On 13 Jun 2022 21:51:18 +0100 (BST)
Theo <theom+news@chiark.greenend.org.uk> wrote:

> Java Jive <java@evij.com.invalid> wrote:
> > Despite others' replies up to this point, all of which I've read, I
> > have to report that trying to keep my tablet charged via the USB
> > socket of my Skoda Fabia doesn't really work reliably. Without any
> > warning, after some distance, I find the tablet turning off, and
> > when I examine why, I find that its battery is completely
> > exhausted, despite it having been plugged into the USB socket all
> > the while the car was moving.
>
> If you leave the tablet turned on, ie don't shut it down, it's
> possible you aren't running the engine long enough to give it much
> charge. eg if you drive for half an hour, if the USB socket is only
> giving it 500mA, it's only received 250mAh. The battery could be
> 5000mAh, so that's a topup of 5%. Then if you leave the car parked
> for a few hours it'll run down that charge. Eventually it'll run down
> the battery enough to turn off, but then the car won't charge it very
> much next time.
>
> This is especially bad if you have location and mobile data turned on
> - the tablet may be chatting to Google/etc, which eats the meagre
> charge you received.
>
> It's why a fast charger makes more sense in a car than many other
> places, because you often only spend short periods in the car and you
> engage in heavy battery-draining activities (satnav, music streaming)
> while doing so.
>
> > I seem to get better results from the cigarette lighter adaptor
> > that I used with previous cars that had no USB socket.
> >
> > Worse still, I copied a load of music onto my tablet to have
> > something to listen to on a recent long trip to a family do, but
> > could not get the car to recognise the tablet as a storage device.
>
> The car is probably expecting a USB Mass Storage device, ie a USB
> stick. The tablet probably doesn't present as that - Androids are
> usually PTP or MTP, while I'm not sure if iPads do anything except
> iTunes.
>
> (Android 2 and 3 supported USB Mass Storage, so there are old guides
> floating around about how to enable it, but they don't work on modern
> tablets. The problem is you had to unmount the storage from the
> tablet before the computer could see it, which is awkward for
> anything the tablet wants to use)
>
> I'm not sure if there's a workaround to make an Android export Mass
> Storage for a subset of files - maybe there is if you're rooted.
>
> > So for me, it has to be tablet, for the Navigation app, connected
> > to the cigarette lighter socket, and a USB stick in the USB socket,
> > which seems unnecessarily retro.
>
> Try playing music from the tablet and connecting to the sound system
> via Bluetooth?
>
> Theo

Are you sure that the USB connection in the car is actually putting out
a supply voltage? It could be just using the communication ability,
but not putting out voltage on the power pins.
--
Davey.

On 17/08/2023 11:19, Davey wrote:
>
> Are you sure that the USB connection in the car is actually putting out
> a supply voltage? It could be just using the communication ability,
> but not putting out voltage on the power pins.

FWIW, in response to your post I've just gone out to the car, set the
engine going, and connected the phone to the USB socket, and it says
that it's charging on the lock screen. I'd like to be able to believe
it, but, given my experiences described upthread, I think I must reserve
judgement.

--

Fake news kills!

I may be contacted via the contact address given on my website:
www.macfh.co.uk

Java Jive wrote:

> I've just gone out to the car, set the engine going, and connected
> the phone to the USB socket, and it says that it's charging on the
> lock screen. I'd like to be able to believe it

I've never known a USB socket in a car that doesn't provide power, but
I've known some that don't provide *much* power.

If the tablet is being used for e.g. google maps navigation, I could
easily imagine it draining the battery despite being on charge.

On Thu, 17 Aug 2023 12:46:25 +0100
Java Jive <java@evij.com.invalid> wrote:

> On 17/08/2023 11:19, Davey wrote:
> >
> > Are you sure that the USB connection in the car is actually putting
> > out a supply voltage? It could be just using the communication
> > ability, but not putting out voltage on the power pins.
>
> FWIW, in response to your post I've just gone out to the car, set the
> engine going, and connected the phone to the USB socket, and it says
> that it's charging on the lock screen. I'd like to be able to
> believe it, but, given my experiences described upthread, I think I
> must reserve judgement.
>

Thank you for taking the trouble to go and check. So the question is
indeed one of supply vs. demand.
--
Davey.

On 17/08/2023 13:46, Andy Burns wrote:
>
> Java Jive wrote:
>
>> I've just gone out to the car, set the engine going, and connected
>> the phone to the USB socket, and it says that it's charging on the
>> lock screen.  I'd like to be able to believe it
>
> I've never known a USB socket in a car that doesn't provide power, but
> I've known some that don't provide *much* power.
>
> If the tablet is being used for e.g. google maps navigation, I could
> easily imagine it draining the battery despite being on charge.

Yes, it was being used for navigation, so probably your explanation is
the correct one.

--

Fake news kills!

I may be contacted via the contact address given on my website:
www.macfh.co.uk