Perhaps a better way to word your request is to ask for a
minimal current drain USB outlet to which I can give you a more useful answer.
For instance the Blue Sea dual USB outlet only pulls 0.015Amp which would take 3,333 hours to suck 50 Amps out of a battery.
12/24V Dual USB 2.1A Charger - Blue Sea Systems
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Jim _ My Adventure Blog:
http://suntothenorth.blogspot.com
2018 TRD Off Road Premium
ARB on-board compressor - RadFlo coilovers & rear suspension - Engel freezer-fridge - All Pro LCAs - African Outback roof rack, RCI skid plates