USB Y Split for power

I've just got a simple question, which I was surprised to not find anywhere. A long time ago, I had a portable drive which had a single usb cable to two ends. One end had data + power, and the other end had just power. This was to supply more than 5v to the drive. I want to recreate this, do I need to do anything except splice another cable (with just the power + ground) into the one I have? Do I need to put anything in between them? Thanks, Ivan

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Lurch8 years ago
I've got a couple of cables like this for external drives, they are in parallel, not series, so will provide 5V @ 500mA. Saves external PSU's for some older laptop drives that take more than 250mA. As you say, easiest way is just to get an additional cable and splice the power pair onto an existing cable. Make sure you isolate the data pair where you cut the end off.
ocelot117 (author)  Lurch8 years ago
I'll check it out. I'm using this for a modified xbox controller (original xbox to pc usb) which seems to not be getting enough power.
Lurch ocelot1178 years ago
A quick Google tells me Xbox controllers want 400mA @ 5V so that would appear to tally up with your results of it not working with 250mA. ;)
ocelot117 (author)  Lurch8 years ago
Thanks a lot, I'll get right on it. Having it at 500mA won't hurt anything will it?
Lurch ocelot1178 years ago
No. The current rating is the maximum that the USB ports can supply, the controller will only take what it needs up to that limit.
ocelot117 (author)  Lurch8 years ago
Thanks again. Also, when I splice them together, what should I do with the unused data pair?
Lurch ocelot1178 years ago
They'll just need isolating from each other and anything else to prevent shorting. Either individually tape them up or place them in some sort of insulated connectors.
110100101108 years ago
there are 5 V in usb you cannot connect them in series with another 5 V from usb to make 10 V
ocelot117 (author)  110100101108 years ago
I didn't think so. . .I know there is a way to do this though. I'm no electronics expert, can anyone help me out?
voltage doubler with capacitors ? inverter ? (scaled up joule thief)