Solve : Question about power adapters, wattages, voltage and amps?

1.	Solve : Question about power adapters, wattages, voltage and amps?
Answer» I have a laptop that has two ratings: 18.5V/3.5 mA and 19.0V/4.74mA. This means the watts is 64.75 for the first rating and 90.06 for the second (P=IV) I have a charger that is rated 19.5V/3.34mA, which means the power supplied is 65.13W The wattage of the charger is close to that of the first rating of the laptop. Does that mean the charger will work? Or is it something to do with the voltage and amp rating? Also, how is it that the laptop can take both ratings of 64.75W and 90.06W? Some adapters have Auto-Switch for use in either the Americas or the rest of the world. They deliver more power on the 240 VAC mains. Quote from: shashgo on September 02, 2013, 10:42:37 AM I have a laptop that has two ratings: 18.5V/3.5 mA and 19.0V/4.74mA. This means the watts is 64.75 for the first rating and 90.06 for the second (P=IV) I have a charger that is rated 19.5V/3.34mA, which means the power supplied is 65.13W The wattage of the charger is close to that of the first rating of the laptop. Does that mean the charger will work? Or is it something to do with the voltage and amp rating? Also, how is it that the laptop can take both ratings of 64.75W and 90.06W? mA??? You mean A.What laptop is this? I've seen some take two DIFFERENT chargers, but usually only the amps rating will differ, not the voltage - a higher amp adapter will usually be used to charge the battery quicker, or to charge a secondary battery. Usually it's not a GREAT idea to use a charger supplying a different voltage. Amps are "pulled" so you can use a charger with as high an amperage as you like, the laptop will only pull what it's designed to. If you had a 4A charger and the laptop needed 3.5A, it would take 3.5A. Voltage is "PUSHED" so the laptop can't choose to only use, say, 19V from a 25V charger, it gets what the charger gives it. There's usually a little tolerance in the voltage it can take, somewhere around 5-10%. I wouldn't use a different voltage charger personally, I would only use a genuine charger of the correct rating. You may get away with it but for the sake of £10 for the right charger, I wouldn't bother.The OP said: Quote I have a laptop that has two ratings: 18.5V/3.5 mA and 19.0V/4.74mA. This means the watts is 64.75 for the first rating and 90.06 for the second (P=IV) It would help if the OP gave the name and model of the laptop. It is ODD tat the laptop would should have two ratings. It is not rare for a laptop to have a range of allowed charger ratings. Let me explain. The original design could be a battery pack between 10 to 14 volts. [1] The original pack could be a pack that is near 14 volts Later, a replacement pack, even from the manufacturer, may be enclose to 10 volts. Not unusual.. The motherboard has on BOARD switching mode regulators the give the right voltage to the system. Also, there are regulators that limit the charge to the battery pack. The best designs use 'smart' chartering systems where the charge is monitored to not overcharge the battery pack. [2] In any case, it is wise to consult the manufacturer of the laptop for the exact information. [1] footnote.Both Ni cad and Lithium ion cells are use in laptops. But the cells vary slightly in full voltage. The manufacture would anticipate the switch over to the preferred battery pack. Therefore the design is for a battery pack that is from 10 to 14 volts fully charged. [2] footnote. A switching regulator, unlike a liner regulator, does not waste power to achieve the right voltage. A m explanation of how a switching regulator works is beyond the scope of this topic. Just believe that it really does work.

Answer»

I have a laptop that has two ratings: 18.5V/3.5 mA and 19.0V/4.74mA. This means the watts is 64.75 for the first rating and 90.06 for the second (P=IV)

I have a charger that is rated 19.5V/3.34mA, which means the power supplied is 65.13W

The wattage of the charger is close to that of the first rating of the laptop. Does that mean the charger will work? Or is it something to do with the voltage and amp rating?

Also, how is it that the laptop can take both ratings of 64.75W and 90.06W?
Some adapters have Auto-Switch for use in either the Americas or the rest of the world. They deliver more power on the 240 VAC mains.
Quote from: shashgo on September 02, 2013, 10:42:37 AM

I have a laptop that has two ratings: 18.5V/3.5 mA and 19.0V/4.74mA. This means the watts is 64.75 for the first rating and 90.06 for the second (P=IV)

I have a charger that is rated 19.5V/3.34mA, which means the power supplied is 65.13W

The wattage of the charger is close to that of the first rating of the laptop. Does that mean the charger will work? Or is it something to do with the voltage and amp rating?

Also, how is it that the laptop can take both ratings of 64.75W and 90.06W?

mA??? You mean A.What laptop is this? I've seen some take two DIFFERENT chargers, but usually only the amps rating will differ, not the voltage - a higher amp adapter will usually be used to charge the battery quicker, or to charge a secondary battery.
Usually it's not a GREAT idea to use a charger supplying a different voltage. Amps are "pulled" so you can use a charger with as high an amperage as you like, the laptop will only pull what it's designed to. If you had a 4A charger and the laptop needed 3.5A, it would take 3.5A. Voltage is "PUSHED" so the laptop can't choose to only use, say, 19V from a 25V charger, it gets what the charger gives it.
There's usually a little tolerance in the voltage it can take, somewhere around 5-10%. I wouldn't use a different voltage charger personally, I would only use a genuine charger of the correct rating. You may get away with it but for the sake of £10 for the right charger, I wouldn't bother.The OP said:
Quote

I have a laptop that has two ratings: 18.5V/3.5 mA and 19.0V/4.74mA. This means the watts is 64.75 for the first rating and 90.06 for the second (P=IV)

It would help if the OP gave the name and model of the laptop. It is ODD tat the laptop would should have two ratings.

It is not rare for a laptop to have a range of allowed charger ratings. Let me explain. The original design could be a battery pack between 10 to 14 volts. [1] The original pack could be a pack that is near 14 volts Later, a replacement pack, even from the manufacturer, may be enclose to 10 volts. Not unusual.. The motherboard has on BOARD switching mode regulators the give the right voltage to the system.

Also, there are regulators that limit the charge to the battery pack. The best designs use 'smart' chartering systems where the charge is monitored to not overcharge the battery pack. [2] In any case, it is wise to consult the manufacturer of the laptop for the exact information.

[1] footnote.Both Ni cad and Lithium ion cells are use in laptops. But the cells vary slightly in full voltage. The manufacture would anticipate the switch over to the preferred battery pack. Therefore the design is for a battery pack that is from 10 to 14 volts fully charged.

[2] footnote. A switching regulator, unlike a liner regulator, does not waste power to achieve the right voltage. A m explanation of how a switching regulator works is beyond the scope of this topic. Just believe that it really does work.

Solve : Question about power adapters, wattages, voltage and amps?

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