On the design front, I see the v1.3 module is using a TPS62933DRLR to generate the +5V rail from whatever voltage comes in. Given the input voltage will have dropped across the schottky diode and there will be some degree of drop at the power supply and across the lead from 5.0V it looks like the choice of a buck converter prevents generation/restoration of 5.0V will impact to the +5V rail? I see quite a few schematics showing use of linear regulators on the modules to make a clean local 5V supply so perhaps this has less impact than one might think?
I just measured a few power sources at the GND- VIN+ pins and at +5V rail with a multimeter and aforementioned 8 module load, here are the numbers in descending order:
- Variable wallwart 2.5A PSU set to max 12V: in 11.93V, 4.86V
- Smartphone USB-C charger + good quality USB-C lead: 8.64V, 4.86V
- Raspberry Pi 15W PSU: in 4.73V, rail 4.46V
- 5000mAh power bank (charged recently) with very short lead: in 4.45V, rail 4.19V
- 5000mAh power bank with long lead: in 4.20V, rail 3.95V
- Power strip USB type A with long lead: in 4.14V, rail 3.89V
Was a buck/boost converter considered for making the +5V to deal with, say, 3V-13V input?