There can be times when you need to install an additional cigarette lighter or accessory port to a car battery.
Perhaps you want an additional 12V port in a car that is always hot or your appliance – a power inverter, an air pump, a tire inflator has a cigarette male plug that you’d like a socket for it to plug into.
Fortunately, you can wire an accessory port or cigarette lighter socket direct to a 12V battery. Knowing how to connect a cigarette lighter socket safely to a 12V battery can help you get your appliances working reliably and safely.
This post provides tips on how to connect a cigarette lighter socket safely to a 12V battery.
Which Cigarette Lighter Socket Connection to Use – Always on or Switched?
Always on circuit
Yes, you can wire a 12V cigarette lighter socket directly to a 12V battery. This is useful if you want the appliance to be supplied with battery power even when the car ignition is turned off.
The downside to this is it can drain the battery if the accessory is not switched off.
If you need the socket powered down when the ignition is off, locate a fuse in the fuse box that is switched by the ignition.
Extend the “hot” side of the wire to the central terminal of the cigarette lighter socket. Make sure to install an inline fuse to protect against overloading the circuit.
The switched connection prevents battery drain by also disconnecting the accessory from the battery when the ignition is off.
How to safely wire a cigarette lighter socket to a battery?
To wire the cigarette lighter socket safely to the battery, you need to select the right wire gauge, get the polarity right and install a suitable fuse rating for protection.
What Wire Gauge for a 10A 120W Cigarette Lighter Socket?
You can use a 12 or 14-gauge wire to connect the cigarette lighter port to the battery.
The power consumption of connected accessories should be limited to 120W to prevent damaging the wires.
Keep the wires as short as possible to minimize voltage drop.
Fuse Size for a 10A, 120W Cigarette Lighter Socket
Size the fuse rating based on the wire gauge connected to the cigarette lighter. Depending on the power handling capability of the cigarette lighter socket you can use a 10A (10A, 120W) or 15A (15A, 180W) fuse for the cigarette lighter socket.
Connect the inline fuse as close as possible to the battery on the positive battery wire.
Wiring the Cigarette Lighter Socket to the Battery
Connect the socket to the battery as follows:
Which Wire to Connect to the Positive Battery Post?
If the cigarette lighter socket comes with preinstalled black and red wire, connect the red wire from the socket to the battery post marked positive, and the black wire to the battery post marked negative.
If the cigarette lighter socket or accessory does not have any wiring, connect the red positive wire to the copper/bronze colored terminal and the battery positive post, and run an appropriately sized wire from the brass (silver) terminal on the cylindrical housing to the battery negative post.
Should you accidentally switch the connections, you risk damage to the appliance if the appliance does not have reverse polarity protection.
How to Check if the Cigaretter Lighter Socket has Power
To check if the cigarette lighter socket works or not, try the following:
#1. Some cigarette lighter male plugs connected to an electrical accessory have an LED indicator that lights up when plugged into an energized socket.
#2. You can also plug in a known working accessory to check if it is working or not.
#3. Alternatively, use a DC voltmeter with a male plug to insert in the socket to check the voltage output of the socket.
To wire a cigarette lighter socket safely to a 12V battery, make sure you select a suitably sized wire gauge and fuse size. Connect the socket positive and negative terminals to the corresponding battery positive and negative posts to avoid damage to the electrical accessory.
Whenever in doubt, consult a qualified auto technician.