I have a 2016 13 in Macbook pro. I did some research and the design capacity of the battery is 5550 mAh. I purchased a 26800 mAh RAVPower external USB-C power bank to charge my laptop. I specifically got this one because it has a really high capacity and is 30W, which is enough to charge a MBP. I use it whenever I'm not near an outlet. It works fine, except it takes the whole battery to charge my laptop once. I don't know a whole lot about batteries and I assume there would be some power loss charging the internal battery from the esternal, but the battery is 4.8 times the capacity of my internal laptop battery.

The only reason I can think that it would eat through this much battery is it thinks its connected to wall power and it does not use power as efficiently? Is this a software issue, a hardware issue, can you compare batteries just based off of mAh?

The latptop is a 2016 13 in Macbook Pro with touchbar. It has a 2.9 GHz Core i5. Here is the battery I am using.


Not sure about the 2016 one, but the 2012 macbook pro battery is ~11V. Assuming that your battery is also 11V, that means it contains 5.550*11=61.05Wh of energy. Your ravpower power bank probably (read: definitely) uses li-ion batteries, which are typically quoted at 3.7V (which is their nominal voltage). This means they contain 3.7*26.8=99.16Wh. In theory this should be enough to charge your macbook 1.5x, but the capacity is probably less than 26800, and the conversion is not 100% efficient, etc etc.

Macbooks also use li-ion, but in a different configuration, giving rise to a different terminal voltage.

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    This is why a (m)Ah rating can be deceptive. Compare (m)**W**h instead if possible. – DoxyLover Nov 7 '17 at 18:36

This is a 18650 8-cell design, as the Amazon picture shows. enter image description here

They claim to use Panasonic cells. Panasonic 18650 cells don't have capacity much above 3000 mAh, no Li-Ion can do better than that. Therefore the overall "RAVPower" battery capacity can't be better than 3.6*8*3 = 86 Wh.

Battery conversion to Type-C voltage is likely 80% efficient,, say 85%, and the Macbook has also losses when charging its 60 Wh battery (61 Wh per BeB00 calculations). Therefore we have 86*0.85*0.85 = 62 Wh delivered, which is barely enough to charge the MBP once, or exactly as you did observe.

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