Second what you been doing,here search phantom replacement remote batt on Google this comes up,,,,you might even have one lying around 7.4 volt,,cut and chop plug
Well my p3s was brought in 2016,,remote still work fine,p4 was brought 2017,remote still work fine,,after most flights it's back on charge,I never let it run down ,some run all weekend on same without charging till 2 lights or flat,,,I never do this,,my opinion,,way I see it fully charged is a good strong signal as well,,we don't fly on 50% drone batt so why fly on 50% remote batt,keep it charged my advice