hpi trophy hump pack problem

[moggy12]

my son has just bought a secondhand nitro hpi trophy we bought a hump pack for the buggy i can connect straight to the battery input on the receiver works fine but is live all the time original battery box which holds 4 aa batterys are connected to a switch which is soldered is there any way of having the hump pack in the car and be able to switch car on/off with the switch ? both me and my son are new to nitro i race electric touring cars thanks for any replies