week's workout each, get a few charge/discharge cycles for it to reference against, and those figures should stabilize into something reasonably accurate.

Run the laptop from full charge to the point where it shuts down for depleted battery; this is how you'll get the most accurate baseline.

mnem
Partially charged.

 

To find real battery capacity I count the time that it runs while discharging the battery under the refresh

Rapidly changing estimates in windows point to a bad cell

Keep us up to date on your findings

 

I think the changing is due to the power management of the Intel CPU
If you monitor the CPU you will see the speed changing often
If the speed change, the used battery current change too.

See picture, green is CPU speed, and Blue is CPU usage.

 

Thanks guys, I'll use it and watch it a bit longer.

 

I have also seen (new to me) batteries do the same thing. I have seen them show 4+ hours... Then be dying on me 30 minutes later. You need to recalibrate them a few times as suggested and then put it through its paces for a few hours to see.

 

The battery indicator calculate depending on your usage thats is why it changing from time to time. In idle it will be stable but when you are working with the machine it will be I say proportional. The heavy you used(multiple tasking) the chances of discharging the battery in less time. Its the way it is. You can not say it exactly how many hours but of course it will be longer on just stay it open or in idle. An excemp..tn if the battery is deffective.


ohlip

 

That is what i tried to say in my answer above (I have a little trouble to explain in English )

 

Thanks guys for the thoughts. You may be right as my CF-29 gives the same widely ranging readings. However, I don't think it is a useage issue as you suggest; the readings were taken while the computer was idle (had just been turned on,left standing for a few minutes for any startup processes to be completed and before any programs were started) and all the readings were taken over a period of not longer than 1 minute. I also hope the alternative you suggest of the battery being defective isn't the case since that would mean all three batteries are bad - and the CF-19 was just purhased new from someone here on the forum. I'll keep using them for a while and re-run the experiment and let you know what happens.

 

You will need to let them run on battery and see how long before shutdown
I have seen cf-18 batterys last 15min,40min,1hr30min,1hr.50min,3hr and more
It depends on the battery condition
Batterys if new should last for quite some time
If sold used....well it's a gamble