Wiring Hi/Lo Beam

[farmerj]

OK, showing ignorance here but need someone to confirm what is probably obvious.

I added a 6" light bar to my XC a while back, with harness and relay. Now I am upgrading to the LED and want to add in the Low Beam.

I purchased a new SPDT switch (two position) to replace the single-throw that I was using to run the light bar, thinking that I would just run a wire from the switch to the low beam.

But that's not how it works, right? Do I have to run a second harness and relay back to the battery for the Low Beam (as well as the high beam)? Or is there a way to simplify?

Thanks,

Jeff

 

[farmerj]

Another way to ask this question might be, "Do I need to use relays to run lighting or can a powered wire run from the battery to the switch and from there to the light?"

 

[Neil E.]

Really depends on how high the lighting load actually is. Most aftermarket lighting kits always include a relay. This is because the supplier has no way of knowing if your headlight switch can carry enough current.

Hook it up like this: lightweight lead from your positive supply goes to common on your toggle switch. Power comes out one side going to the High Beam Relay coil. Power comes out the other side going to the Low Beam Relay coil. Both relay coils get grounded with lightweight wire from your negative supply.

Heavy wiring goes from positive supply to both relay contact inputs. Heavy wiring out from the contacts to the respective high or low beam. Heavy wire from each light to your negative supply.

 

[farmerj]

This is making sense, Neil.

So yes, both high and low circuits each need their own relay. And if my switch could handle the load, I don't need relays. Right so far?

The light is 45W and the switch is 6A = 72W. So in theory, I can go w/o relays...

I already have a high beam relay in place from my other light. Could I try the low beam without a relay, using a fuse to protect the system if it doesn't work? (my switch was cheap).

 

[Neil E.]

Based on those specs you should have no problem with the low beam being handled only by your switch.

 

[farmerj]

And a last set of questions (I think!) about the "positive supply" source.

(1) I've hooked my grip heaters to ac/yellow as you suggested in another thread. Is this because ac is more efficient than dc?

(2) Should I hook up my dc lighting to the battery, or to a hot wire directly out of the regulator/rectifier - or does it matter? I want to minimize draw on the battery.

(It tends to drop voltage as I ride, I'm in tight singletrack and not in the upper rpms much).

Thanks for your contributions on this forum, Neil.

 

[Neil E.]

Grip heaters to AC since there's only so much stator output. If you put them on DC you risk running your battery down.

DC lighting will wind up on the battery anyway. It's all the same circuit after the regulator/rectifier. The DC comes from AC on the white wire (max voltage output wire on the stator). The max voltage is needed for battery charging.

It's up to you to organize how you use the lights. A low output one could be used as a running light so you show up to other forest users. Use the high output only for night riding. When I used my DC lighting at full power for night riding, the battery would run down enough after an hour that I'd need to kick start. If you had a light that would work on AC you could put it on the AC circuit (yellow wire).

There's no free lunch on a stator that only produces about 70W. That's why the specs on offroad lighting are important.

 

[farmerj]

But if there's "no free lunch" (I believe you here) then why does it matter if a light is hooked up to ac or dc? The light will pull the same number of watts either way.

Or do you "get a little more" because ac is more efficient?

Draw from the ac side will still run the battery down, won’t it?

 

[Neil E.]

No, devices connected to the AC output won't run down the battery. Having everything on AC would be best, the only downside is at some point all the lights would be dim. The factory setup that has the loads on AC and the DC only for battery charging is the right way to go.

 

[farmerj]

10-4, and I didn't state my question very well. Running stuff off of AC won't run down the battery directly, because it's a different circuit.

But if the stator puts out 70W and I load the AC side with 70W, there isn't anything left to charge the battery...right? So as I'm using the battery (e.g. electric start) it will draw down, being impacted by the loads on the AC side...???

If that's the case, I'm still dense and take it that the advantage to AC is:
(1) It's a bit more efficient because it isn't going through a rectifier and having the signal "cleaned up", and
(2) If you leave your lights (or other load) on it won't drain the battery.

Is that about right?

 

[Neil E.]

In reality the only advantage to AC is that the engine has to be running for anything to operate. Thus if your AC lights are always switched on, they only light up when the engine is running. I wouldn't say AC is more efficient on a motorcycle, but it sure is for long distance transmission of electrical grid power. The ability to be easily transformed up or down solves problems due to distance.

The only reason for DC is battery charging (or for something that won't work on AC). The downside is running the battery down from excess load or a device that stays powered on.

I suppose it's possible that maxing out the AC could reduce the stator voltage on the white wire and then battery charging would suffer. The real benefit of the old sytem with a separate winding powering the CDI, is that you can always kickstart the engine.

 

[farmerj]

Thanks for all the time on this one, Neil. I think I get it now, and have set things up per your recommendations!

Jeff