Short lived halogen DC lights

jimskau

I have recently replaced more halogen lightbulbs in my 12V DC circuit, than my economy likes to endure. I am beginning to suspect my direct connection to my 1000 Ah battery store via a 6 Amp DC fuse to be the problem. On a normal night my batteries will be at 12.8 Volts going down to wards the 12,5V. Could it be, that I the halogens burn out due to the slightly higher voltage of a fully charged battery store? Would it help to introduce some resistance in the circuit?
As allways thankfull for your patience and helpfullness. Jim Skau 8-)

crewzer

Re: Short lived halogen DC lights

Jim,

My understanding is that 12 V halogen bulbs are designed to operate from 12 V maximum. They are apparently quite intolerant of "high" voltage, and even 12.6 V or 12.8 V will dramatically shorten their useful life. This may indeed be what's behind the early bulb failures you've experienced.

You could put a dropping resistor in series with each bulb to reduce the voltage by 0.8 V or so. Burning off 0.8 V for a single 12 V / 10 W bulb would require a resistor value of 1 Ohm rated for at least 1 W.

Another option might be to buy (or design and build) a PWM dimmer like these: http://bluesea.com/category/8/33/productline/205

HTH,
Jim/crewzer

BB.

Re: Short lived halogen DC lights

Scroll down on this bike light page and you can see the comparison between voltage/lumens/life for a typical filament bulb (not sure the plot applies to halogen)--but you can see how dramatically life is affected by voltage:

http://www.myra-simon.com/bike/lights.html

For example:

105% over voltage (12 volt -> 12.6 volts)
~120% lumens
~108% power
~55% life (1/2 life)

-Bill

System2

Re: Short lived halogen DC lights

For all my lighting, I've switched from halogen to CF lamps, through a small inverter. I use more 4 watt CF's than the higher wattage ones and find they out preform a 10 watt halogen, in light output and by far in life. A couple have 3 years use, on every evening and no failures. More light, less heat, less wattage, longer life. Speaks for itself. :-D
Wayne

niel

Re: Short lived halogen DC lights

in the charging of the batteries is where the worst problem lies because the voltage goes above 14v. i've experienced this with my leds as well, as it prematurely burned one out. i will have to either put more resistance in line or put a regulator on my leds, but you could also put diodes in line if the current isn't too high. each diode will drop about 1/2v. i think radio shack still sells the 25 pack of 1amp diodes for under $3 and 3 packs for under $1. unlike the resistor, the diode has to be put in right as it is polarized. put it in wrong and you'll get 0v. btw, they would be in series with the load just like a resistor would be and you can use more than one of them. do not put either in parallel, or in other words, not across the + and - as this could short it out.

jimskau

Re: Short lived halogen DC lights

Thank you very much guys! :-D