Battery Life

The iPhone XS comes with a 2658mAh/10.13Wh battery, while the XS Max has a capacity of 3174mAh/12.08Wh. Again, it’s to be noted that although both phones are quite large form-factor devices by now, Apple’s battery density still largely lags behind the competition. While yes, it’s true that the XS Max’ battery is the biggest that Apple has ever used, it still pales in comparison to the 3500 to 4000mAh that other vendors now employ in the same form-factor.

As we saw in the SPEC analysis, the one advantage that Apple has is an enormous lead in terms of power efficiency of its SoC, which largely makes up for any gap in the battery capacity deficit.

Our web browsing test is a mixed-to-heavy workload that iterates through a set of popular webpages that are hosted on our server. The test loads a web page, pauses, scrolls through it, pauses, and then continues to the next in the set, repeating all over when done. Brightness is fixed at 200cd/m².

Web Browsing Battery Life 2016 (WiFi)

The iPhone XS saw a very slight degradation compared to the iPhone X in our test. The 19 minute deficit isn’t terrible, but it does come at a surprise given that Apple had promised improved battery life for the new model. What’s happening is that likely our test is a tad heavier in its workload than what Apple and many other vendors internally test to advertise as the daily battery life of their devices.

The iPhone XS Max came in at 10.3h. Again while this is still good, it’s a degradation over the 11.83h of the iPhone 8 Plus. Here it’s easier to rationalise the difference; the OLED screen of the XS Max is just more power hungry and also has a larger area than the iPhone 8 Plus. Here the increased battery capacity isn’t enough to counteract the panel’s increased needs.

As to why the iPhone XS saw a degradation over the X, I’m not too sure. I did rerun the test on the iPhone X to make sure iOS12 hadn’t impacted the devices – and I got a runtime just 10 minutes lower than what I had tested on the iPhone X back around in January, so the iOS upgrade certainly doesn’t seem to have affected the battery life.

It should be relatively safe to assume that the new A12 should be more efficient in its workloads, even with the increased performance that it brings. One thing that we can’t really verify is the power efficiency at intermediate performance states, as that’s also where CPUs perform a lot of their work at.

We also have to keep in mind the connectivity factor: the new iPhone’s seems to sport a new Broadcom BCM4377 WiFi combo chip which we don’t know much about. Most importantly the new XS have also switched over from a Qualcomm baseband (in our test unit of the iPhone X) to a new Intel XMM7560 baseband.

I’ve generally given up on LTE testing after a few years ago I had run into some serious issues regarding a misconfiguration of my mobile carriers’ baseband stations as they did not have CDRX enabled. This caused an almost 20-30% battery life degradation on Huawei’s devices – and if I hadn’t debugged the issue with HiSilicon I’d probably be none the wiser. Fact is, cellular battery life testing is a lot harder than one would think, and without having a controlled environment, I’m very hesitant to resume cellular battery life testing.

That being said, I will revisit the iPhone X vs iPhone XS battery life topic while on LTE over the weekend and post an update to the review.

Overall, the battery life of the iPhone XS and XS Max are good – they don’t quite reach Apple’s claimed improvements, but that also just might be something that will vary from use-case to use-case.

Display Measurement & Power Camera - Daylight Evaluation: Zoom and Scenic


View All Comments

  • Andrei Frumusanu - Friday, October 5, 2018 - link

    Hello all,

    This article is still fresh off the presses - I'm sure there's still typos/grammar to be fixed in the coming hours.

    Just a general note; this is my first iPhone review, and hopefully it makes up for AnandTech not having a review of the iPhone 8's/X last year. Unfortunately that happened in a time when there was no mobile editor with the site anymore, and I only rejoined after a few months after that.

    As always, feel free to reach out in the comments or per emails.
  • OMGitsShan - Friday, October 5, 2018 - link

    As always, this is the iPhone review to wait for! Thank you Andrei Reply
  • versesuvius - Friday, October 5, 2018 - link

    Potato. Reply
  • Jetcat3 - Friday, October 5, 2018 - link

    Wonderful review Andrei! Just a few minor quibbles for the capacities of each li-ion battery.

    Xs is 2658 mAh
    Xs Max is 3174 mAh

    Keep up the good work!
  • wicasapa - Friday, October 5, 2018 - link

    one thing was not clear in the display section ... the Xs display (OLED) uses more power on a black screen compared to 8's LCD at the same brightness?!! this doesn't sound right! or is this power draw attributable to something else (face detection sensors, etc.)? Reply
  • Andrei Frumusanu - Saturday, October 6, 2018 - link

    No, that's accurate. It's part of why the new phones regress in battery over the LCD iPhones. Reply
  • DERSS - Saturday, October 6, 2018 - link

    You asked about the display's matrix controlling logic. It was found out through patent research that Apple has developed LTPO TFT Technology for that, however it is so far is confirmed to only used in the displays LG Display makes for Apple Watch. For smartphone OLEDs Apple has older simpler technology designed for the transistor layer as these big OLEDs are already super pricy anyway. And additional manufacturers like LG Display where Apple has started to implement manufacturing of iPhone XS/Max displays only has very few Tokki Canon equipment sets so they can not really low the manufacturing pricing down. (And Apple can not move to a different equipment as it has designed iPhone X/XS/Max displays only for Tokki Canon equipment). Reply
  • wicasapa - Saturday, October 6, 2018 - link

    I understand the regression on the battery test you run, it is basically browsing the web, which is by and large a white background and generally above the 60-65% threshold for the crossover of efficiency between OLEDs and LCDs. it actually makes sense for OLEDs to be less efficient in web browsing-based battery tests. however, I was surprised that you measured less efficiency on a pure black screen! Reply
  • Andrei Frumusanu - Sunday, October 7, 2018 - link

    Actually the web test is varied, I have a few lower APL sites and even some black ones. Reply
  • tipoo - Sunday, October 14, 2018 - link

    Common misconception - OLEDS don't just turn off fully for pure blacks, it takes active power to create a black. When they're off they're a murky grey. Reply

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