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Can I effectively take a 3 ft standard cell phone charger (AC to microUSB, 750 mA at 5V) and lengthen the cord to 6 ft by splicing the cord or am I going to lose something in the mix? Do I need to account for the length of the cord when they are such short lengths?

mattz
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A couple things.

  1. Charging cables run up to 1.8 amps under the usb spec. I have an answer about it here.
  2. Yes, it will work. Please make sure to use heat-shrink or electrical tap to avoid shorts.
  3. USB runs relatively high speed and 6 feet is further then you might think, this can significantly degrade performance on the communication, not an issue for just charging. There are cables out there that come 6 foot or more.(ignore this if it is a wall outlet to USB charge adapter)
  4. If you are using a wall charger and it is only giving you 750mA you are getting half of the capacity you could be getting. If you phone can handle it, higher end phones will, you will be able to charge in less than half the time. (ignoring the charging characteristics of the last 10% of a lithium battery)

Just a quick list of things that might help. Your splicing the data cables will hurt the data quality and probably radiate some noise. I do not think there are any communication protocols on a harmonic of USB, so it should not matter one bit.

Community
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Kortuk
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    Looking at my phone charger right now (one with a permanent cable with micro USB connector on the end), it's just a pair of wires molded together (a la lamp cord or whatever it's called), so concerns about using a charge cable for data may be moot. – Nick T Mar 31 '11 at 02:58
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    @NickT, It seems I may have misunderstood. The "charging cable" is a wallwart with a usb end? ignore point 3 for that. – Kortuk Mar 31 '11 at 03:01
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Adding 3 feet shouldn't be any problems at all. The USB power spec allows for some voltage variation, and the added 3 feet isn't going to exceed that spec at all. In fact, it will hardly be noticeable.