Laptop Chargers

Batteries
1

Hi All,

I have a weird question, or maybe not. I should know the answer, but just want to make sure my brain does not work overtime over a stupid question, hence I’m posting it here.

Can you charge a 19v laptop with a 20V source? (I’ve test a 19.5V, and it works)
I know that all the laptops have a DC-DC converter, but I’m not sure what the limits are for those DC-DC converters.

Reason - You do get PD power banks that have a 9V,12v and 20V output to enable fast charge.
so i want to enable the 20v to charge the laptop, IE, ups for the laptop.
I’m already using the 9v/12v to keep some routers running.
But can the 20v charge a 19V laptop?

Thanks in advance for all the great answers.

2

It should work, but getting it wrong is expensive, and there isn’t really any way to know ahead of time.

I would get the 20V (or maybe 24V somewhere) and pass it through a cheap buck converter, those 3A ones.

Other option is to Google for a “USB-C adapter charger” for your model laptop. You get a bunch of them that have USB-C and the specific charger plug for your device. Something like https://www.amazon.com/Cablecc-Adapter-Emulator-Trigger-4-01-3mm/dp/B07W5M54PV

Not really sure if it’s that much less risky than sticking 20V straight in though. :slight_smile:

3

There is a 99.9% chance that it will work. I have looked at many laptop schematics, and all the components on the input side can handle quite a bit more than 20V on every single schematic.

I would not recommend using a buck converter, those cheap ones are usually not well designed, and not always even stable under all conditions.

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4

So i am looking at one of those typeC to laptop chargers. All they do is to trigger the 20v on the supporting powerbanks.
They don’t really do anything other than enabling the 20v. Im using the 12v to do the routers.

5

thank you.
The Powerbanks gives the 5/9/12/20v, the cable only triggers it.

You will find the 20v mostly on the 30w and larger powerbanks.

I guesting the Powerbanks are useing a buck/boost converter,
as the batteries are 3.7V.

6

If the laptop charger is a dumb charger that has no “third line” signal to show the laptop that it is an approved charger, you can simply add a standard 1N4001 diode to the DC source output, as the diode has an 1.1v forward voltage, so your 20v output drops to 18.9v.

1N4001 to 4007 diode.pdf (169.8 KB)

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7

Adding a 1A diode here might not be the best plan…

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8

Mmmm, also true …

9

This is the first check you need to do…
If it isn’t then power the laptop from your 20V supply directly. (The laptop converts this to the array of voltages it requires)
It’s not impossible that the PC manufacturer has built in a voltage check but not on such a small voltage difference. I’ve come across this with a WiFi unit: It wants 12V op die kop (believe it or not)

10

I’d go with a 1N5407 (3-ampere). But people need to keep in mind… they get hot at higher current levels. You can put two in parallel, it works well enough.

On the topic of the 1N4001. Has anyone actually seen one in real life? I’ve only ever seen the 1N4007… it seems the cost difference is so small that people don’t bother with the lower voltage options and everyone just uses the common-as-weeds 4007.

Edit: A good source of old slightly-used 1N4007 diodes… every darn LED light bulb that blows has at least 4 of them :slight_smile:

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11

Well then, try your power bank with 20V selected…
The problem with power banks is that their batteries are LiPo cells wired in parallel and they use a boost converter to convert to higher voltages. This isn’t a problem with a USB supply (5V) recharging a cellphone.
However with a laptop you’re dealing with way more battery capacity at a much higher voltage.
You would be better starting off with a higher voltage… :space_invader:

12

What I have done when my laptop battery was flat (during a power outage) is using a 12V and 6V SLA battery connected in series. The 6V batteries are not common. I bought a couple of these years ago and they are still going: Cartronic Sealed Lead Acid Battery 6 Volt 12 Amp WP12-6 – Carter Direct South Africa
Not the most elegant solution but it worked for hours…