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Power Adapter Spec Question


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5 replies to this topic

#1 ikonoqlast

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Posted 12 October 2017 - 02:01 PM

I need a new power adapter for my laptop.  The original specs say 19v, 45w, 1.74a.  For a replacement do I need those exact specs? Or, if there is wiggle room, where and how much?  I have seen more 65w and 90w adapters than 45.  One 65w adapter I saw did specifically say 'compatible with 45w'.  

 

Also, for various reasons I can't get mail, so I need to buy an adapter in-store.  Amazon, ebay, and any sort of delivery are out.  All the big box stores (WalMart, BestBuy, etc) I have checked have adapters, but not for in store pick-up, let alone in stock in store.  Are there any smaller retailers in Phoenix, specifically Paradise Valley area, that sell this stuff?

 

I will have a great deal of trouble and expense getting a manufacturer part and I can't actually afford it, 



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#2 Kilroy

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Posted 12 October 2017 - 02:06 PM

No, it doesn't have to match exactly.  I'd look for a Targus adapter at Best Buy or Walmart as those are normally stocked locally.



#3 oklahsam

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Posted 12 October 2017 - 02:35 PM

It does need to be 19v. for the amps, you want it to be at least what the original adapter was.

 

The 45W is simply 19v x 1.74a. So for a 65W adapter, you would need a 19v, 3.42a adapter.

 

You can go lower on the amperage, but you might run into situations where it's not enough power to charge it at the same rate, if at all.



#4 mjd420nova

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Posted 12 October 2017 - 03:17 PM

No mention of the model number or manufacturer so a universal adapter may not work.  Some units are actually two supplies, one to run the unit and the other to charge the battery, notably some DELL units.  The higher wattage rating just means it will supply more current at the stated voltage, no harm there.



#5 oklahsam

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Posted 12 October 2017 - 03:53 PM

Right. My point was more that just because it says the right wattage, doesn't mean it will work. Voltage is the last MOST important to get right.

 

Edit: Yeah, typed that out real quick on my phone and didn't notice the error.


Edited by oklahsam, 12 October 2017 - 05:47 PM.


#6 Chris Cosgrove

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Posted 12 October 2017 - 05:44 PM

I think there is a typing error in your last post #5.

 

The voltage is the most important figure, with the power rating second. 19 or 19.5 V will be completely acceptable, if you go below 19V you risk not charging the laptop, if you go significantly above 19.5V you risk overloading it.

 

If, as your original specs say, 45W then a 45W or 65W charger would be entirely suitable. Watts are simply Volts x Amps and so long as you don't exceed the specified voltage by more than 5 or 10% - more than 10% is a 'significant' amount - then you should have no problems. Without getting too technical about it it is the voltage that generates current into any given load, not Watts or Amps.

 

Chris Cosgrove






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