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What does Whr stand for ? ( laptop batteries )

Posted on 2004-10-15
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What does the Whr stand for when they're describing laptop batteries ?

Err . . along the same lines, how do you tell about how long it will last on a charge from the description ?  (  e.g. : 65 WHr 8-cell battery )
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Question by:drivensnow
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by:georgecooldude
ID: 12324870
This article as an explanation. Read it fully. Takes a while to sink in.

http://www.planetanalog.com/showArticle.jhtml?articleID=16600417

Hope it helps ya! =D
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by:Caseybea
ID: 12326037
"Watt Hour".    It's a measure of power draw.    The higher the "Whr" rating of a laptop, the more battery juice it draws.   Likewise, the higher the "Whr" rating of a battery, the more juice it supplies.

It's VERY difficult to tell how long a battery will last for a particular laptop-  as no two laptops are the same.  Battery lifetime under one charge varies with all of the following conditions:

* Screen brightness  <<-- Big one here.
* Whether or not wireless networking is in use (radio signals require more power)
* type and speed of processor
* Number of simultaneous applications running
* Power-conservation settings of the laptop ("turn off screen after 5 minutes of no activity"), etc.   <<--- BIG one here.
.... and so on.

Take vendor "battery charge" time numbers with a grain of salt.    "Your mileage may vary".

With ONE laptop, and ONE battery--- the lifetime of one charge can vary from a little as 30 mins to and hour, up to 3.5 hours or even higher-- and it ALL depends on how the laptop is being used, the the power conservation settings.

The best recommendations I can give?

a) Buy the best battery your money can buy.   Stay away from NiMH batteries- they wear out faster.  LI (Lithium Ion) etc are better.

b) Buy a SPARE battery, and keep it charged.  So when a critical battery runs out, you can swap.    

c) Option to check out:  Compare prices-  sometimes TWO "regular" batteries for laptops can be cheaper than "one" super expensive one, and you'll have a lot more lifetime and running time.

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by:DktrYes
ID: 12326108
Watt hour.  It is a measure of power consumption.  It doesn't mean the battery will last for 65 hours.  

My guess on your mileage would be about 3 hours.

Here's how I guessed.  65 watt hours is about 6.5 amp hours at 10 volts.  (watts = amps X volts)  I am assuming your battery is supplying  10 volts to the laptop.  It maybe 10, it maybe 18.  I just used 10 because it is likely and I had to pick a number.

A laptop uses about 2 amps per hour doing easy stuff (not watching a DVD or keeping an internal modem up)  So that puts your life from that battery at about 3 hours if you are typing a spread sheet or playing Solitaire.

You can see though if you use 18 volts instead of 10 or if you use more amps per hour how your computing time drops.

hope this helps,
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rid earned 155 total points
ID: 12326518
There isn't much to add really... :)
WattHour. Stamped on a battery is describes the energy that the battery can deliver once fully charged. It is usually based on a calculation of the current capacity (mAh or Ah) multiplied with the nominal voltage during discharge (say 14 V or something for a common laptop battery). In actual practice it means you could draw one Watt from the battery for 65 hours if the battery is rated 65 Wh - or 65 W for one hour, if the battery can handle such a heavy draw; a more normal scenario would be perhaps a laptop taking 20 W and draining the battery in like 3 h or so.
/RID
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Author Comment

by:drivensnow
ID: 12377469
Thankee very much. :)  

I get it now.
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