Comparing ThinkPad Battery Discharge Rates

[underclocker]

I've been using a T41 with an R51 Intel mobo as my around the house, daily web-surfing and email machine. In addition to being silent and cool running, a reasonably fresh 6 cell battery is good for over four hours of web-surfing with the screen set to four of seven or fairly bright.

Using MobileMeter, it's clear why, the battery discharge rate hovers around 10 watts per hour. The battery capacity is around 45Wh, so 4 plus hours seems right.

I picked up a beautiful Z60t, which is a rough equivalent to a T43. The strange thing is that the discharge rate on the Z60t is 15 watts per hour - it uses 50% more power to do the same thing. I really can't figure out why. The T41/R51 has an Intel GPU, 1.7GHz 400MHz bus Dothan CPU, 2 x 512MB PC2700 RAM and a 60GB 5400 PATA drive. The Z60t has an Intel GPU, 1.73GHz 533MHz bus Dothan CPU, 2 x 512MB PC2-4200 RAM and a 60GB 5400 SATA drive.

With a 37Wh 4 cell battery and similar LCD brightness, I was expecting 3.5 hours of runtime, however, I barely get 2.5 hours.

Is the 533MHz bus (Sonoma platform) platform that much less efficient than the initial Pentium M boards with the 400MHz bus (Carmel platform)? All drivers are current on both machines and I verified the discharge rate on another Z60t. Are others seeing the same discharge rates on Z60t's (and T43's)?

I'm planning on taking a closer look at R60's and T60's to see how they fare. With a 10Wh discharge rate, I think it'll be hard to beat the T41/R51 for a basic 14" machine.

[visionviper]

You would be surprised by how much difference there can be between laptop platforms and power consumption.

[gnurbs]

hey, i have a quite different setup, but i can only second that there are big differences: me and my sister have each an x40, one with p-m 1.4ghz@600MHz:700mV, 512+512mb ram, 2200bg wlan, Modem extension card. consumes at least 8.8W. The other one with p-m 1.2ghz@600:716mV, 2100b wlan, 512+256mb ram, bluetooth+modem ext. Consumes at least 7.2W. Though i got it running @ 6940mW, but with only 512mb of ram, no wlan, no modem+bt

I'd call that differences in configuration minimal, I mean it's the same board, almost same processor and so on

[Terrahawk]

It's quite interesting how power consumption seems to increase with each recent generation of laptop platform. The only reversal that happened was when the original Pentium-M and 855 chipset were introduced.

What I've noticed is:
- When I had an X21 (Mobile Pentium-III 700 MHz), I could get it down to 8.5W by turning everything down - screen brightness, removing the PCMCIA wireless card and just watching the power meter.
- The R40 (Pentium-M 1.7 GHz, 1GB RAM, IBM wireless Mini PCI abg II) would typically idle at 9W during normal use, but if I shut down the wireless, removed the DVD drive and turned down the screen brightness, it would go down to just under 8W at idle.
- My current X31 (Pentium-M 1.6 GHz, 2GB RAM, IBM wireless Mini PCI abg II) performs just about identically to the R40. However, it drops to about 7.8W when everything is turned right down.
- My T42p doesn't go below 10W in general. It has a Dothan Pentium-M 1.8 Ghz, ATI FireGL chip, and a DVD-RW drive, 2GB RAM and a SXGA+ display (the others are XGA) so I'd expect it to be a little more power hungry than the X31 and R40. The Dothan uses more power at idle but less at 100% usage.
- We also have a Z60m and that uses 15W at idle typically. It has a Pentium-M 2.0 GHz, WSXGA+ display, Intel 2915ABG wireless, 2GB RAM and a DVD-RW drive. I can't make that thing drop below about 13W at all despite turning everying I can off and down. I haven't removed the DVD-RW drive though...
- I've done a bit of work with a Toshiba Portege R100 (1.0 GHz Pentium-M, 1.25 GB RAM, Intel 2100B wireless) and it idles typically at 8W.

And then, I've read on here about people getting their T60s and other more recent models down to below 15W. Yes, power consumption has increased but I think battery capacity may have moved to match it exactly - you can expect about 4 hours with a new machine, and you could back in 2003 too. Well, my R40 when I bought a new battery got over 6 hours.

Just speculation, but if higher-end Atom netbooks had their internals replaced with Banias Pentium-M technology, we may have a winner on our hands. The Atom itself uses a low amount of power but it is the surrounding equipment that evens everything out. I have an Eee Pc 701, and it lasts about 3 hours on a 38Wh battery. My X31's battery only has about 20Wh capacity left, and it lasts 2 hours. Time per Wh is fairly close between the two.

Oh yeah, I'm aware that the Eee 701 doesn't have an Atom. I don't think the Atom-based models have improved in battery life though.

[dr_st]

With everything turned off, screen brightness at minimum, and computer absolutely idling I can get my T60 1952-F76 (14" SXGA+ T7200 GMA950) down to 10-11W. Even managed to go to something like 8.5-9W once, but only briefly.

Normal average consumption with WiFi on, brightness at maximum or close to it and a mixture of low and high power tasks seems to be about 18-19W (judging that it lasts me about 3 hours on the 6 cell battery, whose capacity is close to original).

[underclocker]

This is a bit of an eye-opener for me. I never really focused on discharge rates since I was using an X40 for travel and a T4x for most other purposes.

Laptops have grown much more powerful, but the fact that they use roughly 50% more power than the first generation Pentium M machines should really be reflected in the overall machine design - inlcuding the incorporation of the battery!

Widescreen 14" Z60t's, Z61t's, R61's, T61's, R400's & T400's with 4 cell batteries, the only batteries that are flush fitting, are a cruel joke. With anything more than light use, those machines are really only good for 90 mintues. Early 14" Pentium M machines from IBM, like the R40's, had internal, flush mounted 8 cell batteries. I recall that they ran close to 5 hours.

I'm thinking for this reason and due to the thickness, weight, off-set LCD bezels, quick wearing plastics and keyboard, the 14" R61/T61/R400/T400's may wind up as one of the worst ThinkPad designs in history. At least the Z60t/Z61t's were slim, lightweight and elegantly designed.

Current, non-ultra-low power laptops, should have flush 6 cell batteries at a minimum. In my opinion, anything less is a poor design and borders on consumer deception. Does the average consumer or corpate user really expect a new, modern laptop to have 90 minutes runtime?

[dr_st]

I'm thinking for this reason and due to the thickness, weight, off-set LCD bezels, quick wearing plastics and keyboard, the 14" R61/T61/R400/T400's may wind up as one of the worst ThinkPad designs in history. At least the Z60t/Z61t's were slim, lightweight and elegantly designed.

Totally agree. Reached that conclusion a while ago.

[Aroc]

It's not exactly fair to compare a R40 and X31 with a T42p and a Z60m[/m]. Neglecting the differences between the displays (bigger displays generally consume more power, but not always), the two latter units probably had discrete video adapters whereas the X31 (and perhaps) the R40 did not. We generally lose about 1 hour or more on battery when comparing the same model with a discrete video option to one with the integrated intel video option. The Intel video ones also run cooler, which is a nice effect too.

As much as I like this Thinkpad T61p, the nVidia quadro fx 570m 128MB video adapter is an absolute barn buner. I get about 3:35-3:45 on the 9-cell battery. Compared with the smaller Thinkpad X61s where I get 5:35-6:20 (or so) as of late on its 8cell. I can super stretch it to 7-8 hours, but you need to just about run at the lowest settings and I can't manage to read the display when I do that.

[Terrahawk]

In the examples I mention, all the Thinkpads I have observed have separate ATI Radeon graphics chips. The R40, X31 and T42p have the same basic spec, only differentiated by form factor and display metrics. The Z60m is a completely different platform featuring the Intel 900 series chipset with PCI Express and DDR2 (supposed to be more power efficient at 1.8V) versus the 855 chipset with AGP and DDR1 (2.5V DIMMs).

X21 - 12in XGA, ATI Rage Mobility 4MB
X31 - 12in XGA, Mobility Radeon 16MB
R40 - 14in XGA, Mobility Radeon 7500 32MB
T42p - 14in SXGA+, FireGL T2 128MB
Z60m - 15.4in WSXGA+, Mobility Radeon X600
Portege R100 - 12in XGA, Trident CyberBlade 32MB

I've also had the opportunity to try out a Dell Latitude D600 (Pentium-M 1.6GHz, wireless and SXGA+ display with i855GM graphics) and a Compaq nx9000 (Pentium 4-M 1.8 GHz, no wireless and ATI Xpress 200 integrated graphics) and they seem to be significantly behind the curve compared to the Thinkpads. Dell - 15W idle and Compaq - 18W idle.

[craigmontHunter]

My t41 with every thing set to minimum will idle at about 6.45 watts and I can type at just under 8 watts normally With wireless on it is 7 and 9 watts. This means that my old (2003, 41%) battery will give me about 2:30 in runtime, just eneough for what I need. It looks like we are taking a step forward and back at the same time .

[Aroc]

Hello -

That's disappointing as the power consumption on this X61s (with 12 inch ultralight screen option and Intel L7700 1.8GHz CPU) consumes more power (8-10Whr on average) than your cited T41 values. The original Pentium M notebooks were quite the battery sippers!

Sorry I got the X31 confused. I thought is used the integrated video similar to its Dell sister the Latitude D400. I apologize for the mixup. I do now recall that the X31 had the discrete video.

[Unknown_K]

Out of curiosity how do those numbers compare to the ancient Pentium 1 era laptops for run time?

[Terrahawk]

No idea... I have an old Compaq K6-2 laptop thingy that I could try out

[Unknown_K]

I have a bunch of working batteries and could probably get 1.5 hrs out of them, but they are old and I asume not holding the charge a new one would (or maybe they are?).

What I was getting at is do newer Thinkpads batteries last longer then they used to by design? I asume the load a P233MMX 380XD for example would be less then a new dual core model with 3d GPU and fast SATA HD, or am I wrong there? So has battery technology improved enough to overcome the bigger load and give you more run time? Would a new battery design make an old 701cs run 8 hours on a charge?

[Esben]

The T42 I had, with discrete R9600, 2 GB RAM and 7200 RPM harddrive would also idle at around 7.8w with brightness down, wireless off and Windows XP. It was undervolted to 600 MHz/0.7v.
In comparison the X60s would idle around 7w with brightness down, normal TFT, 2 GB RAM, 64 GB SSD and Windows 7. The X300 I currently have gives similar dissipation with Windows 7. With 67Wh battery it gives 6-9 hours of battery life.

An undervolted Pentium-M has a very low power consumption. It's true that the Core 2 Duos use more power, but they're also much more powerfull. If you want lower consumption, opt for a laptop with LV or ULV processors and integrated graphics. Getting a LED-backlit display greatly reduces the extra power consumption from increasing brightness. From lowest brightness to a more usable brightness (up 5 notches) only increase consumption by 1w.