Which Port identifies battery charger?

Discussion in 'General Electronics Chat' started by kiruthikar, Dec 4, 2010.

  1. kiruthikar

    Thread Starter New Member

    Dec 4, 2010
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    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
     
  2. mik3

    Senior Member

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

    AAC Fanatic!

    Oct 29, 2009
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    Probably the level because the OS can usually tell you the battery is getting low.
     
  4. mik3

    Senior Member

    Feb 4, 2008
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    This does not require the charger to be plugged in the laptop. It monitors the voltage across the battery.
     
  5. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Duh! Guess I am not thinking. :)

    But the laptop still knows when the battery is being charged.
     
  6. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    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.
     
  7. tom66

    Senior Member

    May 9, 2009
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    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:
     
  8. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    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.
     
  9. t06afre

    AAC Fanatic!

    May 11, 2009
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    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.
     
  10. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    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.
     
  11. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    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.
     
  12. steinar96

    Active Member

    Apr 18, 2009
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    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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