So, you've got a battery that sits at 12.6V max, and you apply a large load to it.
How exactly do you get a voltage spike in that scenario?
Let's Figure Out the Headlight Bulb Issue
I'm guessing when you start the car and the alternator begins to generate power (>14V)?~tc~ wrote:So, you've got a battery that sits at 12.6V max, and you apply a large load to it.
How exactly do you get a voltage spike in that scenario?
Here's an interesting post on current (not voltage) spikes when lights are turned on: http://theeshadow.com/files/volvo/hidcomp.html
This bit is interesting and perhaps very relevant to the solution:bootymac wrote:
Here's an interesting post on current (not voltage) spikes when lights are turned on: http://theeshadow.com/files/volvo/hidcomp.html
Why does Volvo consider it necessary to regulate the voltage to the stock halogens; and why don't other manufacturers do it?The CEM in this vehicle regulates the voltage going to the low beam to 13.0+0.2v using PWM modulation of a JFET, and monitors current flow presumably through a low value shunt resistor.
David
VAG vehicles also have a voltage regulator specifically for headlights, as mentioned earlier. It's controlled electronically and the output voltage can be set by a user (with the appropriate software). I'm sure other manufacturers have this too but not on all vehicles, likely due to manufacturing costs. It may become mainstream in the future thoughmurcod wrote: Why does Volvo consider it necessary to regulate the voltage to the stock halogens; and why don't other manufacturers do it?
It's clear that over voltage is an issue. If Hella's claim wasn't enough, vehicle manufacturers are also addressing this problem.
Samir, it appears that a voltage regulator for the headlights is your solution. If you find a way to make this work, please share! It would be interesting to see and learn
That's kinda what I'm thinking after seeing what you posted about manufacturers doing.bootymac wrote:Samir, it appears that a voltage regulator for the headlights is your solution. If you find a way to make this work, please share! It would be interesting to see and learn
Of course, my simple solution will be to either remember to manually turn them on and off like I do on all my other cars, or just set it to auto and deal with the lack of 'real' headlights during the day.
Did some testing today. Engine idling, low beam on - head light voltage at rear of the bulb= 13.95V ; battery voltage was 14.46V at the same time.
So, with increased revs both those voltages are only going to climb. The figure I got of 13.95V is already above the previously mentioned 5% over voltage level (of 13.86V) which supposedly halves bulb life.
So, with increased revs both those voltages are only going to climb. The figure I got of 13.95V is already above the previously mentioned 5% over voltage level (of 13.86V) which supposedly halves bulb life.
David
Those voltages are dead on for what is required for the battery to charge. Bulb manufacturers must know this, bulbs have to be OK at least to 14.4V.murcod wrote:Did some testing today. Engine idling, low beam on - head light voltage at rear of the bulb= 13.95V ; battery voltage was 14.46V at the same time.
So, with increased revs both those voltages are only going to climb. The figure I got of 13.95V is already above the previously mentioned 5% over voltage level (of 13.86V) which supposedly halves bulb life.
2011 Sport SLS with nav Black Pearl Metallic
murcod wrote:Did some testing today. Engine idling, low beam on - head light voltage at rear of the bulb= 13.95V ; battery voltage was 14.46V at the same time.
So, with increased revs both those voltages are only going to climb. The figure I got of 13.95V is already above the previously mentioned 5% over voltage level (of 13.86V) which supposedly halves bulb life.
Good info, thanks for testing and sharingmurcod wrote:I forgot to mention, I had the headlights on before starting the engine (with the multimeter on Max Hold.) The peak was only 13.96V - so no significant spike was picked up by the multimeter at engine start up.