Shelly Uni to Control Shelly 1 Plus relay to turn on Heatpad

Hi guys

My problem:

I have lifep04 batteries and I want to protect them from the cold… my idea is I want to measure the input charging voltage with ADC (this works)

if the input voltage rises (battery charger comes on above 12.5v ) and the outdoor temp is below 5c then the uni switches the 12v Heatpad on (Shelly 1plus controlling the Heatpad)

Will this work ??

thanks but how could i do this?? Temperature sensores are on Uni