Tower light question

I am putting 6 piaa 55w lights on my tower. I custom made the brackets, it is being powdercoated at this time. My Question is on how to wire the lights. The Piaaa's come with all the wire, switches and relays. I am mounting 3 front and 3 back. Can I just add one light to one of the harness and be OK. (The front and back will be on different switches, 3 lights each) Can I just splice one extra light into the harness that is designed for two lights? or will this cause a problem?

Thanks

all depends on the length of wire run and the size of the wire, i hope you have an upgraded alternator watts\volts= current ...about 25 amps while running plus your stereo????

I would turn one more around so you have four back with two forward. You are right about having the lights so you can control them front and rear. When driving it is easier to turn off the front lights and drive using shadows or moonlight. The more rear facing lights the better for the rider.

Bob is dead on about the alternator. Right after upgrading everything on my boat, I could smell the new 100+ amp alternator cooking off the fresh coating when riding at night.

I went with the higher alternator, I am going to run the shortest distance I can with the wire. I am going to run 10ga as the ground to all lights so I can just have one ground coming down the tower. I will run two 10-12 ga for power. I also will set up a perko switch and another battery. Just wanted to make sure that adding the other light to the harness would not overheat the relay, or something. I might regret the set up on the lights 3 and 3, but it looks better on my set up. But the style before function thing could get me on this one. Thanks for the help!

Turtle:

Not quite sure what you mean by adding one light to the harness. If you have an existing two light setup, and wire in a third light, you might exceed the rating of the existing wiring harness. If there is a switch and/or relay, you would need to know its rating to know if it was being overloaded or not.

As for a single ground:

There are two issues that you should be concerned about. The first is the ability of the wire to survive (safety issue) and the second is how well you expect the lights to work. (Dim, yellow lights suck).


6 lights at 55 watts each will draw 330 watts, or about 28 amps.

For the safety issue, a 10g wire should be able to carry about 32 amps and not rise above 140 F on a 100 degree day. The ground wire may get pretty warm to the touch but it should survive.

A 10g wire, carrying 30 amps, will drop 5% of the voltage in 10 feet, which is about as short of a run as you will likley get. Add another 2-1/2% for the power side. At best you would get about 11 volts to the lights. I would expect a few more percent getting to the switch, some drop throught the switch/relay, losses at all the connections, etc. Don't be surprised if you measure 10 volts across the lights......

I recommend running the biggest wire you can manage.

Turtle,

Aren't you going to need more wire to go up the tower than what is supplied in the kit? You should probably be using at least 12 AWG wire for each set of (3) lights, even better would be 10 AWG. If your harness is at least that size, then I wouldn't see a problem with just tacking another light onto the existing harness. Otherwise you could just add a length of wire onto where your harness would splice into the run through the tower.

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Rod, I just completed a setup on my X-Star last night. I ran two pair of 10 gauge wire, used 30 amp relays to shorten the distance to the switches. The wire run from the battery is about 13 feet.

One set are 2 150 watt KC Daylighters, the other set will be 4 55 watt PIAA style lights.

I measured voltage last night and was not getting the drop you are describing. I was measuring 12.45 volts at the lights and this was without the engine running.

A person could manage to run 2 guage up the tower, but it would be a pain in the a$$, expensive, and totally un-neccessary.

Chaun

I was going to say what Peter said--you need more lights pointing backwards. Forward pointing lights don't work as well as night vision. The forward lights are only good for docking/low speed driving.

Add two more lights--have six pointing back and two forward...

Chaun:

Your voltage readings do not make sense. What type and what size battery are you running?

Since most people would be running a 27 series lead acid battery, I will base my disussion on that.

A "new" standard lead acid battery, at 70 degrees F, 100% charge and NO current flowing should have a voltage reading of 12.6 volts.

A typical battery of this size would have a amp-hour capacity of about 100 amp-hours. Switching on 520 watts worth of lights would put a load of around 40 amps on the battery, which would be a 2.5 hour discharge rate. That exceeds any of the charts I have available, so I will use the three hour rate as being the closest.

At a three hour discharge rate, the voltage at the terminals of a fully charged lead-acid battery will be about 11.7 volts. How do you get more than that at the top of the tower?

Working the tables the other way, and assuming that there was no loss in the wiring at all (bad assumption) a voltage of 12.4 volts implies that your battery was only being discharged at a 10 hour rate. So either your lights weren't drawing more than 10 amps (which doesn't jive with the watts you stated) or your battery is 300 amp-hours or larger.

I am also not sure of what you are saying your setup is. You say you have "two pair" of wires. You also refer to one set in the present tense ("One set ARE 2 150 watt) and the other in the future tense ("will be").

If your setup is a pair of 10g wires per 150 watt light, then you have a great setup. Each wire is only carrying about 12.5 amps, so the drop will be minimal.

If I understood Turtle correctly, he was considering a setup that had all 330 watts (28 amps) returning through a single 10g wire. That's a little different.

For curiosity sake, run your measurement test again. First, with everything off, measure the voltage right on the battery. Then turn the lights on and measure again. Then measure right at the lights. I would like to know what those three numbers are.

Rod

Thanks everyone for all the help!!

Rod,

Should I run two ground wires, one ground wire for three lights? I have the room. I am going to take the harness and check the rating on the relay, It might be easier to remake the entire harness with a higer rated relay and larger ga wire. Thanks for all the help on this!

If you are going to run both sets of lights at the same time, then I would recommend running either two 10g wires or a single 8g