This is typically the sign of a capacitor somewhere in the system that is retaining charge, completely disconnecting will allow that stored charge to dissipate.
this post was submitted on 16 Nov 2025
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Back in the day, it used to be recommended that you push the power button while its unplugged to discharge the capacitors. I don't know if it still works.
I work in IT and see this a bit. I put it down to voltage where it shouldn't and it takes a while for it to dissipate.
One protip, with which I've resurrected countless laptops and even a server:
Shut it down, pull the power chord, remove the battery (or hold down the battery reset button on modern laptops), then hold the power on button for a couple of seconds.
It'll drain all capacitors and remaining voltage.
power chord
Power cord :)
I do love the idea of ressurecting electronic devices by playing music for them, though.
I jam Holy Diver when my electronics act up.
I heard the cover version, Holy Driver, works great for software.
pull the power chord
EXCELLENT !! 🎶🎵🎶🎵🎵🎶🎶🎶🎶🎶🎶
Party on, Wayne.
Or: a software glitch in need of a hard reset.
Most electronics have a lot of capacitors to stabilize the input voltage.
When the device is in some low power state, it can take a surprisingly long time until these run out of their charge after disconnecting external power.
This is actually part of it though it's more nuanced with smaller form devices, than say a desktop computer, that run on very little power and have parts from lots of different manufacturers rather than integrated motherboards.
Firmware sometimes needs a hard reset to get past bugs, and sometimes a capacitor or two have enough power to keep a low power memory chip active for days, weeks, months, or longer.
Problem at a high level is with devices that are not well integrated because a lot of products these days are a mishmash of pre-made rather than purpose-made components from various companies, and some have some kind of firmware running in local memory and they try to cache information rather than reloading each time to speed up startup times.
Could be a motor driver chip for focusing the lens from some fly-by-night manufacturer with buggy firmware throws an error that the main device interprets as a potential for a catastrophic failure and refuses to start up to prevent what it thinks might cause damage or user injury. But maybe really its just a bug.
That chip stays charged and continues to throw the error when the main board does startup checks and every time the battery is put back in, it replenishes the charge in the driver chip. Finally once it loses charge and has to load from scratch and actually runs the checks again it doesn't remember that it previously threw an error and the current checks don't trigger the error anymore, so it's "fixed". Could be that there is a part close to catastrophic failure or could have been a bug that triggered it, but for now it's fine. Just a wild top of my head example, but the basic idea is there. Also, could be something physically is lose and it got knocked into a place where it's making enough contact this time, but might get lose again shortly after.
Always hard to say without a trained technician or a good product with good error handling. But good error handling isn't profitable anymore. That means more development and testing time up front and less likelihood of the user having to replace the product sooner and since competition is more scarce these days, there's no incentive to make better, longer lasting products.
It wouldn't surprise me if an accidental load of static electricity got inside the electronics. Would certainly take a while to dissipate through air, especially air trapped inside the device.
Nevertheless, it might be worth trying grounding all the terminals that usually connect to the battery.
We recently even had that for our car.
ABS stopped working, along with other things like remote car opening and also the turn signals for some reason (rest of lights still worked)
Repair shop didn't find any errors in the electronic log, but on a wimp disconnected the battery and let it sit there for a while.
All just worked normally again after that.
While this is typical software glitch behaviour, it is slightly disturbing in a car, especially involving safety relevant functions like ABS and ESP...
Cars are all software these days.
That's one of the concerning parts:
It's a 15 year old Škoda, probably one of the cars depending on the fewest lines of code by now...
Well, by 2010 that would be a Volkswagen though wouldn't it? Either way, it's new enough to be mostly software control, though not entirely drive-by-wire.
Well, by 2010 that would be a Volkswagen though wouldn’t it?
Yes, has one of the infamous engines that came with the fraud motor control...
But comparing it to modern cars... Crazy what has changed in the time since then...
E.g. we had a water bottle crashing against the main display some years ago, since then it only shows colored smears.
Only downside is, that you now don't know any more, which radio station is currently playing.
In a new car, you probably wouldn't even be able to control AC and heating any more.
I guess I will try to cling to that car as long as possible,..
That's not software, that's almost certainly purely electrical. More specifically, disconnected/floating ground/return lines. Car computers need 0 Volts to look like 0 Volts and 12V to look like 12V, but floating grounds can cause 0 to look like -4 and 12 to look like 20.
Strong chance that the battery terminal connections were corroded or not tightened down enough to get good contact and that by disconnecting/reconnecting the new connections were better.
-- spacecraft software/electrical engineer who cosplays as a backyard mechanic
I don't think so.
The negative terminal of the battery just has a single 30cm long line directly connecting it to the car chassis.
And if that is "floating", the main current source is disconnected and the whole car is completely without power.
So, sorry to have to disappoint you, but that's not it.
Not necessarily
In electrical engineering floating just means there is nothing forcing a particular conductor one way or another. All a battery does is try and force its two terminals to be ~12V apart, what happens coming off the battery terminals is a different story. If you had a bad connection to the terminals a resistance could have been there, itself driving a voltage difference depending on the current passing through it.
Interesting that your car routes all return through the chassis, I've never seen that before. Admittedly I've only ever worked on US or JDM cars, but the ones I've worked with typically have separate return lines for the electronics, a dedicated thick one for the engine and then the engine is what connects the chassis to battery return.
No disappointment, just a fun interesting problem and learned something about European cars.
Interesting... All my cars up to now (mostly German brands) had the direct connection between negative battery terminal and chassis.
But as already said, newest car is already 15 years old, so might have changed by now...
The topic of contact resistance is a separate one, would show as voltage drops during heavy load situations. Similar to high internal battery impedance during winter especially for an older battery, when all the lights go out when starting the engine. This is mainly due to the high start current drawn by the Diesel engine (Diesel engines also being uncommon in the U.S. afaik?), so the electronics are designed to cope with this severe voltage drops.
Yeah, US and JDM cars are predominantly gasoline engines. Engine start current draw is similar between the two engine architectures but gasoline engines with their spark plugs would certainly cause noise on the ground line during normal operation which is probably the biggest reason for the dedicated ground line. The digital electronics would also be sitting behind a down regulator that I'd be willing to bet isolates the ground as well.
I still lean towards the original topics failure mode being electrical based not software. Software faults tend to be highly repeatable and almost always persist across full power drains since, assuming no underlying electrical issues exist, computers execute software instructions perfectly every time. Given the exact same set of inputs and the exact same timing, they'll get back to the same state. And that would have been happening since the factory.
Degraded electronics could be feeding new or unexpected inputs into the computers that trigger different software state transitions that then lead to unintended or unexpected behavior, but things would have to be going pretty off the rails for the system to pass all of its built in tests and not realize something has gone wrong.
Another possibility is the mechanic found loose harnessing, connectors, did a few different unplug/plug cycles and then only told you about the battery.
Varies device to device, but it could have been a thermal shutdown. It got too hot and stopped working. Starting working again when it cooled off enough.
All remaining electricity needs to be removed. That can take hours, days.