How cable length and chargers affect charge rate

I recently purchased a handful of Monoprice micro USB cables in 3 different lengths. I thought it would be interesting to test the different cables with two different chargers and share the results.

Test Equipment:
Load: Samsung Galaxy Note 2, Custom 4.3 ROM (Carbon), battery @60%
Measuring tool: Charge Doctor (USB voltage and amp meter)

Stuff to test:
Cables: 12", 36" and 72" Monoprice micro USB cables
Charger 1: Samsung 2.0A USB charger (Stock Note 2)
Charger 2: Asus 1.35A USB Charger (Stock Nexus 7, 2013)

Assumption:
Each of the Monoprice USB cables are made with the same gage wire, visually they look the same.

Method:
Phone turned on, camera app loaded, attached the test USB cable photographed the results on the amp meter. I tested each of the 3 cables the same way and repeated the tests with the 2nd charger. Did it all within 10 minutes so that the amount of charge on the phone didn't change significantly.

Results: (See attachments)

Analysis:
- The Asus charger, even though it is capable of putting out 1.35A and even though the phone is capable of accepting at least 1.0A (demonstrated with the Samsung charger), it could only deliver .73A
- The Asus charger seemed to max out at .73A as the 12" and 36" cables had the same results
- The graph indicates the Samsung charger may be able to do better with an even shorter cable

Conclusions:

1) The shorter the cable the faster the charge, but there's a limit
2) The higher amps the charger is capable of, the faster the charge, there must be a limit but I only had 2 chargers to test
3) Duh!

Scrawson said:

Awesome data. As expected, there is a difference between the current rating on the charger, max current draw on the phone, and actual use, but I didn't expect it to be so much.

I'm curious how much my charger setup gets and concerned that if I did get up above 1A I might overheat my phone. Next test is battery temperature after a few minutes of charging at various currents.

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Good idea, I even have an IR instant read thermometer, but it'll take more time to test. To give the battery time to heat up I'd assume I'd have to wait at least 5 minutes, then I'd have to let it rest to get back to room temperature, that might take even longer. If I get ambitious I'll do it.

buster_friendly said:

Easy answer.

It does not.

(unless you have a cable so long, the voltage drop over the cable brings the voltage below 4.75V)

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The tests I did certainly seem to indicate cable length does affect charge rate.