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Windows 7: Battery Calculation Error (thinkpad R51)

11 Apr 2012   #1

XP, 7 32/64bit
Battery Calculation Error (thinkpad R51)

So, I got this old (2005-ish) laptop that was pretty new, almost unused and put 7 on it.

Before I did, however, I did some benchmarking of the battery. ~3 hours to charge it from nothing, and ~40-45 minutes in the bios before it shut down, dead. Decent enough for a 5 year old battery.

However, it doesn't work that way in windows. Obviously I would not be expecting a full 45 minutes, as windows uses more power then just sitting in the bios, idle.

What would happen is, the LED on the machine shows battery power; steady green at approx 75-100%, and it starts to flash at less then 75, increasing in speed until it dies.
In windows, it seems that from 100% to ~75%, the battery LED is green and windows reports that it gets down to around 75% battery left, then it sends itself into hibernation.

Upon reboot, the battery LED is blinking like it doesn't have any power left, and windows reports 0% battery remaining.
HOWEVER, I can keep the PC running for a good half hour after that, with 0% battery.
Additionally, if I let the battery drain totally, boot into windows, and start recharging it, it charges up to around 25% until it jumps to 100%.. Additionally, the LED turns green.

No idea what is wrong. Windows seems to be interrupting the normal, functional function of the battery LED while not getting correct readings. The battery works, but with windows, it does not.

Ideas? thanks

My System SpecsSystem Spec
11 Apr 2012   #2
Microsoft MVP

Windows 7 Ultimate X64 SP1

I don't think windows had any control over the laptop's LED. That would be on the BIOS of the machine. My first thought would be that the battery is bad even though it will operate a short time. Is it the same age as the laptop?

You can try fully charging and then running it down completely 3-4 time and see if that helps.
My System SpecsSystem Spec
11 Apr 2012   #3

XP, 7 32/64bit

I would assume the battery is the same age as the laptop.

I'm over four complete charge/discharge cycles. I am also 100% sure that, for two of them, they were just in the bios, and lasted about 40 minutes before the battery failed.
I'm starting to think I might try clearing the cmos.. Think that would help at all?
My System SpecsSystem Spec

11 Apr 2012   #4
Microsoft MVP

Windows 7 Ultimate X64 SP1

I don't think clearing CMOS will help. If the machine has a BIOS update, that might though.
My System SpecsSystem Spec
12 Apr 2012   #5

Windows 7 Home Premium 64-bit

There is not a lot you can do to improve the battery life of an old battery - even if it has had relatively little use, sitting idle will not helps its condition. I have an old T21 (around the same vintage laptop) and the best I can get out of the battery is just over 30mins and that was after a lot of effort to improve it. You can, of course, buy a new one but these are expensive.

There is also the freezer method which I have not personally tried but you may want to see if it helps...

How to Rejuvenate an R51 IBM Battery |
My System SpecsSystem Spec
12 Apr 2012   #6

XP, 7 32/64bit

I'll give that a try. However, as far as I can tell, the battery doesn't need a rejuvenation. It holds its charge for an acceptable time, considering its age. The problem lies in its ability to report its charge to the bios and windows
My System SpecsSystem Spec
12 Apr 2012   #7

Windows 7 Ultimate SP1

This gives some 'relatively' useful information. Including, but not limited to the capacity of your battery (design capacity) and the last full charge cycle.

I not long ago had issues with a battery in my laptop (quick discharge, Windows kindly telling me to 'Consider Replacing my Battery'). With this tool i identified that my design capacity was around 71000, yet my last full charge was around 11000.

An obvious difference. For me i depleted my battery a few times, recharged while off. It corrected my issue (At least for the time being).

SO run this from a Command Prompt

powercfg -energy

This will generate a report after 60 seconds and might contain information that may help.
My System SpecsSystem Spec

 Battery Calculation Error (thinkpad R51)

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