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27 W/hr-battery, means 7 hr notebook life?

Forum Laptops & Notebooks : General Laptops & Notebooks - 27 W/hr-battery, means 7 hr notebook life?

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Archived from groups: comp.sys.laptops (More info?)

I see that Dell's new X1 notebook has a 3-cell 27 W/hr-battery. If I
assume voltage is 15v and current is 4A, then it consumes 15/4=3.75W.

27/3.75= 7.2 hrs. I guess this can't be actual battery time?

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Archived from groups: comp.sys.laptops (More info?)

>I see that Dell's new X1 notebook has a 3-cell 27 W/hr-battery. If I
>assume voltage is 15v and current is 4A, then it consumes 15/4=3.75W.
>
>27/3.75= 7.2 hrs. I guess this can't be actual battery time?

Sounds about right. Since it's really just a Samsung Q30, i would skip
the middleman and save yourself some nightmares.

http://www.engadget.com/entry/1234000913038231/

--------
AJ

Reply to Anonymous

Archived from groups: comp.sys.laptops (More info?)

"Jan" <janoleolsen@hotmail.com> wrote:
> If I assume voltage is 15v and current is 4A, then it consumes 15/4=3.75W.

Huh?

Reply to Anonymous

Archived from groups: comp.sys.laptops (More info?)

Jan wrote:
> I see that Dell's new X1 notebook has a 3-cell 27 W/hr-battery. If I
> assume voltage is 15v and current is 4A, then it consumes 15/4=3.75W.
>
> 27/3.75= 7.2 hrs. I guess this can't be actual battery time?

Power = volts * amps. P = 15*4 = 60 watts. Energy = Power * time : time
= energy/power = 27 watt-hr/60 watt = 0.45 hours. This doesn't fly
since the assumption of 4amps continuous load is wrong and the 15 volts
could well be only the overvoltage required for battery charging.

You really have to work this the other way around on the basis of a
total system work cycle, taking into account the performance
characteristics of each device on the system: hd, optical drive,
display, cpu, ram, etc for a schedule of user functions on the laptop.

Q

Reply to Anonymous

Archived from groups: comp.sys.laptops (More info?)

Without doing the math a 27 Watt hour battery would run your laptop about 1
hour.

"Jan" <janoleolsen@hotmail.com> wrote in message
news:1112460116.561223.56630@g14g2000cwa.googlegroups.com...
>I see that Dell's new X1 notebook has a 3-cell 27 W/hr-battery. If I
> assume voltage is 15v and current is 4A, then it consumes 15/4=3.75W.
>
> 27/3.75= 7.2 hrs. I guess this can't be actual battery time?
>

Reply to Anonymous

Archived from groups: comp.sys.laptops (More info?)

It's 15 volts, and if the current is 4 amps, that is 60 watts, or 60
watt-hours per hour. A 27 watt hour battery would be exhausted in less
than 30 minutes. Something's wrong here, but it's not my calculations
(I'm a degreed EE and an FCC license Amateur Radio Operatior and
Broadcast Engineer for over 40 years).

Gary Helfert wrote:

> Without doing the math a 27 Watt hour battery would run your laptop about 1
> hour.
>
> "Jan" <janoleolsen@hotmail.com> wrote in message
> news:1112460116.561223.56630@g14g2000cwa.googlegroups.com...
>
>>I see that Dell's new X1 notebook has a 3-cell 27 W/hr-battery. If I
>>assume voltage is 15v and current is 4A, then it consumes 15/4=3.75W.
>>
>>27/3.75= 7.2 hrs. I guess this can't be actual battery time?
>>
>
>
>

Reply to Anonymous

Archived from groups: comp.sys.laptops (More info?)

I believe the battery is actutally rated 27W-hr, not Watts/hr. and you are
correct 15V @ 4 amps equates to 60 watts, however this is the maximum
expected power. It assumes there may be times you are making full use of
your computer, screen on maximum brightness, playing songs on your dvd
playing and charging a dead battery all at the same time. It is the charging
of an discharged battery that just about doubles the power requirements.
If your computer did not have to deal with charging the battery your power
would be about 27 Watts, thus your battery would run out in 1 hour.

"Barry Watzman" <WatzmanNOSPAM@neo.rr.com> wrote in message
news:424F63A0.7040704@neo.rr.com...
> It's 15 volts, and if the current is 4 amps, that is 60 watts, or 60
> watt-hours per hour. A 27 watt hour battery would be exhausted in less
> than 30 minutes. Something's wrong here, but it's not my calculations
> (I'm a degreed EE and an FCC license Amateur Radio Operatior and Broadcast
> Engineer for over 40 years).
>
>
> Gary Helfert wrote:
>
>> Without doing the math a 27 Watt hour battery would run your laptop about
>> 1 hour.
>>
>> "Jan" <janoleolsen@hotmail.com> wrote in message
>> news:1112460116.561223.56630@g14g2000cwa.googlegroups.com...
>>
>>>I see that Dell's new X1 notebook has a 3-cell 27 W/hr-battery. If I
>>>assume voltage is 15v and current is 4A, then it consumes 15/4=3.75W.
>>>
>>>27/3.75= 7.2 hrs. I guess this can't be actual battery time?
>>>
>>
>>

Reply to Anonymous

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