HP laptop smart PSU wattage

[Stefan Steff]

Is there any software/program what recognize the PSU wattage attached to a HP laptop?... like DELL has in BIOS/Battery status...?
Thanks!
S.S.

[piernov]

Your question was pretty clear, other people do not seem to know how AC adapter detection works but still try to educate you…

Anyway it's a matter of firmware and software, i.e., is the raw voltage reading or the value after conversion exposed to the operating system, e.g., through ACPI, or is it possible to read a register from the EC that would give this value. And does the EC firmware or BIOS even contain a conversion formula or table (from the voltage reading to the power rating), rather than just a threshold. If you can only access the raw voltage it's not that useful since you can already figure that out by knowing what is the lower resistor value on the board (e.g., by measuring it or by looking a the schematics). Sadly I don't have a definitive answer to any of these questions
This can be of interest though : https://omenmon.github.io/cli#adapter
And would suggest it's only a threshold (but maybe it's not the case on all HP laptops).

That said, we can already build a table ourselves with what we have (some values are already floating around on the forum), but not all the power bricks have the exact same value, there's probably a range for a given power rating.
I have a black tip 230W (genuine HP 19.5V 11.8A) that measures 99.85 kΩ here.

[stj]

impossible, the only reason some dell & HP can do that is because there is a rom chip in the psu with the model and serial number in it

[piernov]

HP relies on a voltage divider with the upper resistor inside the power brick. The resulting voltage is read by the EC. However I don't know if the EC exposes any readings to the operating system.

[stj]

thats not the maximum wattage though, just a voltage detector

[Stefan Steff]

Thanks for the answers.

I know how is the DELL PSU built, based on DS2501 ID chip and the power adapter configuration is read from there.
Memory content example: DELL00AC090195046CN09T2157161543835EAL03 where 090 is the wattage,1950 is the voltage and 046 the amperage.
So, if you buy a writable DS2502 you can make a whatever wattage PSU you want to your DELL...

But, the ThinkPad Vantage can recognize the wattage of the attached PSU and is also resistor based like on HP with the only difference that the resistor is to GND not VCC.
Like in this table:
36 W 7,3 kΩ
45 W 120 Ω
65 W 280 Ω
90 W 550 Ω
135 W 1 kΩ
170 W 1.9 kΩ
230 W 4.6 kΩ
300 W 8.6 kΩ

So I think if Lenovo can read the wattage why can't do the same the HP...
Thanks,
S.S.

[CapLeaker]

Some of the Lenovos are not only detecting it in the Bios but also in the “Vanatge” app too. It will distinguish between 30, 45, 60, or even 100W power supplies. This doesn't matter if it's the original charger or off brand. How does it distinguish what PSU is what? Since off branded PSU's do work the same way on certain Lenovos, I think that has to do with the USB-C charging and the IQ.
Obviously there are different chargers (USB-C vs the old barrel style) so we have to compare apples to apples too.
Basically said this thread is useless, unless we know what we are taking about (brand, model number, pics etc) and everyone is on the same page.

[Stefan Steff]

Maybe I don't formulate the question in the right way...try an other approach...
I wish to see on a HP laptop, when I insert the power adapter the wattage of the power adapter.
On DELL in BIOS i see instantly in battery status , ex. AC Adapter 130W.
On Lenovo Vantage I see also Power adapter 90W or 45W if I insert a smaller power adapter...
Now how can achieve the same thing on HP laptops ?
The purpose is to find a resistor value for a 200W (19.5V * 10.3A) adapter for my lab supply (50V/15A) because I don't own such a power supply to measure the resistor value.
If in some way I can display the wattage for different resistor values I can find the right value.
Or if somebody has a such power adapter and can measure the resistor value that will be wonderful.
Thanks.
S.S.

[stj]

if the laptop wasnt designed to do it then it wont work.
not unless you add loads of stuff.
the resistor ones use different values as codes - it's all in the bios routines.

you would need to replace the charger cable with one that has more cores and change the connector to support more pins.
then put a 1wire eeprom or a resistor in the charger - resistor isnt reliable due to voltdrop in the cable,
and THEN you need to write your own software to read it - probably via the SPI bus using a microcontroller as a A2D or 1wire interface.

still wanna do it?

[piernov]

Your question was pretty clear, other people do not seem to know how AC adapter detection works but still try to educate you…

Anyway it's a matter of firmware and software, i.e., is the raw voltage reading or the value after conversion exposed to the operating system, e.g., through ACPI, or is it possible to read a register from the EC that would give this value. And does the EC firmware or BIOS even contain a conversion formula or table (from the voltage reading to the power rating), rather than just a threshold. If you can only access the raw voltage it's not that useful since you can already figure that out by knowing what is the lower resistor value on the board (e.g., by measuring it or by looking a the schematics). Sadly I don't have a definitive answer to any of these questions
This can be of interest though : https://omenmon.github.io/cli#adapter
And would suggest it's only a threshold (but maybe it's not the case on all HP laptops).

That said, we can already build a table ourselves with what we have (some values are already floating around on the forum), but not all the power bricks have the exact same value, there's probably a range for a given power rating.
I have a black tip 230W (genuine HP 19.5V 11.8A) that measures 99.85 kΩ here.

[Stefan Steff]

Your question was pretty clear, other people do not seem to know how AC adapter detection works but still try to educate you…

Anyway it's a matter of firmware and software, i.e., is the raw voltage reading or the value after conversion exposed to the operating system, e.g., through ACPI, or is it possible to read a register from the EC that would give this value. And does the EC firmware or BIOS even contain a conversion formula or table (from the voltage reading to the power rating), rather than just a threshold. If you can only access the raw voltage it's not that useful since you can already figure that out by knowing what is the lower resistor value on the board (e.g., by measuring it or by looking a the schematics). Sadly I don't have a definitive answer to any of these questions
This can be of interest though : https://omenmon.github.io/cli#adapter
And would suggest it's only a threshold (but maybe it's not the case on all HP laptops).

That said, we can already build a table ourselves with what we have (some values are already floating around on the forum), but not all the power bricks have the exact same value, there's probably a range for a given power rating.
I have a black tip 230W (genuine HP 19.5V 11.8A) that measures 99.85 kΩ here.

Thank You for the answer, the omenmon.github.io/ is very educative. I will check it out for sure to see what info can I get from the laptop in -Bios (Smart Power Adapter Status:...) and -Bios Adapter commands
For now the ~100 KΩ value is enough information.
Thanks,
S.S.

[RethoricalCheese]

230W should be around 75k IIRC. It was not as simple as a single resistor in those chargers so directly measuring it was not quite enough in my case. Had to reverse engineer the schematic to get the right value.

I made a device which identifies Dell and HP chargers based on wattage and also detects if that middle pin loses connection when moving the cable around. Because middle pin losing connection was most common on these chargers.