I believe that daytime running lights improve your visibility and probably
can help avoid accidents, so I leave the lights on all the time.

Then I woke up to the drag on the electrical system and was surprised.
A pair of 55 Watt low beam bulbs and four 29.5W parking lamp bulbs equals
16 Amps. Then there's other current draw with dash lamps, relay coils,
and other bulbs so the grand total is more.

My multimeter will only measure up to 10 Amps, so I better not try to measure
the headlight circuit current. Does anyone know what the current draw is?

The bad news is that the alternator charging away at <16 Amps all the time
is providing unwanted drag on the engine and lowering fuel economy.

The good news is that there are LED replacements for many of the bulbs
that use a fraction of the current.

for example the #1156 bulb is rated at 27 watts or it draws 2.0 amps
and an LED replacement draws only 140 ma or 0.14 Amps

There's some websites where people searching for fuel economy unhooked the
alternator and made some jury rig to run the waterpump and they found maybe
10% increase fuel economy/ MPG . No alternator isn't great for an 850 that needs fuel injectors and electric fuel pumps and a computer.

I'd like to have daytime running lights without the high current draw of all
the old incandescent bulbs, and wonder what it will mean to gas mileage.

Then there's the expense of LED replacements:
Here's the first place that I found that has a nice website and lots of options:
http://www.superbrightleds.com/
You can look up a variety of cars , and they seem to have it right.
They have daytime running light replacements, (That must go into my non-existent
fog light sockets) but NO HEADLIGHT replacements.

I was told that there are now aircraft LED landing lights, so perhaps someone
has a headlight replacement for the Volvo 850 now?

Comments?

Bill

oops I meant this for the 850 page, but can work with any Volvo

I'm also a believer in DRL's. I have a set of Bosch fog lights that were issued back in the 80s. They are rectangular and use H3 bulbs. I have them rigged up to a ignition-switched circuit on the fuse block so they always come on while running and go off when the car is shut off. There's a toggle switch mounted in the center console so I can turn it off if needed when the ignition is on.

Like you, I'm also interested in LED-replacement lamps. SuperBrightLEDs.com seems to have the best selection of direct-replacement lamps. I bought some 1156 red LEDs to replace the running tail lights on my '84 240 and I'm happy with them. The brightness pretty much matches that of the 5W filaments.

I also bought some 1157 LEDs with a blinker circuit for my 142 and those work pretty well. The brightness is also close to a 25W filament 1157.

I haven't found any good H3 LEDs to use in my fog lights, so I keep using the filament bulbs.

Your parking lamp bulbs are each only 5Watts, so about 20W total there. (Turn signals and brakelights are about 25W). Instrument and licence plate bulbs are very small so maybe a total of 10-12W? Headlights at 110W for both. Total with everything on...say 140W. One horsepower is equal to 746Watts so even if the alternator is only 50% efficient, it is consuming around 1/3HP to power those lights. The fuel economy difference would be very small.

And the alternator's regulator makes sure it only generates enough electrical power to hold system voltage at about 13.5-14V, it does not shunt or "waste" power. Just supplies what's needed.

More to the point, I don't like Volvo's DRL setup of turning everything on. I modified all my cars to run only the high beams, at 50% wattage, with a dash switch to kill them if I want to park with the engine idling.

DRL's are a potential lifesaver around here with forested mountain roads with only occasional passing lanes and tall trees throwing shadows on the road and a "strobe" effect from sun and shadow on your windshield. Anyway, they've been a regulatory requirement in Canada for about 20 years on new vehicles.
--
Bob: Son's XC70, daughter's 940, my 81 and 83 240's, 89 745 (V8) and S90. Also '77 MGB and some old motorcycles

Hi Volvodad,

Thanks for your considered reply.

I agree that DRL's are important to prevent accidents, certain color cars can
blend in with the daytime background giving you no early warning that they are there.

I'm still waiting for the right ammeter to see what the load is for headlights.
I'm dealing with an 850 now and there's 4 tail lights, 2-head lights, 2 front running lights, Liscense plate lights, and a number of bulbs that are not used all of the time- Brakes, Turns, backup, etc that aren't so important.

It might be interesting to carefully check gas mileage on the highway with and
without headlights (In those places not requiring it)

and in my case, where I'm doing mostly low speed around town driving
and my gas mileage is ratty, it may be that the alternator drag on the engine
and constant shifting, may impact mileage a lot. ie the drag of an extra 15-20
amps of a charging alternator might mess up the ECU shifting strategy and keep
the RPMs too high for a longer period? That load expressed in watts may seem low, but don't forget that the engine is rated at a certain horsepower at
some high rpm and that at a low RPM it's another story, where that constant
alternator drag might be more significant.

How much does it cost to run AC? Does it wreck mileage more at low rpm than at
highway speeds?

Thanks, Bill

Hi Volvodad,

Thanks for your considered reply.

I agree that DRL's are important to prevent accidents, certain color cars can
blend in with the daytime background giving you no early warning that they are there.

I'm still waiting for the right ammeter to see what the load is for headlights.
I'm dealing with an 850 now and there's 4 tail lights, 2-head lights, 2 front running lights, Liscense plate lights, and a number of bulbs that are not used all of the time- Brakes, Turns, backup, etc that aren't so important.

It might be interesting to carefully check gas mileage on the highway with and
without headlights (In those places not requiring it)

and in my case, where I'm doing mostly low speed around town driving
and my gas mileage is ratty, it may be that the alternator drag on the engine
and constant shifting, may impact mileage a lot. ie the drag of an extra 15-20
amps of a charging alternator might mess up the ECU shifting strategy and keep
the RPMs too high for a longer period? That load expressed in watts may seem low, but don't forget that the engine is rated at a certain horsepower at
some high rpm and that at a low RPM it's another story, where that constant
alternator drag might be more significant.

How much does it cost to run AC? Does it wreck mileage more at low rpm than at
highway speeds?

Thanks, Bill

I might be wrong, but this is how I understand this issue:

2 big things - the driveline accounts for 80-95% of your efficiency loss for a car, and the alternator is constantly generating a bunch of unnecessary power. It's sort of like a nuclear reactor. It always operates at 100%, but it shunts excess voltage to ground via the voltage regulator (and wastes it) when there is nothing using the power.
Maybe my understanding of a voltage regulator is too simple (looks like it actually varies the strength of the magnetic field), but the principle is the same - the alternator consumes a constant amount of energy, and reducing the load on it does not make it consume less, it only reduces how much of the generated energy is wasted. I think.

The main thing is that everything uses so much more fuel than the alternator that it's really not worth trying to improve. Reducing air drag (with a skid plate/belly pan and possibly adding one to the rear bumper cover like one bricker did) would make more difference than anything. Heck, removing your car's FM antenna would probably make a difference.

Now, if we could talk about an alternator with an electric clutch or electric power steering (or maybe, maybe electric instead of mechanical engine fans if you rarely exceed 2000rpm), we might see a difference in fuel economy. Maybe.

Cheers

Hi Will,

Checkout this nice site:
http://oljeep.com/gw/alt/edge_Alternator_Theory.html#Section_1

There's a lot of info there about alternators, and I see that
the author has a way to check alternator brushes with a screwdriver
and testing magnetism. (I'm going back to read more!)

Alternator output varies with load. You can test that yourself by
setting the belt tension too loose, then as you add electical current load,
finally the belt will slip, and the alternator won't keep up with the load.
Once this happened to me in a snow storm, I had the heater fan/defroster on full, the rear window de-icer on, and the headlights (Just leaving work)
I also had some 2 meter ham radio, and stuck in traffic to get to the highway.
(The battery went dead with the engine running)
That car, happy to report, wasn't a Volvo, a was a Ford (Company car)and afterwards the alternator belt had to be bar tight to deliver rated output.
(I break wind in Ford's general direction!) :-(

Thanks, Bill

HMMmmmmMMmmMmmmm.... you're definitely right. Changing the magnetic field strength will definitely change the resistance to motion in it. And I've experienced the belt slipping myself. For a while, it would slip when first started, unless I turned off my headlights for a moment and then turned them back on.

I think the much bigger picture is still the inefficiency of everything except the engine itself. The drivetrain, tires, bearings, and inefficient capture of heat being blown out the exhaust is much more significant than alternator load.

Also in some conditions, I think DRLs make cars blend in more - especially light colored cars on a highway during a high-glare time of day. A silver car on a hot day in open country with its lights on can just blend into the glare coming off the road. USUALLY, DRL's are safer, but I swear it's not all the time.

Since the Volvo lights use full power, it is indeed likely that the extra load on the alternator would affect fuel economy to a small degree, but I doubt if it's measurable. You could always try an A/B test by removing the bulbs. It's possible the fuel savings would not be as great as the cost of converting to LEDs. Of course, it would not be legal to operate a vehicle without running lights if that model had them when the law came into effect.

Interestingly, many domestic cars had modules to run the headlights at lower wattage and some makes didn't use the taillights since the law didn't require it. Not sure if that was to improve fuel economy or save the bulbs.
--
1992 745 approaching 500k km

I found two more tail lights so add another 4 Amps of alternator load.

What does it cost in engine performance and MPG to run AC?
Then wonder about alternator drag on MPG.

I've found a raft of small bulb replacements, but so far no replacement
for the headlight modules.

After checking Autozone's prices for filament bulbs this AM there's
more incentive to switch to LEDs. They don't fry at 15 volts are are rated
10,000-30,000 hours. Great for instrument clusters in the 850 that are harder
than a 740 to get at.

Bill

Not only are LEDs more efficient than tungsten bulbs, they last a lot longer and turn on and off instantly. Most fancier new cars no use them, as well as transport trucks. Definitely a worthwhile upgrade.
--
1992 745 approaching 500k km