USB cables differ greatly with regards to their resistance. Too big a resistance can prevent devices from working or make them charge slowly. So, what about USB-C cables?
I took my power bank, some USB-C cables, two USB-PD trigger PCBs, a multimeter and a small electronic load, put all of them together and devices a small test setup: First, measure the open circuit voltage at the end of the cable. Then, put 2.5 A of current through it and measure again. The baseline is a USB-PD trigger that is directly connected to the power bank (“no cable”). That module is larger than the other and thus potentially suffers from more voltage droop. Thus, it is a fine baseline. The other, small module will be attached to the USB-C cables. The column “relative power lost” describes how much power is lost in the cable, compared to what the power supply theoretically outputs (open circuit voltage * 2.5 A). The “no cable” case shows which amount is lost in the power bank, the connectors and the USB-PD adaptor.
Numbers
| Type | Length (m) | Voltage w/o load (V) | Voltage w/ 2.5 A load (V) | ΔV (V) | ΔV, cable only (V) | Resistance (Ω) | specific resistance (Ω/m) | Dissipated power (W) | Relative power lost (%) |
|---|---|---|---|---|---|---|---|---|---|
| no cable | 0 | 20.07 | 19.88 | 0.19 | 0.19 | 0.076 | 0.475 | 0.95% | |
| ??? thick plug | 1.6 | 20.07 | 19.25 | 0.82 | 0.63 | 0.252 | 0.1575 | 1.575 | 3.14% |
| Baseus 5A | 0.5 | 20.08 | 19.8 | 0.28 | 0.09 | 0.036 | 0.072 | 0.225 | 0.45% |
| Baseus 5A | 2 | 20.08 | 19.51 | 0.57 | 0.38 | 0.152 | 0.076 | 0.95 | 1.89% |
| Anker PowerLine+ | 2 | 20.09 | 18.99 | 1.1 | 0.91 | 0.364 | 0.182 | 2.275 | 4.53% |
Words
It’s apparent that the most expensive cable (Anker PowerLine+) performs worst: Its specific resistance is 139% worse than the Baseus (2m) and 16% worse than some random no-name cable (“thick plug”, 1.6m) that I had lying around. Put into user-centric terms: If I attach my phone to the Anker cable, it would charge 2.6% slower than with the Baseus cable or 1.4% slower than if I would use the no-name cable. I didn’t expect this and I’ll keep an eye on those Baseus cables. They are totally worth their 2 €!