While I love technology, I also like optimisation, so when it comes to my daily driver phone, it’s not going to be a flagship device. At the moment, I’m running a Motorola moto g84 5G based around a mainstream Qualcomm Snapdragon 695 SoC, 12GB RAM, 256GB UFS 2.2 Flash memory and with a nice 6.5″ P-OLED FHD+ display. For my purposes, it’s been quite satisfactory – with the only quirk being the lack of eSIM capability. Nevertheless, I take care of my digital devices – they are always in a case, covered with a screen protector, kept away from liquids and questionable power supplies, which definitely helps them endure into obsolescence.
It’s been generally trouble-free for me – the upgrade from Android 13 to 14 was nice and smooth. Last month, the upgrade to Android 15 finally rolled out to me, but then things started going a bit downhill.
The Symptoms
One of the best things about USB-C is the reversibility of roles – with the same connector and cable, a phone can be a device connected to a host laptop, or it could be a host to a storage device. Using the phone as a host for devices enables nifty gadgets like USB-C thermal cameras, several of which I’ve reviewed in the recent past. This capability is sometimes known as USB On-the-Go (OTG).
Unfortunately for me, I just so happened to be reviewing another USB-C connected device when I noticed that my phone simply wouldn’t reliably detect a device that was previously working and reviewed with this particular phone. I cleaned the connector, tried an extension cable, tried reversing the plug – no dice. But as soon as I connected the device to a different phone or computer, it detected just fine. The device did not seem to be at fault.
Some phones, for privacy reasons, had a USB-OTG toggle switch which could be used to disable the port. I looked, but there was no such thing for the g84 5G. Even more baffling is that while one particular device didn’t work with the g84 5G – the OTG capability wasn’t entirely “dead” as there were the occasional product which would work or do so unreliably. This is in some contrast to online threads where users had no luck at all using USB-OTG with the g84 5G – the difference for me is that it had always been working until recently.
The problem with constant updates is that it’s hard to pin down when things “break” and even if we did, there’s no going back because of modern “locked” bootloaders, signed firmware and downgrade protection. But then again, perhaps the issue is just purely co-incidental with the upgrade – and the upgrade had nothing to do with it. That is also a possibility …
A Problem?
So, why would a USB device be flaky? I wondered if the port was simply damaged – perhaps a freak ESD event making it flaky. But when I was testing the port, I made a scary discovery.
Using my trusty Fnirsi FNB58 as the test load – nothing connected downstream and the FNB58 terminating the CC lines for power – the supplied VBUS was 5.50V. This is well out of USB specifications which should range from 4.75V to 5.25V.
More interestingly, this overvoltage didn’t seem to be unregulated – it seems a very deliberate 5.50V or thereabouts across multiple plug insertions and unplugs. At first, I thought that an output load switch MOSFET may have blown and connected some unregulated power to the output, but to my surprise, when the CC termination was removed, the port power stopped being supplied, suggesting the output load switch was working fine.
More than this, the phone retains perfect fast (TurboPower) and standard charging functionality and data transfer functionality with a laptop (MTP). So the port doesn’t seem to be problematic, at least, from a hardware perspective.
To see if it was just something about the FNB58 as load that was making the phone unhappy, I used an extension cable and set the FNB58 to pass-through the CC lines. On the far end, I had a USB-C thermal camera attached – its idle draw is visible above but the voltage remains a stubborn 5.50V.
This is not a great condition as it can lead to damage to connected devices, so I disconnected the device and for now, no more USB-OTG with the g84 5G.
Just to be sure that it wasn’t the FNB58 being the culprit – the same thermal camera attached to a different Motorola moto g54 5G had a solid 4.996V which is just peachy – the thermal camera started up right away.
Just in case it was my imagination – I referred back to my ThermalMaster P2 review which confirms – the port on my g84 5G was giving out a nice 5V back in September 2024 …
My particular moto g84 5G has a model number of XT2347-2 and is on retapac channel (retail Asia-Pacific). At present, it has Android 15 with updates to 1st August 2025 and a Kernel version 5.4.284-moto-14997-g99645e6c6a88 dated 25th July 2025.
Could this be a problem in a port control or PMIC driver? Maybe they somehow requested 5.50V rather than 5.00V? It looks a bit too regulated to be an accident … or perhaps someone was being greedy trying to power a hefty spinning USB external hard drive and thought upping the voltage would help overcome cable losses? Or perhaps my phone developed a very “unusual” type of failure?
Warranty … or Not?
This had me thinking – should I send my phone back for warranty? Migrating phones is an absolute pain in a world where so many things are tied to a smartphone – and it’s not likely I have another phone that’s just as nice to swap over to. But more than that, I’m not sure if it would fix my problem.
But just to be sure, I checked the Motorola Support pages where it unhelpfully told me my device was out of warranty since 29th July 2025. Clicking on “Incorrect warranty status?” gives me this window –
Looks like they did not account for their own terms when they decided to tell me it was out of warranty –
According to their own linked Motorola Legal pages – the g84 5G in Australia is covered by a 24-month warranty, meaning that I am still technically under warranty coverage.
Conclusion
As a result, I reach a rather baffling conclusion. My moto g84 5G is giving connected USB devices 5.5V, which is much too much, but otherwise is working perfectly as I’d expect. This seems to have happened after the latest update to Android 15 – so is this a software bug? Or perhaps a coincidental hardware failure of some sort? Nevertheless, this is not a good result as connected devices could suffer damage and many simply won’t operate at all.
If anyone else has a Motorola g84 5G updated to Anrdoid 15 and a suitable USB voltmeter that can read the supplied voltage when connected to a USB-OTG device, I’d very much appreciate knowing – does yours give 5.50V too? Or is it just mine?
Oh … and shame on Motorola for potentially misleading customers about their warranty status!
UPDATE 25th September 2025
Inspired by comments left on the post, I dug further into the port’s behaviour under load, running a full I-V curve on the port when connected via a USB-C to USB-A OTG adapter.
The port managed to sustain 1.07A of load before OCP kicked in and shut down power to the port. Unplugging and replugging restored power. The voltage did drop in a straight line, which I suspect is due mainly to ohmic losses in the USB-C OTG adapter. Even just prior to OCP, the voltage did not return to the 4.75V to 5.25V USB Vbus window.
When unloaded, the ripple appears as a characteristic switcher with power saving mode and spread-spectrum, with acceptable ripple averaging 44mV peak-to-peak.
At 500mA (standard USB port load), the characteristic is much smoother and close-to-sinusoidal. Ripple averaged 16mV peak-to-peak which is very good.
This all seems to support my suspicion that the port is operating “correctly” but is just not configured correctly (i.e. by software) or has suffered some odd failure in voltage setting but regulation, switching and protection all seem to be functioning as normal.
UPDATE 4th October 2025
I’ve been having a think about whether this 5.50V is a hardware or software issue, when it came to me that the bootloader firmware is probably one that doesn’t get updated all that regularly, so perhaps booting into Fastboot or Recovery might help. If it shows a 5V VBUS, then we know it’s not hardware.
Unfortunately, I tried this but no dice – it turns out I’m getting 5.50V too. It doesn’t mean that it’s necessarily hardware as the fastboot/recovery system may have gotten an update. But I thought it might have been a quick way to check … so it was worth a try.
But then, a reader was kind enough to point me to this link which suggests the USB-IF had an ECN to raise the VBUS to 5.50V at the source with the introduction of USB-C connectors to ensure that they can carry the full 3A with a legal voltage at the device end. As a result, it’s actually apparently legal to have a USB-C connector with a VBUS of 5.50V. In that case, this is a “no fault found”, but the problem is that many devices would have been designed with the expectation of a 5.25V maximum VBUS (especially those with low current demands and/or USB-A/B connectors). Given that the phone doesn’t even supply 3A output, the choice of a 5.50V VBUS is also at odds with the original intention of the ECN.
So perhaps I’ve reached a logical “end” to this saga – it’s time to find a USB-C to USB-C extension and graft in a power diode …