Charging a tablet from a 12 volt socket.

This is the charger I use. I have an 8 inch Galaxy Tab like yours. This charger brought my tablet from 35% to 85% while it was chart plotting over about 2 1/2 hours this morning. The charger has two usb ports , 4.8 A between the two. It also has a cig socket so you can plug other stuff in.
 

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Lots of replies helping specify a more robust supply.

Perhaps consider a simple thing to reduce consumption before making any changes.

Turn the screen off when not in use!
 
Petronella said:
For the last six years I have run the excellent SailFreeGPS app on an old Huawei tablet charging continuously from a 12 volt cigarette lighter socket with the usual USB car adapter plugged into it. It runs all the time on passage. It just charges quicker than it drains it's battery. That is, it works great.

After many thousands of miles and lots of sun it has deteriorated and I needed to replace it. I bought a second hand 8" Samsung tab A with the same micro USB connection as the Huawei but unfortunately this device drains faster than it charges so is no use.

So I'm looking for a small (8") tablet that you know will run continuously from a 12 volt socket. Basically it must charge faster than it drains so it is always fully charged. Any ideas?
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Install one of these. Convert 12v direct to 5v 5A. More than enough to run the tablet
24V 12V To 5V 5A Power Supply Buck Converter Step Down Converter Charging Module–OKY3502-4 – OKYSTAR
 
Plum said:
Fitting a higher current output charger is a good idea but will not make a difference if the tablet is only drawing, say, 1amp from a 3amp charger. One of these is really useful to measure the actual current draw of the tablet. Will also highlight the difference in your charging cables, some are more efficient than others:
Pardon our interruption...
(USB-micro and USB-C versions are available)
Click to expand...
I have one of those and they are brilliant. Excellent value at £3.95. I found a huge difference in current with different cables so I sorted my cables and attached labels so that I could select the best ones to use on the tablet. They also let you know if the 5V supply is dropping when you draw current. Some cheaper adapters go down to 4.9V which further restricts the power going to the tablet.
 
geem said:
Install one of these. Convert 12v direct to 5v 5A. More than enough to run the tablet
24V 12V To 5V 5A Power Supply Buck Converter Step Down Converter Charging Module–OKY3502-4 – OKYSTAR
Click to expand...

That looks good, Working voltage: DC 9V–36V, Output voltage: 5.2V/5A/25W

As already said above, some will not charge at a fast enough rate compared to usage. I experienced this using the scan strut device (link below), but at Input Voltage: 12V & 24V DC, Output Voltage: 5V (+/- 5%), and output at 2.1A (about 10W) I still ran out of juice using iPad as plotter, switched on all the time. So as you say, the larger power output should do.

Scanstrut SC-USB-01 USB Socket Waterproof (12V/24V)
 
For an 8-inch Samsung Galaxy Tab A, the recommended charging power is typically around **15 watts**. This is because the device supports fast charging at this rate, although it may not utilize higher wattages efficiently. The stock charger often comes with a lower power rating, such as 7.5 watts, but using a 15-watt charger can potentially reduce charging time, especially when the screen is off.

Here are some key points to consider:

- **Charging Speed**: The difference between a 7.5-watt and a 15-watt charger can be noticeable, especially if you're charging with the screen off. However, if your device doesn't support higher wattages efficiently, the charging time might not decrease significantly.
- **Charger Compatibility**: Ensure that the charger is compatible with your device's charging protocol. For Samsung devices, using a charger that supports USB-PD (Power Delivery) is recommended, as some devices may not support Quick Charge (QC) due to their processor type.
- **Cable Quality**: The quality of the charging cable can also affect charging speed due to voltage drop over longer cables.
 
Thanks all but unfortunately I don't think it is quite so simple. I have plenty of 12v adaptors that will continuously charge my Samsung tablet via a USB C cable so the adaptor is not the problem.

It appears though that my old, new to me, 8" Samsung tablet with the USB Micro slot is looking for a Samsung (or equivalent) wall charger. If it sees one it charges easily fast enough to keep up with the drain. If it doesn't see a wall charger though and only sees a 12v adaptors it only charges at 0.5 amp, not enough to keep up with the drain.

So I'll repeat my original question. I'm looking for a small (7" or 8") tablet that you know will run continuously from a 12 volt socket. Basically it must charge faster than it drains so it is always fully charged. Any ideas?

Thanks all.
 
Petronella said:
So I'll repeat my original question. I'm looking for a small (7" or 8") tablet that you know will run continuously from a 12 volt socket. Basically it must charge faster than it drains so it is always fully charged. Any ideas?
Click to expand...
As per above:

Check that the 12v-charger is compatible with your device's charging protocol. For Samsung devices, using a charger that supports USB-PD (Power Delivery) is recommended, as some devices may not support Quick Charge (QC) due to their processor type.

Surely a tablet will be able run continuously off it's compatible 12v-charger - unless the tablet is broken. On that note - is it updated to latest software version? The charge management is controlled by the tablet's software..
 
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Petronella said:
So I'll repeat my original question. I'm looking for a small (7" or 8") tablet that you know will run continuously from a 12 volt socket. Basically it must charge faster than it drains so it is always fully charged. Any ideas?

Thanks all.
Click to expand...
For occasional use when I’m sailing on other boats, I have a Lenovo Tab with Raster charts of UK coast. It’s now more than 5 years old so doubtless NLA. I bought it because it had a reputation for long battery life and will charge from cigarette lighter socket quicker than its drain while in use.
 
bluerm166 said:
It appears that micro usb 2.0 takes 2.5w or 2.1 A at 12v. My Tab A 10.1 uses this and is happy to increase battery charge in use.I doubt that the 8" tab A in question uses the ancient micro USB 1.0 standard.
Maybe Petronella is using an older 1.0 A c/l adapter which was ok for the Huawai tablet but not for the more demanding Samsung.Or has a suspect cable ,as noted by others above,which restricts its real charge rate.
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2.1A @ 12V = 25.2W
Miss placed decimal point easy to do.
 
I had a Hudl2 with this problem. Never found a solution.

Now have a Lenovo 8, which has a USB C connection. I link a power block to it which works well. Maybe using a block might help?
 
Petronella said:
Thanks all but unfortunately I don't think it is quite so simple. I have plenty of 12v adaptors that will continuously charge my Samsung tablet via a USB C cable so the adaptor is not the problem.

It appears though that my old, new to me, 8" Samsung tablet with the USB Micro slot is looking for a Samsung (or equivalent) wall charger. If it sees one it charges easily fast enough to keep up with the drain. If it doesn't see a wall charger though and only sees a 12v adaptors it only charges at 0.5 amp, not enough to keep up with the drain.

So I'll repeat my original question. I'm looking for a small (7" or 8") tablet that you know will run continuously from a 12 volt socket. Basically it must charge faster than it drains so it is always fully charged. Any ideas?

Thanks all.
Click to expand...
You still miss the point, get a charger that's suited for the tablet. See post #27

Or one of these Amazon.co.uk

Or one of the many others available.
 
Plum said:
Fitting a higher current output charger is a good idea but will not make a difference if the tablet is only drawing, say, 1amp from a 3amp charger. One of these is really useful to measure the actual current draw of the tablet. Will also highlight the difference in your charging cables, some are more efficient than others:
Pardon our interruption...
(USB-micro and USB-C versions are available)
Click to expand...
Please stop posting useful links direct to the seller of the item.

I've now bought one because it seemed a good idea at the time!!!!
 
PaulRainbow said:
You still miss the point, get a charger that's suited for the tablet. See post #27

Or one of these Amazon.co.uk

Or one of the many others available.
Click to expand...
I'm a believer (rightly/wrongly) that a mismatched charger is the possible cause of fires with these devices, I will only use a charger..eg.Samsung/Samsung
 
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