Fog Lights and Battery/Alternator Longevity

[OriginHacker21]

I recently got a 2013 Honda Civic. Everything is stock. I finally sat down and programmed everything the way I wanted. There is an auto option on the headlights so they automatically turn on when dark, off when daylight, and stay on when I shut off my car/unlock it for 60 seconds (I changed it to 30 or 15, can't remember). I programmed the fog lights to be on automatically too.

Question 1: Does driving with fog lights harm battery/mpg significantly enough to not run them? I find with them on I get a lot less people high beaming me thinking I have my brights on. Coming from the Midwest (Iowa) - we did this a lot over there for that very reason.

Question 2: After I get out of the car, the fog lights, interior lights, and headlights are all on for 15-30 seconds. I think this is pretty cool as my 2004 Sunfire had no such technology, but, is this going to kill my battery over the life of the car? I do a lot of 2.9 mile trips to/from work (8-10 mins).

The battery in the Civic seems a *lot* smaller than the one I had in my Sunfire.

Thanks,
-Paul

 

[SwampSurvivor]

While I can't comment on how it will affect the battery, I will say that my Focus has the parking lights on all the time when you walk away and it's extremely aggravating.

 

[1999nick]

Some people have their "fog" lights aimed rather high, looking like high beams, and I usually give them a shot of my high beams. I have a rather low opinion of anyone deliberately using their fog lights when there is no fog.

 

[JHZR2]

Originally Posted By: 1999nick
I have a rather low opinion of anyone deliberately using their fog lights when there is no fog.


Me too.

But let's do the math... what is a foglight bulb, like 55W for an H1 I guess? So burning two of them is about 110V... 110W/14V=~8A.

So on a 120A alternator, youre using around 7.5% of its capacity.

Lets assume you drive 120000 miles with them on over the lifetime, at an average of 40MPH. That's 3000hours of foglights burning.

3000hr*110W=330000Wh or 330kWh. A gallon of gas is about 33kWh, but an ICE is only around 25% efficient, and an alternator is maybe 75% efficient. So, to get 330kWh you need to figure it out:

1 gallon of gas is 33kWh thermal, which is 33kWht*0.25kWhb/kwht*0.75kwhe/kwhb=6.18kWh electric /gal

So to make 330kWh, youll need to burn 53 gallons of gas.

So at $3.50/gal, burning your foglights will cost you $187 plus bulbs.

Higher loading on the alternator will shorten its life, but how much is dependent upon rating and how much else you put on it.

Burning foglights and headlights (assume 220W and the battery voltage, as opposed to alternator voltage is 12.6 of less) takes around 20A.

Reserve capacity is hpow many minutes a battery will discharge at 25A. A group 51 battery will have an RC of abour 65 minutes, so at 20A vs 25, it will be more like 70 minutes.

So youll deplete around 1.25% SOC each time you do this. Personally, I wouldnt unless you drive very far compared to the number of times you do this. 60 seconds will more than deplete a surface charge, and then your battery will sulfate, getting worse since the next load it sees is the starter. If you had a group 49 or an H9 battery, it might not be a hige deal, but no way Id do it on a wimpy honda electrical system/small battery.

 

[OriginHacker21]

Originally Posted By: 1999nick
Some people have their "fog" lights aimed rather high, looking like high beams, and I usually give them a shot of my high beams. I have a rather low opinion of anyone deliberately using their fog lights when there is no fog.


Agreed - I tested this against the garage and it looks like my fog lights are pointed on the ground (aren't they supposed to be pointed upward?). I've been getting high-beamed a lot but since I started using my foggers it's helped since most people realize those go off when you have your highbeams on.

But yes, had a truck last night absolutely blind me cuz his fog lights were pointed right at my face.

Edit: Based on the above post, I won't be running my fog lights anymore. Was wondering what people thought about that too.

 

[OriginHacker21]

Originally Posted By: JHZR2
Originally Posted By: 1999nick
I have a rather low opinion of anyone deliberately using their fog lights when there is no fog.


Me too.

But let's do the math... what is a foglight bulb, like 55W for an H1 I guess? So burning two of them is about 110V... 110W/14V=~8A.

So on a 120A alternator, youre using around 7.5% of its capacity.

Lets assume you drive 120000 miles with them on over the lifetime, at an average of 40MPH. That's 3000hours of foglights burning.

3000hr*110W=330000Wh or 330kWh. A gallon of gas is about 33kWh, but an ICE is only around 25% efficient, and an alternator is maybe 75% efficient. So, to get 330kWh you need to figure it out:

1 gallon of gas is 33kWh thermal, which is 33kWht*0.25kWhb/kwht*0.75kwhe/kwhb=6.18kWh electric /gal

So to make 330kWh, youll need to burn 53 gallons of gas.

So at $3.50/gal, burning your foglights will cost you $187 plus bulbs.

Higher loading on the alternator will shorten its life, but how much is dependent upon rating and how much else you put on it.

Burning foglights and headlights (assume 220W and the battery voltage, as opposed to alternator voltage is 12.6 of less) takes around 20A.

Reserve capacity is hpow many minutes a battery will discharge at 25A. A group 51 battery will have an RC of abour 65 minutes, so at 20A vs 25, it will be more like 70 minutes.

So youll deplete around 1.25% SOC each time you do this. Personally, I wouldnt unless you drive very far compared to the number of times you do this. 60 seconds will more than deplete a surface charge, and then your battery will sulfate, getting worse since the next load it sees is the starter. If you had a group 49 or an H9 battery, it might not be a hige deal, but no way Id do it on a wimpy honda electrical system/small battery.

WOW. This is exactly what I wanted to know. Really appreciate the time you took to write all that out. Definitely helps my "OCD." Won't be running fog lights anymore and will program car to not leave headlights on before/after car starts/shuts off. Thank you.

-Paul

 

[eljefino]

As for the battery thing 30 sec after shutdown, that's burning off a battery "surface charge" that was just put on there by the alternator. Won't hurt it, measurably. Besides, you'll replace it after half a dozen winters anyway-- it's not like you'll get an extra two weeks of life and be able to measure that.

 

[JHZR2]

Originally Posted By: eljefino
As for the battery thing 30 sec after shutdown, that's burning off a battery "surface charge" that was just put on there by the alternator. Won't hurt it, measurably. Besides, you'll replace it after half a dozen winters anyway-- it's not like you'll get an extra two weeks of life and be able to measure that.


That depends. If "King Arnold's Domain" implies some sort of place where the weather is very consistent and nice, like Monterey or something like that, the battery could last 10+ years. Here in NJ, my parents' low-option vehicles have typically lasted >10 years, and we get fairly hot and cold.

Unless you have a spoecific accounting for how many Ah the surface charge is (its a feaction of an Ah, if that, as it is really a capacitance), its all speculation that surface charge will be all that is depleted.

 

[OriginHacker21]

Originally Posted By: JHZR2

That depends. If "King Arnold's Domain" implies some sort of place where the weather is very consistent and nice, like Monterey or something like that, the battery could last 10+ years. Here in NJ, my parents' low-option vehicles have typically lasted >10 years, and we get fairly hot and cold.

Unless you have a spoecific accounting for how many Ah the surface charge is (its a feaction of an Ah, if that, as it is really a capacitance), its all speculation that surface charge will be all that is depleted.


I haven't updated location yet. King Arnold is Arnold Schwarzenegger when he was Governor of California. I live in Victorville/Apple Valley, California now (vs LA earlier). We see -10F (snowed handful of times last year) to 118F+.

 

[SubLGT]

Originally Posted By: OriginHacker21
...................I do a lot of 2.9 mile trips to/from work (8-10 mins)................


This is what will kill your battery early.

 

[meep]

forces upon the alt from natural belt tension are going to be far greater than the added load from another 8 amps. load applied to the brushes is miniscule and rpm-dependent, tho all other factors being equal, more juice out would mean more juice in. But so hard to measure b/c the numbers aren't that big, and there are plenty other, bigger variables in play.

so many other factors! A/C use. amount of time driven at night vs day. power window, seat, butt heater, whatever...

it makes sense that the added load would cause added wear, but likely not measurable considering all other factors.

I've tried to find correlation between daylighting and mpg. while I can do the math, I have yet to see it reflected in the real world in my own experience at the pump.

I wouldn't sweat it either way.

 

[Fission]

While not strictly on topic re: battery/alternator longevity, I'm opposed to using fog lights in times where there is not dense fog. They're not daytime running lights. Fog lights are aimed differently and have different light spread. I'm surprised to see that people flash their high beams at you less often when you're driving around with fog lights and low beams compared to just low beams.

My recommendation is to program your auto-headlights as you see fit, but to leave the fog lights as manual operation only for the rare occasions that they're needed.

 

[eljefino]

Look into your fog lights with them off and see if you can see the light bulb's filament.

If it's shielded with "bulb dip" or a housing-mounted gizmo, it'll be less glary than one without.

Low beam headlights have the bulb dip, generally speaking, while highs don't. If you have two filaments in one bulb, like a 9004, the one you can see is the high.

 

[Ken2]

1 hp = 746 Watts
110 W ÷ 746 = 0.15 hp needed for that additional load on the alternator to power the two 55W fog lights.

 

[OriginHacker21]

Originally Posted By: eljefino
Look into your fog lights with them off and see if you can see the light bulb's filament.

If it's shielded with "bulb dip" or a housing-mounted gizmo, it'll be less glary than one without.

Low beam headlights have the bulb dip, generally speaking, while highs don't. If you have two filaments in one bulb, like a 9004, the one you can see is the high.


Forgot about this thread. Yes, the fog lights are Philips H11 LL 12v 55w bulbs - and have a coated tip dipped in dark black rubber like material.

I've done some testing and it seems like most of my fog lights beam on the ground under my headlights but at the same time they have a slight glare upward as well - but not anywhere near the luminosity of the headlights. Which makes them pretty useless I imagine in real fog?

Had a cracked fog light. Dealer wanted $400 to fix it. I went to an OEM Honda parts and got the fog light part for $80 and replaced it myself via a youtube video in about 2.5 minutes. Dealer is doing everything it can to keep me from coming back.

 

[Hokiefyd]

Originally Posted By: OriginHacker21
I've done some testing and it seems like most of my fog lights beam on the ground under my headlights...


Correct; that's where they should be aimed. Fog lamps are to be aimed very low to the ground.

Originally Posted By: OriginHacker21
Which makes them pretty useless I imagine in real fog?


The purpose of fog lamps is to illuminate the sides of the road when in very dense fog. Obviously, this limits their effectiveness to very slow speeds only. That's all they're designed for. Most fog lamps are very mis-used. They shouldn't be used unless there's dense fog or very adverse weather conditions. Many countries have laws against using fog lamps unless there is actually...fog. The United States doesn't, so you see all types of fog lamp use here...during the day, on clear nights, as DRLs, as headlamps by themselves with the headlamps off, etc.

 

[JHZR2]

You just look oh so cool running fog lamps at all times!!

I did a calculation a while back regarding the long term costs of running lights.

See here:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=3065795

 

[OriginHacker21]

Originally Posted By: JHZR2
You just look oh so cool running fog lamps at all times!!

I did a calculation a while back regarding the long term costs of running lights.

See here:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=3065795


Actually I stopped using my fog lights right after starting this thread thanks to your advice. Serious - stopped using them. I only recently had to deal with replacing one because my front left fog light shattered (not sure how) - and I had to replace it.

So haven't used my fog lights for a long time - other than to test the leveling of the new fog light I just installed yesterday.

I appreciate the time you took to respond with all that info. Was really awesome

 

[OriginHacker21]

Originally Posted By: Hokiefyd

Correct; that's where they should be aimed. Fog lamps are to be aimed very low to the ground.

The purpose of fog lamps is to illuminate the sides of the road when in very dense fog. Obviously, this limits their effectiveness to very slow speeds only. That's all they're designed for. Most fog lamps are very mis-used. They shouldn't be used unless there's dense fog or very adverse weather conditions. Many countries have laws against using fog lamps unless there is actually...fog. The United States doesn't, so you see all types of fog lamp use here...during the day, on clear nights, as DRLs, as headlamps by themselves with the headlamps off, etc.


Funny, I figured fog lights were supposed to be aimed up. Thanks for the info! My 2004 Sunfire had fog lights and for the 9 years I owned it (246k miles thanks to this forum) - I used the fog lights maybe 2-3 times. They were made out of glass too but never had to replace them for shattering like I did my Honda just recently.

 

[SatinSilver]

How much was it to replace the cracked fog light? I have a cracked fog light on my 05 Toyota Matrix(driver's side). Don't want to spend a small fortune trying to fix it.