weirdwilbur

I am using a 12 volt 18 amp battery to power a school bus taillight (single element S109 1156LL), a 15 watt halogen driving light and four, 2 ½", 13-LED truck clearance lights as turn signals. All of the wiring is 14 gauge through a bus bar. Everything works beautifully.
Now I want to bring my ignorant fumbling closer into line with proper wiring.

What gauge wire should run between the bus bars and the battery?
What size fuse should I install between the Positive terminal and the Positive bus bar?
Do the lights need to be fused?
If so, what size should the fuses be for each of the three?

And, not to start a family fight or anything, but, what does "vc" mean among your people?

Thank you for your time.

colleen c

The main fuse and wire size from battery to bus bar will be determine of how much load you will eventually add on to the bus in conjunction to your current load. If you are planning to add more stuff later, then just go with a larger wire size so you can expand without having to change wire size later. Just put the fuse as close to the battery as possible. It will also depend on your max current discharge of your battery. If your battery can only discharge X amount of current then size the wire and fuse for that value. Typically speaking, a 14 wire is good for 20A, a 12 wire good for 25A, and 10 wire good for 35A.

Whenever you go from a larger gauge wire to a smaller gauge wire, it is recommended to add the correct fuse size at where the transition took place to avoid burning up the smaller wire. Check the led tailight wire size and fuse it to that.

"VC"? Dunno. Usually V is for volt and C is for amps. In this case, I think it may be refering to Volt * Current? If that is what it is, then that value might be Watts. Don't take my word on it

Edit: After a quick electrical symbol check, I found some stuff pertaing to that VC. One was listed as a variable capacitor which I think is less common and the other is Voltage Clamping such as the use of MOV (varistor) across the line voltage to help with spike voltage and etc.....

seeker333

https://www.bikeforums.net/forumdispl...cling-%28VC%29

colleen c

OH. I was thinking electrical terms since the OP question was in the same post.....Duh

weirdwilbur

How rude of me. I posted this question and got diverted by fate. Colleen. Thank you. The fuse location, and wire size change is exactly the level of stuff/detail I need. I have found that the battery specs want me to use a #6 wire from battery to bus. Massive. I love it. I want to group all the fuses in a plexiglass tube between the cranks. If I read you properly, I can run the same, stock, smaller gauge wire that came installed with them, out to the lights from the fuses? That would solve a few problems if it's cool to do.
I want to cap both ends of the tube that will hold the fuses. It rains here. Will they be happy sealed up in there, or should I vent the tube?
Thank you seeker333. VC=Vehicular Cycling - a good find. Of much interest.

colleen c

Try to keep the fuse location as close to the bus bar as possible. After the fuse holder and a properly sized fuse, you can use the original OEM wires from the individual lights. You will need to find out what size of wire are each component are to match the fuse size.

weirdwilbur

Perfect. The bus bar is in a box under my seat. Placed where I want it, the plex tube with 6 fuses will be 6 inches away from the bus bar. I still need your opinion of wether or not to provide the fuses with a stream of fresh air. I would like to put end caps on the tube to keep them clean and dry, but that will put them in a closed space. I assume that if they get hot it will indicate that I've done something wrong. What do you think?

colleen c

Capping off the tube to keep them dry from the element is good but you should try to allow for a little vent for air. Reason being that not having enough vent inside the tube may build up moisture condensation. The condensation will lead to corrosion and electrical contact failure.

I suggest before finalizing the system, turn on all your electrical load to high and feel the temperature of the insulation of each wire after about 10 minutes or more. The wire that runs warm to hot can possibly be undersize and you will need to increase that particular wire size to accomondate the load. In reality this should not even occur if the fuse is match to the wire gauge. The fuse should open before the wire gets warm.

TacomaSailor

Simple voltage drop calculations show that 20 AWG copper wire with a 4' (one way) run at 18V and 1.3 amps (23 watts) at 80 degrees F would give a drop of less than 0.125 volts at the lights. Even 22 AWG would give only a 0.17V drop.

I do a lot of 12 V wiring on boats and have found the voltage drop calculations to be pretty good indicators of the correct wire size.

weirdwilbur

Thank you Colleen and Tacoma. You guys have given me enough to make me dangerous again. I am looking forward to eliminating a number of feet of 14 gauge wire. The bulky nature of that material gave me a few ugly intersections, but it works. I will use your information to make it more rational.