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eenk · 10-09-2015, 03:24 AM

There is a certain percentage of voltage difference to 5V allowed. The spec says +/- 10% so voltage may go up as high as 5.5V. Many cheap junk USB power supplies actually work undervoltage when there is medium to heavy load, sometimes even barely reaching lower 4.5V.

The 5.1V overvoltage boasting is simply and plainly advertising crap. If there would be real overvoltage, you would have by now an expensive door stop made by Kobo. Kobos are, as are other USB powered devices are, designed to spec, any overvoltage outside the spec can destroy it.

I guess your previous power supply was so bad it couldn't even supply 4.5V. Google for USB power supplies tested by a skilled electrical engineer: there is so much non-spec crap on sale that is even highly dangerous, as it was improperly design, so there can be shorts between mains and USB. There's sadly a reason for several deaths in Mainland China due to non-secure USB power supplies.

10-09-2015, 03:24 AM	#16
eenk carrier lost Posts: 62 Karma: 14000 Join Date: Aug 2015 Location: 2001:db8:e:b00c::f00d Device: Kobo Forma, H2O v1, Aura HD	There is a certain percentage of voltage difference to 5V allowed. The spec says +/- 10% so voltage may go up as high as 5.5V. Many cheap junk USB power supplies actually work undervoltage when there is medium to heavy load, sometimes even barely reaching lower 4.5V. The 5.1V overvoltage boasting is simply and plainly advertising crap. If there would be real overvoltage, you would have by now an expensive door stop made by Kobo. Kobos are, as are other USB powered devices are, designed to spec, any overvoltage outside the spec can destroy it. I guess your previous power supply was so bad it couldn't even supply 4.5V. Google for USB power supplies tested by a skilled electrical engineer: there is so much non-spec crap on sale that is even highly dangerous, as it was improperly design, so there can be shorts between mains and USB. There's sadly a reason for several deaths in Mainland China due to non-secure USB power supplies. Last edited by eenk; 10-10-2015 at 02:04 PM.