With life getting more connected, the number of gadgets we need charging is on the rise. But, while modern cars have more power points to keep us juiced up, older cars struggle to keep up.
Technically, the only power outlet in the car is your cigarette power plug. It wasn’t even originally meant to power your electronics. It was designed to power a cigarette lighter back when smoking was cool, and cars had more ashtrays than cupholders.
Since this port delivers 12V, you can use an adapter to turn this power into something your devices can consume.
How Many Amps Can the Cigarette Port Produce?
Also known as the 12V auxiliary power outlet, the port is designed to deliver anything between 10Amps and 20Amps.
The rated power varies depending on your car’s manufacturer. An excellent way to find the exact amperage your port can deliver is by:
- Consulting your user manual
- Looking for the fuse on the cigarette port’s circuit. The port will produce something less than the fuse’s rating.
To be on the safe side, we will go with the lowest rating of 10 Amperes.
How Much Power Can I Draw from the Auxilliary Power Port?
With the amperage in mind, it’s a matter of applying a formula to determine how much power you can draw from this port.
Power = Voltage x Amperes
Traditional passenger cars work on a 12V nominal system. Note that this figure can fluctuate between 9V and 14V depending on whether the alternator is running at full force or not.
The optimal power from the plug, in this case, will be
12V x 10 Amps = 120 Watts
If you are in a semi, a bus, or an RV with a 24V nominal system, you can draw more watts from the auxiliary power port:
24V x 10 Amps = 240 Watts
Is This Enough to Charge My Devices?
Yes. The power from an auxiliary port is more than enough to keep your phone, tablet, and even laptop juiced up. You’ll need to do some math, though.
A decent 15W charger for your smartphone or tablet draws around 1.5 Amps from the 12V outlet.
Charging four phones at a go will draw 1.5 x 4 = 6 Amps. Add something for losses, and you will get around 7 Amps.
This is a reasonable limit if you are running the charger from a 10 Amp circuit. Adding something to the circuit brings you closer to the overloading limit.
If you opt to charge a MacBook Pro, you will have a charger that outputs around 90W of power.
This will draw 7.5 Amps. If we generously compensate for losses, you will get around 8.5 Amps.
This leaves you with barely enough power to fast charge an 18W smartphone.
How to Use the Power from My Auxiliary Port Safely
Since overloading the cigarette port is easy, you’ll need some discipline to stay on the safe side when using it. Luckily, you don’t have to change your lifestyle to do this drastically.
Treat it as a Single Power Port.
You will hardly overload this port if you treat it as a single power port. Don’t think of it as the mains power board to power everything in the car. That’s the role of the main connectors on your battery terminals or at the fusebox.
Avoid Power Extenders at All Costs
Power extenders can easily trick you into overloading your auxiliary power port. They will give you extra cigarette ports and multiple USB ports. The temptation to charge or power various devices at a go once you have additional ports is almost irresistible.
Avoid Charging Multiple Devices at a Go
If you have more than one device onboard, plan and charge a maximum of two small ones at a go.
Remember, you can charge multiple smartphones at a go, but you cannot charge two tablets or laptops at a go as they draw more power.
Don’t Power Cameras from the Port.
Some people who add dash cameras to their car (or CB radios) take the easy route and power them from the auxiliary port. This will throw you off. It will limit how much power you have left to charge your valuable gadgets.
How to Run Extra Power Into Your Car’s Cabin
If you feel like you might need more power in your car than the auxiliary port can provide, you can do what car audio installations do: run it straight from the battery.
Since you are drawing power straight from the source, you can use a reasonably sized fuse and a thick enough wire to pipe in the extra Amps you need to keep the cabin powered.
I prefer this approach if:
- You are planning to install extra charging ports (especially USB C and thunderbolt charge points)
- You want to install aftermarket amplifiers, a subwoofer, or display screens
- You want to install aftermarket ambient lighting
- You want to run an inverter to power AC mains plugs in the car.
Dashboard cameras can pigg-back on the auxiliary power port or your stereo’s power. After all, most stereo circuits deliver slightly more power than the radio will ever draw.
Running extra power into the cabin is a massive project. Get an automotive electrician to do it if you are not sure of yourself. Nonetheless, it involves:
Find Out How Much More Your Car Can Give
Your car’s alternator can only generate so much power. This means there is a limit to how many amps you can pipe into your car’s cabin. Typically, you won’t need an alternator upgrade unless you live off your vehicle (camping) or run high-power sound systems.
If you need more than your car can produce and still charge the battery while running core electronics, consider:
- Toning down your ambitions
- Getting an alternator upgrade
- Getting a secondary (house) battery and a charging system
- Installing auxiliary power (solar panels or a way to charge from the mains)
Plan and Wire the Interior of the Car
There is no point in bringing extra power into the car if you haven’t already figured out where it will go.
Start by planning where all the extra ports and connectors will go. After this, create a wiring plan taking into account:
- The amperes that will be running through each wire. Plan to size your wires properly for the power and voltage rating
- Where you will run the wires through
- The main terminal block that will connect to the positive wire from your battery’s positive terminal
- Sizing and fusing the main positive terminal from the battery
- Wiring the main positive power into the car’s cabin
- Fuses are Everything
There is a reason every single circuit in your care is already protected by a fuse – fire. Your car’s battery can produce enough power to burn up the coating on most wires.
Fuses are there to ensure that your wiring never gets to see such amps. Your new circuit should also have similar fuses installed as close to the power source as possible.
- The main positive lead should have the fuse as close to the battery as possible.
- Extra positive terminals connecting to the main lead should have their fuses as close to the terminal block as possible.
- You will have to install a secondary fusebox in your car for this.
Can I Use Unused Terminals on My Fusebox?
Getting extra power from all those unused fuse slots is tempting – especially if the fusebox is already in the cabin. However, this is not wise, especially if you are running high power draws.
This could be a problem because:
- Just because the fuse slot isn’t used doesn’t mean it’s not connected to something.
- The main cable leading to the fusebox and might not handle the extra power draw.
- The main fuse to the fusebox might not be rated for the extra power you are about to draw.
Can I Replace a Low-Rated Auxilliary Port Fuse With a Bigger One?
No. You shouldn’t. The wiring that went into the car was designed to handle the power it’s fused for safely.
A bigger fuse might not blow in time. This means the wires will overheat. If it is too bad, they might catch on fire and burn down your vehicle.
The Auxilliary Plug Should Be Enough For Daily Use
If your car is a daily driver that you use to drive your family on holiday trips now and then, the auxiliary port should be enough.
All you have to do is plan your charging times well. For example, you could top up other devices at home, the hotel, or Airbnb and avoid crowding the port while in the car. Moreover, you could schedule charging so that everyone charges at a different time.
Additionally, consider getting a high-quality power bank that charges when no one is using the port (or charges in the house) and spreads out more power around when on a road trip.
If You Permanently or Semi-Permanently Camp
If your car serves as a camper now and then, consider having a professional wire it for that purpose.
After all, you will need extra luxuries like coffee makers, additional lights, and other power-hungry devices to make your life comfortable. In this case, you will even need spare batteries to prevent you from draining the start battery when parked for a while.
You could consider getting bigger portable power stations with AC power output for better comfort. You can charge this slowly via the auxiliary port and drain it fast during peak hours without damaging your car.
Getting a propane or gas generator will also sort your problems without straining your car.
Bottom Line
While old cars might struggle to power modern-day devices, they still have enough juice for the casual user. Power users can still get more power piped in if they follow the correct procedure.
Newer car models are wired to deliver more power, though. In addition, they will have more front and rear USB ports that can charge USB C devices and provide mains AC power without extra modifications.