Laptop chargers, How do they work ? Is the power supplied constant or variable depending upon the load created by the system

[Dr_Dissection]

My story in short. My laptop is broken and the repair person has "fixed it", It boots but he told me that I would have to replace the battery and the keyboard as the power key is broken but I think It's all crap. As a Student, I can't afford the first party repair, So I am thinking of running it straight from the wall. I would love any explanation how laptop chargers/ power supplies exactly work 

thank you

[Latvian Video]

I havent tested, but im assuming the voltage just is constant

[Zando_]

Same as any other power supply, they supply whatever power the device on the other end asks for, up to their wattage/current limits. You can run a laptop off only wall power fine, plenty of people do it with old machines that have dead/missing batteries, and I've regularly done it when troubleshooting laptops. 

[AbydosOne]

5 minutes ago, Dr_Dissection said:

Is the power supplied constant or variable depending upon the load created by the system

Voltage is constant (with margin of error); current is variable based on need; power = voltage × current.

[Latvian Video]

2 minutes ago, Zando_ said:

Same as any other power supply, they supply whatever power the device on the other end asks for, up to their wattage/current limits. You can run a laptop off only wall power fine, plenty of people do it with old machines that have dead/missing batteries, and I've regularly done it when troubleshooting laptops. 

I used to run my old laptop without a battery just fine, also tested my new laptop without one, as it drains the battery under heavy load

[OhYou_]

Voltage is not constant, it depends on the load. 
Voltage should remain within spec if the charger is sized for the load you put on it. It is something you dont really have to worry about, but just for informational purpose, something like a type-c charger at 1w is 20v and 100w is probably close to 17v. This is due to voltage drop across the cable, and power supply inefficiency. 

Laptop power draw is highly dependent on: battery cond, battery temp, battery SoC, and the laptop power draw itself.
Since the battery is out of the picture, the laptop power draw will be a bit less than its rating. 
In my general experience, most laptop chargers have at least 35W of overhead so they can charge while under load.

I'm not sure what your goals are, but if it is to run the laptop on it's original charger without a battery, it *should* be perfectly fine. 
If your goal is to run it on a lower wattage power supply, I guess one about 35w less would be a starting point.  

[peoples21Champ]

4 hours ago, Dr_Dissection said:

My story in short. My laptop is broken and the repair person has "fixed it", It boots but he told me that I would have to replace the battery and the keyboard as the power key is broken but I think It's all crap. As a Student, I can't afford the first party repair, So I am thinking of running it straight from the wall. I would love any explanation how laptop chargers/ power supplies exactly work 

thank you

I run my gigabyte areo 16 xe4 from the wall since March 2022 no issues can't use it unplugged as battery life isn't there 3hrs max if im lucky what i get for owning a laptop that likes to consume energy

Had the original charger or something go out causing it not to turn on requiring warranty) did buy a new charger from Amazon with the same specs still didn't work. That was back in November 2022 still have it plugged in even when its turned off or standby.

 

 

 

[E-waste]

On 1/24/2023 at 4:52 PM, peoples21Champ said:

battery life isn't there 3hrs max

This is actually really good!  No, it's not the 10 - 18 hours like a tablet but there are things you can do to improve this:

 

Go ahead and buy a replacement battwry, and treat it well!

 

Note: For unknown reasons, the ideal range for li-ion batteries is 40 to 60%.  Elon Musk (sells batteries etc) in 2008 on jay leno's garage shared this bit of information and it's quite interesting.

 

In windows advanced power settings, set minimum CPU level to 0% when on battery and set maximum cpu level to somewhere like 75%.

 

Set the "critical" battery level to 30% or even 40% and set the machine to sleep.  More on sleep timers shortly.

 

Set the low battery level to 45% and try to start charging soon.  You can choose "nothing" as the action but still allow the notification.

 

For charging, it seems you can't set a critical or "low" charging level to alert you when you reach a certain charge level like 80%.

 

So let's say your laptop goes to sleep, well there is a timer setting for when to eventually shutdown but save what's in sleep mode.  This is hibernate.  After maybe an hour or two seems reasonale

 

There is also "hybrid sleep" which is confusing, as it does both at the same time: ram standby and before power down to normal standby, it saves the ram to disk.  You can quickly resume without full startup again but when does the machine fully powr down?  I guess it uses the hibernate timers still, but I'm not sure.

 

iPhones since day ONE prevent the user from booting the device if turned off until it has 15% charge.  Recently Apple added a feature to stop charging at 80% unless ypu're using it, so it stops overnight.  Also for just $69 you get a battery replacement.