Many automobiles--such as the Honda Odyssey--are wired so that the power access points and cigarette lighter receptacles are powered only when the engine is turned on. This is a safety feature which preserves the battery from being drained while the engine is not running. However, there may be times--such as on a camping trip--where a low-drain device such as a portable radio or cell phone charger may require electrical power. In this case, an "always-on" power access point can be useful.
Cut a length of black electrical wire that will reach from the battery to the desired location inside the vehicle. Cut an equal-sized length of red wire. Strip ½-inch of insulation from the ends of both wires and route both wires from the battery to the location of the power-access point.
Place a spade terminal over the battery end of the black wire and crimp the terminal to the wire. Place the remaining spade terminal over the battery end of the red wire and crimp the terminal to the wire.
Loosen one of the top bolts on the negative battery terminal connector and place the spade terminal connected to the black wire between the bolt and the battery terminal. Tighten the bolt so that it holds the spade connector snugly to the battery terminal. Repeat this step for the positive battery terminal and the red wire spade connector, respectively.
Place a wire splice connector over the end of the black wire that is inside the auto. Insert the black wire from the cigarette lighter socket assembly into the splice connector and crimp the connector to the wire pair. Place a wire splice connector over the end of the red wire that is inside the auto. Insert the red wire from the cigarette lighter socket assembly into the splice connector and crimp the connector to the wire pair.
