Performance on battery is a disaster

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MacBook Air 13" Retina 2019

Repair information and guides for the minor refresh of the Late 2018 MacBook Air, with the same model number (A1932) and EMC number (3184). This model features a True Tone display and a slightly revised battery.

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btherieau @btherieau

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Posted: 2 days agoAug 31, 2026

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Performance on battery is a disaster

Howdy friends. This problem feels like it's a new one. I installed the iFixit replacement battery for this 2019 Intel Macbook Air not too long ago and for a little while, the results were amazing. Nearly all-day battery life, perfectly fine performance while untethered, and I couldn't have been happier.
Now, under Sonoma 14.8.9, the machine runs like garbage on battery, with 'kernel_task' freaking out and stealing the CPU. Once I plug back in, it's fine.
(I've reset NVRAM and PRAM and reinstalled macOS).

Any thoughts about this? It's really weird behavior and I'm leaning towards the idea that battery temp sensors are reporting back correctly, but who knows?

I ran CoconutBattery on and off the charger and I can't see too much difference. The temperatures are pretty high, but I don't know how I'd fix that. See?

Answer this question I have this problem too

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2 Answers

Theo Grefalda @user5136121 Rep: 716 14 5 3 · Answer 1 · 2026-09-02T14:41:56-07:00

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Theo Grefalda @user5136121

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Posted: 18 hours agoSep 2, 2026

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I think that this is a normal operating temperature, based off of my screenshot (Although not a 2019 MacBook Air):

(And yes, I am well aware of the battery life. Yes, I will replace it, no I don't have the battery with me, and no, I do not need the link for the battery.)

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Thanks Theo! I really appreciate the help and I'm glad I can tick that off the list.

16 hours agoSep 2, 2026 by btherieau

@user5136121 - As batteries age they do tend to get warmer under charge. What happens I the charge power is not being stored instead it's turned into heat. Just be careful as the battery cells will puff up and can rupture which you don't want.

13 hours agoSep 2, 2026 by DanJ

@danj 👍, although it showed the same battery temp with my 2012 Unibody MBP that had a "lightly" used (200+ cycles), so I would still assume that this is the optimal operating temperature.

12 hours agoSep 2, 2026 by Theo Grefalda

@user5136121 - Well... Cycles do count, but it's not the only factor, as age is the other! As the chemistry breaks down over time.

Many things we enjoy have limits, like bread. We won't eat a moldy slice would we😣 a batteries lifespan is about 4~5 years.

1 hour agoSep 3, 2026 by DanJ

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DanJ @danj Rep: 502.2k Self employed contract worker 35 346 977 · Answer 2 · 2026-08-31T19:40:28-07:00

DanJ @danj

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Posted: 2 days agoAug 31, 2026

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Let's see what the battery and SMC tell us. Install this gem of an App CoconutBattery to gather the battery and SMC data in a screen snapshot of the Apps Main window. Here we need two snapshots one while the charger is connected and a second when on battery alone. Post both images here for us to see.

I'm thinking SMC is having a problem. I'm not sure is this is a software or firmware issue.

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Sounds great. I’ll try t and check in with results.

2 days agoAug 31, 2026 by btherieau

@btherieau - Well. The temp is a bit high but that could be coming from the CPU. The battery looks healthy otherwise!

How much free storage does your NAND Flash have? I thinking your issue is not enough free space for the OS to run given what you are running.

13 hours agoSep 2, 2026 by DanJ

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