Higher wattage chargers

Discussion in 'MacBook' started by retailacc, Mar 7, 2018.

  1. retailacc macrumors member

    retailacc

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    #1
    So I am reeding that this is acceptable (like using the 61W USBC included with 13" MBPs). I asked Apple to be sure, and this is what they said. Thoughts?

    Screen Shot 2018-03-07 at 2.54.58 AM.png Screen Shot 2018-03-07 at 2.56.11 AM.png

    Thanks!
     
  2. sergeyz macrumors member

    sergeyz

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    #2
    I would agree with them. Using lower wattage chargers is definitely normal, higher - not so good as far as I know
     
  3. Hyuga macrumors regular

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    #3
    It doesn't matter what usb-c charger you use, it will always take only what it needs.

    If you connect 87W charger to MacBook, it will only take 30W out of it. Thats why there is handshake in usb-c pd protocol.

    --- Post Merged, Mar 7, 2018 ---
    I got myself MacBook from development side, put it to my 87W charger, and it gives following information:

    AC Charger Information:



    Connected: Yes

    ID: 0x1656

    Wattage (W): 30

    Serial Number:

    Name: 87W USB-C Power Adapter

    Manufacturer: Apple Inc.

    Hardware Version: 1,0

    Firmware Version: 1070068

    Charging: Yes


     
  4. Mike Boreham, Mar 7, 2018
    Last edited: Mar 7, 2018

    Mike Boreham macrumors 68000

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    #4

    Absolutely! I use my 12" MacBook with an 87 W charger all the time, having confirmed with Apple Support.

    It's the same as plugging a 1 amp device into a 13 amp wall socket (UK) ....the device only draws as much current as it needs.

    Although I was very confident it was OK, I felt the need to check with Apple Support because the 87W MBP charger charges my MacBook at 20V, while the supplied 29W MB charger charges at 15V, but both are 30W. Some battery packs charge at 20V and some at 15V. Apple basically say that as long as the battery/charger is USB-PD compliant it is OK. See this thread.

    The Apple support Document on the subject is a bit ambivalent, because they recommend using the right charger for the laptop, but also say it is fine to use a higher wattage one:

    "Power adapters for Mac notebooks are available in 29W, 45W, 60W, 61W, 85W, and 87W varieties. You should use the appropriate wattage power adapter for your Mac notebook. You can use a compatible higher wattage adapter without issue, but it won't make your computer charge faster or operate differently. Lower wattage adapters don't provide enough power."
     
  5. sergeyz macrumors member

    sergeyz

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    #5
    Thank you guys for the information, I did not know that.
     
  6. maerz001 macrumors 65816

    maerz001

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    #6
    This was always possible to do. Even before usbc. MagSafe is interchangeable and the USBa chargers from iPad for iPhone and vice versa
     
  7. iPodClassic1 macrumors member

    iPodClassic1

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    #7

    Thanks, this is what I needed to know. I have a Maxstorm charger, and I was using the power charge port, but someone recommended me to use the 1A port instead, and I noticed my battery hasn't degraded that much.
     
  8. retailacc thread starter macrumors member

    retailacc

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    #8
    this goes against what's being said on this thread.
    --- Post Merged, Mar 18, 2018 ---
    So I connected my 61W USB C charger, and system information reports a charging wattage of 53W... Not 30 like some users here report.

    Any thoughts?
     
  9. Mike Boreham macrumors 68000

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    #9
    When I reported that my MacBook charges at 30W with my 87W MBP charger I was measuring voltage and current with a Satechi USB meter, not looking in System Information. I am away from home so can't plug in to the the 87W charger to see what System Information reports at present.

    Whatever SI says I am confident that the physics of the situation, plus Apple's KB article are correct, and that it is quite OK to use a higher wattage compatible charger.
     
  10. iPodClassic1 macrumors member

    iPodClassic1

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    #10
    And why is that?
     
  11. Mike Boreham, Mar 18, 2018
    Last edited: Mar 18, 2018

    Mike Boreham macrumors 68000

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    #11
    The second sentence of the Apple document I quoted in post #4 basically says compatible higher wattage adapters can be used without issue, but lower wattage adapters don't provide enough power.

    That document and this thread are about MacBooks not iPhones/iPods (which I suspect you might be referring to since you mention 1A ports, and because of your username). But the same is true. It is OK to use a 10W or 12W iPad charger on an iPhone which is supplied with a 5W charger. Apple supports this, and sell the 12W charger as compatible with all iDevices.

    The difference between phones and computers is that Apple decided from the iPhone 6 onwards that it would allow the phone to accept more current from a higher rated charger (as explained here), so a higher rated charger will charge more quickly. On MacBooks the 87W, 61W and 29W chargers all charge the 12" MacBook at the same rate.
     
  12. Maxx Power macrumors 6502a

    Maxx Power

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    #12
    I think there are two topics discussed here and they are being muddled a bit. When it comes to modern smart phones, a lot of them support some form of quick charge. This type of charging uses higher power to quickly charge the battery. However, as the battery charges, it dissipates heat. Fast charging means more heat dissipated. As phones have very little surface area to dissipate the heat and battery packs take up a large volume inside the devices, charging-related heat is a big concern to the longevity of the batteries. If you google around a bit, you'll see a lot of user reports of fast charging or quick charging doing detrimental things to the longevity of their batteries. Instead of referencing a bunch of anecdotal user reports, see two excerpts from various sources below about fast charging and wireless charging, both regarding heat output and battery health.

    "Wireless charging can be incredibly convenient if your phone can do it, but it's not without its disadvantages. The inductive, wireless chargers out there today have this nasty habit of generating a fair bit of waste heat. And while wasted energy is just a bummer in general, that heat will also toast your battery in the process. That's no bueno. It's a little less convenient, but standard plug-in charging is going to keep your battery in better shape, especially if you're some place warm to begin with." from https://gizmodo.com/how-to-take-care-of-your-smartphone-battery-the-right-w-513217256

    "Regular charging using a standard 5V 2A ( conventional charger ) should be preferred mode with fast charging resorted to when actually needed." from https://android.stackexchange.com/questions/138597/fast-charging-by-qualcomm-3-0-impact-on-battery

    This is topic (1). Obviously for this topic, using lower power chargers that limit the current output while staying at the appropriate voltage(s) lengthens battery life.

    Topic (2) that appears to be discussed at here involves the rate of charge of a laptop-class device using various chargers. Most laptops have yet to jump on the bandwagon of fast/quick charging. I believe quite a few of Apple's modern laptops already feature some form of quick charging. What's different about laptop-class devices as compared to phones is that the size of the battery occupies a much smaller volume fraction inside the device, that due to active cooling (e.g., fans), the batteries do not heat up nearly as much and the other major heat-producing parts (e.g., CPU) are located typically much further away from the batteries. Hence, heat-related degradation of laptop batteries as compared to that of phone batteries is much less of a concern, at least for now. In practice, on most laptops, you can use a power adapter above or below the OEM specifications of the laptop, provided that the voltage is close to the range accepted by laptops (Apple's laptops for example, can accept anywhere from about 14.5 volts to about 20 volts in the MagSafe days and any MagSafe laptop can accept any voltage in that range to charge, only the rate will be different and under load, you may actually drain the battery in some cases).

    So in my opinion, the smaller devices like phones and so on, do benefit from slower charging. The larger devices like laptops generally do not, or the effect is so small that it is negligible. In the future, this may well change as demand for quick charging in laptops due to increases in battery power density and integration pushes the designs up against the engineering envelope.
     
  13. Mike Boreham macrumors 68000

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    #13
    I am back home now and my MacBook is connected to the 87W Apple USB-C charger normally supplied with the 15" MBP.

    The only place I can see a wattage mentioned in System Info is in the attached screenshot which confirms that the charger connected is the 87W Apple USB-C charger and the wattage is 86. The other screenshot is the Satechi meter showing 19.7V 1.39A = 27.5W. Coconut battery is showing charging with a net rate of 15W but of course the machine is in use. Without the charger Coconut shows discharging with 7W so the input rate to the battery is 22W. I don't know why the Satechi and Coconut disagree, but there is probably a good explanation and the numbers vary with time. Probably some of the current being supplied to the machine (Satechi) is going somewhere other than the battery (Coconut).

    Screen Shot 2018-03-19 at 12.57.31.png IMG_8793.jpg
     
  14. bdj33ranch macrumors regular

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    #14
    i used to have a white 13” MacBook (60W charger?). I bought an extra Apple charger for it but at a higher wattage (85w? it’s not with me as I write this) that was compatible with the 15” MBP at that time. When I upgraded to my current 15” rMBP (late 2013) a few years back I kept the 85W charger and bought the little adapter to convert it from “old” to “new” MagSafe connection. I’ve been using it (the old 85W charger) with my rMBP for over 4 years now with no problems.
     
  15. retailacc thread starter macrumors member

    retailacc

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    #15
    Excellent write up. Thanks for that, it clears up a lot of confusion in this thread.
     
  16. iPodClassic1 macrumors member

    iPodClassic1

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    #16

    Thanks for such detailed reply. However, I was meaning my Macbook 12. I charge it using the 5V 1A outlet from my Xtorm charger, and not 5V 3A/12V 1.25A outlet. I noticed that when I used the most powerful one, my battery degraded a bit. Using the 1A outlet showed no degradation.


    What I meant is, I'd rather my laptop not drawing enough current than drawing more than it's supposed to. I can't believe that these devices can 'limit' the amount of current received by it.

    It's like the old myth that you can leave a phone to charge constantly that once it charges the charger will stop the charge. I have had iPods and iPhones batteries super degraded because of this.
     
  17. bernuli macrumors 6502a

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    #17
    Using lower is not normal. Normal would be normal, but lower would be abnormal.

    If anything I think better to go with higher wattage.
     
  18. Mike Boreham, Mar 19, 2018
    Last edited: Mar 19, 2018

    Mike Boreham macrumors 68000

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    #18
    That's physics! Ohm's Law:

    Volts = Amps x Resistance

    or

    Current = Volts / Resistance

    Same physics that means you can plug an electric lamp into the same wall socket as an electric heater. The light bulb takes the current it wants and the heater takes the current it wants, according to their resistance. The wall socket doesn't try and push the heater current though the light bulb. Just as the 87W charger doesn't try and push 87W watts into the 12" MacBook, as confirmed by the data I gave.

    If you are using 5V and 1A you are charging at the rate of 5W. I mentioned earlier that the MacBook uses about 7W doing normal things. So if it is using 7W and being supplied with 5W it is discharging even while plugged in.
     
  19. Maxx Power, Mar 20, 2018
    Last edited: Mar 20, 2018

    Maxx Power macrumors 6502a

    Maxx Power

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    #19
    This is technically correct, but I want to point out that the devices like laptops and phones do not behave as resistors. There is a bunch of essentially buck converters and charge pumps that non-linearly regulate voltages and controller ICs that monitor the power distribution, for example to the battery. Nonetheless, your conclusion is still perfectly valid, because as far as the charger is concerned, it can't ramp up voltage to dump more current into these devices because (1), the voltages are fixed on the chargers and (2), the converters and charge pumps inside these devices will just resort to smaller duty cycles before the monitoring ICs shut them down entirely.

    In a similar manner as an example, although not technically identical, you'll notice that switching-type power supplies and adapters frequently have a wide 90 - 240 volts input voltage and these adapters offer the same output regardless of input. In other words, ramping up the input voltage on these non-linear devices does not cause the output to also rise, so there is in general no way to "push" more power through the output side by changing the input side. In fact, higher input voltages (to a point) on these kinds of devices actually increase the device's efficiency and lowers internal heat production. Typically power supplies for PCs run more efficient on 220 volts than 110 volts, for example. So in fact, increasing voltages on these types of devices significantly lowers the current draw, such that the total power consumed is equal to, or less than that at lower voltages.
     
  20. Mike Boreham macrumors 68000

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    #20
    I know I was oversimplyfying...I was trying to keep it simple!
     
  21. iPodClassic1 macrumors member

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    #21
    that's a very nice explanation. Though I personally don't believe that a lamp or a heater (artifacts that work based on turning electricity into some kind of heat/light energy), can be compared to a battery, that is supposed to store that energy.
     
  22. Maxx Power macrumors 6502a

    Maxx Power

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    #22
    You can think of a battery as having an "effective resistance" given its state of charge. Charging circuits for lithium-based batteries these days charge the battery in several stages, each stage has a certain characteristic in terms of current and voltage. See http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries. Pay particular attention to the graph that shows each stage of the charging process. You will see that in each stage, the relationship is still ohmic, but the effective resistance of the battery changes. In stage one, constant current stage, the resistance rises rapidly and the voltage must be increased to achieve the constant current charge. You can think of a battery and its charging circuit to behave like a spring, where the resistance increases as the battery saturates. Otherwise, the relationship between current and voltage is still ohmic but the resistance is now variable depending on the state of the battery's charge. My point here is that all charging circuits modulate current into the battery by controlling the voltage.

    The heater and lamp are also variable resistance. At low temperatures, the heating elements have lower resistance and at high temperatures, the resistance is much higher. This is actually why incandescent lamps usually die when you turn them on and not during usage. When you turn on these lamps cold, the inrush current is much greater than operating current and the weakest spot of the filament overheats and breaks, and you often get a bright flash.
     
  23. iPodClassic1 macrumors member

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    #23
    That was interesting, thank you for taking the time to explain it! I see what you mean now.
    So you say I should use the full blast port on my power brick instead the 1A ?
     
  24. Mike Boreham macrumors 68000

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    #24
    As I said earlier (post#18) if that is 5V 1A it will only charge the MacBook very slowly with it not in use, and not at all if the MacBook is being used.

    I am not a fan of third party chargers, and prefer using an Apple supplied one.
     
  25. iPodClassic1 macrumors member

    iPodClassic1

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    #25
    I'm not a fan of them either, but what am I supposed to do when my battery is reaching 50%? I don't want to let the battery fully die on me. I don't think that's good for it.

    This is the battery pack I have:
    [​IMG]


    I've been using the 5V 3A port at first, would charge really fast, but noticed that the battery would not last as usual. After switching to the 5V 1A, now the battery life seems more 'normal'. Given the year the laptop has been used.
     

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31 March 7, 2018