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I just bought this product: "Jackson PT1USB" as an attemp to get a portable charger for my netbook, ipad 2 and smartphone.

Now I am bit worried after reading in the product "total connected load to both usb sockets must not exceed 1 amp"

From my other usb chargers I read that they provide 1 amp and read that the Ipad can use up to 2. I connected my S3 phone and ipad2 for some seconds and they seemed to charge fine.

My netbook charger only outputs 2.1 amp so I guess it should be fine with the overall 10 amp limit.

I don't know much about this so I would like to know if there is any risk connecting all the devices at once. Can I damage them?

m.Alin
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Adrian
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1 Answers1

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Damage is unlikely. Most likely what will happen if you overload the USB charger is that it will either drop its voltage or cut out altogether. If it drops its voltage, then things won't charge right. If it cuts out, then it will be like it is off. It may cycle on for a short time every few seconds while the overload persists.

Actual overload is also unlikely,however. USB 2.0 only provides for 100 mA per device without enumeration, and 500 mA after requesting and being granted the extra current. Without special communication, your devices have to assume they are plugged into a normal USB port and not draw more than the maximum current for such a port. There is a reasonable chance that your devices are well enough behaved to not overload a ordinary USB port and only draw extra power form their special branded chargers after some private communication. However, this will mean that these devices will take longer to charge their batteries as fast. You can't have it both ways.

Olin Lathrop
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  • I will have to look, but the way the USB charging spec was written to my memory the device pulls up to 1.8A or stops if the voltage sags to 4.5V, so a charger should just sag to 4.5V when it reaches max load. I am not sure about the 4.5V – Kortuk Sep 18 '12 at 09:47
  • If the *devices* obey this USB charging spec you mention, then that is even better. I haven't seen that spec, so I don't know how a device is supposed to know it is connected to a compliant charger or a ordinary older USB port. Either way though, it seems no harm should be done, and if the charger spec was followed all around, then it will even charge well. – Olin Lathrop Sep 18 '12 at 14:34
  • I discussed it on an answer I wrote [here](http://electronics.stackexchange.com/questions/5498/how-to-get-more-than-100ma-from-a-usb-port/5581#5581) a long time ago. If you short the data lines it tell the device it is a charger. – Kortuk Sep 18 '12 at 19:18