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installing lightbar, amp draw question

6.3K views 30 replies 10 participants last post by  SHADOW 1100T  
#1 ·
OK, I plan on spending a day or two bolting on all my winter chrome purchases; here is my question - i have heard about not stressing your start switch on the Honda, what is the best way to hook up my Cobra lightbar? thru the fuse box, but which one? Thanks for anyone who has done this before, so i don't spend time re-inventing the wheel (more time to ride!) J3C
 
#3 ·
With out a doubt Gonzo's harness is a very simple way to go but if your a DIYer here's another way to go, if you want to turn them on your self you will need a switch if you want to have them go on with your Hi or Lo beam you can do it this way, get a 4 or 5 prong relay, from the battery run a wire to 30, from 87 run a wire to your lights and one to ground from your lights, depending on what you decide to do run a wire from the Lo beam wire or the Hi beam wire or the switch which is hot on one side to 85, and a wire from 86 to ground, now when you hit Hi, Lo or turn on the switch the light bar will light up, the wire from the battery or the hot wire to the switch must have a fuse. If you use a switch pick up power from a key on power source, any wire will do because there's very little amp draw, if you don't you will have to remember to turn the lights off every time and that isn't gonna happen,,,read in dead battery here. :cry: , if you use the headlight the light will shut on start up and key off just like they do now.
 
#4 ·
The way I have mine wired up is a little different than most.

I'm pretty picky about making things look stock and not having extra
wires hanging off the battery post and such.....

I took the fuse box off the bike and took it apart.
It had 2 empty fuse positions that weren't used.

I used some angled spade connectors and wired in both fuse slots.
I wired one side to the main bus and the other one goes out to the devices.

So, I went from the fuse box out to a relay and then from a the relay up
to the lights.
I have two sets of driving lights and used each fuse slot to put the lights
on their own separate fuse.

It's a lot of extra work to do what I did, but it looks factory installed.

But yes, no matter what, you do need to put it on a relay.
I use the running lights to energize the relay so my lights are on
any time the key is on. I also have a switch block mounted to the master
cylinder reservoir that interrupts the power line to energize the relay
so that I can turn the lights on and off.
 
#7 ·
SHADOW 1100T said:
i beleive the 2 empty slots Litnin is talking about are the extra fuse slots, cool idea :wink:
Nope. The two spare fuse slots are not part of the bus.
They are separate slots.
The ones I used are inline with the bus... just have the connectors
inside missing.
They are designated for something that my bike doesn't have, but
I can't recall off-hand what they were for...
 
#8 ·
Easy Rider 2 said:
litnin said:
I have two sets of driving lights .......
Does that mean 4 extra lights total?
If each one is ~60 wats, then that's an extra ~ 20 AMP draw on the electrical system.
I think it is highly unlikely that the charging system will be able to keep up with that much extra load.
Yes, I have four lights total.
No, each one is not 60watts. Each one is 35 watts for a total draw of
about 10 amps...
No, that doesn't over-load the charging system. The VLX has a very good
charging system... much better than that of the bigger bikes.
The VLX doesn't have the charging issues that the bigger Shadows have.

While it's not a lot, I've saved several watts also by running all LED's.
Everything bulb on my bike is an LED, with the exception of the
aux lights and headlight.
 
#9 ·
#10 ·
litnin said:
No, each one is not 60watts. Each one is 35 watts for a total draw of about 10 amps...
No, that doesn't over-load the charging system.
Check.
After seeing what you have to do to get at the battery, I plan to take VERY good care of mine........first thing being installing a pig-tail for the battery charger!!
 
#11 ·
Easy Rider 2 said:
litnin said:
No, each one is not 60watts. Each one is 35 watts for a total draw of about 10 amps...
No, that doesn't over-load the charging system.
Check.
After seeing what you have to do to get at the battery, I plan to take VERY good care of mine........first thing being installing a pig-tail for the battery charger!!
Yeah, I'm not too fond of how they placed the battery... but for balance
and center of gravity, it's good.

I wish they would have made it so you didn't have to remove the fuse box
to get to the positive side of the battery though... that's really a PIA.
 
#12 ·
J3C
Check the capacity of your charing circuitry.
The alternator output on my SS750 is about 300W (IIRC) so I had less than 50W to play wiith (no lightbar for me). It might not be a problem on a daily commuter, since you;d just be able to charge the battery in the evening, if needed.

Regards
Yuriy
 
#13 ·
Your bike draws 250 watts just by itself?!?!?

How did you calculate that?

By measuring each circuit, I've come up with 135 watts to run the bike, including the headlight. Sure, it draws a bit more than that if I turn on the turn signals or light the brake lights, but those are intermittent and the battery won't mind running those for the small percentage of the time that they are in in relation to the rest of the time that the bike is running at charging RPMs.

So, my bike has a 340W (at 5,000 RPM) stator capacity. That leaves me with 200 watts free to play with. That's more than enough for a light bar and my heated grips.

--Justin
 
#15 ·
SHADOW 1100T said:
How does one figure the total wattage a bike will use, go through the book and add all the watts up or is there a simple way to do it.
Yep, that's pretty much all there is too it.

Then take your total watts and divide by 14 and that will give you
a pretty close total current (amperes) draw.
 
#16 ·
+1! I bought his new Hydra Harness.... Gonz does excellent work...
David, does your lightbar have a built in switch? Mine does & I'm wondering if it is a 'dead' switch with the Gonzo harness ? lights on full time? Any pics of how the harness looks once installed?

I also like the Litnin "mean & clean" sounding install..

Hhmm, lots of good ideas here. I will know more when I start pulling it apart (just a side cover to access my battery). I knew this group would have some brillant suggestions, thanks to all. J3C
 
#17 ·
tubes_rock

According to my shop manual the alternator does about 330W @5000 RPM.
I imagine the drop is somewhat linear, and since I rarely run the motor at 5000RPM I'm not getting 330W for sure.
Then, I have a 60W head light, 3x running light at about 15W each, then I have 2 carb heaters at 12W each (13 oHm @ 12V give a little under 1 A each) plus 3-5W of spedo light. (I might be over estimating, but I was trying to be careful)
So far I have ~145W +/- :) plus whatever the gas pump and ignition coil use. Not sure how much the average draw is...

Please tell me if I'm smoking something, but it didn't look like I have enough juice for a light-bar.

Thank you
Yuriy
 
#18 ·
ycroosh said:
tubes_rock

According to my shop manual the alternator does about 330W @5000 RPM.
I imagine the drop is somewhat linear, and since I rarely run the motor at 5000RPM I'm not getting 330W for sure.
Then, I have a 60W head light, 3x running light at about 15W each, then I have 2 carb heaters at 12W each (13 oHm @ 12V give a little under 1 A each) plus 3-5W of spedo light. (I might be over estimating, but I was trying to be careful)
So far I have ~145W +/- :) plus whatever the gas pump and ignition coil use. Not sure how much the average draw is...

Please tell me if I'm smoking something, but it didn't look like I have enough juice for a light-bar.

Thank you
Yuriy
Okay, so 60 + (3 x 15) + (2 x 12) = 134W.

Ignition draws about 2 amps on average (it spikes and drops because it's pulses) so that's another 24 watts. The fuel pump is very spikey in it's current draw since it's a solenoid with a spring. The solenoid loads the spring, and the spring does the work, so it only fires ones every several seconds, so we cal cancel out the math on it. So, that's 158W to run the bike.

The stator output is not linear because of the way it works in relation to the voltage regulator. The stator actually puts out about 100 volts at full power, and the voltage regulator cuts it back to 14V. So, as long as the stator is putting out at least 30V, you have good power. The difference between 3000RPM and 5000 RPM is not very much, according to my meter. Riding around at 3000RPM is a Sunday cruise.

So, that being said, as long as your at cruising speed, you have about 300 watts to play with. Your bike pulls 160 (rounding) so you have 140 left over. Remember that you want some wattage left over to charge the battery, but adding a 2 x 50W light bar is not out of the question. I use 35W bulbs in my light bar, and the system has no trouble running 70W worth of light bar and my 33W grip heaters, along with everything else.

You should be okay, but use the 35W bulbs if it will help you sleep better at night! :wink:

--Justin
 
#19 ·
tubes_rock, thanks for doing the math (been a loooong time since my Ohms law & Boolean logic days! :shock: ) - i was following along to make sure I had enough juice, but it looks like no problemo.
J3C
 
#20 ·
I put this together in attempts to map the stator output on my 95 VT1100C. The first and second columns showing watts and amps are for an aftermarket stator that claims 20% more power over stack. The third and fourth columns are for a stock stator. The figures are a linear extrapolation from the Honda figure of 329 watts @5000 rpm.
This has been butchered from an Excel file so please excuse the formatting.


RPM MPH Watts Amps Stock Amps
5000 100.13 395 30.4 329 25.3
4500 90.12 316 24.3 253 19.4
4000 80.10 253 19.4 202 15.6
3500 70.09 202 15.6 162 12.4
3000 60.08 162 12.4 129 10.0
2500 50.06 129 10.0 104 8.0
2000 40.05 104 8.0 83 6.4
1500 30.04 83 6.4 66 5.1
1000 20.03 66 5.1 53 4.1
 
#22 ·
salem said:
The figures are a linear extrapolation from the Honda figure of 329 watts @5000 rpm.
Hang on...

A linear extrapolation means that you had Excel calculate these numbers figuring that 0 RPM mean 0 watts, and 5000 RPM means 329 watts, and just applied a linear gradient to make the numbers fit. It means that these data are not based on real-world measurement at all and that at no time was a volt, amp or wattage meter ever connected to the bike to verify these numbers.

Please tell me you're not publishing these numbers as fact, because using my meters and real-world test methods, I can tell you with complete certainty and world-verifiable evidence that the correlation between RPM and wattage output is in no way linear.

How exactly did you come by these numbers?

--Justin
 
#23 ·
I can tell you with complete certainty and world-verifiable evidence that the correlation between RPM and wattage output is in no way linear.
You are correct Justin. That's why I stated the disclaimer that the figures were linear. As my bike has no tach, this is the only way I could graph it out. And let's face it- the Honda spec of 329 watts @ 5000 rpm isn't really any help to find output at 55-75 mph. These figures were generated by converting engine rpm to mph and applying the respective power output for that rpm to the mph. I had posted earlier looking for input on rpm at different speeds, but did not get the info needed to calculate the output.

These figures were never meant to be beyond question, just ballpark numbers to try to better balance stator output with demand.

If you can post a more accurate curve, I could sure use it.

Mike
 
#24 ·
I do have the numbers at home, but only for my Electrosport stator. What found though was that 90% of the rated power was available at just over 3,000 RPM. The jump from 3,000 RPM to 5,000 only provided an extra 10% beyond that.

--Justin