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I would like the freedom to power my laptop from an external battery to avoid very frequent cycling between 100% and 90% (say 2 or 3 times a day) due to my unique work/travel habits.

I've never bought an external battery large enough for a laptop; so I have no experience using them. Googling finds plenty of material on units that can recharge a laptop, but I am not sure if they recharge a laptop running at full power, say doing a numerical calculation while watching YouTube via USB hotlinking to 4G with my iPhone which is also being recharged via USB.

Of course the above scenario is the worst case, but it could conceivably happen on a long train ride after a busy day.

I am often moving around a lot and even on public transportation and simply can not plug in to mains power as frequently as I would like.

  • MacBook Air (Retina, 13-inch, 2020)
  • 1.1 GHz Quad-Core Intel Core i5
  • Intel Iris Plus Graphics 1536 MB
  • macOS 10.15.7
  • iPhone SE-2
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  • 3
    Sounds like you need to test it for yourself.
    – Solar Mike
    Jan 22 at 6:51
  • @SolarMike No, it does not sound like that. Are you certain nobody in this community can answer nor can can anyone find one? I think there is enough information out there to formulate a reasonable answer, especially if the answer turns out to be “no” or “I do this and it works”. Your comment seems spurious, uninformed and unhelpful to me, what is the value in posting it?
    – uhoh
    Jan 22 at 7:28
  • 2
    You would need to enable the WiFi hotspot on your phone then (which of course needs more power). But ok, if you want to use the hotspot via USB, then plug it into the MB :-)
    – nohillside
    Jan 22 at 14:56
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    So, 12V battery, 24V battery, 48V battery or 96 V battery? then will you be using an inverter to provide mains (230V Ac or 110V AC) to the "standard" charger or will you provide Dc directly to the mac?
    – Solar Mike
    Jan 22 at 20:04
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    @solarmike Let’s assume the OP is talking about powerbanks here :-)
    – nohillside
    Jan 23 at 7:17

1 Answer 1

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What will tell you if a power bank is capable of charging your laptop under load is how much power it can provide vs. power the laptop consumes. How do you know how much power your laptop consumes? The size of the power supply that came with the laptop should give some idea as Apple will size the power supply to the power demands of the laptop.

How can you know how much power a power bank can provide? You will have to look closely at the specifications. If you are lucky then the manufacturer will spell that out clearly for you. If you can't find that spelled out for you then you can do some math on the specs you can find. Volts times amps equals watts. If you can find volts and amps then you can get power.

It also helps to keep in mind the USB-C specs on power delivery as that will at least provide a sanity check on the numbers you get. USB Power Delivery 3.0 is limited to 100 watts, 20 volts at 5 amps, so most power banks will not exceed that. USB Power Delivery 3.1 is still quite new but if you do happen to find a power bank that meets this spec then it is possible to see the power bank supply up to 240 watts.

Another rule to keep in mind about USB Power Deliver is that it does not allow for more current than 5 amps. If some power and voltage combination adds up to more than 5 amps then check your numbers, there's likely an error somewhere.

Given the growth in power consumption of laptops lately it is quite possible you won't find a power bank that is powerful enough for your needs, the market just hasn't had enough time to catch up. Good luck though.

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  • Thank you for your answer! So in principle my MacBook Air (Retina, 13-inch, 2020) will happily run from a battery as long as it can deliver sufficient power and perhaps is recognized by Apple as a suitable product? The laptop queries each USB device connected, including power sources, and it will know that it's a battery and not a wall plug converter. I just want to confirm that my laptop won't say "No thank you, I can charge from you while asleep but I won't accept power from you right now because I'm doing a critical task" or similar.
    – uhoh
    Jan 23 at 0:54
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    I don't know if an Apple laptop knows or cares if the supply that is plugged is a battery or supply connected to mains. USB-PD has a means to negotiate voltage and keep current draw within certain bounds. As far as I know Apple laptops will not change their behavior on drawing power based on being powered up, asleep, or powered off. Whether the laptop charges or not is dependent on if the power in is greater than power consumed. Even if a power bank cannot provide enough power to charge it can still extend use time by lowering rate of power drawn from the internal battery.
    – MacGuffin
    Jan 23 at 1:04
  • I see, as long as they can negotiate successfully, perhaps "batteryness" is a non-issue.
    – uhoh
    Jan 23 at 1:06

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