does 65W charger help in performance?

Suvan

I have the non G variant of acer aspire a515-43. do you think getting a 65W charger will help? many 3500u laptops (cheaper than mine) ship with a 65W charger while mine comes with a 45W power adapter.however, the G variant of the laptop comes with a 65W power adapter.

Does the G variant have any performance(cpu) advantages over the non G variant?

aphanic

Correct answer, it may. It's not about the voltage, but about the amperage (current) that you're able to draw from the charger.

First of all, both chargers ought to output the same DC at the same voltage, or you have a risk of damaging your equipment (I think there's a 5-10% tolerance thing for that, but don't take it for granted). The difference is how much current they're able to output at a given time, a 45w power adapter at 19V is able to output up to 2.37A give or take (take into consideration that there are losses too).

A 65w adapter that also outputs at 19V is able to provide up to 3.42A. If your laptop (which is the one choosing how much current it wants, it's always the peripherals) requires asks for more than 2.37A the 45w adapter would be insufficient while the 65w would have a higher ceiling so to speak.

Performance improvement is debatable, because we enter the realm of throttling: thermal throttling if it gets too hot (it'd then draw less current), power limit and current limit throttling if the power regulators inside can't cope or aren't designed to run past a certain current threshold, etc.

In essence, there's much more to take into consideration than changing the power adapter, it may not make any difference at all, or it may do. The only way to know for sure would be to monitor how much it is being drawn by probing in between the adapter and the laptop with a power meter (hard) or doing it between the power adapter and its connection to the outlet and making calculations (much easier). Maybe even monitoring the laptop for those kinds of throttling if at all possible. That's why I didn't say it will, but it might, or it might now. Hard to tell.

PS. There's also efficiency to take care of regarding measuring things in the power outlet, because it's not the same if the charge is operating at half capacity than at 80% its capacity for example, it's a whole other world.

jai3

@aphanic If charger is labeled as 45W. So, what will be the minimum Watt power it can supply practically, considering all the losses..?? Want to know your opinion.

Suvan

@aphanic the tdp of the 3500u is 25 watts. is the 45W charger sufficient for it?

aphanic

Your question is easier to answer @jai3, a 45w power adapter is going to supply 45w at its rated voltage. The difference in efficiency comes at what it draws from the wall outlet (which is not always the same, depends on, at the very least, the temperature of the adapter but also its design).

I can try to explain it with phone chargers, because it's what I have at hand and what I can measure well both input and output. The device connected to the adapters is always the same and tolerances for the measurement off of the wall socket are +-0.1w for the sake of consistency, even if just a little haha.

Lets begin with an unbranded one:
 - Drawing 10w from the wall socket, it was outputting 1.72A at 5.02v, which is 8.63w. So its efficiency at that rate is 86.34%.
 - Drawing 6w from the wall socket, it was outputting 1.09A at 4.77v, so 5.20w, efficiency already fell to 74.27%.

You can see that at different loads (1.09 vs 1.72) and with great variation in output voltage (it was a crappy adapter anyway), it is better to use such an adapter with high requirements. You won't have 100% efficiency because there's always different kinds of losses, but it comes to show that the same adapter behaves differently at different loads.

Another one, branded this time:
 - Drawing 11w from the wall socket, it was outputting 1.82A at 5.08v, so 9.25w, efficicency at 84.05%.
 - Drawing 12.5w from the wall, it was outputting 1.82A at 5.94v (QC 3.0), which is 10.81w and its efficiency 86.49%.

Those are the typical efficiencies of well made adapters, here's another one, also branded (but different brand):
 - Drawing 12.5w, it was outputting 1.7A at 6.27v (QC 3.0), so 10.66w, efficiency of 85.27%.

And lastly one of those that came with a branded (branded different from the others, btw, in all of this examples is synonymous of reputable) phone, rated for 5v 1.5A max output:
 - Drawing 9.5w, it was outputting 1.58A at 5.25v, so 8.30w, efficiency of 87.32%.

And that's the price we sometimes pay for cheap electronics, cheap and unnamed adapters while they may work and be effective, they may not be very efficient. Think all that was in cold, as they get hot things change for the worse. In desktop power supplies there is a certification some brands go through for their products that guarantees a minimum of efficiency at different demands.

It is more important there because here we're talking about very low consumptions, but a 650w power supply may be drawing 780w from the line if it's not too good or 689w if it's top of the line. The difference comes out of our pockets in the long run as the electrical bill haha. If you wish to know more about that certification for desktop PSUs here you can see a table with data: https://en.wikipedia.org/wiki/80_Plus#Efficiency_level_certifications

aphanic

Suvan said:

@aphanic the tdp of the 3500u is 25 watts. is the 45W charger sufficient for it?

TDP is more complicated to explain, as far as I understand it it's not a measurement of how much a certain part is going to consume but rather how much heat the cooling system needs to be able to dissipate for it to operate effectively. That's why 7w TDP processors often come with just a bare piece of aluminium strapped to the motherboard (cheap... at least put some copper in there manufacturers.. tsk tsk), while 45w TDP parts require serious copper pipes with vapor chambers, fans and fins.

That out of the question, my guess is that the engineering team behind each laptop assessed how much energy it needed at a given point and gave a charger for that case accordingly. That's probably why we see 65+w adapters when dedicated graphics cards are present in the system, because overall they'd consume more, but it really varies.

For example, I'll try to keep it simpler this time, I have an A515-54G, because it has an MX250 onboard I was given a 65w power adapter. What happens if I add an HDD as a secondary drive? They could add 3 to 5w power consumption when rolling. What if what I add is a SATA SSD? Their consumption is generally lower, closer to those 3W but when in stressful situations, some more, some less, again many factors.

Or screens, what if I replaced the screen for another that consumed more? Or the various ones a same model mounts, because not all of the A515-54Gs come with the same panel and they consume a different amount of power. That's' why I think there's gotta be headroom included in the power adapter that we're given. Or it should be, in an ideal world, who knows, I never got to measure it.

It would be interesting (and I'll do it in a min and update this post) how much it'd draw from the wall when demanded as hell.

EDIT:

So, here are some data, although I wasn't taxing the laptop completely I gave it a good go (no 3D gaming though). The power rating (+-0.5w) is what the power adapter was drawing from the socket:

- Turned on, resting: 5w (no kidding, just started Windows and that's it).
- 1 USB 3.0 drive connected (2.5'' to suck the energy off of the USB port): 7.5w
- 2 drives connected, USB 3.0 and 2.5'': 9.5w
- 3 drives connected, USB 3.0 and 2.5'': 11.5w
Now:
- Intel XTU benchmarking with AVX2: 20-55.5w alternating and stabilizing in betweet at times.
- SANDRA's GPGPU Image processing benchmark: 39-45.5w
- Prime95, Small FFTs; 47-56w, sustained at around 53.5w sometimes.
- Cinebench R20: 15-52.5w, tougher when it had to render the fur obviously.

Max. transient peak measured was 62.5w.

During all of the testing the laptop was current, power and thermal throttling at one point or another (= less performance to avoid excessive heat or damage to components). And now that's mostly resting, just me with a browser typing things (and the 3 disks still connected) it's at 13.5w.

All of that is drawn from the wall socket, with losses because of efficiency means the laptop was actually consuming at its peak around 53.13w, assuming an efficiency of 85%. Given that the power adapter is capable of delivering up to 65w, I'd say it was a good match. So the same could be applicable to computers that ship with 45w adapters.

Ahhhh in all of these tests I took the battery out to measure the power consumption of the machine itself, it the battery were connected as it usually is the consumption could be higher if it also needed to be charged. I felt like that detail was worthy of mentioning too.

jai3

aphanic said:

Your question is easier to answer @jai3, a 45w power adapter is going to supply 45w at its rated voltage. The difference in efficiency comes at what it draws from the wall outlet (which is not always the same, depends on, at the very least, the temperature of the adapter but also its design).

I can try to explain it with phone chargers, because it's what I have at hand and what I can measure well both input and output. The device connected to the adapters is always the same and tolerances for the measurement off of the wall socket are +-0.1w for the sake of consistency, even if just a little haha.

Lets begin with an unbranded one:
 - Drawing 10w from the wall socket, it was outputting 1.72A at 5.02v, which is 8.63w. So its efficiency at that rate is 86.34%.
 - Drawing 6w from the wall socket, it was outputting 1.09A at 4.77v, so 5.20w, efficiency already fell to 74.27%.

You can see that at different loads (1.09 vs 1.72) and with great variation in output voltage (it was a crappy adapter anyway), it is better to use such an adapter with high requirements. You won't have 100% efficiency because there's always different kinds of losses, but it comes to show that the same adapter behaves differently at different loads.

Another one, branded this time:
 - Drawing 11w from the wall socket, it was outputting 1.82A at 5.08v, so 9.25w, efficicency at 84.05%.
 - Drawing 12.5w from the wall, it was outputting 1.82A at 5.94v (QC 3.0), which is 10.81w and its efficiency 86.49%.

Those are the typical efficiencies of well made adapters, here's another one, also branded (but different brand):
 - Drawing 12.5w, it was outputting 1.7A at 6.27v (QC 3.0), so 10.66w, efficiency of 85.27%.

And lastly one of those that came with a branded (branded different from the others, btw, in all of this examples is synonymous of reputable) phone, rated for 5v 1.5A max output:
 - Drawing 9.5w, it was outputting 1.58A at 5.25v, so 8.30w, efficiency of 87.32%.

And that's the price we sometimes pay for cheap electronics, cheap and unnamed adapters while they may work and be effective, they may not be very efficient. Think all that was in cold, as they get hot things change for the worse. In desktop power supplies there is a certification some brands go through for their products that guarantees a minimum of efficiency at different demands.

It is more important there because here we're talking about very low consumptions, but a 650w power supply may be drawing 780w from the line if it's not too good or 689w if it's top of the line. The difference comes out of our pockets in the long run as the electrical bill haha. If you wish to know more about that certification for desktop PSUs here you can see a table with data: https://en.wikipedia.org/wiki/80_Plus#Efficiency_level_certifications

 
aphanic WoW..very nice explanation. Thank you for all your efforts