Daytime running lights

[white exec]

I do too. Rover P6 originally had 75W tungsten 'sealed beam' (probably from Lucas) for inner main beam, and bloody awful they were too. Quite yellow. Rover started an unwelcome trend with puny dip beam: spec for the dual-beam outers was 70/37.5 !

I never had a car with 5-3/4" lamps but that did not accord with my recollections so I looked it up. The dips were 60w/37.5w and the mains were 50w. There is an alternative dip/main SB available with 60w/50w filaments.

My 3500S sported 4 x 100W on main beam, 2 x 80W on dip. Relays and wiring upgrade essential.

Those are/were illegal units I'm afraid.

You're right on both accounts, Paul.
The OE lamps were 60/37.5, not 70 - and the 100/80s could well have been illegal, but back in the late 70s and 80s there was far less publicity about this, and precious little enforcement. If you were inconsiderate enough to have poorly adjusted headlights, or lights mounted high up (eg on a cab roof), you might be picked up. The 3500S never failed an MoT in the 14 years I owned it, but did light its way rather well. Our BX was similarly lamped, and truly excellent.

In contrast, the RHD XM (on dip) came as a bit of a shock, but has been acceptably sorted by using Osram Nightbreakers or Philips Xtreme, both standard 55W H1's.

[xf1ref]

Hi Marc, if you will use 8ohm resistor the current will be bigger and the heat dissipated grater. But I don't think is a problem because I saw you want to mount the resistors on metal and the operating time for corner lights is short. The only thing I don't like is the light color of cornering led's, d1s and daylight led strip have 4300k but the cornering has a much bigger temperature.

[GiveMeABreak]

Yes, I saw some that are more bluish than white. The XBD cree has a temp of about 6000 k so should match my side lights.

I did manage to find the specification sheet of the LEDS I'm going to fit. Not the actual LED bulb, but for each LED. I'll get the relevant info and post it here, then perhaps we can work out what should be an optimum resistance to a) not under power the LED, but also not to over power it, whilst taking the additional load. I'll try and get it on shortly.

[GiveMeABreak]

Here are the specs direct from CREE themselves. So this obviously applies to a single LED. The bulb I am getting below contains 5 of these individual LEDs. Click to zoom the tables so you can read them.

So using this info, and the original PH19W filament bulb being 19 Watt - so we assume that is the power that will be supplied to the LED.

[van ordinaire]

Both my 3500S's &, I think, 2.5PI had those 75w mainbeams which were only good compared with the more common, standard 5 3/4" units. e.g. I recall they were better than the lights on my MkIII Zodiac! However, they were soon replaced by ersatz Hellas from a Lada Riva (an excellent source of surprisingly good cheap lamps) fitted with similarly uprated bulbs (& my trademark relay install that allowed the foglights to come on with the headlight flasher!). Similar set-ups were used on a BMW 323 (now with 130w mains) & a succession of XJ40's (which had H4's in both pairs, so the inner mainbeams gave way to LHD dips for foreign travel, simply by swapping the plugs over). Of course they all passed MoT's, you'd have to pull the bulbs to see they weren't E-marked BUT I do recall with the BM I had to dip the lights on desrted M-ways when approaching junction signs! As for modern lights, all I can is the projector dips on the Cadillac are rubbish, even with upgraded bulbs!

[GiveMeABreak]

I think you guys need to start a Rover thread!

[CitroJim]

I think you guys need to start a Rover thread!

Good idea! I particularly love Rovers

[white exec]

My first source of Hella 5.75" units was scrapyard cars. Later bought new Hella units, which were cheap enough.
You reminded me about the huge reflective kickback from large signs on deserted night-time motorways - I remember having to switch to dip to knock it out.

Those circular Hella halogen units were extraordinarily efficient - Cibie nothing like as good. VW, BM, Dolomite, Stag, 2500, P6 all got the smaller ones, and no end of vehicles the 7" versions, even the Mini. The 4 x 7" conversion for the Range Rover looked particularly impressive.

[GiveMeABreak]

Hi Marc, if you will use 8ohm resistor the current will be bigger and the heat dissipated grater. But I don't think is a problem because I saw you want to mount the resistors on metal and the operating time for corner lights is short. The only thing I don't like is the light color of cornering led's, d1s and daylight led strip have 4300k but the cornering has a much bigger temperature.

So just to get back to the resistance issue, the data sheet indicates:

• The forward voltage for the white LED (which this is), as being 2.9 Typical and 3.5V Max
• The car battery Voltage at 12V
• The DC Forward Current (mA) as 1000

(a) So V(supply) - V(Drop) / I (Current) shows the resistance to be 8.5 Ohms
or
(b) If the car battery whilst running is 13.8V (average), then 10.3 Ohms

So according to the data sheet the MAX Forward Current for the LED is 1000 mA, which indicates this would achieve the maximum brightness. On the second Diagram, the 'Cool White' Flux characteristics chart (looking at the top row) say calculated minimum lumens at 700 mA are 210lm and 271 lm at 1000 mA.

So would I be right in saying that if I increased the Ohms (resistance) that I would be reducing the power going through the LED and consequently reducing the lumens? I.e. if I put in an 11 Ohm resistor, this would reduce the current to 750 mA and this would reduce the brightness - as per the following chart?

One last thing - All this relates to a single LED chip, so would we need to change the calculations to take account of the 5 LEDs within the bulb housing?

[xf1ref]

Marc, I think the Led's chip are connected in series, I don't know if all 5 or only 4 and one with a resistor, but you can supply directly to 12V or 14.4V when the engine is running.
The big resistor is only to simulate the original bulb (and his resistance) , and it does not influence the cree led...maybe just a little voltage drop.

[GiveMeABreak]

Ok, thanks for the feedback - I've ordered everything now, so will see what happens!

[white exec]

Most of these LED T5/T10...G4...type lamps have one small resistor per LED, which makes them 12v capable.
Easily seen on the versions not encased in aluminium.

[GiveMeABreak]

Ok, so I completed my project and I've done a 'How To'. It's in a new thread as it's a bit long:

C5 X7 HP19W Cornering Light LED Upgrade

[xf1ref]

Nice, indeed LED matches the xenon. In future I want those Led's.

[GiveMeABreak]

Thanks - they are indeed brighter than the 7.5 W ones I had used for the HP24W - so I also replaced the HP24W ones with the same type as the HP19W - a much better light in the daytime now.