Author Topic: External power supply pinouts for HP Envy laptop?  (Read 2512 times)

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Offline elroyTopic starter

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External power supply pinouts for HP Envy laptop?
« on: December 28, 2023, 03:03:13 am »
I sometimes use an HP Envy laptop to record SDR data overnight. The AC power adapter is way too RF-noisy, so I generally run it from an external 20vdc battery bank -- the one I have is called a MaxOak K2, bought from Amazon. It's worked fine. The laptop's internal battery by itself doesn't last through the night.

Unfortunately I misplaced the cable to connect the battery bank to the laptop, and the U.S. MaxOak people said they didn't have one available. It appeared that the HP laptop takes a 4.5mm x 3.0 mm barrel connector, sometimes called a "blue tip". I ordered what seemed like a generic replacement from Amazon.

Checking the HP-provided AC power adapter with a meter, there's 20vdc between the center pin and the outer barrel surface, and also 20vdc between the inner barrel surface and the outer barrel surface.

Checking the generic cable I just bought, the center pin goes to a blue wire, the outer barrel goes to a black wire, and the inner barrel goes to a white wire.

I'm inclined to connect +20vdc from the battery bank to the blue wire (center pin) and -vdc to the black wire (outer barrel), leaving the white wire (inner barrel) disconnected.

Does this sound best? Does a laptop want or need to sense voltage from the inner barrel for any reason?
 

Offline nightfire

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Re: External power supply pinouts for HP Envy laptop?
« Reply #1 on: January 01, 2024, 02:42:54 am »
In my experience with the HP Probooks/Zbooks at work, which should use the same power supplies, we sometimes encountered moments where notebooks did not want to turn on when the power supply was not rated for their demand.

Best example was a Probook 650 G1 in a docking station. PSU for that notebook was rated 65W, the dock was rated 90W- and somehow someone plugged in a 65W power supply in the dockingstation. Probably still would have been sufficient, but the thing did not want to turn on and showed only some LED signals.

I found this, maybe helpful:
https://forums.tomshardware.com/threads/hp-smart-pin-psu-is-there-a-voltage-resistance-chart.3688865/

Bottom Line: HP uses the middle pin as a signal pin, probably in form of a resistance divider, to signal important values between notebook and power supply.
 

Offline nightfire

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Re: External power supply pinouts for HP Envy laptop?
« Reply #2 on: January 01, 2024, 03:01:53 am »
Addendum:
http://nerdipedia.com/wiki/tiki-index.php?page=Smart+laptop+charger

Seems to be quite complete including a detailed desciption, but for probably some older version of the Power supply.
 


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