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Battery reset gauge - lower capacity

2009-10-27, 11:35 AM


I have question about Battery gauge reset feature.

Recently my notebook's full charge capacity drops to 80% (57Wh design capacity about 45Wh real capacity). The Power manager announce me that it is right time to perform battery gauge reset. I said ok, I will do it over night. Before I started reset I closed all applications and give it a try. In the morning I found, that the reset doesn't help at all and even drops to 38Wh (68%). To be honest I haven't been just disapointed I was angry. I used Lenovo feature to lower quality of my HW? Ok, maybe I went wrong.. I said to me. I will try it again. I restarted computer, have the background services as clean as possible and try it again. Now I have only 65% of designed capacity and wondering if there is (hopefuly) some way to get more energy to my battery. Is it possible?

My configuration.
Lenovo ThinkPad T400 - 6 battery cell (1 year old)
Windows 7 (64b)
PowerManager 3.05

Thanks for any advice or explanation.


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Re: Battery reset gauge - lower capacity

2009-11-15, 14:34 PM
I got the same problem recently. Same configuration w/ yours except OS is Windows Vista.

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Re: Battery reset gauge - lower capacity

2009-11-15, 21:58 PM



I found, that the reset doesn't help at all and even drops to 38Wh (68%).


Battery Maintenance matches the Power Manager baseline of calculated battery  capacity (from what is usually many partial discharge cycles) to the actiual measured capacity determined by doing a a full discharge/charge cycle.


Depending on your actual battery usage pattern, the battery capacity reported by Power Manager may either go down or up as the new baseline is established.


How many cycles do you have on your battery?








I don't work for Lenovo

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Re: Battery reset gauge - lower capacity

2010-01-12, 13:53 PM

I realize this post is a few months old, but I didn't want to create too many new threads, and this sounds kinda like one of my many issues with my new T400 running Window 7 Home Premium. I understand that there is a known problem with Windows 7 affecting maximum battery percentages, but from what I could tell, it seemed that this was an effect caused by upgrading to W7 from a previous OS, and was the maximum reading when running on battery power, not the maximum reading on AC power, but if I am mistaken on that, please let me know. I'm also not sure if the OP meant that the battery gauge wouldn't read above 80% while it was plugged into AC power and supposedly charging, or if they meant that it charged to 100% on AC and then almost immediately dropped to 80% after it was unplugged.


I've had my ThinkPad for a week, and being snowed in, have not had the need to run it on battery power yet. Saturday night my cat unplugged the AC plug from the surge protector, which I didn't notice until the battery gauge dropped to 99%, and I plugged it back in. After the gauge had stayed at 99% for several hours, I tried restarting to see if that would help, but it didn't. Shortly after that, I checked the Power Manager, and at the time, it read 100% while the battery gauge was reading 99%. 24 hours later, despite several restarts, it was still reading 99%, but this time when I checked the Power Manager, it too was reading 99%. I noticed the little plug icon next to the BG, and wanted make sure that was the charging indicator, so I unplugged it for less than 5 seconds, and the plug icon disappeared and the BG immediately dropped to 98%. Plugged it back in in, plug icon came back, seeming to indicate that it is charging, but the BG stayed at 98% for a while. Restarted, no luck, checked the Power Manager, and it too was at 98%, where they are both still stuck.


I searched the forum and found this thread and read about the battery gauge reset function. I finally found the info about the BG reset on the PC, and there is a note that before running it with a Li-Ion battery (mine is 4-cell), you must first charge it to 100%, which implies to me that this is for resetting the BG when the top percentage is reading low while on battery power, not AC. Is it safe to run the BG reset function if I can't get the top AC charge up to 100%? Running the reset requires running down the battery to zero and then plugging it in again, but I am worried that if that does not solve the problem, that the battery will be completely dead and won't be able to be recharged above that level on AC charge. :smileysad:


From the BG reset info, I understand now that using AC power all the time can affect the charge life of the battery, but again, it seems to be referring to the top percentage on battery power, not AC. If I am mistaken though, is it possible or normal for the top charge on AC power to drop that quickly, in a week?  I ran a hardware diagnostic, but everything passed, so it seems like a software or OE issue. :smileysad:

Any suggestions or ideas on what I am probably doing, or did, wrong and how to fix it?




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Re: Battery reset gauge - lower capacity

2010-01-12, 14:45 PM

Hi Annnastasia!


The default behavior is that the battery starts charging when it drops below 96%.


You can see this if you go to Battery Maintenance in the Power Manager.


Your T400 is new, and you shouldn't need to run a battery gauge reset.

USB-C: Just cos it fits don't mean it works.
I don't work for Lenovo. I'm a crazy volunteer!

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  • Message 6 of 6

Re: Battery reset gauge - lower capacity

2010-01-12, 15:23 PM

Doh! Thanks, yeah, just found that. I unplugged it to drop it down to 95%, and plugged it in and it just got back up to 100%. :smileyhappy:

I am concerned though that it took less than a minute to drop it from 98% to 95%, and that the time estimate in the Power Manager started reading that there was well over 4 hours of battery power at 98%, but as the percentages quickly dropped, so did the time, so that at 95% it was reading 2hr15min. It also estimated nearly 40 minutes to fully charge, but did finish in about 20mins. Is it normal for battery percentages to drop 5% in under a minute, but at least 20 minutes to recharge the same amount? Is it normal on a week-old PC that has not been run on battery power yet, for the Battery Gauge/Power Manager percentage to drop that quickly, or does battery power never really start at the full charge percentage? Is the near-the-top 3% of power really supposed to equal over 2 hours, despite dropping within seconds, while the bottom 95% is also equal to over 2 hrs? I assume I must be reading and understanding things wrong. *need emoticoms for confusion and worry*

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