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Released September 21, 2018. Models: A1921, A2101, A2102, and A2104 / Available as GSM or CDMA / eSIM or nano-SIM / 64, 256, or 512 GB / Silver, Gold, or Space Gray (Pronounced "iPhone 10 S Max.")

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The iPhone XS Max often restarts, sometimes in an endless loop.

The iPhone XS Max often restarts, sometimes in an endless loop.

My phone frequently restarts, for instance, it suddenly restarts while I'm using it. After the restart, the battery level is at 10%. This 10% lasts a long time, even though it's based on the charge level after reboot. Sometimes, the restart results in a normal battery level, while other times it's at 10%, and this 10% remains constant. Below is my restart analysis report, hoping someone can provide an explanation.

Here's the restart analysis report for reference: 

{"bug_type":"210","timestamp":"2023-08-12 23:17:59.00 +0800","os_version":"iPhone OS 16.6 (20G75)","roots_installed":0,"incident_id":"D3F44D40-AA84-4DC1-9E9A-1B1F78F31C2F"}
{
  "build" : "iPhone OS 16.6 (20G75)",
  "product" : "iPhone11,6",
  "socId" : "8020",
  "socRevision" : "11",
  "incident" : "D3F44D40-AA84-4DC1-9E9A-1B1F78F31C2F",
  "crashReporterKey" : "0fb9d45f15bc9d0139f8c3f0ef4762bce241074d",
  "kernel" : "Darwin Kernel Version 22.6.0: Wed Jun 28 20:51:42 PDT 2023; root:xnu-8796.142.1~1\/RELEASE_ARM64_T8020",
  "date" : "2023-08-12 23:17:59.77 +0800",
  "panicString" : "panic(cpu 0 caller 0xfffffff02c5e536c): SMC PANIC - ASSERT: smc\/bms\/battery.cpp\n - BMSTask(4)\nASSERT: smc\/bms\/battery.cpp\n\nRTKit: RTKit-2062.142.1.release - Client: AppleSMCFirmware-3424.140.21.0.4.iphone11-imola.REL\n!UUID: b7a3fa21-7489-3aeb-a83d-057e7f95e7ae\nTime: 0x00000005e120f4bb\n\nFaulting task   4 Call Stack: 0x000000000002bfd0 0x000000000002b9a0 0x000000000002b7b0 0x000000000002d860 0x00000000000173b8 0x000000000001ee28 000000000000000000\n\nChinook ASC Async error info: \nl2c_err_sts 0x10001bfc00000000, l2c_err_adr 000000000000000000, l2c_err_inf 000000000000000000\nlsu_err_sts 000000000000000000, fed_err_sts 000000000000000000, mmu_err_sts 000000000000000000\ndpc_err_sts 000000000000000000\n\nMailbox (0): (0)\n  Inbox  AKF_KIC_INBOX_CTRL = 0x00020001, AKF_KIC_MAILBOX_SET = 0x11111101\n  Outbox AKF_AP_OUTBOX_CTRL = 0x00020001, AKF_AP_MAILBOX_SET  = 0x00000000\n\n    dir   endpoint      timestamp           msg\n    ====  ============  ==================  ==================\n    [RX]        user01  0x00000005e0012a94  0x544730420000c013\n    [TX]        user01  0x00000005e001303c  0x000000000000c000\n    [RX]        user01  0x00000005e00154a0  0x544730420008d010\n    [TX]        user01  0x00000005e0017ff0  0x000000000008d000\n    [RX]        user01  0x00000005e00191fc  0x423053530000e013\n    [TX]        user01  0x00000005e001b160  0x000000000000e000\n    [RX]        user01  0x00000005e001bb1c  0x423053530008f010\n    [TX]        user01  0x00000005e001da7c  0x000000580002f000\n    [RX]        user01  0x00000005e001e478  0x4230525300000013\n    [TX]        user01  0x00000005e0020268  0x0000000000000000\n    [RX]        user01  0x00000005e00225a4  0x4230525300081010\n    [TX]        user01  0x00000005e00241e4  0x0000001500021000\n    [RX]        user01  0x00000005e00264c0  0x4230464700002013\n    [TX]        user01  0x00000005e0028110  0x0000000000002000\n    [RX]        user01  0x00000005e002a3f0  0x4230464700083010\n    [TX]        user01  0x00000005e002c0b8  0x0000000000083000\n    [RX]        user01  0x00000005e002d054  0x4230414300004013\n    [TX]        user01  0x00000005e002d500  0x0000000000004000\n    [RX]        user01  0x00000005e002e254  0x4230414300085010\n    [TX]        user01  0x00000005e002e828  0x0000fe6500025000\n    [RX]        user01  0x00000005e002fc84  0x4230495600006013\n    [TX]        user01  0x00000005e003194c  0x0000000000006000\n    [RX]        user01  0x00000005e00322c4  0x4230495600087010\n    [TX]        user01  0x00000005e0034224  0x0000fe6500027000\n    [RX]        user01  0x00000005e0034e54  0x4230434800008013\n    [TX]        user01  0x00000005e0036ac0  0x0000000000008000\n    [RX]        user01  0x00000005e00374a8  0x4230434800089010\n    [TX]        user01  0x00000005e0039358  0x000000ee00029000\n    [RX]        user01  0x00000005e003b670  0x544730560000a013\n    [TX]        user01  0x00000005e003cec8  0x000000000000a000\n    [RX]        user01  0x00000005e003dc20  0x544730560008b010\n    [TX]        user01  0x00000005e003e284  0x000000000008b000\nRTKit Task List:\n   name                    | pri     | stack use | status     | resource | warning\n 0 rtk_ep_work             | 057     |   640\/2048  | SEMWAIT    | 0x4ac20 | \n      0x000000000001e324 0x000000000001f2cc 0x000000000002c32c 0x000000000001ee28\n\n 1 power                   | 000     |   832\/2048  | RUNNABLE   | 0x40d80 | \n      0x000000000001e324 0x000000000002b134 0x000000000002ad6c 0x000000000001ee28\n\n 2 Misc                    | 019     |  1440\/4096  | SEMWAIT    | 0x37cb0 | \n      0x000000000001e324 0x000000000001f2cc 0x000000000000dee0 0x000000000000f6f4 0x000000000001b4fc\n\n 3 InductiveTask           | 019     |  1296\/2048  | RUNNABLE   | 0 | \n      0x000000000001b268 0x0000000000020b54 0x0000000000006c20 0x000000000000c160 0x0000000000008e00 0x000000000001ee28\n\n 4 BMSTask                 | 019     |  1424\/2048  | RUNNABLE   | 0 | [Faulting task]\n\n 5 PMUEventTask            | 019     |  1040\/2048  | SEMWAIT    | 0x462a0 | \n      0x000000000001e324 0x000000000001f2cc 0x0000000000003e20 0x000000000001ee28\n\n 6 APComms                 | 019     |  1296\/2048  | SEMWAIT    | 0x45690 | \n      0x000000000001e324 0x000000000001f2cc 0x000000000002c32c 0x000000000001ee28\n\n\n\nSleep Count: 127406\nWake Count:  105409\nDuty Cycle:  28\nSleep Count: 127406\nWake Count:  105409\nDuty Cycle:  28\n\nRTBuddy(AP): Debug info:\n_iopStatus = 0x8\n_powerStateChangeLocked = false\nMailbox Status:\nIDLE_STATUS: 0x00000028\nMAILBOX_SET: 0x00000000\nMAILBOX_CLR: 0x00000000\nINBOX_CTRL: 0x00020001\nOUTBOX_CTRL: 0x00021101\nAP->IOP Mailbox

Previous usage scenarios:

Even with the original battery, I experienced similar issues with high restart frequency. It would restart automatically after being fully charged, and the battery level would still be around 20%. This 20% would last quite a while. I suspected it was a battery problem, so I replaced both the battery and cells. However, after replacement, screen responsiveness issues emerged. The screen didn't respond to touch, and upon inspection, it was identified as a motherboard problem. The motherboard was repaired, and the screen works fine now. However, the frequent restarting problem persists. Initially, a repair technician thought it could be related to the battery cells, so a new battery was installed, but the issue remained. The technician further examined it but couldn't pinpoint the exact cause, as there's no consistent pattern to the restart intervals.

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I would be interested to see the panic log you linked to, but the link doesn't work for me. You can upload the .txt doc right into your post, or copy-paste.

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I added in the first big of the panic log that I grabbed from your other post since that link did work.

This is still definitely in battery territory. It references the BMS (Battery Management System) multiple times and based on your description, I would wager the device is not getting good "gas gauge" data. That is to say, the information that tells the phone how charged the battery is is missing, or garbled. There could be some issues with the battery connector, or some of the components around the connector which assist in relaying this data to the CPU (the SMC specifically, as is mentioned here in the panic).

Some images of what the board looks like in the area of the battery connector would be helpful,

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First of all, thank you very much for your patience!

Yes, you guessed it right, my battery level was inaccurate.

However, I also tried to replace the whole battery before, but the problem still exists, so I think it should be ruled out because of the battery?

But at present, I have no alternative to solve my problem.

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Thanks a lot for your answer.

In your reply I see that you indicate that there may be some issues with the battery's connector or around the connector.

If I understand it as the circuit board of the battery or some components around the circuit board, then I took it to the maintenance master to check the circuit board, but the maintenance master told me that there was no problem with the circuit board.

The suggestion of the maintenance master, let me try to replace the chip.

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Because my mobile phone restarts irregularly, the only regular time is when charging at night, when I wake up in the morning, when I check the analysis log, the phone restarts many times, and the interval is about 1-2 times every few minutes. .

When I unplug my phone from the charger, it restarts erratically. Sometimes it restarts continuously, sometimes it takes 5-6 hours to restart.

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My interpretation here is that I'm thinking there's a problem with the I2C bus used for communicating with the battery.

I pulled some schematics of the iPhone XS Max, and the BMS communicates over I2C0_SMC. That signal goes to a chip labelled USB-PD and another one labelled Yangtze Charger. It looks like there's a level shifter circuit right next to the battery and of course caps and resistors in the line.

Although I have reference designators for those components, I don't have a board file that shows me where they're physically located, at least not yet.

However, the other thing of interest is that those signals appear to go through the interposer, meaning they're transferring from the top board to the bottom board (or vice versa). So in addition to the possibility of a missing or damaged component, there's also the chance that the interposer has flexed and broken some pads. That, of course, will take expert-level microsoldering repair, unfortunately if that's the problem.

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@dadibrokeit That sounds very much like I would expect. I can look up locations if need be. But the XS Max board is extra weird. There is a small section of the board around the SIM tray that goes to only one level of board and then another small section at the bottom that's sandwich board again. I feel like all the charging components are in that segment.

@ownstupid I would definitely be looking into Yangtze if that wasn't the chip that was already recommended to replace (assuming you replaced it).

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