Batteries 1 or 2 batteries

[yak man]

i have a 30cc yak with 1 A123,2300 mha battery running ign,42 % optic kill ,and spectrum 8000 receiver, looking to add an other battery and switch to run receiver and remove extisting wire from receiver, but when i do this red light for ign goes out, like to keep orginal battery , switch, wiring and indicator light together for ign.,looking for help why red light goes out when unplugged from receiver thx bill