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If I take use a USB Type A to USB Type C cable, (like this) and plug it into a wall converter similar to the ones that come with iPhone charger (basically just a little box that plugs into a wall and has a female USB Type A port), will it be safe to plug the USB Type C end into my new MacBook pro to keep the battery from dying?

I just need it to maintain the battery level and I want to make sure it's not going to damage the overall life of the batter.

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Yes, and it is safe. I did charge my 15" MBP from various sources - power banks and adapters (USB Port of a Tesla Model S was my favorite), and it can take around 13W. Just make sure that your adapter supports 10-15W, 5W is quite slow. Unfortunately the port does not support Quick Charge.

When idling, the system consumes around 6W, charging will be impossible while using with something more cpu/gpu intensive.

And if you decide to cheat and try to connect a second charger, it will not combine the power, but instead choose the one with higher power rating.

TL;DR: It's possible. It's safe (It'll cause 100% use on your adapter, might heat it up). Perfect for emergency use or when weight is important. Not useful if you plan to do extensive work.

  • So it looks like if I go from a wall port like I described or from my Thunderbolt display I only get 5 Watts which is not enough to charge my laptop. Do you know if there is a way to get more juice? Is there some sort of USB hub that would increase the wattage to my macbook? – Abe Miessler Oct 24 '17 at 23:19
  • @AbeMiessler unfortunately no. To get more juice you have to use USB-PD (Power Delivery) and this means USB-C to USB-C. There are some combined adapters like "Anker PowerPort+ 5 Ports USB-C", but they're not worth the size. btw, current (2016-2017) MacBooks are very efficient and probably 13W + your battery should be enough to run a full workday. – mspasov Oct 24 '17 at 23:33
  • I just ordered one of these guys: amazon.com/dp/B00OQ19QYA I'll let you know how it does. – Abe Miessler Oct 24 '17 at 23:35
  • Hmm, I have a new idea. Xiaomi Type-C USB-C Power Adapter 45W (Great value for 20USD, comes with USB-C to USB-C cord too. Just check the this review) + USB-C HUB (For example Lenovo 7-in-1 USB-C, but cheaper/better options are available). This in theory should charge your MacBook and give you few USB ports (this hub is rated 900mA, cannot charge phones fast trough the USB 3.0 ports). – mspasov Oct 24 '17 at 23:53
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I'm able to charge my MacBook Pro with my Xiaomi power bank 10000mAh with QuickCharge 3 and it works perfectly! :)

  • 1
    Can you add some details on how this answers the question asked above? – nohillside Jun 16 '18 at 12:02
  • What was charge voltage\current? Or how much time it took to charge and what was initial mabook battery charge? – dir Jun 4 at 17:24
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I don't think that will work. According to Apple, power adapters for Intel-based Apple notebooks are available in 45W, 60W, and 85W varieties. Although you should always use the proper wattage adapter for your Apple notebook, you can use an adapter of a higher wattage without issue.

An iPhone charger delivers 5 Watts (5 volts at 1000 mA). A Retina iPad mini charger delivers 10 watts (5.1 volts at 2100 mA).

Not enough power to charge a MacBook Pro. Plus the new MacBooks have a much longer battery life than do the old ones. It is actually good for the battery to be allowed to fully discharge. It is not good practice to leave your MacBook Pro on AC power all the time. If you work where there is always AC power available, once a week, unplug the computer and let it run on the battery until it goes to sleep. If you are worried about losing work, just unplug the computer overnight.

It is not good to fully discharge the lipo battery in your laptop. Unlike the older ni-cd or ni-mh batteries, li-po cells should never be discharged completely or charged to above 80%iirc. While the battery is in these states the cell is stressed. The damage doesn't occur from leaving the battery on a charger for a long amount of time but from being kept at a capacity above or below it's ideal rating. You could trickle charge it all you want, if it never goes above 80% you would be doing your battery a service.

  • I never answered if it was safe. Yes, as the other answer states, it is safe. But it is like saying if I put my wet fingers across the terminals of a 9V battery, is it safe? Yeah, but why would you want to? Because in the scenario you describe it will charge so slowly as to be useless. And it won't charge at all if you are using the computer. So sure, in an emergency, if you need to charge and have absolutely no other way to charge and have a ton of time to wait, go for it. – NormG Oct 24 '17 at 4:53
  • Your advice sounds like the advice for very old NiCd or NiMH batteries which laptops haven't used for years. It's very bad for lithium batteries to be fully discharged at any time. Usually a battery pack will shut of protectively well before zero. It is also bad to leave them 100% charged for long periods. Li-ion batteries give the longest life if used between 20% and 80% and should not be left at 100% for long periods. My Samsung laptop offers a power management option to limit battery charging to 80% for maximum life when used mostly on charger. It is 8 years old and still has pretty much fu – Alex Apr 14 '18 at 9:07

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