Which Port identifies battery charger?

Thread Starter

kiruthikar

Joined Dec 4, 2010
2
When I plug in the charger to the laptop, what is the means of communication between the laptop and the battery, i,e, what signal is generated when a charger is plugged in and where is it generated. How does the laptop know that a charger has been plugged in and allows battery charging? How to get control of that point
 

mik3

Joined Feb 4, 2008
4,843
It might sense the output voltage of the charger or it can be a simple microswitch which is activated by the charger plug.
 

shortbus

Joined Sep 30, 2009
10,045
Isn't the battery charger voltage slightly higher than the battery voltage? Just like in a car, the alternator voltage has to be higher than the battery to charge it. The alternator would just be substituted for the charger in the laptop situation.
 

tom66

Joined May 9, 2009
2,595
Isn't the battery charger voltage slightly higher than the battery voltage? Just like in a car, the alternator voltage has to be higher than the battery to charge it. The alternator would just be substituted for the charger in the laptop situation.
Usually much higher. You can build smaller switchmode converters if they operate on higher voltages. E.g. my laptop has a 19.5V power supply but only an 11.1V battery. Charging is managed probably through a buck (step-down) converter, unlike in a car, where voltage is just supplied from the alternator. If you tried the same trick with Li-Ion or Li-Po you would get a sizeable explosion. :eek:
 

shortbus

Joined Sep 30, 2009
10,045
tom66 - I was just using the car as a analogy. The laptop will just sense the higher charger voltage, no switches or other sensors like the other posters were saying.
 

t06afre

Joined May 11, 2009
5,934
Most modern Laptop chargers also have some sort of digital communication with the PC. In most cases the PC will not chrage the battery unless the correct power supply is plugged in.
 

thatoneguy

Joined Feb 19, 2009
6,359
Most modern Laptop chargers also have some sort of digital communication with the PC. In most cases the PC will not chrage the battery unless the correct power supply is plugged in.
Newer notebooks will pop up a message stating "Unauthorized Charger" or "Use xxxx Brand chargers only". There isn't a way to easily add that into a non<brand> charger.
 

Kermit2

Joined Feb 5, 2010
4,162
I haven't meet a battery yet, that I couldn't charge with the proper size alligator clips and my trusty CVCC power supply.

Doing it for a one off is all fine and dandy, but if you need to charge up everyday... spend the money and get the proper charger.
 

steinar96

Joined Apr 18, 2009
239
Laptops normally use batteries made from lithium ion cells which require constant monitoring to have any lifespan at all. This is usually done via a battery managment system which monitors each cell indivitually in a "pack" of cells which the battery is made of. In a laptop i would assume that the BMS system is a perihperal part of the computer and hence able to communicate with the rest of the system. Such as alerting when the BMS system is about to cut power off to preserve the batteries or when they are being charged.
 
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