charging cable with a usb on the other end?

[drolem]

Has anyone found a charging cable that has a USB on the other end? I have a portable charger with USB ports only and I'm looking all over, haven't found anything yet.

While i8n theory such a device can be made using a DC to DC converter, it would be highly impractical given the how limited USB is.

The power brick can supply about 3 A at 12V, for 36 Watts of power, and if you want that much power through USB, you would need slightly over 7 Amps. USB 2.0 speced at 0.5A, USB 3.0 at 0.9A, charging ports at 1.5A, nonstandard implementations up to 2.1A.

So in essence, USB simple can't supply the necessary current, and you can't just change the spec -- the connectors and cabling need to be able to handle that much, and I don't think that's reliably possible with the current connectors.

 

[silkrooster]

Problem is, I have been searching and can not find any specs on the surface USB connector. Those specs would tell you if the usb connector could accept a charge or not. In theory if the connectors are wired up to accept a charge it would charge the battery at a slower rate than the power brick simply due to the difference in voltage.

The formula is volts X amps = wattage.
ex.
3A x 12V = 36W
1A X 5V = 5W

 

[Nicola]

Problem is, I have been searching and can not find any specs on the surface USB connector. Those specs would tell you if the usb connector could accept a charge or not. In theory if the connectors are wired up to accept a charge it would charge the battery at a slower rate than the power brick simply due to the difference in voltage.

The formula is volts X amps = wattage.
ex.
3A x 12V = 36W
1A X 5V = 5W

The speed of recharge is not due to the difference in voltage, it is due to the difference in power.
Regarding the voltage, if the SP3 has internally a voltage booster (which I doubt) it would recharge. If such booster is not present the battery would not charge at all, since the chemical reaction would not start (not even slower)

 

[silkrooster]

That booster you are talking about, is called a transformer. It steps up the voltage from 5 volts to 12 volts. As long as the diodes are there for allowing the voltage to travel one direction, it is perfectly feasible to charge the battery via the usb connector. What I mentioned is the same as the innards of the power brick, except the brick steps down the voltage from 120 to 12.

 

[Nicola]

That booster you are talking about, is called a transformer. It steps up the voltage from 5 volts to 12 volts. As long as the diodes are there for allowing the voltage to travel one direction, it is perfectly feasible to charge the battery via the usb connector. What I mentioned is the same as the innards of the power brick, except the brick steps down the voltage from 120 to 12.

Technically, talking about "transformers" is incorrect, since a transformer is based on a completely different concept (a transformer is what you find inside the main power brick). It would be correct talking about "converters".
The same way, the diode allow "current" to travel, not "voltage".
Furthermore, diodes allow current to flow in one direction and not the other one (it's one of the main principles of diodes). If you apply reverse voltage, the diode cuts off the current.

 

[syclone]

Has anyone found a charging cable that has a USB on the other end? I have a portable charger with USB ports only and I'm looking all over, haven't found anything yet.

Short answer - I can't be done!

The SP3 power supply outputs 36 watts. Even if you could build a DC TO DC converter 5 - 12 volts it would need a current capacity of 8 to 9 amps. Such a USB device doesn't /can't exist. You can't violate Ohms law.

 

[wertzius]

I don't understand the discussion. It is not technically possible. Period.

 

[syclone]

I don't understand the discussion. It is not technically possible. Period.

AMEN!

 

[EHoskinson]

The problem is that your battery pack with USB output is 5v and is designed to charge devices through the USB port. However, the Surface is a 12v device and charges through the "magnetic" port and NOT the USB port. You cannot charge it via the battery pack you have. The proper voltage AND power is required to properly charge a device. A 12v device requires a 12v power source with the proper amperage available to charge as does a 5v device requiring 5v with the proper amperage. You cannot charge a 12v device with a 5v power source unless there is properly designed voltage step up circuitry involved and the necessary amperage.

 

[bluegrass]

Woah woah woah. Please speak regular human to me. I have no previous computer experience and lost you past USB. But yea I have a battery pack that I would just like to be able to charge my sp3 with. The battery pack only has USB ports. Thanks for all your responses!!

I have some of those too. They were sold for charging devices that can be charged by plugging into a USB port of a computer, ect. You battery pack outputs 5 volts via its USB ports. You will need to purchase a different battery pack that can output 12 volts. That's just part of the solution though. You will need to fine a 12 volt charging pack that has a cable that can plug into the charging port on the SP3. It is very rare at this time to find a battery pack that has a connector that can plug into an SP3.

Mikegyver is the only one I know of at this time and they are quite expensive. Mikegyver asks $90 for just a cable that can plug into the charging port on the SP3 that has a round connector on the other end. You could adapt this cable to a 12 volt battery pack (that has enough amperage) to charge the SP3. I think you could purchase a Microsoft SP3 charging pack for less than this cable and then cut the cable off the charger to use on a 12 volt battery pack. Mikegyver portable charges for the SP3 will run from $200 plus to over $400, depending on the amperage of the packs. I think this subject has been beat to death before on the forum so I won't go any further with trying to find a solution for your dilemma.

 

[gangolfus]

Mikegyver is the only one I know of at this time and they are quite expensive. Mikegyver asks $90 for just a cable that can plug into the charging port on the SP3 that has a round connector on the other end.

Amazon's got dozens of them listed, most for <$12. I bet eBay has that many as well. I use it with a $100 Anker battery pack also purchased from Amazon.

Battery pack: http://www.amazon.com/gp/product/B00B45EOYS/
Cable: http://www.amazon.com/dp/B00PBGVQQU/

There's the entire project for $110.

 

[tony8154]

Amazon's got dozens of them listed, most for <$12. I bet eBay has that many as well. I use it with a $100 Anker battery pack also purchased from Amazon.

Battery pack: http://www.amazon.com/gp/product/B00B45EOYS/
Cable: http://www.amazon.com/dp/B00PBGVQQU/

There's the entire project for $110.

How many times can this battery pack fully charge the surface pro 3?