Power supply - can I use 90 watt with a 65 watt T61

[GhostriderTx]

My T61 came with a 65 watt supply. We have a few extra 90 watt supplies we ordered for T60's with the AC/DC option for travel. I would like to use one on airplanes. I think I should be OK going to a larger power supply but wanted some opinions.

[erik]

yes, you can use a 90W supply with a 65W system but not the other way around.

[Roadster]

yes, you can use a 90W supply with a 65W system but not the other way around.

Huh? My T60p came with a 90W A/C Adapter, but I use the smaller 65W A/C Adapter (sold as a compatible accessory for the T60p model on the Lenovo website) with it when I travel. The laptop seems to work perfectly fine with either adapter.

[erik]

Huh? My T60p came with a 90W A/C Adapter, but I use the smaller 65W A/C Adapter (sold as a compatible accessory for the T60p model on the Lenovo website) with it when I travel. The laptop seems to work perfectly fine with either adapter.

the p models draw a lot more power and need the extra wattage to be able to power the system and charge a dead/low battery simultaneously.   this can over-stress the power controller on your system planar and ultimately cause damage.   trust me, there's a good reason why your T60p came with a 90W.

[Hellbore]

My T61P came with a 90 watt adapter and let me tell you, that mother gets HOT! That tells me it is working hard... I wouldn't risk using a 60 watt adapter!!

[Roadster]

Huh? My T60p came with a 90W A/C Adapter, but I use the smaller 65W A/C Adapter (sold as a compatible accessory for the T60p model on the Lenovo website) with it when I travel. The laptop seems to work perfectly fine with either adapter.

the p models draw a lot more power and need the extra wattage to be able to power the system and charge a dead/low battery simultaneously. this can over-stress the power controller on your system planar and ultimately cause damage. trust me, there's a good reason why your T60p came with a 90W.

Thanks for pointing that out. I stand corrected. I went back to the Lenovo website, re-checked the A/C power accessories listed for my T60p model number (8741W1C), and the 90W adapter was, indeed, the only one listed. (The 65W adapter is listed for the T60 model, and I must have stumbled upon that by accident.)

Although I've been traveling with the 65W adapter (due to it's smaller size), the mini-dock I purchased came with an extra 90W adapter, so I will swap with that for my travel bag going forward.

I definitely like the smaller size of the 65W adapter, but I don't want to damage anything on the system, so thank you for correcting my misunderstanding.

[erik]

I definitely like the smaller size of the 65W adapter, but I don't want to damage anything on the system, so thank you for correcting my misunderstanding.

no problem.   i went through this debate three years ago as i wanted to use the smaller X40 adapter with my T42p.   my father (who has a degree in EE) did some research on this and decided that it was too much of a risk on the internals.   unfortunately larger adapters are the price we have to pay for having performance models.

[joester]

For what it's worth, My T21 came to me without an adapter, so I used a power supply I had grabbed form the scrap bin at work.
12-24VCD @8.33Amp. set to 16VCD.

Seems to work fine for me... never gets hot...and NOT something I would take on the road.

In fact, I'm currently using it to run the T21 and a 600E I'm working on at the same time.

Joe

[whizkid]

Another data point: My T60 (2623-D7U) came with a 90W adapter, as did the dock. I bought a spare 90W adapter too.

[efrant]

[snip]
my father (who has a degree in EE) did some research on this and decided that it was too much of a risk on the internals.
[snip]

Maybe if you were fully-loading both the processor and GPU and having the optical drive spinning, it may not provide enough power. I highly doubt that normal browsing/e-mail/word-processing use sucks 65W of power. I could be mistaken, but I'm pretty sure that many people use their T60p's with 65W supplies, and haven't had problems. Now, if you are running Far Cry, i think the 65W supply would be outta the question.

[erik]

Maybe if you were fully-loading both the processor and GPU and having the optical drive spinning, it may not provide enough power. I highly doubt that normal browsing/e-mail/word-processing use sucks 65W of power. I could be mistaken, but I'm pretty sure that many people use their T60p's with 65W supplies, and haven't had problems. Now, if you are running Far Cry, i think the 65W supply would be outta the question.

i don't know what "far cry" is but i sure as heck won't risk my T61p on a 65W supply while running autocad 2008 64-bit, solidworks 2008, illustrator CS3, and photoshop extended CS3.   if you can back your speculations up with some hard evidence then i'll believe you.   until then, i'll take my father's word for it.

[efrant]

i don't know what "far cry" is but i sure as heck won't risk my T61p on a 65W supply while running autocad 2008 64-bit, solidworks 2008, illustrator CS3, and photoshop extended CS3.   if you can back your speculations up with some hard evidence then i'll believe you.   until then, i'll take my father's word for it.

I agree, I wouldn"t use a 65w with autocad the other software you mentioned. I'll try to get my hands on an old power supply so that I can splice my amp meter to it to get specific power consumption under various conditions for all here. I can tell you anecdotaly though that I have been using my t60p while travelling with a 65w supply for close to a year now, and I have never had a single problem. Mind you, like I said in my earlier post, the only software I would run on it while travelling was a browers, an email client, word, and a dvd player. (Never anything cpu or gpu demanding.) No problems. Nada.

P.S. I too am an elec. eng. Class of '94.

[Roadster]

I agree, I wouldn"t use a 65w with autocad the other software you mentioned. I'll try to get my hands on an old power supply so that I can splice my amp meter to it to get specific power consumption under various conditions for all here. I can tell you anecdotaly though that I have been using my t60p while travelling with a 65w supply for close to a year now, and I have never had a single problem. Mind you, like I said in my earlier post, the only software I would run on it while travelling was a browers, an email client, word, and a dvd player. (Never anything cpu or gpu demanding.) No problems. Nada.

P.S. I too am an elec. eng. Class of '94.

efrant, I'd love to know the results. I'd do almost anything to avoid having to carry that large brick with me when I travel... anything except risk damaging the machine. I'm just a mechanical engineer, so I'll defer to you EEs when it comes to electronics.

[whizkid]

Maybe if you were fully-loading both the processor and GPU and having the optical drive spinning, it may not provide enough power.

Don't forget the big one: charging the battery.

(Also an EE, class of 88. Go Badgers.)

[jdhurst]

The issue with these things is governed by Ohm's Law. So if your ThinkPad does something the small brick can't handle, the voltage will go down (overload) and the brick will overheat. I always just use the brick specified for the ThinkPad - one cannot go wrong doing this. ... JDH

[efrant]

The issue with these things is governed by Ohm's Law. So if your ThinkPad does something the small brick can't handle, the voltage will go down (overload) and the brick will overheat. I always just use the brick specified for the ThinkPad - one cannot go wrong doing this. ... JDH

You are correct jdhurst, but what I think some people here (including me) are trying to say is this: unless the T6x/p notebook consumes more current than the upper limit of the 65W adapter, which is 3.25A (which I doubt, but have yet to verify), it is perfectly fine to use the 65W adapter. Now, granted, if you plug in a multitude of USB devices and a docking station, etc., it will definitely consume more current. However, just the notebook itself, even under high load, may not. Hopefully I, or someone else, can verify the maximum current drain soon.

[erik]

all of this comes down to what my father originally said; it's too much of a risk running the smaller adapter.   he never told me it couldn't be done -- as i'm sure we're all aware that it can -- it's the risk involved that needs to be remembered here.

what happens when you're traveling with your 65W adapter and your boss or client calls and needs an engineering drawing re-rendered or a complex illustration tweaked and you over-stress your system in the process?   your only safest option would be to run on battery power and i know for a fact that my T61p 6-cell doesn't give me more than 1.5 hours of run-time when using heavy apps on full brightness.   while a scenario like this may not pertain to everyone, it could easily pertain to me and that's why i'll never recommend anyone run a smaller brick.   it's too much of a risk.

[efrant]

[snip]
it's too much of a risk running the smaller adapter.
[snip]

Depends on what you mean by too much of a risk -- if we find out that even under max load, the t6x/p only draws 3.2A, then to me, that would not be too much of a risk. Or even if it draws 3.5A under full load, but without the optical drive it draws 3.1A, it still wouldn't be too much of a risk for me.

But at this point, it is all speculation, at least on my part, as I have yet to measure the current drain.

[DavidR]

These are probably dumb statements, but here goes:

I thought that the heat being generated was the brick attempting to dissipate excess power that was not being used. IE when the battery was fully charged, the brick would dump excess power in the form of heat.

I thought that like a car, the laptop runs off of the battery when the battery is installed and the brick simply charges the battery at the same time the battery is discharging. I thought this was one reason laptops were somewhat immune to power fluctuations - whatever happed on the 110V side did not really matter since the laptop was running off of the battery all the time.

[tselling]

I thought the newer thinkpad models: T60/p T61/p X60/s X61/s recoginized which adapter was attached and would just not pull as much current with the smaller adapter (ie. might not charge the battery while running a heavy load). Power Manager tells whether the 65Watt or 90Watt ac-adapter is attached on the Battery Information tab.

[Hellbore]

I thought that like a car, the laptop runs off of the battery when the battery is installed and the brick simply charges the battery at the same time the battery is discharging. I thought this was one reason laptops were somewhat immune to power fluctuations - whatever happed on the 110V side did not really matter since the laptop was running off of the battery all the time.

Well, cars don't quite work that way lol...not sure about laptops, but I don't think they do either.

I think you have a slightly mistaken view of how cars work. The alternator and the battery are simply wired in parallel with each other. The car engine will draw however much power it needs from the 2 sources simultaneously, there is no separation. So basically, the alternator produces MORE power than the car needs to function, the excess power is used to charge the battery. The alternator can also vary how many watts it is generating, if there is more power being used by the engine the alternator adjusts by generating more power. This is what makes an alternator different from a generator. An alternator is more sophisticated and can in effect make itself work harder when needed to produce more power to keep up with the demands. Meanwhile, the battery just soaks up a certain amount of power to charge itself if it isn't fully charged.

So, in a car, if you were to somehow use more power than your alternator can put out (like some guys with the huge stereo) then your alternator will be working at its max power level, but that is STILL not enough, then the voltage level will start to drop below the level of the fully charged battery, at which point the battery will start being drained. Most of the time your battery doesn't get used AT ALL when you are running the engine because the alternator is maintaining a system voltage of about 14 volts whereas the battery only gets used if the system voltage drops below around 12.5 volts or so depending on the battery.

I think laptops don't work the way you say either, it is probably like a car but even more complex. I'm not sure though becuase I haven't looked at the circuitry.

One thing you can do to demonstrate to yourself that the laptop is NOT isolated from the power supply, is try running your laptop without a battery. Yep it works. If it's plugged in you don't need a battery. If the laptop was isolated from the power by only running off the battery, then this wouldn't work.

These are probably dumb statements, but here goes:

I thought that the heat being generated was the brick attempting to dissipate excess power that was not being used. IE when the battery was fully charged, the brick would dump excess power in the form of heat.

I think it's the other way around with laptop power supplies. You are probably thinking of the old-fashioned ones that simply used a transformer and an analog circuit. Those ones would sometimes actually be hotter when you weren't using power because like you say, it was dissipating excess power. Also known as an "eliminator" style power supply. crappy!!!!

I believe laptops now days use a digital power supply that uses pulse-width modulation to rapidly turn the current on and off at different rates to meet the current demands of the laptop. These are much more efficient and they can simply switch OFF when there is no power being drawn. For example try plugging it in with no laptop, viola, it doesn't even get warm.

The more it gets used, the more current flows through resistive elements which in turn generates heat, so the more power your laptop is using the hotter the little box gets. Et viola, when you plug in your laptop and use more power, it gets the box hotter.

Notice for example if you are using your laptop for common daily tasks and your battery is full, you should notice the box isn't getting very hot. Now do the same tasks on your laptop while plugged in, but with a battery that is LOW. Now the box is getting hotter, because it is putting out enough power to run the computer PLUS some extra power to charge the battery.

[erik]

I thought the newer thinkpad models: T60/p T61/p X60/s X61/s recoginized which adapter was attached and would just not pull as much current with the smaller adapter (ie. might not charge the battery while running a heavy load). Power Manager tells whether the 65Watt or 90Watt ac-adapter is attached on the Battery Information tab.

since you have both a T61p and an X61s, would you mind testing the T61p with the 90W and 65W adapters under a heavy load to see if the CPU/GPU is throttled back as a result?   you might be onto something with the power manager comment about which adapter is shown.   i'm very curious about this now.

[tselling]

I haven't noticed any throttling of the CPU or GPU but I haven't measured with any sort of tool. Just it doesn't seem any slower with the small adapter. However, on the Battery Information page of Power Manager I see a difference with Current. With the 90 watt adapter I see it around 3.39 Amps. With the 65 Watt, the current is more like 1.75 Amps. So it will definitely take longer to charge the battery with the smaller adapter.

I thought the newer thinkpad models: T60/p T61/p X60/s X61/s recoginized which adapter was attached and would just not pull as much current with the smaller adapter (ie. might not charge the battery while running a heavy load). Power Manager tells whether the 65Watt or 90Watt ac-adapter is attached on the Battery Information tab.

since you have both a T61p and an X61s, would you mind testing the T61p with the 90W and 65W adapters under a heavy load to see if the CPU/GPU is throttled back as a result?   you might be onto something with the power manager comment about which adapter is shown.   i'm very curious about this now.

[rlchapin]

Well I am looking at getting an additional power supply for my T61.

Besides the size of the power supply there is about an $80 difference in price. EDIT: This is a combo AC/DC pack. The 90W is about $15 more.

Is the argument in this thread more geared to the 'p' models?

On the web site I keyed in my machine type (T61) and code (8891) and it listed the 65W supply as an option.

I am probably going to get (2) of the 65W supplies.

Thanks,
Bob

[uberT]

I see this discussion has been going on for a while. Have we arrived at anything definitive?

I need to order an extra power supply for my T61. I look at the IBM product sheet (web page) for my machine and it sezs either 65W or 90W are accepted.

Thx.

[EOMtp]

I need to order ... either 65W or 90W ...

Get the 65W unit. None of these notebooks consume anything close to 65W when running by themselves, i.e., outside of a dock.

[uberT]

Thanks. Does the port replicator have any impact on power consumption?

[EOMtp]

Does the port replicator have any impact on power consumption?

Any impact? Yes, it has impact. How much and under what conditions does it need the 90W adapter? Well, to put it indelicately, if you have to ask, then use the 90W adapter with the port replicator. (Unless one knows how to walk between raindrops, best if one carries an umbrella!)

[erik]

after getting my X61 i tried the 65W adapter with my T61p and it was markedly hotter than it was while plugged into the X61.   i'd love to use the 65W adapter with all of my systems because of the size but unfortunately do not trust it because of the added heat.

besides, if all thinkpads could safely run off of 65W adapters then there would be no reason to include 90W adapters except with docks.   think about it.

[efrant]

besides, if all thinkpads could safely run off of 65W adapters then there would be no reason to include 90W adapters except with docks.   think about it.

Not necessarily true. Plugging a multitude of USB devices into your Thinkpad (without a dock) could dramatically increase power consumption (past 65W), even if the T6x/p runs fine on a 65W adapter by itself.