Don't know if they are a standard, but you can choose either of them for a spare battery for the Dell Latitude 800/810. Dell doesn't have a "help me choose" button.
ADD: just figured it out.
Whr = work hour
why would the 48 WHr cost $20 more
Don't know if they are a standard, but you can choose either of them for a spare battery for the Dell Latitude 800/810. Dell doesn't have a "help me choose" button.
ADD: just figured it out.
Whr = work hour
why would the 48 WHr cost $20 more
I would bet WHr stands for Watt Hour. A watt is a unit of power, like a 100 watt light bulb. If your computer uses 10 watts then the 48 Whr will last 4.8 hours. The 80Hr will last 8 hours.
Besides capacity, the 9 cell will be a larger size and stick out the back and/or bottom of your computer a little bit and be heavier. If that matters then it's a consideration.
For me? I usually get the big one as the second battery.
Watts but of course! That makes much more sense! thanks
Mike Ki is right.
WHr = Watt*Hour
The 90WHr battery has about twice the battery life of a 48WHr. If you're going to be using battery power on your laptop for more than 2 hours, go with the 90WHr battery. Nothing sucks more than having your laptop battery die when you're watching a DVD on a plane.
aren't batteries rated by Amp*hour???
watt*hour = joule ...
You are right that Watt*hours can be converted to joules. 1 Watt*second = 1 Joule. It is a measure of energy defined by Power * Time.
If you look on your electrical bill, you will find a measure of KWHr, or kilowatt*hours. It is a measure of energy, and can be converted to the SI unit joules.
Batteries, similarly, have a measure of their energy capacity defined in a metric of Power * Time. A 90WHr battery can deliver 90 watts for 1 hour, 45 watts for 2 hours, 30 watts for 3 hours, etc. Power * Time = Energy.
Now, Power = Voltage * Current. Plug this into the equation for energy, and you have:
(Voltage * Current) * Time = Energy.
Watt*Hour and Amp*Hour can be converted between each other, ONLY IF VOLTAGE IS A CONSTANT (this is why you will see amp*hour ratings accompanied by a voltage). Since a LiIon battery manufacturer has no idea what voltage the battery cell will end up powering, they will go with the more universal rating of W*Hr.
Ahh ... I see, thanks.
And I don't pay electric here ;)
Also, Aren't Laptop batteries usually something like 10.8V???
Quote:
Originally posted by kent1146
You are right that Watt*hours can be converted to joules. 1 Watt*second = 1 Joule. It is a measure of energy defined by Power * Time.
If you look on your electrical bill, you will find a measure of KWHr, or kilowatt*hours. It is a measure of energy, and can be converted to the SI unit joules.
Batteries, similarly, have a measure of their energy capacity defined in a metric of Power * Time. A 90WHr battery can deliver 90 watts for 1 hour, 45 watts for 2 hours, 30 watts for 3 hours, etc. Power * Time = Energy.
Now, Power = Voltage * Current. Plug this into the equation for energy, and you have:
(Voltage * Current) * Time = Energy.
Watt*Hour and Amp*Hour can be converted between each other, ONLY IF VOLTAGE IS A CONSTANT (this is why you will see amp*hour ratings accompanied by a voltage). Since a LiIon battery manufacturer has no idea what voltage the battery cell will end up powering, they will go with the more universal rating of W*Hr.
Laptop battery voltage will differ, depending on the laptop.
This is why their batteries are rated as WHr, and not AHrs.
Why can't I ever get my wife or teenage kids to say that?Quote:
Mike Ki is right.