Add Headlight Relays

[Kiwi_Roy]

I was inspired to add headlight relays by this circuit Raz provided.
As an electrical type I was struck by the idea of adding a diode as an alternate source of power if the fuse blows.
Normally the diodes will never conduct but if for some reason the main fuse blows you have the possibility of
having some light provided by the existing wiring.
Adding the relays made a significant improvement to the light brightness, I guesstimate about 10%.
As it was
Headlight Relays.pdf


Update April 2012
Since adding the relays 2 years I discovered that wiring in the relays to bypass the original circuit has some effect on battery charging.
The original wiring expects some drop (0.5 - 0.6 Volts) between the battery and where the regulator senses Voltage and compensates for it.
The end result of wiring directly, the battery gets charged to 13.8 V instead of 14.4 Volts. (this also effects the kits you buy)
I just revised my wiring as below, much simpler, only uses one additional relay, retains the original headlight fuse and makes the charging
as per stock because it has the same Voltage drop.
Modified single relay
Headlight Relay.pdf

Note: I don't show the original headlight relay coil wiring, there are several variations.
If you are happy with the way your bike charges with an existing relay kit I wouldn't worry about the Voltage drop issue.

Roy

[Skeeve]

I was inspired to add headlight relays by this circuit Raz provided.

As an electrical type I was struck by the idea of adding a diode as an alternate source of power if the fuse blows.

Normally the diodes will never conduct but if for some reason the main fuse blows you have the possibility of

having some light provided by the existing wiring.

Adding the relays made a significant improvement to the light brightness, I guesstimate about 10%.

Roy

 

That's a lovely schematic, Roy. I, however, am a complete rube when it comes to the training of the magic smoke, so can you do another schematic showing how to wire the relays so that the low beam stays on as well when hi beam is selected? If the road is dark enough to require high beams, it's dark enough to have both filaments burning...

 

TIA

[raz]

That's a lovely schematic, Roy. I, however, am a complete rube when it comes to the training of the magic smoke, so can you do another schematic showing how to wire the relays so that the low beam stays on as well when hi beam is selected? If the road is dark enough to require high beams, it's dark enough to have both filaments burning...

You may be putting your reflector at risk if you do that. Too much heat. I may be wrong but you should consider it.

 

That said, it's just a matter of putting a diode between the 85 terminal on the high beam relay, to the 85 terminal on the low beam one. The "arrow" should point to the low beam relay.

[Punch]

I was inspired to add headlight relays by this circuit Raz provided.

As an electrical type I was struck by the idea of adding a diode as an alternate source of power if the fuse blows.

Normally the diodes will never conduct but if for some reason the main fuse blows you have the possibility of

having some light provided by the existing wiring.

Adding the relays made a significant improvement to the light brightness, I guesstimate about 10%.

Roy

 

That's a lovely schematic, Roy. I, however, am a complete rube when it comes to the training of the magic smoke, so can you do another schematic showing how to wire the relays so that the low beam stays on as well when hi beam is selected? If the road is dark enough to require high beams, it's dark enough to have both filaments burning...

 

TIA

 

Below is a link to a consolidation of various posts I did on a Ducati forum, as I own a Duc and did this to mine. Do not be daunted, it is really very simple to do. I can't attach it as it is exceeds the file attachment allowance. Clicking on the link will start the download immediately - about 370kb. https://files.me.com/yellowducati/gennzt

 

The major issue is that there is often a big voltage drop between the battery and headlight resulting in lower than ideal Voltage at the headlight resulting in much less light output. On page 1 you will see a chart of roughly how much light you get for a particular voltage at the bulb. I had over 2 Volts loss which meant 30% loss of light output !!!!!!! Mine is now very bright with a standard bulb. If you want to know more about "superbright" bulbs etc. go to danielsternlighting.com, then Tech, then Bulbs

 

Adding a diode - if the fuse blew due to a short, then the same high current will flow through the diode and probably blow it as well. 5 or so amps through a diode would probably also require a heatsink and the diode would add 0.7 V loss.

 

Richard

[raz]

Adding a diode - if the fuse blew due to a short, then the same high current will flow through the diode and probably blow it as well. 5 or so amps through a diode would probably also require a heatsink and the diode would add 0.7 V loss.

You are right, but my initial idea with those diodes was to provide alternate feed if a relay fails, not a fuse. And sure, a diode will have a 0.7 V drop, but it will add 12-13 V compared to what you otherwise get with a failed relay.

 

I haven't added diodes myself, but I imagine one should be able to find cheap rectifier diodes that are big enough to cope with 5A without a heat sink. The power at 0.7Vx5A is 3.5 W, that's pretty moderate.

[Kiwi_Roy]

Adding a diode - if the fuse blew due to a short, then the same high current will flow through the diode and probably blow it as well. 5 or so amps through a diode would probably also require a heatsink and the diode would add 0.7 V loss.

You are right, but my initial idea with those diodes was to provide alternate feed if a relay fails, not a fuse. And sure, a diode will have a 0.7 V drop, but it will add 12-13 V compared to what you otherwise get with a failed relay.

 

I haven't added diodes myself, but I imagine one should be able to find cheap rectifier diodes that are big enough to cope with 5A without a heat sink. The power at 0.7Vx5A is 3.5 W, that's pretty moderate.

I obtained my diodes at Radio Shack, 6 Amps if I remember. To test them I just pulled the new fuse so it reverts back. Even with the additional 0.6 V drop there's still plenty of light. The photo doesn't show it well but I just wrapped the diode leads around the relay pins and soldered.

The new heavy gauge supply to the headlight bucket will be useful for other accessories like heated grips but use a sub fuse that will blow with a short instead of taking out the main fuse back at the battery.

[Kiwi_Roy]

Since posting the 2 relay schematic I have modified mine again to a single relay without diodes.

This was done to appease the flakey Ducatti Energia regulator wiring, it likes to see the current passing through the original headlight relay.

I have now scrapped that regulator for an Electrosport that could care less how the headlights wired.

 

My bike wiring has the headlight current passing through the normally closed start relay contact as I show in the schematic, I think this may be quite unusual for a Guzzi, most just switch the headlight relay coil with the start relay.