How much gas does the alternator take to run?

Let me start off by saying, obviously it doesn't make sense to install a solar panel plus a charge controller to save money cuz it would take forever to make the money back in gas even considering the crazy gas prices in CA. But I know there are some people who use solar panels keep things like fridges and stuff from killing your battery. Have any of you with this set up noticed an increase in fuel economy when your fridge isn't connected? I'm assuming if you have solar then the alternator doesn't have to run as much.
I read an article of this guy who wanted to know how much gas it took to run his alternator and so he bought a shorter belt and installed it so it wouldn't spin the alternator. He drove it like that around town and charged the 12V battery between trips at home. He said he saved somewhere between 10-15% in gas.

 

My alternator requires 3.14444444444444444444444444444444444444444444444444444 gallons per hour, and 1/2 a quart of johnson oscillating bearing grease.

 

Bruh… For real?! Alternator & fuel?!… Come on.

 

OP is on that good good

 

Any time you take drag off the engine (AC, for example) you'll save fuel. However no one in their right mind would realistically do it with an alternator since it does so much more than charge the battery when the vehicle is running. You should be able to run the vehicle without a battery if the alternator is working.

Adding load to your vehicle won't necessarily cause MPG issues as it can only do so much. The bigger concern in that case would be the ability for it to recharge the battery in the first place. If it can't do that then it likely doesn't have the power to run the vehicle.

So to answer your question, in theory having solar to supplement other things shouldn't really affect MPG.

 

I'm reading your comment as you think that the OP thinks the alternator is run directly with fuel.

I'm reading his question as how much does the spinning the alternator cause extra resistance in the belt, and therefore increase fuel usage. the same way the AC compressor causes a decrease in fuel efficiency.

 

Not how it works.




You have to post Friday threads on Friday.


haha, actually people 'running solar' use solar power to charge or top up the batteries (house/ truck/ both?) When the truck is running the alternator powers the truck, as well as recharges the truck battery. There would be no difference to mileage or anything with or without solar. The only thing it is doing is extending battery life by being able to recharge batteries without running the truck.

 

Armchair electrical engineers incoming

 

At max electrical load it would be around 2.5hp. I am not an electrical engineer, armchair or practicing

 

1. If you are good with the Tacoma mpg as is then fine. If you want to improve it there are tried and true ways like
Shedding weight
Skinnier tires with higher air pressure.
Biggest: Change your driving habits! Slow starts, gradual breaking, avoid stop lights, make tip speed 55mph, etc.

2. Getting rid of parasitic hp draw is not practical on modern vehicles. You have the power steering pump, steering rack and pinion, air conditioning compressor. It would cost you many $$$$$ to bridge around those components.

3. If you are really concerned you can A) Move or B) trade it in and buy a Prius.

 

Buy a small generator to power your camper. Some of them will run 8-12 hours on a gallon of gas.

This will power everything but the AC unit and recharge the batteries. You don't need to run it all the time, just a couple of hours a day to keep everything charged and use other electrical appliances as needed. You can buy 2 and plug them together and have enough power to use your campers AC unit. Probably not the AC and anything else though.

A-iPower SUA2300i Ultra-Quiet Inverter Generator with Mobility Kit (CARB Compliant) - Sam's Club (samsclub.com)

This one has proven to work for me. Weighs about 50 lbs.

Of course if you have the money this is the Cadillac.

HONDA Inverter Generator, Inverter, Generator Fuel Type Gasoline, Generator Rated Watts 1,800 W - 60NP35|EB2200ITAN - Grainger

They are good, but I have $800 invested in 2 of the ones from Sams Club instead of $1400 each for the Honda.

 

In Canada the alternator can sap a lot of power due to constant cold starts.

Almost every model on the planet have load sensors now to limit unnecessary charging.

Honestly I charge probably 1 out of every 4 batteries during routine servicing.

 

I think that this has already been thoroughly explained in the ass eating thread.

 

Like I said, it's obviously not practical cuz it would take forever to recover the hundreds it costs for the panels. I was just curious.

 

You should really post a link to the article, because it sounds like the source material is a little suspect. I tried to find it and the only thing I found was about a Geo Metro.
https://ecomodder.com/forum/showthread.php/test-alternator-vs-no-alternator-10-mpg-gain-98.html
Considering a Metro had very small 3 or 4 cylinder engines, I don't think the same output would occur in a truck that weighs more than double.

 

I did consider mounting a very small engine to an alternator as an offroad power source. You want a bit over 2hp of mechanical power available to make 100 amps at 13.6V due to inefficiency. Your alternator does not run near that power level on average. Assuming you drive at 60mph and get 20 miles per gallon you'll be sucking down 3 gallons of fuel per hour. 10% of that is 0.3 gallons of fuel per hour which is a lot for an extra fractional horsepower on a loaded engine.

Another way of thinking about it: if a 1hp average load is 10% of your fuel consumption, then the other 90% of your fuel is making 9hp.

Even at maximum 3hp load, continuous, your buddy must only have a 30hp engine.

Chances are he was babying the throttle or had other forms of confirmation bias in his tests.

And before anyone accuses me of being this or that, consider I work 4 ten hours days so today is my friday, and I cut the arm rests off of my chair because they got in the way of masturbating, so checkmate.

 

Alt is variable, so a little to a lot.

 

OP you can't be serious

 

Roughly speaking..... 1 HP = 746 W. So at 12 Vdc.....Current from 1 HP would be around 62 A.

Or the 130A alternator will be need about 2 HP to run it at full Current. Toss in mechanical losses, then 2.5 HP as 3JOH22A suggested is about right.

Not sure if the 2.5 HP would even blip the fuel consumption.