Thinkpads Forum

what could happen using a 65W (from X60) power adapter on a T60 (T2400, X1300) instead of his own 90W?
the size of the 65W power brick's is half of 90W.

Greetings from Argentina.

First, Bienvenidos a la Forum.

Second, don't do it. you could damage either the laptop, the power brick or both.

James

Captain, I don't think it should be an issue - the 65W adapter works perfectly fine with the T60. I used one for a while with no issues (before I sold it on the forum) on my 15" T60 with X1400 and a T60p 14" with X1400 and there are many threads here that discuss this issue:
http://forum.thinkpads.com/viewtopic.php?t=37460

I'd say that if you can use a 90W, go ahead and use it ... I spoke to a tech sometime back reagarding this and he said it is ok to use it. There are people who know better on these forums agreed, but I can definitely say that the 65W adapter will work as a susbtitue - don't make it your primary charger.

The 65W one takes longer the charge the battery - that is the only difference I could find between using these two adapters. If I am wrong, someone please correct me.

correct me if I am wrong, but isnt P=IV? So if you run a 90W power adaptor at say, 20V, you are putting in 4.5A. If you run the 60W at 20V, you are putting in 3.25A. Given that the laptop doesnt need 4.5A under full load (I hope not cause that is a lot!), I dont see much of a problem at running it at less amps...in fact, it may even prolong the cicuitry in the computer some (though you could fry the adaptor if you do actually pull 4.5A through the laptop). But I forgot my physics a long time ago!

ducky2802 wrote:Given that the laptop doesnt need 4.5A under full load ... I dont see much of a problem at running it at less amps...

Absolutely correct -- the 65W adapter will run a fully loaded T60/p without going "out of bounds". You cannot ruin the laptop and you won't ruin the AC adapter.

I would love to know the scenario by which people think that insufficient current can ruin a laptop! Further, the built-in current-limiting safety features of switching supply supplies are such that one cannot ruin them even if one short-circuits their output, i.e., infinite current draw.

Perhaps if one attached a fully loaded docking station, then one might need more current than the 65W adapter provides. However, for the T60/p without a docking station, one will not use all the power from a 65W adapter, let alone a 90W adapter. Go ahead and use the 65W adapter as your primary adapter. Do so fearlessly and with joy!

The formula P=IV is correct.

Given that "P" (power in watts) is constant (i.e., 65 or 90 watts), and that "I" (current, in amps) is allowed to vary, that means as current increases, "V" (voltage) decreases.

Yes, even a fully loaded T60 will probably not draw more than an amp and a half, so either power supply should be okay. The problem exists when "extra" devices are connected to the laptop. Plugging in two high power USB devices can draw another amp. Using the laptop in a docking station will suck more power depending upon what's installed. The "danger" is that when you start nearing the rated power specification of the AC adapter, two things will happen:

- voltage will drop (or become unstable) due to increased current
- heat will increase

While either of those two things will probably not damage the laptop, the same cannot be said about the power supply. The extra heat and excessive current demands will probably shorten the life of the supply.

If the voltage becomes so low or unstable as to cause a 'brownout' in the laptop, then data loss could occur. I have powered T23 systems (normally powered with 72 watt adapters, 4.5A) with the lower-rated 600E/600X adapters (54 watt, 3.36A) and have never had any problems. However, I only do this for a brief amount of time or only when charging the battery (the system is not on). Mostly because I'm lazy and a 54W adapter is already at hand.

The laptop is always going to draw a certain amount of power (amps) no matter what adpater is being used. It doesn't "know" what's out there giving it power. It WILL "ask" for as much power as it needs. The problem is when it starts asking for more than the supply can give (safely and reliably).

The T60 used to come with 65W adapter then it was shifted to the 90w at least in Kuwait it was like this so i used the 65W adapter
many times on my 15 inch T60 without a problem before shifting to my second 14 inch T60 which came with 90W adapter.

in power management, it will show you what psu is connected, either 65 or 90.

if there was an issue using the 65w i would expect it to flag a warning.

afaik it is ok to use 65w

rkawakami wrote:The formula P=IV is correct.

Given that "P" (power in watts) is constant (i.e., 65 or 90 watts), and that "I" (current, in amps) is allowed to vary, that means as current increases, "V" (voltage) decreases.

This statement is incorrect. Power is not constant, the power consumption is dependent on the load condition. Just because your PSU is rated at 400W, it does not mean it sucks in 400W all the time.
Listen to the other posts. I think 65W is safe.

My t60 actually came with a 65 W power adapter... so i think it would be def. fine.

Rwang wrote:This statement is incorrect. Power is not constant, the power consumption is dependent on the load condition.

Re-read my post again and you will see that I am talking about the rated capability of the power supply and not that it's drawing 65 or 90 watts all of the time.

Yes, of course the "power" is dependent upon what's sucking up the current. The amount of current (and thus the power being delivered) will vary as the laptop is being used. I think I made that point clear. All that I am saying is that if the rating of the power supply is declared to be 65 watts, you will be entering unknown territory if you attempt to draw more than the 3.25A that the supply is designed for.

BTW, I was not aware that the T60 can determine which supply is being used (I don't have a T60). Is there a different plug than the yellow coaxial ones from the 54 and 72 watt supplies used with the 600X and T2x systems?

edit: Checking the tabook (Nov 2006 edition), the T60 options page shows the following:

ThinkPad 65W AC Adapter45
45 Only compatible with the 945GM chipset models

So my guess is that Lenovo knows that the 945GM chipset draws less current than the other models and can safely and reliably be used with the 65W supply.

rkawakami wrote:BTW, I was not aware that the T60 can determine which supply is being used (I don't have a T60). Is there a different plug than the yellow coaxial ones from the 54 and 72 watt supplies used with the 600X and T2x systems?

Yes, it can. The yellow coaxial connectors are different and they have 3 poles.

My T60 originally came with a 65W lenovo ac adapter. If it's not the usual case then I guess I should call them to send me a 90W one.

spt60 wrote:My T60 originally came with a 65W lenovo ac adapter. If it's not the usual case then I guess I should call them to send me a 90W one.

Thinkpads with higher power requirements (like the T60p with power-hungry x5600 graphics) get the 90W power supply. Systems with lower power requirements, like a 14" with GMA950 graphics, get the 65W supply. I don't know where the cut-off is in configuration between the two.