How does the computer works without battery ?

Hello everyone,
I was always wondring how our laptop works when the battery is off and the laptop is plugged into the charger.

I mean how the electricity works in that case, it checks if the battery is connected to the laptop, if it is then it takes the power from it otherwise it take it directly from the AC power.

I wanna know where this check combined and where does it happen ? at "Windows code" or "hardware code" ?
By hardware code I mean if the hardware itself got some chip who check this case.

I'm really interested about this thing and would love to hear from you.

Thanks alot,
Elias.

 

Its on the hardware or near hardware ACPI/BIOS level. It doesn't "check" if you unplug it, it just knows ahead of time what to do.
Batteries also have internal circuitry which the laptop does check every time the battery is used.

Why do you want to know about this?

 

It happens in hardware and the behavior can't be modified by software. It will always draw power from the AC adapter when available, then draw from battery if it can. The hardware that controls this will send plugged/unplugged statuses events via ACPI like another poster mentioned, and you operating system (i.e. Windows) can decide to shutdown if battery levels are low and it was just unplugged, or slow down components that it can to draw less power like the CPU and lower screen brightness.

 

Thanks alot guys for the fast reply, well i was thinking to modify a few things.
I'am a software engineer and i was thinking to add another part to my laptop incase my battery is low and just simply checking if the battery is low so my laptop take his power from the new part that i added.

Thats why i was asking where does this happen the " checking thing ".

So do you think its possible ? and what kind of things i need to know to make it happen ? i mean do i need to know how the hardware works in my laptop works ? and is it even possiable ?

I love these things and i think that i can do eveything just all i need a little help to make it done.

I would love to hear more from you guys, once again thanks for the replies.

 

This is an electrical engineering problem, not software. An easy solution to getting more battery life is putting it before or in the ac adapter. A UPS is pre-made solution to the problem

 

perfect answer

talking about this ac/battery thing, i just wonder why don't those smart phones work the same way. they always draw power from the battery even though it is plugged in for charging. making it impossible to use them as a wifi hotspot 24/7 as the drain rate is faster than recharge rate.

 

get yourself more powerful adapter for your cellphone and you wont have that problem.

 

But a UPS at 120v must be far less efficient than something at 20v...

 

The USB 2.0 spec calls for 5v 500mA or 2.5W total. A 'charging' USB port where no data is passing through can run at 5v and 1.5A for 7.5W total. Although I doubt that 5W extra would put a drain on a battery that's charging.