Edited by MemberChuwi at 10-28-2017 01:04 |
To be honest, l don't trust speculations with PD communication as long as I can't see a sniffer protocol.
PD is not about basic electric properties only. As far as I understand maximum current is statically communicated by a control voltage via dedicated pins. These are not prone to thermal wear the way you describe. The voltage increases (probably more details) are communicated dynamically (electrically its an ac overlay to the static voltage specifying max current needs). If this communication fails the electric properties are irrelevant. The charger sticks at 5V then and that's not enough to charge Hi13.
The oxidation may be true in general but because we don't know materials and any related data your hint remains speculative. There are 4 pins for Vbus and Gnd to spread current so even 3A results in just 0.75A per pin, assuming approximately even distribution. We also know that Hi13 does not use 3A but approx. 2A for charging, simply referring to keyu specs. This results in 0.5A per pin which is the same as USB 2.
Engineering is not about presenting formulas only, it's about interpreting them. The main current is not significantly determined by contact resistance (as long as it's not really extremely high) compared to the load we face here. To push 2A @12V total resistance is about 6 Ohms. I doubt contact resistance will ever reach 10% of this. Even with 5A (20 V) 100W USB charging we get 4 Ohms load resistance. There may be some tiny loss by the cable itself too, still how much total resistance do you expect? You seem also not to unterstand the models of voltage source and current source. A constant voltage step means current can not increase with resistance. Instead current drops. With increasing voltage drop you get of course additional power dissipation, resulting in more heat. To be honest, I've not experienced any significant warming with the plugs during charging yet. The charger warms up slightly, the tablet too. Nothing at all with the cable. I'm curious about your data or assumptions on resistance effects.
To me your explanation remains speculative referring to my experience RavPower's battery did not work to charge my Hi13. Its much more likely that it does not work what's not specified - 12V step. Because it is not officially supported it's prone to firmware changes in chargers, maybe some production batch works, another maybe not. That's my thought on any charger not explicitly specifying 12V . You don't know if it works with Hi13.
The fact that the stronger Aukey charges my Hi13 confirms that PD works with my device. Unclear is to me why the smaller one does not work. It should from electric standpoint but it does not from PD perspective. As it's speced for 12V and 2+A there must be a different problem. I think contact corrosion is very unlikely for complete failure, this would just explain heating plugs or slower charge speed only. I believe it's a PD communication bug... but that's also speculative without a sniffer protocol, it's just a somewhat logical conclusion that makes sense to me...
I don't believe in magical obscure assumptions without a proper evidence as long as there are simpler more likely options. However, magic isn't completely impossible either... just less likely - as long as we have no better facts