Are the 12 volt accessory power ports in the passenger compartment of cars directly wired to the battery (through a fuse or breaker)? My question comes down to is there any difference between using the accessory plug in the passenger compartment and directly hooking an accessory up to the battery? I understand that there are fuses and breakers to limit the current draw, but if I have a device designed to run off the power port in a car, can I just buy a car battery and wire the device to the battery? I want to use this accessory (a fan and a phone charger) away from the car and need to know whether wiring directly up to a car battery will damage the accessory.
If done right, it shouldn’t be a problem. Most car fuses are 10 or more amps. No way should your phone charger be using even 1 amp. The fan could draw more depending on the size of the motor.
However you may be reinventing the wheel here. There are cheap battery packs than can be used to recharge phones. Some use replaceable AA and AAA batteries. Other use rechargeable battery packs. Heck you can even get solar power recharger.
You can also get small fans for use in a tent powered by D or C-cell batteries. You can even get rechargeable D or C batteries.
The cigarette-lighter style accessory ports on cars are either connected directly to the battery (through a fuse) or are on a switched circuit that connects directly to the battery when the car is running, but the circuit is disconnected from the battery when the car is turned off.
As for what you are asking, you can safely connect your fan and phone charger directly to a car battery, as long as you get the polarity right. Accidentally reversing the wires could destroy your devices, depending on how they are designed.
ETA: Make sure you put an inline fuse in your wiring so that an accidental short won’t cause the wires to melt and other potential bad things to happen.
“12 volt accessory power ports,” or “cigarette lighter sockets,” as they were known until about 2000, are just plain 12VDC. Factory or otherwise correctly-installed ones will always go through a fuse, usually a 10A one. (DIY-installed ones could be hardwired to a 12V rail and thus only protected by using their wiring and connection as fusible links, a kind of high-current fuse.)
If you want to power something from 12VDC and it’s not in a car, you can buy 12V power supplies and permanently wire the item to them. Or you can wire an accessory socket to a power supply and plug the device in just like in a car.
I long ago acquired a couple of plug-in 12V-socket adapters and have used them many times to power a car-centric device or save on having to carry two chargers. The car charger works in the car socket or the plug-in socket and the combo is much more convenient than two full chargers.
The more common situation these days is USB power, and you can buy many different kinds of USB power ports - if your car doesn’t have them built in, you can plug in an adapter (even a low-profile semi-permanent one), there are of course wall plugin ones, and the newest turn is wire-in power ports, often with a standard AC socket on one half and two USB ports on the other.
Here’s the older style. While searching, I found the perfect combo, a plug-in adapter with both a 12V accessory socket and a couple of USB power ports.
Great!
thanks all. Just the information I needed.
Over the years I have purchased several self-contained power packs for emergency jump-starting. None have lasted very well. The batteries in them tend to be quite cheap. In addition I have found that the main use I put such devices to is portable 12 V power-though I need to be able to jumpstart a car if/when this becomes necessary. Hence my current plan to buy a new car battery as a backup for the car and equip it with the necessary accessory ports when I need same.
I have seen the new Lithium jumpstart power packs. They seem popular, but I am very unimpressed with the peak current. I think I will stick to lead-acid for now.
1: fuse - accessory ports are fused
2: switch - On some cars, accessory ports are switched (only on when car is on; some may switch off when cranking)
Don’t assume it’s regulated to 12V. The voltage at the battery terminals is generally considerably above that, so that the battery charges. I believe that accessory ports are not voltage-regulated, but I could be wrong.
Definitely! This can range up to 25% plus or 10% minus in actual cars.
So your plain 12-volt battery will probably be more regular than plugging into a running vehicle.
There are 12 volt jump packs like this that have 1 or more 12 volt power point receptacles and 1 or more USB points. we take ours to the hunting shack all the time and the laptops and phone are plugged in all the time. very useful
item. Mine is a CARQUEST store brand for about $60.-
Thanks
I have had several of these type of power packs. My problem is that the batteries in them don’t tend to last very long-a couple of years or so. I want to focus on buying the longest lasting battery I can to maximize the probability that it will actually work as a jumpstarter when I need it. While it is sitting there in reserve I do like the ability to use it as a portable power pack. There is exactly what I want:
but the price is high. I decided to try to build my own. We will see how that works! 
Thats fine.
Just remove all the accessories, before connecting it back to the car’s battery… and don’t reconnect them while 2nd battery is still attached to car.
FYI – my 12 volt socket does NOT turn off when the car does. It ultimately destoyed by ipod battery because it was running a charge to it 24/7. Didn’t hurt the ipod itself though.