Can you use 80 Watt bulbs in low beam housings with stock wiring?
80 watt low beams?
- Thread starter wannafbody
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If you talking about your stock 45~50Watt low beam lightbulb types, the answer is nope.
You'll see one more more of the following if you don't heed the advise:
(1)wiring overheats causing meltdowns and subsequently shorts
(2) your 80Watt lowbeam lightbulb will turn out to be more or less like a 60Watt equivalent due to increased resistance on your circuit
(3) your plastic headlamp housing may melt.
Q.
You'll see one more more of the following if you don't heed the advise:
(1)wiring overheats causing meltdowns and subsequently shorts
(2) your 80Watt lowbeam lightbulb will turn out to be more or less like a 60Watt equivalent due to increased resistance on your circuit
(3) your plastic headlamp housing may melt.
Q.
I thought that might be a possibility, thanks.
I'm thinking the circuit would be fused and that fuse would fail before the wiring melts down. At least that's how it is supposed to work. Sometimes you'll have a genious come along and put in a bigger fuse that doesn't blow and then the whole circuit becomes the fuse that fails!
Q,
One question I have is how does putting in an 80 watt bulb INCREASE the circuit's resistance? The resistance in a circuit like this is more or less a constant, and putting in a load that increases the current flow (80 watts vs 35-55 watts) would actually DECREASE the overall resistance (ohms) in the circuit, causing more current to flow up to the point that a fuse blows or the wire melts. The load is usually the current limiting device in a properly designed and healthy (no corrosion or poor connctions) circuit.
Q,
One question I have is how does putting in an 80 watt bulb INCREASE the circuit's resistance? The resistance in a circuit like this is more or less a constant, and putting in a load that increases the current flow (80 watts vs 35-55 watts) would actually DECREASE the overall resistance (ohms) in the circuit, causing more current to flow up to the point that a fuse blows or the wire melts. The load is usually the current limiting device in a properly designed and healthy (no corrosion or poor connctions) circuit.
I put in higher watt white bulbs (Japan - don't remember the brand) in my Ranger and it melted the connector. The lights were whiter, but actually harder to see. I put the Osram Sylvania OEM bulbs back in and they are actually better, despite less bright.
I don't like the aftermarket bulbs that change the color of the output. They usually do this with a coating on the bulb, which causes the bulb to run especially hot, melting connectors and burning out the bulb prematurely. I just buy the cheapest 2-pack offered and they last longest and work best.
Originally Posted By: bmwtechguy
Q,
One question I have is how does putting in an 80 watt bulb INCREASE the circuit's resistance? The resistance in a circuit like this is more or less a constant, and putting in a load that increases the current flow (80 watts vs 35-55 watts) would actually DECREASE the overall resistance (ohms) in the circuit, causing more current to flow up to the point that a fuse blows or the wire melts. The load is usually the current limiting device in a properly designed and healthy (no corrosion or poor connctions) circuit.
yo!
You need to think Ohm's law (V=I*R) where voltage is equal to resistance times current. Copper wire is not an absolute perfect conductor and comes with resistance in it (if you look deeper into the subject, you'll realise that when you buy copper wires, it is determined by resistance/length).
Granted, we use the same wire that was destined for use in 35Watt lighting system, and assuming that the length hasn't been changed (same wiring harness, no change in wiring gauge, etc.). Let's make an artificial value out of it for ease of calculation (say, 0.5ohms in total wiring-related resistance). Given 35Watt out of a 12VDC bulb consumption, that equates to approx. 2.92Amps.
Using Ohm's law to calculate the total voltage drop (V=I*R), 2.92Amps *0.5ohms =1.46VDC approx.
So, in other words: if you feed a 12V into the system, what your 35Watt lightbulb "sees" is 12V-1.46VDC = 10.54VDC on it's filament end.
Now, let's change the calculation a bit too: with 80Watt bulb: you get 6.67amps and once again, with the total voltage drop would work out to be 3.335VDC, or in other words: your 80Watt lightbulb filament's end will only sees 8.665VDC after the voltage drop!
Finally, to answer your question RE: why putting an 80watt lightbulb would increase the circuit's resistance, first let me feed you with some physics link:
http://www.allaboutcircuits.com/vol_1/chpt_12/6.html
Other than certain metal alloys such as carbon, silicon, germanium, etc. which comes with negative coefficient of resistance (meaning that the higher the temperature, the lower the resistance), all other metals, incl. copper, etc. the higher the temperature the higher the resistance.
In other words: when comparing to you feeding only 2.92amps through that same wire with 0.5ohms resistance under 20C (assuming no change to the copper wire's temperature), when feeding 6.67amps into that very same wire at 20C with 0.5ohms resistance, the wire is gonna heat up more and thus causing the resistance to rise until the wire reach a temperature "equilibrium" point where the resistance will surely be more than that of 0.5Ohms@20C to begin with (could be 0.6? 0.7ohms? all have to be calculated).
Bottomline: when in doubt, don't do silly things RE: retrofitting a 80Watt lightbulb into a harness only capable of 35Watts bulb.
Hope that answers your questions.
Q.
Q,
One question I have is how does putting in an 80 watt bulb INCREASE the circuit's resistance? The resistance in a circuit like this is more or less a constant, and putting in a load that increases the current flow (80 watts vs 35-55 watts) would actually DECREASE the overall resistance (ohms) in the circuit, causing more current to flow up to the point that a fuse blows or the wire melts. The load is usually the current limiting device in a properly designed and healthy (no corrosion or poor connctions) circuit.
yo!
You need to think Ohm's law (V=I*R) where voltage is equal to resistance times current. Copper wire is not an absolute perfect conductor and comes with resistance in it (if you look deeper into the subject, you'll realise that when you buy copper wires, it is determined by resistance/length).
Granted, we use the same wire that was destined for use in 35Watt lighting system, and assuming that the length hasn't been changed (same wiring harness, no change in wiring gauge, etc.). Let's make an artificial value out of it for ease of calculation (say, 0.5ohms in total wiring-related resistance). Given 35Watt out of a 12VDC bulb consumption, that equates to approx. 2.92Amps.
Using Ohm's law to calculate the total voltage drop (V=I*R), 2.92Amps *0.5ohms =1.46VDC approx.
So, in other words: if you feed a 12V into the system, what your 35Watt lightbulb "sees" is 12V-1.46VDC = 10.54VDC on it's filament end.
Now, let's change the calculation a bit too: with 80Watt bulb: you get 6.67amps and once again, with the total voltage drop would work out to be 3.335VDC, or in other words: your 80Watt lightbulb filament's end will only sees 8.665VDC after the voltage drop!
Finally, to answer your question RE: why putting an 80watt lightbulb would increase the circuit's resistance, first let me feed you with some physics link:
http://www.allaboutcircuits.com/vol_1/chpt_12/6.html
Other than certain metal alloys such as carbon, silicon, germanium, etc. which comes with negative coefficient of resistance (meaning that the higher the temperature, the lower the resistance), all other metals, incl. copper, etc. the higher the temperature the higher the resistance.
In other words: when comparing to you feeding only 2.92amps through that same wire with 0.5ohms resistance under 20C (assuming no change to the copper wire's temperature), when feeding 6.67amps into that very same wire at 20C with 0.5ohms resistance, the wire is gonna heat up more and thus causing the resistance to rise until the wire reach a temperature "equilibrium" point where the resistance will surely be more than that of 0.5Ohms@20C to begin with (could be 0.6? 0.7ohms? all have to be calculated).
Bottomline: when in doubt, don't do silly things RE: retrofitting a 80Watt lightbulb into a harness only capable of 35Watts bulb.
Hope that answers your questions.
Q.
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I asked a question and got an excellent, detailed answer! I had not thought that deeply on the resistance of the wire itself and the resulting voltage drop. Thank you for taking the time to enlighten me and my non-engineering point of view.
Would I be correct in saying that if you put in a brighter bulb, say like going from a 35 watt to a 55 watt bulb, wouldn't the WHOLE circuit have a higher current flow (less resistance overall including the load), than the previous complete circuit with the 35 watt bulb? When the fuse blows, this would be an indication that the current is higher than before. And I do understand what you explained that if the circuit is powered and a heated wire or a poor connection creates additional resistance, then the circuit resistance would increase.
For example, I take power off this circuit, isolate it, and measure with my handy ohm meter the resistance of the entire circuit, including the 35 watt bulb load. Then I replace this bulb with a higher wattage bulb and measure again the same circuit. Wouldn't this have a lower ohm (resistance) reading? I realize things can change once powered and you factor in voltage drop and heating of the conductors, etc.
Would I be correct in saying that if you put in a brighter bulb, say like going from a 35 watt to a 55 watt bulb, wouldn't the WHOLE circuit have a higher current flow (less resistance overall including the load), than the previous complete circuit with the 35 watt bulb? When the fuse blows, this would be an indication that the current is higher than before. And I do understand what you explained that if the circuit is powered and a heated wire or a poor connection creates additional resistance, then the circuit resistance would increase.
For example, I take power off this circuit, isolate it, and measure with my handy ohm meter the resistance of the entire circuit, including the 35 watt bulb load. Then I replace this bulb with a higher wattage bulb and measure again the same circuit. Wouldn't this have a lower ohm (resistance) reading? I realize things can change once powered and you factor in voltage drop and heating of the conductors, etc.
Originally Posted By: bmwtechguy
Would I be correct in saying that if you put in a brighter bulb, say like going from a 35 watt to a 55 watt bulb, wouldn't the WHOLE circuit have a higher current flow (less resistance overall including the load), than the previous complete circuit with the 35 watt bulb?
Q-> yes. As a matter of fact: due to different load(more current than intended with a 35Watt bulb load)imposed on the circuit, and the higher current changes the picture entirely.
When the fuse blows, this would be an indication that the current is higher than before?
Q--> Fuse is used for overcurrent protection, and one can easily alter the fuse rating w/o touching on the rest of the circuit (i.e. the wire gauge of the original lighting harness unchanged). That's why there's the universal understanding that "if the circuit/load in intended to be protected by a 10Amp fuse, do not retrofit a 15amp fuse for it may cause fire...yadda..yadda..."
(you get my drift)
And I do understand what you explained that if the circuit is powered and a heated wire or a poor connection creates additional resistance, then the circuit resistance would increase.
Q--> Yes, any poor connection along the circuit will cause heatup due to resistance imposed on it, and that worsen the situation further...
For example, I take power off this circuit, isolate it, and measure with my handy ohm meter the resistance of the entire circuit, including the 35 watt bulb load. Then I replace this bulb with a higher wattage bulb and measure again the same circuit. Wouldn't this have a lower ohm (resistance) reading
Q--> Unfortunately, no. Incandescent filament lightbulb's load is not "linear" so your reading when the lightbulb is "on" and "off" will be different.
Also: a 80Watt lightbulb circuit w/o power, the resistance reading will be dramatically different to that of a 35Watt lightbulb in the same circuit w/o power.
That's why I put on point # 2in my 1st response in this subject *wink*
Would I be correct in saying that if you put in a brighter bulb, say like going from a 35 watt to a 55 watt bulb, wouldn't the WHOLE circuit have a higher current flow (less resistance overall including the load), than the previous complete circuit with the 35 watt bulb?
Q-> yes. As a matter of fact: due to different load(more current than intended with a 35Watt bulb load)imposed on the circuit, and the higher current changes the picture entirely.
When the fuse blows, this would be an indication that the current is higher than before?
Q--> Fuse is used for overcurrent protection, and one can easily alter the fuse rating w/o touching on the rest of the circuit (i.e. the wire gauge of the original lighting harness unchanged). That's why there's the universal understanding that "if the circuit/load in intended to be protected by a 10Amp fuse, do not retrofit a 15amp fuse for it may cause fire...yadda..yadda..."
(you get my drift)
And I do understand what you explained that if the circuit is powered and a heated wire or a poor connection creates additional resistance, then the circuit resistance would increase.
Q--> Yes, any poor connection along the circuit will cause heatup due to resistance imposed on it, and that worsen the situation further...
For example, I take power off this circuit, isolate it, and measure with my handy ohm meter the resistance of the entire circuit, including the 35 watt bulb load. Then I replace this bulb with a higher wattage bulb and measure again the same circuit. Wouldn't this have a lower ohm (resistance) reading
Q--> Unfortunately, no. Incandescent filament lightbulb's load is not "linear" so your reading when the lightbulb is "on" and "off" will be different.
Also: a 80Watt lightbulb circuit w/o power, the resistance reading will be dramatically different to that of a 35Watt lightbulb in the same circuit w/o power.
That's why I put on point # 2in my 1st response in this subject *wink*
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Im running 80/100's in my 98 F-150 without any trouble.
Chris
Chris
If you really want to run a higher wattage, get a headlight harness that hooks to your battery so you don't fry the stock wiring.
Melted headlights are still your problem to deal with.
Melted headlights are still your problem to deal with.
Originally Posted By: bmwtechguy
I don't like the aftermarket bulbs that change the color of the output. They usually do this with a coating on the bulb, which causes the bulb to run especially hot, melting connectors and burning out the bulb prematurely. I just buy the cheapest 2-pack offered and they last longest and work best.
I would love to see your proof on this.
I don't like the aftermarket bulbs that change the color of the output. They usually do this with a coating on the bulb, which causes the bulb to run especially hot, melting connectors and burning out the bulb prematurely. I just buy the cheapest 2-pack offered and they last longest and work best.
I would love to see your proof on this.
"I would love to see your proof on this. "
If he is buying regular headlamps and you're buying something like Silverstars, he's right; see the thread on Silverstars where I posted the reply below.
"If you look at the 9007 lamps on the Sylvania site the rated life for the regular one is 500 low / 250 high, for the long life it's 1500 / 250, and for the Silverstar it's 150 / 90. The Silverstar has 1/10 the life of the long life bulb, and obviously it doesn't have 10 times the light output. "
If he is buying regular headlamps and you're buying something like Silverstars, he's right; see the thread on Silverstars where I posted the reply below.
"If you look at the 9007 lamps on the Sylvania site the rated life for the regular one is 500 low / 250 high, for the long life it's 1500 / 250, and for the Silverstar it's 150 / 90. The Silverstar has 1/10 the life of the long life bulb, and obviously it doesn't have 10 times the light output. "
I used Philips 130/100w H4 bulbs before.
For the wire, I did use some extra wires, harness and relay connecting to the battery directly.
For the housing, after about 4 or 5 years using, nothing happened, my Depo headlights are still good.
Just my experience.
For the wire, I did use some extra wires, harness and relay connecting to the battery directly.
For the housing, after about 4 or 5 years using, nothing happened, my Depo headlights are still good.
Just my experience.
yes, the colored coatings are restrictive... for instance a yellow coating restricts the blues, or the blue coating restricts the yellow/red, meaning that energy is trapped in the bulb capsule. It can't get out as light, so it gets out as heat. But the bulb temp must rise that much more to dissipate the additional heat to the air, instead of being beamed out as light. Higher capsule temp, higher socket temp, higher air temp, and reduced actual light output.
Filters don't "convert" the color, they restrict unwanted colors.
M
Filters don't "convert" the color, they restrict unwanted colors.
M
Question for Quest (if you are still checking this thread):
Can't the voltage be measured just ahead of the headlight connector, with the bulb turned on, to confirm if the higher wattage bulb is a problem for the stock wiring?
The voltage drop will depend on the length and gauge of the wire:
Wire Gauge Resistance per foot
10 .00118
12 .00187
14 .00297
16 .00473
18 .00751
20 .0119
22 .0190
The reason I ask is that I am running high beam bulbs (9005 65W) in the low beam (9006 55W) sockets on my BMW Z3. I did this low cost upgrade. Took a little bit of work with a dremel drill to grind down a couple of plastic tabs on the bulb. I found a huge improvement on this car which has very poor low beams. I have had no problems so far.
Low beam 9006 - 55 watts - 1000 lumens
High beam 9005 - 65 watts - 1700 lumens
So far no issues but it would be interesting if I could confirm the voltage at the light. I am also planning to try this on my 1994 Honda Accord which has the same bulbs.
http://s446.photobucket.com/albums/qq184/mva123456789/BMW low beam upgrade/
Can't the voltage be measured just ahead of the headlight connector, with the bulb turned on, to confirm if the higher wattage bulb is a problem for the stock wiring?
The voltage drop will depend on the length and gauge of the wire:
Wire Gauge Resistance per foot
10 .00118
12 .00187
14 .00297
16 .00473
18 .00751
20 .0119
22 .0190
The reason I ask is that I am running high beam bulbs (9005 65W) in the low beam (9006 55W) sockets on my BMW Z3. I did this low cost upgrade. Took a little bit of work with a dremel drill to grind down a couple of plastic tabs on the bulb. I found a huge improvement on this car which has very poor low beams. I have had no problems so far.
Low beam 9006 - 55 watts - 1000 lumens
High beam 9005 - 65 watts - 1700 lumens
So far no issues but it would be interesting if I could confirm the voltage at the light. I am also planning to try this on my 1994 Honda Accord which has the same bulbs.
http://s446.photobucket.com/albums/qq184/mva123456789/BMW low beam upgrade/
On my last car I bought a very simple harness and relay kit, plug and play, the original connectors feed the harness and relays for on/off/high beam, the harness is powered directly off the battery, the new bulbs fed by the connectors off the relays. I went 55/80 bulbs of some sort, the fixture didn't heat up in a harmful manner. But at 100W, I have no idea the effect. I doubt you'd like the effect of UV damage on the INSIDE of the lens with the hotter bulbs though. I believe even the new E-Code headlights address UV damage from the inside these days.
So, install supplemental relays to protect your wiring (not a bad idea even if you run stock bulbs, as your voltage will be higher at the bulb), and if you run the hotter bulb, pay close attention to the fixture for sign of melt, crispy seals, or excessive temps on the casings, especially under the hood. Too hot for your bare hand is way too hot for the plastic, I'd wager.
So, install supplemental relays to protect your wiring (not a bad idea even if you run stock bulbs, as your voltage will be higher at the bulb), and if you run the hotter bulb, pay close attention to the fixture for sign of melt, crispy seals, or excessive temps on the casings, especially under the hood. Too hot for your bare hand is way too hot for the plastic, I'd wager.
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