Jump to content
sp838

How much power can be safely drawn on the headlight circuit?

Recommended Posts

So the headlight circuit is fused with a 15A fuse. The headlights on high beam draw 65 Watts, which at 12 volts is only 5.4A. What if I added more lights to this circuit? Any reason to think that could cause an issue? The relays the headlight power runs through (starter relay and headlight relay) are both rated for much more than 15A.....

 

So, would be crazy to put more load on this circuit? Could doing that impact anything else? Could the Regulator/Rectifier be damaged?

 

Electrical wizards, please weigh in!

 

 

Share this post


Link to post
Share on other sites

In the early Sport whose Relay#1 is *not* "Livin' Easy*, the current is passed through the NC contacts which (on most micro relays) are rated only 10 amps.

 

Do the "Easy Livin' Test" :rasta:  . . . if your Sport fails, your Relay #1 is livin' stressed  :wacko: already.

 

If it were me, I would run a dedicated hot for auxiliary lights and ground them back to the frame or engine case using a completely separate relay.

 

(And, even then, use high current relays in (at least) Position #1 and especially Position #5)

Share this post


Link to post
Share on other sites

As Docc says, don't overload the existing headlight circuit or you risk screwing up charging which also taps into the circuit. How about just adding a pair of LED spotlights.

On my VII I tapped into the wire going to the dimmer switch and ran it to a relay in the bucket where it picks up High and Low beam to take all the load off the dimmer switch. Relay energized for High, defaults to Low.

 

 

Sent from my shoe phone!

  • Like 1

Share this post


Link to post
Share on other sites

As Docc says, don't overload the existing headlight circuit or you risk screwing up charging which also taps into the circuit. 

 

Very curious about this aspect... Can you elaborate? Can drawing too much power on this circuit damage the r/r?

 

In the early Sport whose Relay#1 is *not* "Livin' Easy*, the current is passed through the NC contacts which (on most micro relays) are rated only 10 amps.

 

Do the "Easy Livin' Test" :rasta:  . . . if your Sport fails, your Relay #1 is livin' stressed  :wacko: already.

 

Awesome, thank you for this! I will run this test. I have some fresh, new lovely relays, pretty sure they are the "high current" type, but I will check all these things. Thanks guys!

Share this post


Link to post
Share on other sites

Ok, so checked my new relays, they are indeed the robust-enough kind. I got them here: http://www.dpguzzi.com/relay.htm

 

Normally Open is rated at 25A @ 14VDC, NC is 20A. Should be good as far as the relay is concerned, but I will still do the Easy Livin' Test. 

 

EDIT: will be using the even more robustier Omrons you discovered.

 

Mainly concerned with the charging circuit and the R/R, I have already burned one up, would like to not do that again :P Hoping Kiwi_Roy can lend some insight there.

Share this post


Link to post
Share on other sites

When I first got my 2001 the regulator was sick so I pulled it apart to see if I could figure out what had happened. At the same time I reverse engineered it and drew a schematic so I could better understand how it's supposed to work.

I found that the regulator senses the Voltage on the headlight circuit downstream of the relay and it likes to see 13.8 Volts between the black reference wire and the case

There's normally a little bit of Voltage drop between the battery and the point downstream of the relay where the regulator measures caused by various resistances (wire, contacts etc.), my 01 was about 0.6V so for the regulator to see 13.8 the battery has to be at 13.8 + 0.6 or 14.4 Volts

 

Now here's the problem, The Voltage drop is not consistent I saw mine normally about 0.6 rise to almost 1 Volt over the winter

At 1 Volt it stands to reason the battery will have to reach 14.8 Volts to make the regulator happy.

Increasing the headlight load (bigger lamp, more current) will create even more Voltage drop, remember Voltage is Current  x Resistance.

 

Getting back to my sick regulator I found that the diodes inside it had become so hot the leads melted off and you could see evidence of arcing. My conclusion as to what caused this was as follows.

There was too much Voltage drop in the reference circuit (perhaps over a Volt) so the regulator pushed the battery Voltage higher to try and reach 13.8. until eventually the solder melted.

The charge current for a battery is not linear with Voltage, it goes up exponentially with increase in Voltage,(this is over simplification but I suggest it lead to overheating because the regulator never got a break). The battery would be Overcharged because the regulator only saw a portion of the real Voltage and concluded it needed topping up.

 

I think the solution is fairly obvious.

 

 

 

It would be interesting to take a Voltage Drop survey from the owners, it's a good time of year when the bike has been languishing in a garage all winter it only takes a second.

Before touching anything, with the key On measure the Voltage between battery + and the red/black wire where the regulator double plug connects to the loom this is the Voltage Drop.

Now re-seat the relays in their sockets, I think you will find the Voltage Drop is less.

 

Note: the early VIIs like my 2001 had more Voltage drop because they have 2 relay contacts in series with the headlight, the Normally Closed Start Relay 30/87A and Headlight Relay 30/87, later ones only have the headlight relay 30/87.

 

You may wonder why the factory wired the bike that way, I can only guess.

The Ducati Energia regulators draw quite a bit of current from the reference circuit, ~ 15 milliamps so they had to have a way of disconnecting it from the battery so as not to run it flat when the bike is not running. Putting it on the headlight relay seems like a reasonable solution. 

Modern direct connect regulators only draw a fraction of the current 0.3 milliamps but still I find I have to disconnect my new regulator over winter where I never had to disconnect the Ducati Energia wired to the headlight.

Sorry about the long winded explanation

Share this post


Link to post
Share on other sites

Ok, so checked my new relays, they are indeed the robust-enough kind. I got them here: http://www.dpguzzi.com/relay.htm

 

Normally Open is rated at 25A @ 14VDC, NC is 20A. Should be good as far as the relay is concerned, but I will still do the Easy Livin' Test. 

 

EDIT: will be using the even more robustier Omrons you discovered.

 

Mainly concerned with the charging circuit and the R/R, I have already burned one up, would like to not do that again :P Hoping Kiwi_Roy can lend some insight there.

Let's be aware that the ratings on the Chinese GEI may be more than a little suspect.  And also that, contacts are rated two ways: "inrush" and continuous. The ratings shown for the GEI are not likely for continuous current which is what is required across Relay#1 NC (early V11) and Relay#5 NO. Most micro relays are rated 10amp/20amp *continuous*.

 

The GEI are just not "robust enough" in those positions, and "may be" fine in other positions.

 

Lots on this, with links and history and spec sheets, in Relay Alternatives.

Share this post


Link to post
Share on other sites

 

I think the solution is fairly obvious.

 

What would the solution be to someone who isn't as well versed as you?

 

Looking at the wiring diagram, I can see where there is power coming into the r/r from the headlight relay, the same power line that gets split up to various things including headlights, brake lights, horn, dash lights and low fuel/oil pressure sensors... I have an aftermarket r/r made by Rick's Motorsports. It doesn't use standard diodes, it is "mosfet" transistor based. I have it wired directly to the battery positive, bypassing the stock wiring and fuse. So I don't know if it behave the same way as the stock ones do as far as sensing voltage etc.

Share this post


Link to post
Share on other sites

SP838,

             Yes your aftermarket probably doesn't use the headlight circuit as a reference so in theory you should be able to increase the load.

I gave up on the Ducati Energia as well, nothing wrong, it's the Guzzi wiring that lets it down.

 

As for those wimpy wires going to the dimmer switch.

I tapped into the Red/Black wire at the main connector under LH side of the tank and ran a fat wire to the headlight bucket where I have a single relay feeding the High & Low filaments, one wire from the dimmer switch picks up the coil to switch to High Beam, defaults to Low Beam, made a huge difference to headlight brightness. I also added a decent ground wire from the headlight back to the main chassis.

Somewhere I read increasing the Voltage to the lamp filament pays back 5 fold in lamp brightness.

 

The old recycled relays are good for projects like that.

Share this post


Link to post
Share on other sites

SP838,

             Yes your aftermarket probably doesn't use the headlight circuit as a reference so in theory you should be able to increase the load.

I gave up on the Ducati Energia as well, nothing wrong, it's the Guzzi wiring that lets it down.

 

As for those wimpy wires going to the dimmer switch.

I tapped into the Red/Black wire at the main connector under LH side of the tank and ran a fat wire to the headlight bucket where I have a single relay feeding the High & Low filaments, one wire from the dimmer switch picks up the coil to switch to High Beam, defaults to Low Beam, made a huge difference to headlight brightness. I also added a decent ground wire from the headlight back to the main chassis.

Somewhere I read increasing the Voltage to the lamp filament pays back 5 fold in lamp brightness.

 

The old recycled relays are good for projects like that.

That's very elegant, Roy. In my dumbassosity, I put a separate relay for high and low beams on the Aero Lario.. :homer:

Share this post


Link to post
Share on other sites

The r/r I have installed from Rick's Motorsport does not have the signal input circuit. Just two yellow leads from the alternator, red wire to the battery, black wire to ground, and blue wire to the dash. So I don't think the voltage drop business from the headlight circuit should affect it.

Share this post


Link to post
Share on other sites

The r/r I have installed from Rick's Motorsport does not have the signal input circuit. Just two yellow leads from the alternator, red wire to the battery, black wire to ground, and blue wire to the dash. So I don't think the voltage drop business from the headlight circuit should affect it.

You are right, it's not effected by the headlight circuit, the modern regulators sense the Voltage from the battery wires.

I tried to access the wiring diagram to check on what the blue wire to dash is doing but I couldn't, is it a light or does it pick up from the ignition?

Share this post


Link to post
Share on other sites

The blue wire out of the r/r connects to the very same red/black headlight circuit power via a dash light bulb, which is supposed to indicate poor charging. The plot thickens... Wiring diagram for early V11s attached.

1999_V11_sport-wiring.png

Share this post


Link to post
Share on other sites

Via the bulb is ok, that doesn't effect the regulators output Voltage

All the regulator does is ground that wire to turn the light On, you can test the lamp by touching the pin to chassis.

Share this post


Link to post
Share on other sites

Soooo, that my headlamps are separated to dedicated circuits might be leading my Ducati Energia to charge at 14.2v (good for the PC545 AGM battery instead of that R/R's preset 13.8v (which is not perfect for the AGM)?

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...