Battery voltage 16.7 V instead of 14.4 V, why?

[mhca]

Hi

I just got a new 8 cell battery for my almost 3 year old IBM X41.
The old 4 cell only had 46% of original capacity.

I noticed that it had a voltage of 16.7-16.8 V. I thought this was just because it was old and used but my new 8 cell battery is also having a high voltage at 16.7 V instead of the rated 14.40 V.

Is this normal or is it my X41 that sucks out too much voltage? Something I should worry about or just live with?

Regards Martin

[independent]

There is an interesting thing with battery voltage.
The way they are rated is at their voltages not when they are charged but flat--in general (there is a new technology rated differently (LiFePO4) but that is another story).
So, all batteries quoted run at higher than quoted voltages. Often, a quoted voltage is the voltage when the battery is flat. So, a 12v car battery is flat when it's 12v but full when it's 12.7v. Other battery technologies have greater voltage ranges, so that's what your seeing. Conversely, my thinkpad x31 has a 10.8v battery but it runs normally at 12+ volts when charged.
hth

[mhca]

Okay. Nice to know. Thanks

[keithsketchley]

An overall point to be made about batteries is that their discharge characteristics vary. For example, conventional carbon-zinc/alkaline and such non-rechargeable batteries drop voltage quite a lot as they discharge, whereas a nickel-cadmium type does not - it quits suddenly. (The nicad's voltage drops only slightly as the battery is discharged, until the point where it drops dramatically thus is not useable.)

Some equipment is sensitive to voltage - my darn Nikon digital camera does not effectively use the charge in its batteries, I can use the ones it rejects as depleted in flashlights and such.

My limited experience with fancy battery chargers for RV batteries and the x41 computer is that you probably won't get much more function time when it goes below 30% charged. I don't know how the time remaining is calculated by Lenovo software, I'd be wary of it, I know automotive/RV is usually done simply on voltage but detail chemistry affects that, hopefully Lenovo does better.

I have noticed the indication is slow to update. There may be a calibration routine in the Power Manager software to cover capacity reduced by wear from use, but I do not know if that data is stored in the battery itself thus valid for spare batteries.

And hot-swapping of wedge batteries while running on batteries doesn’t work.