Issue with powering Jetson Nano from Boost-Buck converter

I have a Nano on a mobile platform being fed from several 18650 batteries - nominally 7.4V
This setup was working fine when the main module was a Raspberry Pi 3B and the boost-buck was a 2A one.
I purchased several others at 3A and 4A in anticipation of swapping the RPi with the Jetson

I should say there is a 1602A LCD panel connected via i2c to the nano and its back-led is enabled.
Also the power is input via the barrel plug.

Yesterday I started with the 4A one and the Nano just sat there - no boot, no green light
I then cycled through all the boost-buck devices and the results were

  • no boot, no green light
  • no boot, no green light, 1605 back light on
  • no boot, no green light, 1605 back light flickering
    until I ended up with the original 2A one
  • boots fine, green light on, 1605 back light on

All these power modules are just ebay things so who knows what you really get but the ‘specs’ for the 4A one contain

  • Output ripple: 20mv (12V 3A)
  • operating frequency 180KHZ

I dont have an oscilloscope but the multimeter has a min/max setting. When using this voltage briefly drops a few tenths of a volt when Nano is connected.

So, Can anybody help please with any known ‘sensitivities’ about powering the Nano
Any brand of Buck module that is know to work?
Any other great ideas ?

Thanks for the help

Sorry for the late response, is this still an issue to support?