I used their cable which was supplied with the board, and it works. It is a USB-C to USB-C. It is short, about 15-20cm, as you have mentioned. But then, to check the drop, I also made my own cable connector using the male USB-C connector bought, which was rated for 5A. Something like https://wmsc.lcsc.com/wmsc/upload/file/ ... 464651.pdfTo avoid voltage drops, the 5A connections should use at least 18AWG cables (lower numbers better), as short as possible. At the converter's higher input voltage, the current (and therefore voltage drop) is proportionately less, and also less significant as a proportion of the voltage -- but cables should still be thick and short.The problem with 5V 5A negotiation might be that the connectors of these converters will drop significant voltages. If cables are present between adapter and converter, that drops more voltage as well. The voltage drop gets very worse at this 4-5A range. Special cables might make sense at very high currents.
The "negotiation" is irrelevant to the voltage loss -- given that the Pi needs 5V (within 5%) and given that its current needs are determined by its workload and peripherals, whether 5A is negotiated or not, the actual current used is the same, within the PSU's limit.
I'm not sure what you mean by "special cables". There are of course many unsuitable cables, but "thick and short" covers the needs. Also, avoid having more plugs and connectors than necessary. If you are making cables, ensure the connectors are rated for 5A.
The connector was actually having a very significant loss than the cable when I used a thick-short cable. LLCR for the above connector is about 40mOhm for VBUS, which I believe would be about the resistance of the contact. The cable was dropping significantly less voltage as it was thicker when compared to the connector. I used a AWG 14 cable at 5cm.
Regarding negotiation, what I meant was the negotiation between the normal adapter and the Pi. What I meant was that, if 5A is negotiated and about 4A is drawn, if the cables are not very short and thick as you have mentioned, the cable might end up losing significant voltage over it. We both have the same point to make. Thick, short, good connector.
By special cables, I meant, cables which are very short and made with thicker conductors, with 5A or better rated connectors. The normal cables available in my country are usually longer, though rated for 5A. They are usually designed for mobile phones. I used a One Plus Dash Charging USB-C to USB-C cable (65W) 6.5A rated at 5V cable which was the one easily available, and it ended up losing very much voltage at 4-5A. Shorter cables were hard to find in my nation, at least, which were rated for 5A. So, it made it hard for me to get a high rated, short length cable. There were many cables rated for 5A or better, but they ended up dropping voltage a lot as they were long.
Since my cable assembly wasn't that great, I ended up using their cable after I had fun with the custom cable.
If the connector-cable assembly had about 40-50mOhm resistance, it meant a drop of 200mV to 250mV at 4-5A. Removing the connector improved this a lot for me.
Apologize for the confusion caused as we both were having the same point.
That board also had soldering pad. So, it looked better wrt to the voltage when I soldered the output of the 5V converter board and used single connector for Pi's input. The voltage drop over the cable reduced a lot when I did this.
Statistics: Posted by johnny7 — Fri Aug 23, 2024 5:43 pm