How to charge a tablet from dc power supply?

[Danke]

 

[SparkyGage]

I am not sure if this is the exact model but here is a link. I think that is it. It says 7volts. I will have to ask my mum later for the specific model since she is good at keeping receipts so will most likely have the details. That is the closest one I have seen but there are loads of similar models by that company so not 100%.

Ok, that is a Tablet-PC running windows and not a your standard iPad/Galaxy equivalent. You will want a specific 12v adaptor intended for that device that can both regulate and step down (CONVERT vs INVERT) to the correct voltage.

I have an almost identical Acer Tablet PC (that keyboard dock looks identical).

 

[wholybee]

This one is not new, depending how many years old you define as new. It is about 5-6 years old.

It doesn't charge by usb that I can tell. There is only the 3 pin plug linked earler. I tried plugging usb to some smaller thin one on the device but didn't do anything so I guess that port is just an output.

Ok, I wasn't understanding. Is the adapter you linked before the *exact* adapter for the tablet, or one similar? If that is the adapter for the tablet, you can cut the wire off of it, use a 3 Amp fuse, and connect it to a 12V battery or power source. Or source the correct connector for the tablet if you don't want to cut the wire.

USB is only 5v, so a USB socket/wire will not work.

 

[wholybee]

Why would direct to battery via fuse block result in slower charging? I thought that would be the most efficient.

That answer was only applicable to a newer tablet that charged via USB. Direct to battery is 12V. USB is 5V. PD is whatever the device wants, up to 48V. PD will convert the voltage to what is required. If the device wants more than 12V it will get it, and charge faster.
But now that I understand you have a 12V device, PD is not applicable.

 

[wholybee]

This discussion has too many pictures and links to stuff that isn't *exactly* what Gueyog8a7 has.

Gueyog8a7, what we need to see is a picture of the ACTAUL device in question. A picture of the charging port, and any text that describes the voltage and current requirements, and the same from the current charger.

This stuff is not universally interchangeable. Showing a link to something similar will possibly result in unpreparable damage to the device. So I suggest not proceeding until you can see the EXACT device.

 

[Gueyog8a7]

Ok, that is a Tablet-PC running windows and not a your standard iPad/Galaxy equivalent. You will want a specific 12v adaptor intended for that device that can both regulate and step down (CONVERT vs INVERT) to the correct voltage.

I have an almost identical Acer Tablet PC (that keyboard dock looks identical).

That answer was only applicable to a newer tablet that charged via USB. Direct to battery is 12V. USB is 5V. PD is whatever the device wants, up to 48V. PD will convert the voltage to what is required. If the device wants more than 12V it will get it, and charge faster.
But now that I understand you have a 12V device, PD is not applicable.

The device may not have been the exact one, or at least I wasn't sure at the time of writing but now think it is having looked in windows system details, but the charger is the exact one as I got my mum to take a picture of the exact one we use.

Anyway I have had success! I happened to find a couple of those barrell connectors in an electrical box of my mother's in the garage. So I checked the polarity with the adaptor and connected it to some 11a wire and wired straight to the fuse box, with 4 amp fuse, and hey presto it worked! I am not sure of the charging speed yet but I have it charging now. People are saying it can charge slower in some instances but won't direct to battery give it the ideal charge capability since the device chooses the charge and will draw as much as it wants from the battery?

This way was as simple as wiring up any other 12v device so no idea why people would go the convoluted dc to ac to dc route unless their device didn't allow a direct to battery connection like this.

 

[wholybee]

There was a misunderstanding early on about the application. With a UBS connector using PD, it would charge faster the more convoluted route. In your case, it will be the same.

 

[Gueyog8a7]

There was a misunderstanding early on about the application. With a UBS connector using PD, it would charge faster the more convoluted route. In your case, it will be the same.

Well unfortunately it isn't working . It seems only the charging light changes but doesn't charge or sooo slow as to be imperceptible. There is also a charge indicator when the tablet is open where you can look at the actual percentage and time to full charge and it would go down not up.

I had left it charging for 2+ hours and this using the original mains supply would have given full or near full charge however it hadn't budged when connected to the van battery source.

Interestingly I seem to be having similar underpowered problems with my usb ports too. If I am using my desktop computer to plug my ereader in then it charges it within about 4 hours or so but I had it on all day yesterday, probably 6-8 hours and it showed no indication of life after that time.

It can't be all the 12v connections having issues though since lights, fans and the diesel stove/heater (before it broke for other reasons!) have worked fine.

I can't say anything conclusively about the usb ports as I haven't tested much with it yet and that is the first thing I tried to charge with it but certainly is different to charge times on PC. The usb ports are rated at 4.8 single plugged and 2.4 both plugged. What kind of amps does a desktop pc circa 2013, so not top of the line tech like today, produce? I have trouble believing it is because of lower output of usb sockets compared to computers but really not knowledgeable on that. So different connection but same or similar issue so maybe related in some way so worth mentioning.

 

[Rednecktek]

Why would direct to battery via fuse block result in slower charging? I thought that would be the most efficient.

Because the fuse block will limit you to 12v where a PD charger can convert that up to 20+ volts. So if you have a 2a port at 20v that'll charge faster than a 2a port at 12v.

 

[Gueyog8a7]

Because the fuse block will limit you to 12v where a PD charger can convert that up to 20+ volts. So if you have a 2a port at 20v that'll charge faster than a 2a port at 12v.

Ok, well both the usb port's charge rate and tablet charging lead are as good as useless so what can I do? Please don't say the only way is to do the inverter method of dc to ac to dc .

I have been charging for 1.5 days via the usb port now a little puny e reader and still no signs of life from it where it would have charged in 3-4 hours if plugged to pc.

 

[Rednecktek]

Remember that a bog standard USB port, which is every USB 2.0 port on a computer, is only 5v @ 0.5a or 2.5w max charging.

Maybe I missed it, but did you ever find a picture of the factory charger we can see the output specs on? That might give a clue as to why it's not charging up right. Is that the 12v/3a wall wart you posted earlier? Next question would be does that wall wart charge the tablet correctly? If the factory wall wart doesn't charge it up, the problem may be in the device.

 

[HarryN]

In order to power one of the newer USB ports that can really power the newer devices, then you need to raise the DC input voltage.

One approach is to buy a DC - DC converter that takes in your existing 12 volt DC - outputs 24 or higher voltage.

Feed your higher power / higher voltage USB port with this higher voltage.

Make sure to select one that can really work with your device, and carefully read the reviews, because there is a whole lot of junk on the market.

Some of the newer phones and tablets can charge in the 70 - 100 watt range and a lot of the USB ports being sold can only do that for relatively sort periods of time before they over heat.

 

[Gueyog8a7]

Remember that a bog standard USB port, which is every USB 2.0 port on a computer, is only 5v @ 0.5a or 2.5w max charging.

Maybe I missed it, but did you ever find a picture of the factory charger we can see the output specs on? That might give a clue as to why it's not charging up right. Is that the 12v/3a wall wart you posted earlier? Next question would be does that wall wart charge the tablet correctly? If the factory wall wart doesn't charge it up, the problem may be in the device.

So you are saying that usb on computers are less rather than more powerful than a 12v in a van if mine is 2.4/4.8? I have plugged it into the pc this morning and still not come to life and stopping and starting charging so the e reader might have finally given up on me after 10 or so years. It was in a bad state anyway and various things broken on it

I have yet to try with other usb devices so will have to do that to gauge if the usb ports are at issue or the e reader.

First time I am reading about wall warts . Yes the one I pictured is the exact one used and it charges it fine within a couple of hours.

 

[Rednecktek]

So you are saying that usb on computers are less rather than more powerful than a 12v in a van if mine is 2.4/4.8? I have plugged it into the pc this morning and still not come to life and stopping and starting charging so the e reader might have finally given up on me after 10 or so years. It was in a bad state anyway and various things broken on it

Yeah, USB 1 and 2 are only 2.5w, it wasn't until USB 3 came out that we got more power, but that 5v really cuts things down.

I have yet to try with other usb devices so will have to do that to gauge if the usb ports are at issue or the e reader.

First time I am reading about wall warts . Yes the one I pictured is the exact one used and it charges it fine within a couple of hours.

Odd that the 12v wall wart charges it well but a direct to battery 12v connection doesn't. That makes no sense at all.

 

[Gueyog8a7]

Yeah, USB 1 and 2 are only 2.5w, it wasn't until USB 3 came out that we got more power, but that 5v really cuts things down.

Odd that the 12v wall wart charges it well but a direct to battery 12v connection doesn't. That makes no sense at all.

I thought you said the issue was due to the wall wart being able to go to 20v+? Even so doesn't the fact is ramps back down to 12v make that a moot point? Is there some way to troubleshoot what is going on?

 

[wholybee]

Well unfortunately it isn't working . It seems only the charging light changes but doesn't charge or sooo slow as to be imperceptible. There is also a charge indicator when the tablet is open where you can look at the actual percentage and time to full charge and it would go down not up.

I had left it charging for 2+ hours and this using the original mains supply would have given full or near full charge however it hadn't budged when connected to the van battery source.

Interestingly I seem to be having similar underpowered problems with my usb ports too. If I am using my desktop computer to plug my ereader in then it charges it within about 4 hours or so but I had it on all day yesterday, probably 6-8 hours and it showed no indication of life after that time.

It can't be all the 12v connections having issues though since lights, fans and the diesel stove/heater (before it broke for other reasons!) have worked fine.

I can't say anything conclusively about the usb ports as I haven't tested much with it yet and that is the first thing I tried to charge with it but certainly is different to charge times on PC. The usb ports are rated at 4.8 single plugged and 2.4 both plugged. What kind of amps does a desktop pc circa 2013, so not top of the line tech like today, produce? I have trouble believing it is because of lower output of usb sockets compared to computers but really not knowledgeable on that. So different connection but same or similar issue so maybe related in some way so worth mentioning.

I am even more confused than before. I thought we were talking about a Tablet PC. Now an ereader? And the picture of the charger you posted was not USB, but you are able to charger via the USB on your laptop? This stuff is not interchangeable, I reiterate my previous request, we need to know EXACTLY what you are trying to charge, or else it won't work and you might damage it.

The battery is 12V. A USB Socket is 5 volts(internally it converts 12V to 5V). Those 2 power sources are not interchangeable. And a USB port with PD has electronics (a small microcomputer) that talks to whatever is being charged and adjusts it's voltage to what is being asked for. Something that uses PD can not be charged any other way. Maybe the issue with your USB ports is that you need USB/PD.

But anyway, we need to see the exact device you need to charge, and if possible the charger that it was sold with that works with it.

Regarding power from a USB port on a computer, probably 2A. The original spec for USB many years ago was 0.5A.

 

[Gueyog8a7]

I am even more confused than before. I thought we were talking about a Tablet PC. Now an ereader? And the picture of the charger you posted was not USB, but you are able to charger via the USB on your laptop? This stuff is not interchangeable, I reiterate my previous request, we need to know EXACTLY what you are trying to charge, or else it won't work and you might damage it.

The battery is 12V. A USB Socket is 5 volts(internally it converts 12V to 5V). Those 2 power sources are not interchangeable. And a USB port with PD has electronics (a small microcomputer) that talks to whatever is being charged and adjusts it's voltage to what is being asked for. Something that uses PD can not be charged any other way. Maybe the issue with your USB ports is that you need USB/PD.

But anyway, we need to see the exact device you need to charge, and if possible the charger that it was sold with that works with it.

Regarding power from a USB port on a computer, probably 2A. The original spec for USB many years ago was 0.5A.

The usb thing was another matter. Indeed I did muddy the waters mentioning that. Forget about that .

The charger I pictured earlier is the EXACT charger used to charge the tablet. The tablet charges as expected from the wall plug.

It does not charge using direct connect with same 2.1mm barrel connector when direct connected via fuse block to the battery (delete the mentions of usb from your mind ).

I thought I would try again yesterday and just the same. The charge goes down and time to charge just goes up while showing as connected and charging light changes colour.

 

[wholybee]

The usb thing was another matter. Indeed I did muddy the waters mentioning that. Forget about that .

The charger I pictured earlier is the EXACT charger used to charge the tablet. The tablet charges as expected from the wall plug.

It does not charge using direct connect with same 2.1mm barrel connector when direct connected via fuse block to the battery (delete the mentions of usb from your mind ).

I thought I would try again yesterday and just the same. The charge goes down and time to charge just goes up while showing as connected and charging light changes colour.

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.

 

[Supervstech]

The usb thing was another matter. Indeed I did muddy the waters mentioning that. Forget about that .

The charger I pictured earlier is the EXACT charger used to charge the tablet. The tablet charges as expected from the wall plug.

It does not charge using direct connect with same 2.1mm barrel connector when direct connected via fuse block to the battery (delete the mentions of usb from your mind ).

I thought I would try again yesterday and just the same. The charge goes down and time to charge just goes up while showing as connected and charging light changes colour.

Some electronics require precise voltage to function.
The charger outputs 12V your battery likely outputs over 13…

 

[Andrewr05]

Some electronics require precise voltage to function.
The charger outputs 12V your battery likely outputs over 13…

So, they could still use their battery bank, but could probably get away with just getting a ~12v* to 12v dc-dc regulated converter.
They're usually only like $15 shipped.

*likely accepts something like 9-14v