Can I charge my laptop battery at 20V and 5A if the specs state 19.5V and 3.33A?

[Silver_Is_Money]

Will this get me to 19.23V on the center pin (blue wire)?

[Silver_Is_Money]

Perhaps a better way of presenting how to send 19.9V to the white wire of the 4.5mm-3mm Jack, and 19.23V to the blue wire of the 4.5mm-3mm Jack for my HP ProBook Laptop computer:

Oops, I forgot to define R2 in my image.  R2 = 10K Ohms.  Will this work?

[Solder_Junkie]

A very interesting thread. My old Asus laptop (a Vivobook) charged and ran well from a generic 12 Volt to 19 Volt laptop car adapter. The adapter only has 2 wires in the cable, indeed several generic car adapters have 2 pin adapters to use with a variety of different laptops...

My replacement laptop is a Dell Vostro and presumably uses the inner part of the DC connector "sleeve" as some sort of sensing that a valid charger is being used (thanks soldar for the diagram). Any idea how to fool the laptop into accepting a generic 2 wire charger, or should I pay the Dell price for an adapter (72 GBP plus 7.4mm to 4.5mm adapter)?

Thanks
SJ

[MrAl]

Hello again,

I was wondering what to do with that 'blue' wire too because I have a laptop with the same connector and I often thought about using a different wall wart but was not sure how to handle that blue wire.  I'd hate to burn anything out.
I can apply just about any voltage from 3.3v up to maybe 30v, so 19.5 volts I can get right on the money 19.500 volts, but I'd have to know what to connect to that blue wire.  If it is a communication line, that would probably be too complicated, but if someone opened up their wall wart they would know right away if there was a chip in there or just a couple of resistors.  Hopefully just a couple of resistors.

[DavidAlfa]

The laptop has a charger controller, will work just fine.

[Silver_Is_Money]

The laptop has a charger controller, will work just fine.

HP laptops seem to look for a unique voltage on the center pin.  And by year and laptop series this center pin voltage is different, such that you are forced to use the correct wall wort for your model and year of laptop.  They apparently refer to it as a "Smart Pin".  My concern is as to what they mean by "Smart".  Unconnected my HP wall wort's center pin reads 19.15V, while the jack reads 19.87V (with + on the inside wall, and - on the outside wall).  Perhaps when connected this center pin "Smart" voltage changes.  I can only make a voltage divider that sends one 'fixed' voltage (19.87V) down the white (inner shell wall) wire leading to the jack, and another 'fixed' voltage (19.15V) down the blue (center pin) wire of the jack.  I hope that works so I can run my computer (and the oscilloscope which uses it as it's screen) in the field.

[IanB]

HP laptops seem to look for a unique voltage on the center pin.  And by year and laptop series this center pin voltage is different, such that you are forced to use the correct wall wort for your model and year of laptop.

This has not been my experience, unless it has changed recently. My company for a long time sourced laptops from HP, and so we had many different models and years floating around, and all sizes of power bricks from small travel bricks to giant docking station bricks. All of them were interchangeable. Any HP power brick would work with any HP laptop or docking station.

My best guess is that the centre pin might indicate the power rating of the power brick, so the laptop or docking station could know how much current it could draw. For instance, a laptop might show a message saying something like, "The connected power supply is too small, so the performance of the laptop might be limited."

[Silver_Is_Money]

This has not been my experience, unless it has changed recently. My company for a long time sourced sourced laptops from HP, and so we had many different models and years floating around, and all sizes of power bricks from small travel bricks to giant docking station bricks. All of them were interchangeable. Any HP power brick would work with any HP laptop or docking station.

My best guess is that the centre pin might indicate the power rating of the power brick, so the laptop or docking station could know how much current it could draw. For instance, a laptop might show a message saying something like, "The connected power supply is too small, so the performance of the laptop might be limited."

If that's so, then perhaps I should just solder the white and blue wires together and feed both with 19.5V.  But some have measured their center pin roughly at the voltage I discovered, and some measured 18V, and one guy measured only 8V on the center pin (blue wire).

[IanB]

I just measured a 150 W HP power supply that I have lying around, and the main voltage was 19.7 V, while the center pin was 19.5 V.

[Edited to clarify make of power supply]

[Silver_Is_Money]

I just measured a 150 W power supply that I have lying around, and the main voltage was 19.7 V, while the center pin was 19.5 V.

Is it intended for running (or more technically correct, charging) an HP laptop?

[Bud]

Perhaps a better way of presenting how to send 19.9V to the white wire of the 4.5mm-3mm Jack, and 19.23V to the blue wire of the 4.5mm-3mm Jack for my HP ProBook Laptop computer:

Oops, I forgot to define R2 in my image.  R2 = 10K Ohms.  Will this work?

No you cannot use a voltage divider with such values. Use the Ohm's law to calculate the current that will flow through the divider to see why.

[Silver_Is_Money]

No you cannot use a voltage divider with such values. Use the Ohm's law to calculate the current that will flow through the divider to see why.

I consulted a ChatBot and then confirmed it via this online voltage divider calculator.

https://ohmslawcalculator.com/voltage-divider-calculator

[IanB]

Is it intended for running (or more technically correct, charging) an HP laptop?

Yes, it is an HP power supply--19.5 V, 7.7 A, 150 W.

A 90 W HP power brick (19 V, 4.74 A) shows 19.6 V as the main open circuit voltage and 19.0 V on the center pin.

[nightfire]

Having some Probooks at work, and also doing some appliance testing of the power supplies, the voltage differs a bit between generations.
Older stuff was around 19V, more modern PSU do the 19.5V- but as far as I am aware, for the notebok itself does not matter.
Open circuit voltage of those 19.5V versions are often around 19.8V when measured with a multimeter.

Just for interest: Which model is your Probook, and Generation?

For the wiring maybe this helps: https://www.parkytowers.me.uk/thin/hp/hp_psu.shtml
Have not checked if this still applies to the recent PSU of HP.

[tunk]

I consulted a ChatBot and then confirmed it via this online voltage divider calculator.

Technically it's correct, but it assumes that the output
impedance/resistance is 1-2 orders of magnitude higher.
Or, what's the voltage if there's a 10k resistor in parallel
with R2? And with 100k, or 1M?

[Silver_Is_Money]

Is it intended for running (or more technically correct, charging) an HP laptop?

Yes, it is an HP power supply--19.5 V, 7.7 A, 150 W.

Once again it shows that the center pin voltage is below the jack's voltage.  There must be significance in this, but what that significance is remains a mystery.

I popped open my HP laptop wall wort and confirmed directly at the output pins that there is a measured 19.87V on the white wire, and 19.15V on the blue center pin wire.  I didn't further disassemble it whereby to see how the 19.15V is generated.   The center wall is positive, and the outside wall is negative on the 4.5mm x 3mm Jack with center pin.

As an aside, I've heard that Dell leaves the center pin blue wire disconnected.  No idea as to the truth value in this.

[Silver_Is_Money]

Having some Probooks at work, and also doing some appliance testing of the power supplies, the voltage differs a bit between generations.
Older stuff was around 19V, more modern PSU do the 19.5V- but as far as I am aware, for the notebok itself does not matter.
Open circuit voltage of those 19.5V versions are often around 19.8V when measured with a multimeter.

Just for interest: Which model is your Probook, and Generation?

For the wiring maybe this helps: https://www.parkytowers.me.uk/thin/hp/hp_psu.shtml
Have not checked if this still applies to the recent PSU of HP.

The back panel identification is completely worn away, but the battery model# 805292-001 indicates Probook 430 or 440.  The date of the battery states 11/2016.  It is 14.8V, 44Wh, and something like 2790 mAh.  I bought it used/refurbished a good number of years ago.  I can't remember how many years that might be though.  And I have no way of knowing if the 2016 dated battery is original whereby to pin down a date for the computer mfg..

Edit:  I'm running Linux Mint on it.  Is there a means in Linux whereby to assess better model number and date info?

Edit #2:  A fading sticker to the right of the touch-pad states Intel CORE i5 Inside.

[nightfire]

In the BIOS setup screen should be the serial number displayed. Usually beginning (at least here in germany) with something like 5CG......  With that, on the HP.com support page you can enter that and HP gives you the right model/generation.

From the age, I would take some bets that this is a 4x0 Probook gen1 or 2, the second number denoting the screen size- 440 being 400 series 14" screen.

[IanB]

I consulted a ChatBot and then confirmed it via this online voltage divider calculator.

Be aware that ChatBots can be very unreliable with technical questions, especially ones involving numbers or calculations.

[tooki]

While it is true that in modern laptops there are many LV regulated power rails derived from the input main power rail (e.g. 0.8V, 1V2, 3V3, 5V), in some laptops the full input voltage/current is supplied to the battery. Some laptops have lower voltage batteries and step down the input to something like 15V, 12V or 8V for charging, while others do take the full 19-20V into the battery. I can't swear to it but I'm pretty sure not all use a separate buck regulator to "cap" the battery voltage. More likely, I'd expect either the BMS, or the main input MOSFETs before it even gets to the BMS, would monitor the input voltage and shutdown in an unsafe over-voltage scenario.

Not a snowball’s chance in hell that the bolded sentence is true.

The only conceivable thing would be if a laptop put the entire battery circuitry — BMS, safety, and charger IC — in the battery pack itself. Then you could deliver raw voltage to the pack. But I don’t believe for one second that any laptop ever made puts raw AC adapter voltage directly onto a lithium battery itself without a charger circuit in between, because doing so would be wildly reckless and such a thing would never pass safety review, never mind legal review.

[Silver_Is_Money]

In the BIOS setup screen should be the serial number displayed. Usually beginning (at least here in germany) with something like 5CG......  With that, on the HP.com support page you can enter that and HP gives you the right model/generation.

From the age, I would take some bets that this is a 4x0 Probook gen1 or 2, the second number denoting the screen size- 440 being 400 series 14" screen.

Thanks!  It is indeed a model 440 G3.

[Bud]

No you cannot use a voltage divider with such values. Use the Ohm's law to calculate the current that will flow through the divider to see why.

I consulted a ChatBot and then confirmed it via this online voltage divider calculator.

https://ohmslawcalculator.com/voltage-divider-calculator

Seems you missed that I asked to calculate the Current through the divider, not the Voltage. You want to supply 5A or something to the battery. That means 5A have to flow through the divider. This will never happen even remotely. You can ask your buddy GPT to calculate Current but it will be better for You if you do it yourself, this will give you understanding of Ohm's law.

[Silver_Is_Money]

Seems you missed that I asked to calculate the Current through the divider, not the Voltage. You want to supply 5A or something to the battery. That means 5A have to flow through the divider. This will never happen even remotely. You can ask your buddy GPT to calculate Current but it will be better for You if you do it yourself, this will give you understanding of Ohm's law.

I just watched a video in which a guy disconnected the blue wire after first getting his HP laptop to charge, and while it was actively charging, and the battery continued to charge to full.  But the laptop would not initiate charging with the blue wire removed.  Perhaps the voltage signal from the blue wire is only required whereby to initiate charging. 

In this video the guy made a circuit much like the one I drew above, but where I have a 350 Ohm resistor he placed a 200 KOhm resistor, and where I placed a 10 KOhm resistor he placed a 100 nf capacitor.  Is that a better solution?

Edit:  Adding the video.

[IanB]

Seems you missed that I asked to calculate the Current through the divider, not the Voltage. You want to supply 5A or something to the battery. That means 5A have to flow through the divider. This will never happen even remotely. You can ask your buddy GPT to calculate Current but it will be better for You if you do it yourself, this will give you understanding of Ohm's law.

Not at all. There are no indications that the blue wire has to supply charging current to the battery. It is a signal wire, and probably has to source a few µA at most. In fact, if you look at the connector pin inside the plug, it is very small and thin.

[Solder_Junkie]

Having spent a couple of hours searching the web, the Dell 3rd wire in the charger lead is a data comms wire between the laptop and an IC in the charger. The purpose is to identify the charger, although the cynical side of me suspects it is to discourage the use of 3rd party adapters... I don't know about HP, but suspect it works in a similar manner.

Before I try it, does anyone know if using just a 2 wire connection powers the laptop but doesn't charge the battery? If so, it could be useful as charging with a generic adapter may not be needed when powering from 12V.

FWIW, speaking with Dell Support, they seem to know very little about powering some models of their laptops from a 12 Volt "auto" adapter, even though they sell adapters...

SJ