Use of DC boost circuit for Leaf Halogen main beam

My Nissan Leaf Forum

Help Support My Nissan Leaf Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

HomerJSimpson

Member
Joined
Dec 12, 2021
Messages
5
As I understand it, the 2015 Nissan Leaf (LED/H9 combo) drives it's halogen bulbs at 13.1V DC, rather than at approx 14.4V DC as one would find in an ICE car with an alternator. I believe this is contributing to very inferior main beam halogen brightness/throw, as halogen bulbs perform poorly at lower voltages than designed.

I'm wondering if anyone has played with boosting the DC voltage to the main beams, using a DC boost converter or a voltage regulator?
 
We are aware of the issue, but AFAIK no one has tried to boost the voltage to the headlights. One possible reason for this is that there is a way to boost the voltage to 14.4 for a minute or so, and it seems to have no effect on the brightness of the headlights. What is this method? Turning on the front windshield wipers, believe it or not. Running the climate control, at least in Heat mode, also seems to boost the voltage to 14.4 for a few minutes, or at least while it's running. That one is a bit controversial, but I just observed it myself last night: I have a phone charger plugged in that has a display screen on which it displays, alternately, phone charging amperage, cabin temp, and DC system voltage. It was on 14.4 volts for quite a while, with the wipers off. I think that this was because the power draw from the heating was causing the DC-DC converter to remain in charge mode.
 
Incandescent bulb output is strongly voltage dependent.
FvpK02o.gif


The voltage may be constrained by the wire gauge used in the headlamp circuit. The voltage experienced at the bulb may be significantly less than that measured at the battery. Voltage sag will rob you regardless of battgery voltage and should be corrected as a first action.
If I were concerned my first effort would be to implement a dedicated relay to carry power over heavier wires. This will improve light output in any car in which the (incandescent) bulbs are experiencing voltage sag. You may find the following link useful:

https://www.danielsternlighting.com/tech/relays/relays.html

Note - this does not apply to LED bulbs, where light output is current-dependent not voltage-dependent.
 
I may try to put a volt meter on the main beam connection, to check any voltage variability vis a vis battery voltage. AFAIK, the dipped and main beam circuits are each powered through separate flyback diode-protected relays in the lighting 'computer', so it's very possible there's something else in there that is 'smoothing' voltages to ensure main beam brightness does not fluctuate while battery voltage is skipping about from 13.1V to 14.4V.

I've always seen a very direct correlation between filament bulb brightness and source voltage, so it's manifestation on the Leaf intrigues me. I can't believe that Nissan engineers would not have done something to maximise a constant main beam brightness regardless of battery voltage.
 
Learjet said:
change them out to LED, if it bothers you that much?

While LED will likely solve the voltage-drop problem, the resulting beam pattern is likely to be illegal and unsafe: http://www.danielsternlighting.com/tech/bulbs/Hid/conversions/conversions.html
 
Learjet said:
change them out to LED, if it bothers you that much?

I don't believe in solving one problem by creating a potentially bigger one. My query is solely about improving the halogen main beam output, not about introducing a non-standard light source for which the halogen bulbs reflectors were not designed, and which would immediately render my main beams illegal. So, the use of LEDs in the main beam is not something that interests me.
 
Nubo said:
Learjet said:
change them out to LED, if it bothers you that much?

While LED will likely solve the voltage-drop problem, the resulting beam pattern is likely to be illegal and unsafe: http://www.danielsternlighting.com/tech/bulbs/Hid/conversions/conversions.html

The first step for me is to establish whether there is, in fact, a voltage drop at the main beam. It sure looks like there is, but as others have said, the battery voltage goes up from 13.1V to 14.4V when wipers are operating, and yet this does not appear to affect the light output from the halogen bulbs, which is extremely hard to understand, unless there is some other voltage regulation going on in the main beam circuit.
 
Back
Top