Gaming notebook battery / power consumption

Hi there.

I was interested to know how a laptop with dual GPUs such as the Alienware M18X lasts on battery.

Not, how long is its battery life, but rather what current does it draw at its given voltage. I find it pretty crazy that such a high current drawing device can operate off of such a small battery.

Could you link me to a li-on battery equivelant?

I'm intrigued.

Thanks.

 

It will depend of the usage. At idle, full power (while gaming, for example) or torture testing with unrealistic loads like benchmarks (Intel Burn, for example).

The current is P=IxE

Where P = Power in Watts
Where I = Current in Amperes
Where E = Voltage

So, download HWMonitor and see how much power is being used in the usage you're wondering about and divide that by the rated voltage of the battery. That will be your amperage.


As of the '... can operate off of such a small battery' the reality is it doesn't really (unless mere minutes (at full tilt) are termed 'operating' for you).

For the sake of argument; if the power needs are 100W (while gaming) and we have a 14.8V battery the amperage is ~6.75A. When idling, and the power is (estimated) at closer to 20W with the same battery the amperage is ~1.35A.

(Adjust the above power needs to match the actual reported in HWMonitor and divide by the actual battery voltage rating too). (Also, the type of battery will depend on the workload it is normally driving. Is the original battery Li-Ion too)?

Hope this helps.

 

Well the point is with something like an Alienware M18x you have a battery that can provide power to two GPUs and a CPU at load when playing a game. I'm not sure what figures I'm looking at for a system like that but when you look at external laptop batteries or whatever they cost around 4x as much as an internal battery for a notebook like that and yet can only give you something like 3A at 19V or 4A at 12.

 

That is irrelevant.

That is why I stated 'Also, the type of battery will depend on the workload it is normally driving.'.

The specifications of the battery pack will therefore be matched to the workload, of course.

Doesn't matter what the 'wrong' batteries cost - they won't work in that configuration (with my assumptions above).


Also; most high-end gaming notebooks dramatically throttle the performance (and the necessary power requirements) while on battery power (The MSI Dragon even throttles performance when plugged in and the battery level falls below a certain level: the power adaptor is simply insufficient to power the system fully by itself).

This throttling on battery power may be to keep within the batteries spec's (but that just means they're using the wrong battery anyway at this point).

 

Fair enough

Thanks for your help.

 

You cannot game on battery with the M18x. It is there solely as a stop-gap until you find another outlet. You will run the GPU's at lowest power setting for basic tasks.

 

My M17x R2 throttled so bad if the AC adapter got unplugged, the CPU/GPU, everything went into lag mode, and I had to restart my laptop if it got unplugged. Such a beast should not be run on battery. They throttle the CPU/GPU so the battery doesn't explode trying to power all the power hungry components.

 

Tsunade_Hime,

Wondering how much power the system uses while gaming? Was my 100W assumption close, or is 150W or 200W closer when gaming?

 

I never used a Killawatt, but if you break down individual components: 920XM 55W TDP, 5870M Crossfire is 120W according to Notebook check, SSDs, RAM screen, all the rest of the stuff plugged into my laptop. That and my R2 shipped out with a 240W PSU.

 

Tsunade_Hime,

Thanks; the 240W PSU says it all (even at 80% efficiency; 192W). wow!

 

Most external PSU's are 90% efficient.

See the efficiency marking by energystar: http://www.energystar.gov/ia/partne...International_Efficiency_Marking_Protocol.pdf

For a power supply mark "V" (most laptop ones are): "Power supplies with greater than or equal to 100 watts input power must have a true power factor of 0.9 or greater at 100% of rated load when tested at 115 volts @ 60Hz."

Not Alienware, but similar config, see Clevo SLI power consumption here: http://forum.notebookreview.com/sag...s-sager-np9390-clevo-p375sm-review.html#power

Up to 330W draw form the wall with quad core and SLI 680m!

That being said, it gets up to 2.5 hours on battery with light web browsing!

 

A PSU's rated wattage is its maximum output, not what it pulls from the wall. So for example, a 240 watt power supply can deliver the full 240 watts to the computer. If this power supply is 90% efficient, it would pull about 267 watts from the wall when providing 240 watts output.

 

Exactly. That was the point. If you measure pull from the wall, you can estimate power delivered to the machine by using the PSU's rated efficiency, so if 300W is pulled from the wall that's ~ 300*0.90 ~ 270W.

 

Ah I was completey mis-understanding the efficiency ratings. Because I hear a lot about low end crappy PSUs not being able to deliver their full power rating, I imagine the same with higher end PSUs. So my 750W 80 Plus (No rating) would draw 900W from the wall. I hadn't taken this into consideration when I was measuring the power at full load either. So while I have 600W when using a 7950, 560Ti and 4770K all OC'd at the wall, I'm actually only sending around 450W to the components, right? I Imagine the 7950 is using around 180-190W, CPU around 130W and the 560Ti around 150 which comes out around 465 so I'd say that's about right. Leaving a little overhead for the rest of the components let's say around 480-490?

I thought my power supply was conking out using all these components at the same time but I think things were probably just getting too hot (bad airflow in my case atm) since it's a fairly decent PSU as they go.

Also, I looked into Lithium Ion batteries, and it's possible to get one that draws a crazy amount of power at load. I'm talking a good 30-40A or something crazy. So this no longer seems as unbelievable. These are single 3.7V cells though so I presume you'd combine 4 and divide the output by how many cells you've got or something and then you end up with 10A at 14.8V which'd be around 150W output. I imagine this is likely what that Alienware battery can do, hence why it throttles so much under load because it needs a 240W supply at the wall you've got a lot of missing overhead there.

 

Not only that, but if you drain your battery at max amps, it will get super hot and possibly melt down or explode. You'd drain your battery in minutes too even if it didn't.