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Tech Chat Smart phones - What does "Bootloader battery fall through" mean in plain English?

 
Katie Bush
(@katie-bush)
Illustrious V-Ratter Moderator
Posts: 5078

Hi all,

I've recently bought a replacement smartphone since I broke the previous one (probably repairable) which I'm planning to repair it as soon as I get a few extra tools and gadgets to do the job.

Anyway, the problem with the replacement is/was that it hasn't been very reliable, shutting off its power without warning, and not closing down any software, including its OS, as it does so.  This led to several error messages at the next attempted power up, including "Bootloader battery fall through, connect to PC to access, repair, or reinstall".  Does anyone know what it's actually telling me?

At the moment, and after several restarts, the phone now seems to be working again, but I'm not sure if all is as it should be.

Any ideas, anyone?

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Topic starter Posted : 21/08/2021 10:06 pm
irob2345
(@irob2345)
Reputable V-Ratter Registered
Posts: 263

I don't know the make or model of your phone or the OS, but here are some general observations / suggestions:

The bootloader battery is like the CMOS battery in a PC. It runs the real time clock and other stuff while the main battery is flat or disconnected and sometimes keeps some RAM active to store some low level system settings.

The "fall through" probably means the startup script has not been able to verify correct settings stored in this RAM but has continued on, through the error state, i.e. it has "fallen through". Which is much better behaviour than getting hung up on the error.

Try plugging it into a Windows PC with the USB cable. This might reveal some helpful information.

In the early days of PCs, we used to make a Video On Demand system that used VCRs, routed to school classrooms via cables on a booking basis controlled by software on the PC, whereupon the teacher could operate the VCR remotely via an IR remote control routed back to the source. The PC ran DOS, later Windows, software that would control the router(s) via an RS232 serial cable. We sold many thousands of these systems from the late '70s through to the '90s.

What would happen often is, overnight, a cleaner would unplug the power to the router (to connect a vacuum cleaner) or the DB9 cable would become dislodged. Whereupon next morning the software would pop up a window and report an error message as follows:

Error

No response from MCUxxx  (in large systems there would be more than one router, each with a unique address)

Check power and serial cables.

The phone support call would go:

"I've got an error message"

"What does it say?"

"Check power and serial cables"

"Did you?"

We always tried to make our error messages helpful. People were not used to this!

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Posted : 22/08/2021 3:47 am
Katie Bush
(@katie-bush)
Illustrious V-Ratter Moderator
Posts: 5078
Posted by: @irob2345

I don't know the make or model of your phone or the OS,

Ah yes, what a clown I am. It's a Moto G4 running Android 7.0 OS.

I think I see where you're coming from, and it might even make sense if my suspicions are correct. - The phone is second hand, and is identical to the one I broke.  I rather suspect that the phone has been out of use for some time, and probably enough time to discharge both the main battery, and the RTC battery (which I hadn't really considered before).

Charging the main battery was interesting because from "Charge = 0%" it took only a couple of minutes to read "Charge = 64%" and about as long again to read "Charge = 100%". Clearly, that couldn't be a realistic appraisal of the battery's state of charge.

Powering on, the phone would stay on for about 20 minutes before the battery failed - At which point the phone would not restart. If I connected the charger, the phone would happily power up again, and the battery status would read at about "Charge = 85%". Disconnecting the charger at this point the phone would stay on idle for maybe another 20 to 30 minutes before failing again. Connecting the charger again, let's call it 'jump starting' the phone, the battery would now read 68%. The phone would stay on for about another 20 minutes or so and fail gain. Repeat the jump start, and the battery would read 54%.  From this point on, the battery would not support the phone after a jump start, even though the charge still read as 54%.

On the face of it, it appeared as though the battery was only functioning in the top 46% of its charge capacity, and grudgingly at that, leaving 64% inaccessible. This, I called the 'glass floor'.

After another effort to recharge the battery, I got another 100% reading, and repeated the same procedure as above, with exactly the same results. I concluded that the battery was kaput, and needed replacing, and it may still be the case.

With a little perseverance I kept jump starting the phone at that 54% level and eventually managed to get the battery to stay afloat below 54%. It was a long job and needed a lot of jump starts to get it down from 54% to 38%, from where the battery would work almost as normal again, right down to 12% where it collapsed again. At this point I recharged the battery again, which now took about 3 hours to reach 100% - Let's just say it was a repeat performance, exact same battery charge percentages, jump starts and glass floor.  I got to thinking that this battery has some kind of "memory" issue - I thought Li-on batteries weren't supposed to do that?

It was during this charge/discharge/jump start process that the "fall through" issue, along with other error messages, began to occur.

Over a period of days (about 10, if I recall) of the above, I managed to get the battery to deliver a constant discharge from full to empty, albeit very irregular and unreliable. Depending upon which charger, the recharge is either, about 4 hours (Motorola 1A USB wallwart) to 15 hours (Vodafone 750mA wired wallwart). Charging at the lower rate gives a better performance from the battery in use.

I guess I've effectively reformed, to some degree, the phone's battery?

The problem was that under load (using Google Assistant, or viewing YouTube videos) the phone would shut off with a click, in the midst of whatever task it was performing even though the battery state was still reading at acceptably good figures, after which, on repowering, I saw the error messages and the phone would not boot any further.

Perseverance and persistence have brought the phone to a point where it now boots up to OS and apps being functional, as well as normal phone and text functions.  The problem now is flickering pictures and/or picture with sections missing (Think of a photo with a corner torn off). Right now, it's notifications on the pull down curtain that cannot decide whether to display horizontally or vertically, and flicker annoyingly between both.

Connecting the phone to my laptop (W10) with the phone powered on - Does absolutely nothing!

Connecting the phone to my laptop whilst powered off - Generates a pop up from my antivirus software offering to scan "Linux File-CD Gadget USB Device Drive E:/" Scanning this address returns "No Threats Found".  On attempting to access Drive E:/ the message is "Please insert a disk in Drive E:/".  That's as far as I can get.

I guess the error messages on the phone were meant for a repairer, or service depot, and assumed there would be a PC with appropriate software to gain access to the phone?

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Topic starter Posted : 22/08/2021 3:46 pm
irob2345
(@irob2345)
Reputable V-Ratter Registered
Posts: 263

Hmmmm. Sounds like you need a new battery.

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Posted : 22/08/2021 4:24 pm
Katie Bush
(@katie-bush)
Illustrious V-Ratter Moderator
Posts: 5078

@irob2345 I think so too!

However, I'll play with it a while longer and see if I can draw a little more life out of the existing battery.

The sad truth is, I broke its predecessor whilst attempting to disconnect the battery - The connector is tiny, and oh so impossibly fragile. I could pinch the battery from that one, but I'm loathe to risk the same thing happening again.

We shall see, but for now, your description of what you thought the error message means makes sense enough, and hasn't reappeared since, but the phone's odd behaviour still remains. The battery seems to improve on each charge cycle, but I doubt it will recover fully, and in any case, I doubt it would be reliable, and knowing me, it would let me down when I needed it the most.

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Topic starter Posted : 22/08/2021 5:37 pm