How to charge a tablet from dc power supply?

Some electronics require precise voltage to function.
The charger outputs 12V your battery likely outputs over 13…
I doubt an overvoltage of a couple volts would cause an issue. But a bad connection that causes a voltage drop as current increases certainly would. I think a bad connection is the likely problem.
 
Perhaps there is a bad connection somewhere or cold solder joint on the 2.1mm connector. If there is a bad connection, you would measure 12V at the 2.1mm plug, but if you plug it into a device, it won't actually provide a full 12V. Because it seems fine when not plugged in, it can be difficult to find while testing. But that is what I would look for, make sure all connections and soldering is perfect. And that the source 12V battery is indeed fully charged.
Maybe this could be it since the connector I used was one that was in the garage electrical box and probably over 30 years old. I guess worth buying a new one to try that.
 
Because it is safe, easy and it works !
Also very expensive compared to other options I guess.

I would sooner buy another tablet that could charge by usb out of the box. Or a raspberry pi which was my original plan but since my mum already had this spare tablet I am trying to figure if it will work for me first.

Would the cigarette lighter option also have the same issues? I don't want to use the van's port to drain the starter battery, which I already have issues with if I do not drive for a while, so I am guessing I can buy a port to connect to the leisure battery and also the adapter for the tablet but will the same lack of charge issue likely be the case?
 
Would the cigarette lighter option also have the same issues? I don't want to use the van's port to drain the starter battery,

If the cigarette lighter is on the dash, it is getting probably getting power from the starting battery. Depending on the vehicle, some cigarette lighter outlet may or MAY NOT be power when the vehicle is OFF.
 
So I bought a new connector and tried and still the same thing.

I even tried charging with the first one overnight and by morning nothing perceptible was added,

Something else interesting to note though. There is a second 'wall wort' not made specifically for the device, that is BESIDES, the one I already posted, for clarity. We tried to use it weeks ago and thought it didn't charge however tried again the other night overnight and it charged it but it seems much slower than the intended charger. This second one has a screw turning on the adaptor to alter voltage up to 12v maximum and that was what it was on.

This is what made me think that trying in the van again would work if I waited longer since this second one worked at a slower rate and seemed to fully charge over night on the mains supply in the house. Alas charging from the battery still did nothing that I could see.

So my only options now are cigarette, dc-ac-dc inverter or new tablet that will charge via usb?

What is the liklihood the cigarette lighter way would be any different? I also don't want to plug into my existing cig port since it is connected to the starter batt which would mean buying a port just for this but if it is still 12v why would it be any different than the initially problem of being underpowered?
 
If the cigarette lighter is on the dash, it is getting probably getting power from the starting battery. Depending on the vehicle, some cigarette lighter outlet may or MAY NOT be power when the vehicle is OFF.
Well there is no question it is because I installed the leisure battery electronics myself and no other power but the stock electrics in the van before which would all be via the starter. Don't want to use that for this as it would be in use constantly.

I just found this. Would this likely work or end up being the same as the original issue of being underpowered? I don't see what will change if it will still step down to 12v?
 
Honestly, if even your stock charger isn't charging the device (unless I'm misunderstanding you) then I think there is a problem with the device itself and not the charger.
 
Honestly, if even your stock charger isn't charging the device (unless I'm misunderstanding you)
You are.

The stock charger works flawlessly.

There is a second charger, which is not the standard one, which I tried because it says 12v which I thought might be the same as charging from my leisure battery to compare it. It charges from the mains with that one but extremely slowly.

Not charging at all that I noticed when connecting direct to battery.
 
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