Why is the full charge capacity for the battery on my new MBA less than the full design capacity?

Question

Level 1

10 points

Why is the full charge capacity for the battery on my new MBA less than the full design capacity?

I purchased my MBA from the Apple store one month ago. On first use coconut battery showed 1 cycle already passed and the charge capacity at only 98.7% of the design capacity. Today, the fully charged battery shows at 97.8% of design value.

When fully charged the battery capacity shows as 4283 mAh. This is also the fully charged capacity as shown under System Report/Power. However, the design capacity is stated as 4381 mAh.

Why would the full charge capacity of a battery on a new MBA be less than 100%? Is this because the battery was apparently over 100 days old on purchase (according to coconut battery)? If so, do I have the right to return it to the store and ask for a replacement?

MacBook Air 13", macOS 10.15

Posted on Jan 2, 2020 11:29 AM

Reply

Answer 1

dominic23

Level 10

84,018 points

Jan 2, 2020 1:11 PM in response to dalea23

https://support.apple.com/en-us/HT204054

Reply

Answer 2

dominic23

Level 10

84,018 points

Jan 3, 2020 4:23 AM in response to dalea23

I setup a brand new MBP about 10 days ago.

coconutBattery readings ware inconsistent at best.

I let the Mac run on battery until the charge dropped to about 50 percent.

Recharged it to 100%

Now coconutBattery readings show every reading as normal.

Try running the Mac on battery couple of times until the charge drops below 50% mark.

Recharge it to 100%.

Then test.

Reply

Answer 3

babowa

Level 9

78,562 points

Jan 2, 2020 3:06 PM in response to dalea23

You can take it to Apple and ask, but I wouldn't worry about 1 - 1.5%. And no, they would not exchange the device for that, they may give you another battery which may or may not display 100%. The slow process wearing down begins immediately, so for how long do you expect to see 100%? Mine has been sitting at 98% full for about a year.

Reply

Answer 4

y_p_w

Level 6

17,762 points

Jan 4, 2020 10:22 AM in response to dalea23

It can go up and down, I'm thinking with temperature. My wife's was reporting around 96% when nearly new but goes from 98 to 99% now. The other issue is that there can be normal manufacturing variations in the capacity of a new battery.

Reply

Answer 5

dalea23 Author

Level 1

10 points

Jan 3, 2020 2:10 AM in response to babowa

Thanks for this - it's helpful to know that another user has experienced something similar and that it does stabilise. I had thought that 1.3 % was a substantial drop in a relatively short amount of time. If it kept on dropping at that rate ...

I may call in at an Apple store and ask someone to check it over just to get their feedback. But from what you say I don't need to worry too much.

Reply

Answer 6

dalea23 Author

Level 1

10 points

Jan 2, 2020 2:41 PM in response to dominic23

Thanks. I've read that page before and am familiar with it. It doesn't really help in answering my particular question.

Reply

Answer 7

dalea23 Author

Level 1

10 points

Jan 4, 2020 2:57 AM in response to dominic23

Okay will try this. I've already done this once - run it to 45% of full battery charge and then recharged to 100% - but it had no effect on the CB readings. Will try a couple more times.

Reply

Why is the full charge capacity for the battery on my new MBA less than the full design capacity?

Similar questions