0

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.

migrated from electronics.stackexchange.com Nov 7 '17 at 23:51

This question came from our site for electronics and electrical engineering professionals, students, and enthusiasts.

3

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.

  • 1
    This is why a (m)Ah rating can be deceptive. Compare (m)**W**h instead if possible. – DoxyLover Nov 7 '17 at 18:36
1

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.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.