@jbkiwi @Vinduino Like you I am looking at some ‘off-grid’ sites where I will have solar back-up and also at some sites running on passive/low voltage (vs 24/48V) POE enabled GW’s - I’m running RG186’s in UK/EMEA so hopefully not too much difference with your 191’s.
When I checked with the dev team at Laird I was advised 12v quickly dropped on motherboard and therefore should be good for 6V to 18V range at adapter input , later amended down to 15Vmax due to presence of a fuse on board (should help with limiting regulation and supply losses from solar panel and associated back-up battery). No ‘guarantees’ but if supply not too noisy potential for operation down to <=5V - 4.5V poss but YMMV.
As a test I have run a couple of sample gateways (in benign environments not testing over temp/in the field) from a 5V supply and also from 5V USB power-bank with no issues over many hours…GW was not heavily loaded and was only handling packets from 5 or 6 nodes - so again overall performance may vary if handling 100’s/1000’s of nodes,generating high load and lots of network traffic
Using a simple USB power monitor I was able to test rough order of average current consumption - wasn’t monitoring peaks - and typically saw operation at around 350-400mA…see sample pic attached
During GW startup measured voltage was 5.01 - 5.06V. Actual voltage measured during steady state op was ~4.97V not the 4.94V indicated on display!
Good luck…keep us posted on what you see. I will be running more tests later next month with 4 or 5 new GW’s and will update here also…