How many 12V accessory cords can be run from one socket (with adapter)?

[kdkrone]

92 Q45. I now have the following 12V power cords in my car:

1- for iPod /FM transmitter1- phone charger1- phone Bluetooth headset charger1- Garmin Nuvi GPS charger

Help!! I have a dual socket adapter, so that allows me to run 2 items, but what is the limit of adapters that can be run through the one cigarette lighter socket without melting the wires (I assume it is on a 10 amp fuse but as long as I keep the total cumulative amperage below 10, am I good to go)???

How do others deal with this proliferation of cords??!

ThanksKen K
Modified by kdkrone at 8:22 PM 6/23/2007

[elwesso]

One must konw the power consumption of each thing. In theory one could add dozens of tiny power consumers or one huge one and itd make no difference. The actual number doesnt matter.

P=VI

P=> PowerV=> VoltsI=> Amps

The front fuse cig fuse is rated to 15A so that means you can use 180 watts of power. That should be fine because we all know that batteries run at around 13 volts rather than the calculated 12 volts.. 180 watts seems like a lot of power, and it is so i'd want to stay well under that.

The rears are run in parallel and thats a 20a, so feasibly you could run 120 ADDITIONAL watts through each rear one or 240 total.

Ideally you would like to run a couple from the front and a couple from the back. The thing that blows fuses is when all of the items try to turn on at one time. I dont think theres any listing of peak values (maybe in the device owners manual somewhere?). IMO if your runing a bunch of things where you could get a lot of power itd be best to hook a circuit breaker up so that it doesnt fry the fuse every time. Say so it blows at 12-13ish amps so you dont fry the fuse.

For instance, my XM reciever is rated at 6 volts and 1000mA (or 1A). So thats 6W of power.. I would start showing concern around 50-60-80 watts.

Post up what your devices output voltage and amperage and we can calculate your total rapidly.

I think though the bottom line is if your running a bunch of stuff it might be best to run a wire with its own fuse directly from the battery. You could probably make a slick install in the center console or glove box.

[Skibane]

iPod /FM transmitter: Less than an ampphone charger: Probably right around an ampphone Bluetooth headset charger: Less than an ampGarmin Nuvi GPS charger: Probably right around an amp

You're probably drawing less than 4 amps total, so should be fine running all of them through any socket in the vehicle.

[elwesso]

iPod /FM transmitter: Less than an ampphone charger: Probably right around an ampphone Bluetooth headset charger: Less than an ampGarmin Nuvi GPS charger: Probably right around an amp

You're probably drawing less than 4 amps total, so should be fine running all of them through any socket in the vehicle.

[kdkrone]

Hi, Wes.

I will have to check with each of the companies, but I don't think it will total up to much wattage. We are talking about one Garmin Nuvi 670 GPS, a Motorola RAZR phone, a Kensington FM tranmitter/iPod charger, and a Cardo bluetooth headset for the phone. For example, the 120V charger output for the Motorola phone is 500mA. I will have to call tech support for the others, as I can't find anything in the packaging or online.

But what I was particularly interested in is whether anyone has come up with a slick way to deal with the profusion of these cords. I will investigate the idea of putting in a self-fused socket. (Is one as good as the next?)

Thanks,Ken

[elwesso]

it should say on the actual adapter cord.

[kdkrone]

Actually, that is where I went initially and did not notice that the GPS nav has a 3 amp fuse and I cannot imagine that the others are anywhere near that, so I think I am fine. (The other cords do not have the info on them.) I will look for some places to mount the extra socket or two.

Ken

[mxr662]

P=VI

P=> PowerV=> VoltsI=> Amps

Cool. Wes gets Watt's Law in to a post

I will have to check with each of the companies, ....Ken

You could us a meter set to measure amps hooked in series with each device. You may find the actual current draw to be different from the stated value. Current draw will vary with usage and amount of battery charge in the accessory.

Andy

[qsiguy]

Cool. Wes gets Watt's Law in to a post

Not to be picky but it's actually Ohms Law , got to give "Mr. Ohm" his credit! Love that Ohms Law!

[kdkrone]

Someone sent me the following info that I missed in the Garmin manual:

"It draws 10w max so with P=IE 10w=Ix12v so current draw is 0.833amps."

I can't imagine that any of the other accessories that I have come anywhere close to that, so I should be fine. I will just look for sites for additional socket placement.

Ken

[szh]

Not to be picky but it's actually Ohms Law , got to give "Mr. Ohm" his credit! Love that Ohms Law!

Actually, Ohms Law is any one of the following:

V = I * RI = V / RR = V / I

Seehttp://www.grc.nasa.gov/WWW/K-....html http://www.kpsec.freeuk.com/ohmslaw.htmfor more info.

Whereas,

P = V * IP = I * I * RP = (V * V) / R

are just expressions for DC power calculations (too simplistic for AC, of course). No name for them that I can remember right now ...

Seehttp://www.kpsec.freeuk.com/power.htmfor more info.

Z

[elwesso]

I took my electrical engineering class this past semester.. AC power is way different... Pretty cool though, i found it very interesting even though I only quasi-understood it. Finding apparent power, real power, power factors and phase angles.. good stuff.

Ohm's law is the WIN. The P=VI is just the power equation, whereas ohm came up with his own law...

With P=VI and V=IR you can do about anything with DC circuits assuming you dont have inductors or capactors, which doesnt really add much of anything, just some differential equations which you can figure out without them. L di/dt and 1/C dv/dt which you then use to turn them into equivalent resistances and use ohm's law... In the end, trying to figure out anything you end up using ohm's law somewhere.

[elwesso]

I also forgot that you can simply just add up the amps since everything is running at the same voltage. SIGH! But it was fun talking about electrical stuff.

TECH is probably looking at this stuff and thinking "Hah bunch of newbies there!"