Does charge cord length effect Mintyboost efficiency?
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Does charge cord length effect Mintyboost efficiency?

by lee321987 on Tue Feb 05, 2013 12:49 am

Hello.
Since trace length is so important with switch mode power supplies, I'm wondering if it would be worth it to hack together some really short cords to charge my devices.

Would there be much efficiency gained from going from a 3-foot cord to a 6-inch cord?
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Re: Does charge cord length effect Mintyboost efficiency?

by adafruit_support_bill on Tue Feb 05, 2013 7:36 am

That is a very good idea. All things being equal (wire gauge etc) a short cord will have lower resistance and therefore lower voltage drop and wasted power under load. Long skinny cords do cause charging problems with many phones.
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Re: Does charge cord length effect Mintyboost efficiency?

by lee321987 on Tue Feb 05, 2013 5:09 pm

Thank you.
But what about the inductance and capacitance of long cords?
Don't these have a big effect on SMPS's?
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Re: Does charge cord length effect Mintyboost efficiency?

by adafruit_support_bill on Tue Feb 05, 2013 6:17 pm

Not really. At that point it is all DC going to the phone.
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Re: Does charge cord length effect Mintyboost efficiency?

by Illum3415 on Sun May 11, 2014 2:58 pm

Normally, off the shelf USB cables are pretty well shielded from stray inductance. What may ultimately reduce charge efficiency is the number of contacts across the circuit and the gauge of wire used, every connector to connector interface contributes to resistance, and corrosion on those contacts increase series resistance. There should be negligent effects between using a 3ft cord and a 6ft cord as far as charging is concerned. If data is transferred across those data lines, it may become more of a factor above 6ft, but in terms of a power reference bias I wouldn't worry about it.
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Re: Does charge cord length effect Mintyboost efficiency?

by adafruit_support_bill on Sun May 11, 2014 3:07 pm

There should be negligent effects between using a 3ft cord and a 6ft cord as far as charging is concerned.

That assumes negligible resistance of the 5v and GND wires. While in good quality cables this is usually true, there are may cables of questionable origin - particularly the 'ultra-thin' variety that do cause real problems in charging. I opened up one such cable and found that the conductors were on the order of 30 AWG.
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