Using a less heavy power adapter for the 15’’ 2018 MBP?

asiga

macrumors 6502a
Original poster
Nov 4, 2012
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The move from being used to carrying a MBA, to carry now a new 15’’ 2018 MBA is not being as smooth as I thought: I notice the weight difference in my bag.

The fact is that the MBP is a bit heavier, but I noticed the power adapter is much heavier than the MBA one, and I have the feeling that it’s the culprit for making the weight difference really noticeable.

Do you know if I could use a less heavy alternative for getting my bag lighter?

Thanks!
 

leman

macrumors G4
Oct 14, 2008
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You can use a lower wattage adapter, it will simply charge your laptop slower. It also might not be able to provide enough power if you do heavy work on your machine.
 

asiga

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Original poster
Nov 4, 2012
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You can use a lower wattage adapter, it will simply charge your laptop slower. It also might not be able to provide enough power if you do heavy work on your machine.
The main purpose would be not for charging, but for using it plugged, so it doesn't matter if it charges slowly.

Anyway, my main goal is not reducing the wattage, but the weight (of course they are very related, but if some brand provides a 87W power adapter certified for the 2018 15'' MBP, and with a weight similar to the MBA adapter it would be fine).

From my own measures:

Weight of my old MBA: 1335 gr
Weight of my new 15'' MBP: 1818gr
Weight of the MBA power adapter: 200gr
Weight of the 15'' MBP power adapter: 365gr

So, the weight difference for the laptops only is 483gr.

But taking into consideration the power adapters also, the weight difference becomes 648gr. (1818+365-1335-200=648).

I'm really noticing the difference of 648gr... if I could find a power adaptor certified for the 15'' MBP but with the same weight as the MBA one, the difference would go down to 483gr, which, although far from ideal, would be much more reasonable.
 

leman

macrumors G4
Oct 14, 2008
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Yeah, the weight is definitely noticeable. What I mean with “charging slower” is, if you are using your laptop for heavy duty work (e.g. encoding videos or the like) it’s possible that the power supply won’t be able to supply enough juice, leading to battery discharge while plugged. Then again, I’ve been using a 60W charger via a usb-c display with my 15” for more than a year and I never had a problem, even when running full-core simulations for hours.

The MBA charger might be a bit too weak though. How much is it, 30Watt? For the 15”, I’d recommend a 13” power adapter at least.
 

asiga

macrumors 6502a
Original poster
Nov 4, 2012
807
997
Yeah, the weight is definitely noticeable. What I mean with “charging slower” is, if you are using your laptop for heavy duty work (e.g. encoding videos or the like) it’s possible that the power supply won’t be able to supply enough juice, leading to battery discharge while plugged. Then again, I’ve been using a 60W charger via a usb-c display with my 15” for more than a year and I never had a problem, even when running full-core simulations for hours.

The MBA charger might be a bit too weak though. How much is it, 30Watt? For the 15”, I’d recommend a 13” power adapter at least.
The MBA adapter is 45W. I just found that this page claims that the author uses a 45W power adapter for a 15inch MBP on a daily basis. The adapter announced at that page is this, and it weights even less than my MBA adapter... at the pictures in the Amazon page they even show a picture with a TouchaBar 15'' MBP...

Maybe it could work...
 

leman

macrumors G4
Oct 14, 2008
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Maybe it could work...
You can try :) I don't know the company so I can't comment on the quality. The only thing to be vary about is the fact that that adapter won't be able to provide enough power if you are doing anything intensive on your laptop. But for simple office-type work it should be enough.
 

asiga

macrumors 6502a
Original poster
Nov 4, 2012
807
997
You'll get used to it.
It's a matter of my back: I don't have an injury, but I can feel it stressed after a whole day carrying my bag. The MBA weight was perfect, but Apple preferred to make its bezels slimmer instead of keeping the same size with a larger screen, thus my choice of the 15''MBP. If things continue like this, we'll see a 14'' iPad before a 14'' MBA/rMB.

Back to the point, I think I can reduce all the weights in my bag to the maximum, and get a total weight just about 300gr more than when I carried the MBA. But the power supply is a key component here...
 

Ma2k5

macrumors 68020
Dec 21, 2012
2,186
2,073
London
It's a matter of my back: I don't have an injury, but I can feel it stressed after a whole day carrying my bag. The MBA weight was perfect, but Apple preferred to make its bezels slimmer instead of keeping the same size with a larger screen, thus my choice of the 15''MBP. If things continue like this, we'll see a 14'' iPad before a 14'' MBA/rMB.

Back to the point, I think I can reduce all the weights in my bag to the maximum, and get a total weight just about 300gr more than when I carried the MBA. But the power supply is a key component here...
I mean even though the 15" is heavier, compared to the past it is still significantly lighter than what we used to carry around before - which is what I meant by you'll get used to it. I don't think there is any health concerns from this increase at all and I would prefer to get used to it than use weird solutions like alternative power supplies.

I don't know where you are taking your laptop, but what about either

a) Not taking the power supply, the laptop has great "all day" battery life
b) If you are always going to the same place (work/school) when traveling, keep a spare adapter there
 

AvengerNX08

macrumors member
Nov 21, 2015
87
16
Germany
I have the exact opposite question: What would happen if you used a 100watts charger and a 100 watts pd cable with the newest MBP? Charge faster only? Or improve performance (by supplying more energy to CPU/GPU?
 
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Falhófnir

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Aug 19, 2017
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I think I remember reading you can use a higher rated charger for a smaller laptop (MBP charger for MBA) but not the other way round. I don't know if this is because of the charger not being able to actually power the laptop under load, or if there is a danger of damaging the charger or the computer
 

jlc1978

macrumors 68020
Aug 14, 2009
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I have the exact opposite question: What would happen if you used a 100watts charger and a 100 watts pd cable with the newest MBP? Charge faster only? Or improve performance (by supplying more energy to CPU/GPU?
No impact; the MBP will only draw its maximum design power, so it won't charge any faster or give it extra power.
 

Tensakun

macrumors 6502
Jan 21, 2008
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Akashi, Japan
The MBA adapter is 45W. I just found that this page claims that the author uses a 45W power adapter for a 15inch MBP on a daily basis. The adapter announced at that page is this, and it weights even less than my MBA adapter... at the pictures in the Amazon page they even show a picture with a TouchaBar 15'' MBP...

Maybe it could work...
THIS seems to be the working Amazon link to this product.

Can anyone vouch for either the reviewing website or the manufacturer? As someone north of 60 who packs his Mac for hours every day, I'd love to carry something so light and small as a road charger. But risk wrecking a roughly $3k machine? Jeez, I dunno...
 

Trey M

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Jul 25, 2011
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If it's for infrequent use you can certainly use a low-power adapter, heck I've even used my 29W USB-C adapter to charge my 15'' MBP a few times since it was all I had.

I would advise against using a lower-power adapter on the regular since it will take a toll on your battery's overall health. The battery will have to work harder to stay charged which in turn will create more load cycles on the battery over time. Again I would only be concerned about this if the low power adapter will be used multiple times in a week.

I have the same problem, I hate the 87W adapter, but to be honest with USB-C being as finicky as it is, I wouldn't trust another power adapter with my 3 grand + machine. The cons outweigh the pros and there's a surprisingly limited number of reputable manufacturers that produce USB-C adapters at 87+ watts.
 
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AppleHaterLover

macrumors 68000
Jun 15, 2018
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OP, I'm sure you can find 600g worth of stuff you don't need to have in your bag all the time. Then throw it away. I did this with my stuff and now my laptop bag is much lighter.

Or you could get another bag that's lighter. Or work out some more so 600g isn't an isue.

What you shouldn't do, as Trey M pointed out, is long-term risk the battery on your $2500 laptop to save a few grams on your short hop to and from work.
 

SDColorado

Contributor
Nov 6, 2011
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Highlands Ranch, CO
Another thought....

You didn’t mention what backpack you are using, but you may find that you can shave as much weight difference as exists between the 87W charger and a smaller one by finding a lighter backpack. That would maybe allow you to carry the standard charger still.
 

jlc1978

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Aug 14, 2009
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My 13 charges faster with my 15” adapter
Interesting. How much faster?

MR reported no improvement with a higher wattages:

On my MacBook, the standard 29W charger charged it to 62 percent over the course of an hour, which is the exact same result I got with the 45W charger, so there's also no benefit using 45W over 29W/30W with a MacBook.

It appears there are dimisnihning returns with higher power chargers for Apple devices.

https://www.macrumors.com/review/ravpower-45w-usb-c-power-adapter/
 

jlc1978

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Aug 14, 2009
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asiga

macrumors 6502a
Original poster
Nov 4, 2012
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I have the same problem, I hate the 87W adapter, but to be honest with USB-C being as finicky as it is, I wouldn't trust another power adapter with my 3 grand + machine. The cons outweigh the pros and there's a surprisingly limited number of reputable manufacturers that produce USB-C adapters at 87+ watts.
Yeah, exactly the same conclusion that I arrived to: First, there are no reputable brands producing 87W adapters at this moment. Second, this 2018 MBP was expensive (just a bit below 4000€), and I don't like the risk of reducing its life.

However, if at some point a reputable brand releases a 87W adapter and it's considerably lighter than the Apple one, I'd try it out.
[doublepost=1543498255][/doublepost]
OP, I'm sure you can find 600g worth of stuff you don't need to have in your bag all the time. Then throw it away. I did this with my stuff and now my laptop bag is much lighter.

Or you could get another bag that's lighter. Or work out some more so 600g isn't an issue.
Yes, I got it to the limit: My bag was already very light (just 250 grams!!), but I found an even lighter one (200gr). I'm saving just 50gr in the bag, but every gram counts. I also got rid of more stuff I never use (the ethernet adapter and cable, for example).

At this moment I believe my bag weights the same as when I carried my MBA with the bag full with other things. Not bad, but it could be better if some reputable brand offers a lighter 87W adapter.
 
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robvas

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Mar 29, 2009
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How do you calculate the time scale to compare the two? All I see is a graph that shows current charge rates for 12 hours but no scaling.

I would be intersting to see the current draws for various sized power supplies. 9to5Mac had an interesting article a whule back:

https://9to5mac.com/2018/09/25/60w-usb-c-charger-good-for-all-macbooks/
Do you see the shaded green area? That’s the unit charging.

The line starts out with the small charger then I switched to the bigger one and it starts charging way faster (steeper line)
 

jlc1978

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Aug 14, 2009
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Do you see the shaded green area? That’s the unit charging.

The line starts out with the small charger then I switched to the bigger one and it starts charging way faster (steeper line)
Thanks. I did not know you switched chargers. I wonder if Apple uses the same power control circuittry in 13 and 15" MBP so that both have the same max draw but since a 13" doesn't need as much wattage normally they ship a smaller wattage adapter?

It would be interesting to see some actual tests under controlled conditions to see the impact of various power supply wattages.

Anecdotally, I have seen no significant difference between my 15 charger and lower wattage Macally; but I have no hard data to say what is the actual difference.
 
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Trey M

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Jul 25, 2011
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USA
Thanks. I did not know you switched chargers. I wonder if Apple uses the same power control circuittry in 13 and 15" MBP so that both have the same max draw but since a 13" doesn't need as much wattage normally they ship a smaller wattage adapter?

It would be interesting to see some actual tests under controlled conditions to see the impact of various power supply wattages.

Anecdotally, I have seen no significant difference between my 15 charger and lower wattage Anker; but I have no hard data to say what is the actual difference.
A lot of workflows on the 15 inch MBP will be fine using lower-power adapters. It's just once you get the fans running using more intense applications, or a lot of applications simultaneously, that you'll notice a more significant difference in the battery uptime/recharge rate.