65w vs. 90w power cords

I have a Dell Inspiron 1420 laptop (my personal laptop) that specifies a 65w power cord. I also have a Dell D620 laptop (my work laptop) that has a 90w power cord.

I want an extra power cord to run with either of these laptops. Which should I buy? I don't want to damage either of them, if that's what will happen by using the wrong power cord.

 

Well, the W is the most output the power cord supports.

If - and only if - the voltages are the same are they interchangeable and you can use the 90W one - if the voltage is lower on one, you need two dedicated power cords.

(assuming the plug is the same)

 

Thanks Detlev. Plugs are the same. The input and output voltages listed on the back for both of the cords are identical.

If this is the case, is there a better choice between the 65 and the 90?

 

Well, in this case the only difference is the maximum power draw both adapters support.

So if you use the 65W adapter and your laptop tries to draw 70W the adapter would most likely burn out.

If you use the 90W adapter it can draw anything up to 90W.

So I'd say get the 90W one

Edit:
Only Output voltage is important Input should be the same, its what comes out of your socket

 

Thank you so much for the input! And the education

 

You're welcome

Just some basic physics.

Volts * Amps = Watt
V * A = W

You can control voltage, but can't control Amps - R = V/A (hope I got that one the right way round - its been a while) - Resistance = Volts / Ampere

So the lower your resistance the higher your Ampere (that's the way it should be) - and the higher your resistance the lower your Ampere (provided the voltage is constant)

 

My laptop(see sig) can use power adapters of a lower wattage, but the computer realizes this and will draw less power, sometimes this means the computer cannot recharge the battery. Since your laptops are also Dells, the case might be the same.

 

if you use a lower wattage than intended, the laptop may seem fine

but when you try to increase the power(by stressing your CPU/GPU etc), you may go higher than the wattage by the adapter, and burn it out or have a BSOD

my laptop, dell m1330, comes with a 65W or a 90W adapter.... all depends whether you get the discrete graphics card or integrated graphics

 

Just get the highest one if your PSU's have common connections / voltage, unless you're concerned about travelling weight. The laptop will only draw what it needs. Problems will only occur if the laptop can't draw enough power - and this may happen with an underspecified PSU.

 

With Dell adapters, you won't "burn out" the adapter running two with same voltages, but different wattage ratings. However what your laptop may say is "insufficient power adapter in use". You would then run into issues trying to charge a battery while using your laptop at the same time. I've seen this happen with a 65W and say the larger 800-series Latitudes or their desktop replacement machines. I've also seen this happen with older third-party universal adapters.

However specifically with the equipment you have: I'm almost CERTAIN you can run the D620 with a 65W adapter. I own a D600 and have access to a D630 @ work and both run with the lower rated adapter without problems. They also both have discrete graphics. Check the voltage on both adapters first, but I'm almost certain one is the PA-12 and the other the PA-10 and the voltages are the same. If so, it should be safe to try the 65W adapter on your Latitude. If it doesn't complain, you should be fine with the 65W purchase.

Chances are your company dishes out 90W adapters instead because while the plug is the same on D-series docking stations, they require 90W adapters. They are probably trying to avoid confusion/mistakes for this potential issue.

The 65W has the advantage in that it's physically smaller and thus more portable.

On second thought, your D620 will actually say on the bottom on one of the stickers the Amperage rating. It will also say PA-10 or PA-12 or both. If it says you can use PA-12 (the 65W adapter), for certain you will be safe with the smaller unit.

 

The 90W one will be bigger, heavier, and more expensive, but you'll be able to charge the laptop more quickly while using it. With the 65W, the laptop will use most of the power for its operation, so there won't be much left for charging while it's being used.

 

This is something I'm not sure about with Dell's power adapters.
They have 65watt and 90watt. I was using a 90W on a dell D610(which normally uses a 65watt adapter) and the D610 got really hot.. With the D610's original 65watt adapter it ran at a normal temperature...

^Before that happened, I always thought that you could use the 90watt on any Dell laptop and if you used a 65watt adapter on a laptop that used 90watts, the laptop would just have less power.