Headlight Losses

[Kiwi_Roy]

I was triggered into thinking about this By Raz's Headlight relay addition.

Last night while checking my diagram I took the time to take a few measurements.

Measuring voltage drop from battery to 60/55 Watt headlight I get

1.2 Volts drop on High beam, Voltage across lamp 10.87

1.05 Volts drop on Low beam, Voltage across lamp 10.99

My battery voltage was 12.8

12.8-1.2=11.6 (not 10.87) so obviously there's some voltage drop in the return

wire as well.

If I calculate the Wattage I get 49 Watts at the 60 Watt lamp i.e. a loss of 18%

I suspect the actual light loss is greater than 18% because the light output vs

power input is not a linear relationship.

Obviously ther's much to be gained by modifying the wiring as Raz has done.

While you are at it run a good solid return wire as well.

Roy

[luhbo]

....Obviously ther's much to be gained by modifying the wiring ...

 

That's a standard modification since the early days of 6V car electricity. Guess why

 

Hubert

[Kiwi_Roy]

That's a standard modification since the early days of 6V car electricity. Guess why

I agree with you there but the wiring should be sized to minimize voltage drop.

With 12V system the drop is not such a problem, I was surprised to find it so bad.

Adding relays in the headlight along with decent size supply and return will make

a significant improvement to the light output.

The relays could also be installed under the seat, but more wiring would be involved.

Roy

[raz]

There are already numerous threads on this subject but they are getting old and I see no harm in repeating it. I have no notes but I think that losses is in par with what I had. The difference after relaying was huge. It's also worth every penny to use a high quality bulb IMO. They are still not very expensive.

 

Many people try to compensate the loss by installing a high wattage bulb instead of relaying. This will only result in even greater voltage drop and end up still giving worse light than what you get with a standard bulb after relaying. Also, a 100W bulb can easily ruin the reflector which can be an expensive experience.

[docc]

My headlamp relays are in the headlamp shell with dedicated 16 gauge wires and separate relays for hi and low. Two years ago I installed my spare OMRONs for the relays. Grounding goes by 16 ga. back to the frame (right side of the spine/ fuel pump mounting bolts.

 

I'll have to do the voltage drop test and report back. Two volts lost is astounding! And, you know, it goes through the switchgear = ungood.

 

I am looking forward to going back to a high intensity bulb (Silver Star or PIAA) since I think my broken stator wire was arcing and spiking the bulbs after 4,000 miles.(The PIAA lasted twice as long, but cost twice as much).

[Tom M]

In one of the old threads on this someone recommended getting a headlight relay harness from http://www.easternbeaver.com/ . That's what I did a few years back and it made a big improvement in light output. It was pretty much plug & play except I had to run a new wire for the little running light in the headlight. There wasn't enough room in the LeMans headlight bucket so I attached the relays to the underside of the fairing frame above the headlight. Definitely a good investment

[gstallons]

Moto-International has the relay kits for older Mk-IV series bikes. They should have something for the V11.

[luhbo]

I agree with you there but the wiring should be sized to minimize voltage drop.

With 12V system the drop is not such a problem...

 

I disagree on both. It's not the wiring, it's usually the switch and the poor fuse sockets which are causing the losses, and not the drop itself is the problem, it's the heat at those points which causes (or may cause) problems.

Just touch a shining 20W bulb and feel how comfortable 20W can be

 

Of course I agree that something should be done against those losses ;)

 

Hubert

[Kiwi_Roy]

Of course I agree that something should be done against those losses ;)

Hubert

Raz posted a simple, elegent diagram on the other thread. Easy to implement with few wiring changes.

He figures that with a Halogen lamp and the voltage drop I observed the light loss exceeds 35%.

Adding relays will eliminate any loss due to high resistance joints and contacts.

Roy

[raz]

He figures that with a Halogen lamp and the voltage drop I observed the light loss exceeds 35%.

To give a more credible source for that statement than just your's truly, it's said in this wikipedia article (which in turn states its sources) that the light output [for halogen bulbs] is reported as proportional to voltage to the power of 3.

 

Using the numbers Roy posted this means almost 38% loss of light power. That is a friggin' enormous loss of light power. No wonder my original beam was weak and yellow.

 

Besides I've also heard more than one story of problems with ignition, light or horn switches due to routing the full power through them. Like Hubert said, those voltage drops are heat somewhere!

[Kiwi_Roy]

Besides I've also heard more than one story of problems with ignition, light or horn switches due to routing the full power through them.

Raz,

As a public service, please post your latest relay wiring diagram here on this thread along with an explanation.

I'm sure it will get used by many, myself included. I picked up the wire and parts last night.

Don't need a relay base just 2 different sizes of spade connectors.

What did you do to keep the diodes from overheating (actually the won't as long as the relays and new supply are working)

I will re-use some of the relays I replaced a while back, even if one fails it will be backed up by the diode with a noticable loss in performance i.e. back to standard glimmer.

Regards

Roy

[raz]

Sure. The diodes must be rated at least 5 A and if they are I wouldn't care about overheating. Diodes almost always fail to shortcut anyway, and in this case that wouldn't harm too much. I just used the larger size insulated spade connectors for all of them, because I had plenty of them and none of the smaller. Make double sure you protect all wires from chafing.

 

 

This is just the plain ol' relaying, but with diodes added that will give you light even if the relay fails. I recommend using 1-1.5 mm² wires for the new feed. For slow nations, that's 15-17 AWG.

 

I endorse spreading, without caring the slightest if my name is mentioned or not.

Any disclaimer you or I can think of applies.

[docc]

For slow nations, that's 15-17 AWG.

 

 

Wait, but . . .

[raz]

This version has the added feature that the low beam won't turn on until your engine runs.

 

Roy just realized something I have totally overlooked: the pressure switch is closed when the oil pressure is LOW, not the other way round. This invalidates the diagrams I posted that use the switch for turning off the headlight when engine is not running. It can still be done but you'd need to do it another way. Stay tuned.

[luhbo]

.... It can still be done but you'd need to do it another way. Stay tuned.

 

Use a 5 pin relay. Easy fix and even failsafe.

 

Hubert