T series voltages

[joester]

OK, I'm confused.
On page 41 (Acrobat version of HMM) or page 35 of the hard copy, under the "Checking the ac adapter" section, there is a picture of the plug. Under the picture is "(16-10V).
To the right of the picture is a table indicating voltage should be "15.5-17.0".

Which is correct?

Joe

[rkawakami]

Funny, I've never noticed that before... but I normally go by what is written on the AC adapter itself. The 54 and 72 watt power supplies that I have are rated for 16VDC (nominal) at the plug. Most likely the laptop could tolerate a 10% variation so 14.4V to 17.6V would seem to be an acceptable range.

The "16 - 10V" is obviously a typo. Probably it was meant to be "16 - 18V".

[joester]

I normally would too, but I don't have an official power brick for mine. I'm using an open frame Digital Power Corp. supply adjusted to about 15.5V.
I'll also be going on a trip soon, and if the T21 would run off the 13.8 or so volts from the car, I'll make a simple power plug and take some DVD's for the kids to watch. It sure would be easier than fitting the portable DVD player and the two screens. Lots less wires involved
Joe

[rkawakami]

A couple of the power supplies I have here measured between 16.2 and 16.4V ((Fluke 110 meter) so you may be able to crank up your supply to 16V.

I have never tried powering the laptop directly from the car battery. When running, the car should be providing somewhere around 14V as you said. I don't know if that would be enough to reliably power the system. I use the AC/DC combo power adapter when operating the Thinkpad in the car. It is supposed to provide the regulated 16V that the laptop normally sees. I've verified that the laptop works but have never (as far as I remember) measured any of the adapters that I have. As it's dark and raining at the moment, I can't do it now, but if I get a chance tomorrow morning, I make some measurements.

[joester]

Thanks Ray.
Chan_man gave me a PowerXtender, but it has a plug for TP 355,360,755, and 760 series. These are 16V as well, but the brick relies on feedback from the laptop it's plugged into to set the proper voltage. Plugged into my 760E, it runs at 16V on the nose.
Unplugged, it jumps up to 20V. (BTW: that's with the TP off and battery removed)
I suppose I could figure out the resistance required between what pins of the 5pin D-sub plug to lower the voltage to 16.
Preferred choice would be to find the right cable for the T series.
Already posted on that in the marketplace.

Joe

[Msmax]

Seems to be a NON stabilised power supply circuit.
I do not trust those to power my notebook.

Msmax

[rkawakami]

Okay, with a break in the cloud cover, I got a chance to go out and measure some voltages....

Equipment:
- 2000 323i with a 1.5 year old battery
- Fluke 110 meter
- IBM AC/DC combo adapter FRU 22P9021, P/N 22P9003

Measurements:
- Car battery; engine not running: 12V
- Engine idling: 13.8V
- IBM AC/DC adapter with engine off: 16.9V
- IBM AC/DC adapter with engine idling: 16.9V

The rated output of the adapter is 16V, 4.5A; same as the regular AC-only adapters. All voltage measurements were done without any loading (i.e., no laptop connected) so the output voltage may drop when enough current is being drawn.

[joester]

I guess I'll see what I can come up with. I metered the plug of the one adapter I have, and it has 15K and 622 ohms between 3 pins with one of them common to the both resistors. 15K I have, but 622 ohms is going to end up being a variable.
The brick indicates 5 to 24V output. That's where the "personalized" plug comes into play.

Joe

Thanks Ray, for the measurements.

[rkawakami]

15K I have, but 622 ohms is going to end up being a variable.

You could parallel a 680 and a 7500 together. Comes out to 623 ohms.

edit: Oh, never mind... I see what you are talking about. You need to FIND some resistance that gets you the voltage you want.

[joester]

Right. I looks like the brick detects a return voltage from 2 pins to configure the output.

There's 2 pins to the laptop, but 5 on the brick side of the cord.