Looking at wiring up my CB in my Ranger this weekend, and I figure if I'm gonna bother to do it, I should do it right.

I'm leaning toward adding a new fuse block under the hood, wired straight to the battery, which will also let me add a cigarette lighter (accessory port to the young kids) inside my center console for a phone charger, and leave me a couple more for any future modifications I may want to make. (Make sense?)

So...how do I size wiring for this kinda stuff? CB shouldn't draw more than 10 amps, I wouldn't think, and it looks like a standard cigarette lighter is 15 amps...who knows what else might get wired on there, though- additional bright lights? seat heaters? dashboard coffee pot?

You need to know the loads of your anticipated devices first. Typically #16 wire will handle 13 amps, #14 will handle 15 amps, #12 is 20 amps.
These are based on CEC/NEC and I have seen that a lot of the time that those ratings are exeeded by manufacturers, but if you stay in those limits you will be safe.
When you do have many wires bundled together and they are continously loaded, a derating factor has to be applied due to mutual heating, but I doubt you will have that issue.
I would get some #6 primary wire, use an inline fuse by the battery and run that to your auxillary fuse block, it really wouldn't hurt to run a ground either, makes the connections a little easier.
You've also got to decide whether you want to have any of this stuff ignition switched to avoid possible accidental battery discharge should something get left on...you can do the whole thing or you could just do selected circuits.
If you did selected circuits, it might be simpler to run 2 #10 wires to 2 seperate fuse blocks....one ignition switched, one not.
This is easily done with a relay.

DNFXDLI said:

You need to know the loads of your anticipated devices first.

Click to expand...

The question would've been different, and simpler, if I knew what the anticipated devices might be. The knowns are an unswitched 10-amp for the CB, and an unswitched 15-amp (or should I upsize to 20, just in case?) cigarette lighter to power a phone charger.

I just figure there's a fair chance over the next 150k miles I anticipate putting on this truck, I might decide I want something else. Though, on reflection...auxilliary lights, seat heaters, and pretty much any other high-draw accessory I can think of should all be switched through the ignition, so maybe that should be a separate, later project if/when I decide to add more stuff to the truck.

Typically #16 wire will handle 13 amps, #14 will handle 15 amps, #12 is 20 amps.
These are based on CEC/NEC and I have seen that a lot of the time that those ratings are exeeded by manufacturers, but if you stay in those limits you will be safe.
When you do have many wires bundled together and they are continously loaded, a derating factor has to be applied due to mutual heating, but I doubt you will have that issue.
I would get some #6 primary wire, use an inline fuse by the battery and run that to your auxillary fuse block, it really wouldn't hurt to run a ground either, makes the connections a little easier.
You've also got to decide whether you want to have any of this stuff ignition switched to avoid possible accidental battery discharge should something get left on...you can do the whole thing or you could just do selected circuits.
If you did selected circuits, it might be simpler to run 2 #10 wires to 2 seperate fuse blocks....one ignition switched, one not.
This is easily done with a relay.

Click to expand...

Maybe my answer is to buy a bunch of #10 wire, red and black, and use that for everything. Or #8? No harm in oversizing most of it, right?

You might need to put noise filters in line or you get a lot of spark noise in the radio.

I had this radio wired up straight to the battery in my '97 Ranger, inline fuse as close to the battery as I could, and never had any trouble with noise. (It's got an automatic squelch or noise limiter or some such built in.)

I'm hoping just adding a fuse block to clean up the wiring won't be much different... if it's gonna cause problems I'll just wire the radio straight to the battery like I did before and figure I can deal with other accessories as they come along. I certainly don't need to charge my phone from inside the console- just thought it'd be nice to keep it all out of sight.

john112deere said:

The question would've been different, and simpler, if I knew what the anticipated devices might be. The knowns are an unswitched 10-amp for the CB, and an unswitched 15-amp (or should I upsize to 20, just in case?) cigarette lighter to power a phone charger.

I just figure there's a fair chance over the next 150k miles I anticipate putting on this truck, I might decide I want something else. Though, on reflection...auxilliary lights, seat heaters, and pretty much any other high-draw accessory I can think of should all be switched through the ignition, so maybe that should be a separate, later project if/when I decide to add more stuff to the truck.



Maybe my answer is to buy a bunch of #10 wire, red and black, and use that for everything. Or #8? No harm in oversizing most of it, right?

Click to expand...

Sorry for the delay on answering..I was off fishing

You could run a couple of #10 wires and then take that to a small fuseblock, you could get one out of a junkyard and modify it for what you want.

Bigger wire is always better, less voltage drop and obviously higher current carrying capacity. Only drawback to #8 is you are starting to get into much heavier lugs that require a crimping tool that is normally not available at typical auto stores and not overly cheap.

#10 would probably be fine for what you are talking about...there is what is known as a "demand factor" on circuits...simply put, the chances of you transmitting at full power with your plug in battery charger working at full capacity, your cup warmer full out is pretty slim....and even if it were the case, it would be intermittant.

It's kind of like your house panel...if you have a 100 amp service (as an example) and you add up all the breaker amounts in the panel, you will come up with a number that is probably 3 times the 100 amp main...but the chances of every circuit being loaded at the same time is minimal.

I slapped it together without a fuse block- it's just number 12 straight from the battery to the CB, with a fuse at each end.

This all started out as a quick thing, and I couldn't find an add-a-fuse block that used the same fuses as my pickup, so I just did it quick without doing anything I can't undo. I'll either remove or re-do it later...but I'm leaving at 0430 Wednesday morning, so I wanted something done.

*As I was doing this, I noticed that the fuse on the factory CB wire is a 2-amp, so I guess I overestimated what the draw on that might be a bit.

EDIT: Can't rep ya...but thanks for the help!

Glad to help Ian..also, you can get a feel for what a device might draw using ohms law....I'm not sure what a CB radio transmits at, but let's just say it is 5 watts....and lets suppose that with lights and the circuit operating that it draws another 5 watts...so 10 watts total.

I'm simplifying this...so now we have a draw of 10 watts at nominal 12 volts.

Ohm's law sez that watts is the product of volts times amps..so transposing that would be amps = power/volts...so in this case 10/12 which is .83 amp.
A 2 amp fuse would be used as you only want to load an overcurrent device (fuse/breaker) to 80% of it's capacity.

So lets say your cup warmer is 25 watts.....25/12 is a little over 2 amps....so you can protect it with a 5 amp fuse.

Noise suppression can easily be fixed with a 2200 uf 35V electrolytic cap from the hot to the ground.