Test: Alternator vs. no alternator = 10% MPG gain @ 70 km/h

[oil pan 4]

Many of us could remove the V belt from the alternator and run like that.

[brucepick]

Dipstick was right when he said
1) Don't recharge the battery via the alternator.
2) Use deep cycle batteries.

I would add, based on my experience running with alternator switched off since March 2012:
I have one Walmart marine deep cycle Group 29 lead acid and one 40AH LiFePO4 lithium. Both work well.

The lead acid runs headlights and starter. Lithium pack runs the rest. Each has a range of 3 to 3.5 hours. If headlights not needed total range is about six or seven hours.

Alternator belt is still in place. Alt's charging cable is connected via a battery disconnect switch. So for a truly long road trip I only need to activate that switch.

[dipstick]

Originally Posted by brucepick

Alternator belt is still in place. Alt's charging cable is connected via a battery disconnect switch. So for a truly long road trip I only need to activate that switch.

Be careful as this can blow the computer in some cars... each time you turn it off then on that way there is an electrical punch to that circuit which is like flexing a metal wire back and forth... eventually, SNAP!

As a famous canine once said, "Rutt Row, Raggy!"

As for the belt removal... yes, some can remove, but others may not realize that by trying to do so they can damage their car.

As for the increased number of batteries to replace the alternator... doesn't the added weight kinda defeat the purpose? Just my ignorance falling out one side of my head there... but I'd really like to hear the thoughts on this.

[California98Civic]

Originally Posted by dipstick

Be careful as this can blow the computer in some cars... each time you turn it off then on that way there is an electrical punch to that circuit which is like flexing a metal wire back and forth... eventually, SNAP!

As a famous canine once said, "Rutt Row, Raggy!"

As for the belt removal... yes, some can remove, but others may not realize that by trying to do so they can damage their car.

As for the increased number of batteries to replace the alternator... doesn't the added weight kinda defeat the purpose? Just my ignorance falling out one side of my head there... but I'd really like to hear the thoughts on this.

I have been running an alt cut-off switch on my car for 14 months now, maybe 15,000 miles, and the ECU is fine. I think brucepick might have created confusion in how he described what he is doing. I don't think he has disengaged the heavy gauge power-supply wire from the alt to the batt. Like me, he has, I think, disabled only the signal wires that turn the alt on. Like him, I have a dash mounted switch. I recommend it.

[Uncle Dave]

I was thinking of ways to reduce waist of energy in the operation of car. The starter has quite a bit of weight. There was a period of time that my starter was broken and I had to drive to school. My brother and I would park at the far end of the parking lot. We would roll start it to get it running. At the house we parked it at the top of a slight rise. Roll start in the AM. The real problem was the Walk to and from the car. It was not convienyent. No one picked me up on the fact that most cars can not be started this way. No one suggested that a fold up bike could be used as a spare Tyre.
The problem of taking Rail to work is that there is that last mile. You might walk it.
For most folks we do not think of that.

I used to work on a TV Electronic New Gathering van. We had Two batteries. One did most of the work. However we had a second. That was only used to jump the first if it should be failing, and not do the start alone.

[brucepick]

Originally Posted by dipstick

Be careful as this can blow the computer in some cars... each time you turn it off then on that way there is an electrical punch to that circuit which is like flexing a metal wire back and forth... eventually, SNAP!

As a famous canine once said, "Rutt Row, Raggy!"

As for the belt removal... yes, some can remove, but others may not realize that by trying to do so they can damage their car.

As for the increased number of batteries to replace the alternator... doesn't the added weight kinda defeat the purpose? Just my ignorance falling out one side of my head there... but I'd really like to hear the thoughts on this.

I could foresee some issues if switching while engine is running - though I think California98Civic has been doing that for some time, via the control harness wire(s). In my case I only switch it with engine off.

Alt output cable is switched where it meets battery. I open/close switch only when engine is not running. I disconnect and reconnect the alternator control wires harness at the same time. Built system Mar 2012, about 18,000 miles driven since then. Battery capacity covers a range of about 3 hours with headlights on so I haven't needed the alt since maybe July.

Weight: removed OEM battery, about 25-30 lb. Added 16 lb lithium and 60-65 lb lead acid. Net increase about 51 lb. Would be more of an issue if I did much city driving. However instead, I "invest" fuel to build momentum and then it coasts longer due to added mass. If I don't brake I don't lose my investment of fuel that built the momentum. If acceleration is the game it would be an issue but I'm not afraid of a bit of weight when driving for mpg. I drive car pool too, that adds about 175 lb!

[California98Civic]

Originally Posted by brucepick

I could foresee some issues if switching while engine is running - though I think California98Civic has been doing that for some time, via the control harness wire(s). In my case I only switch it with engine off.

You got it right, bruce. But I don't do this a lot. Generally it is off for the trip, or on for most of a trip, depending on distance. I have not yet encountered any difficulties with the ECU. Maybe it's worth noting that the ELD in these Civics already varies the voltage quite a lot, when operating normally. Under certain conditions with the alt running you see instantaneous jumps from 12.5-14.xx--with amperage jumps too, I think--and all of it regulated by the ECU as Honda designed it. So it seems logical to me that manually switching from a scenario of 12.5 volts to 14.xx shouldn't pose problems. But I am neither an engineer nor a mechanic. I just own a Civic that I hack-up and repair as best I can.

[Nerys]

unless you do hard core city driving (block to block stop and go) or mountanous terrain without ability to EOC. then mass has very little "realized" effect on fuel economy.

I massed 455 pounds (440 now :-) I used to be even heavier.

sister is 350 plus my 200 pounds of crap.

drop off sister and emptying the car has almost ZERO measurable impact on fuel economy

an object in motion remains in motion till acted upon by an outside force.

IE once your "going" at whatever your cruise speed is mass has almost no further impact.

mass only really comes into play during a change in velocity ie accelerations but only positive accelerations (speeding up)

this includes accelerating to a higher speed and "climbing" (which is a vertical positive acceleration even if your not changing speed your Vspeed is changing)

so for many of us steady state highway semi highway cruisers mass is irrelevant. what we want is minimal drag and lower rpm (larger tires)

now you city drivers its a different ball game. you want TINY tires to reduce acceleration loads aero is completely irrelevant and mass is EVERYTHING.

SO if your a cruiser you going to switch to 155/80/13 tires and aero the crap out of your car.

if your a city crawler or mountain crawler your going to want the original 12" tires and you want to STRIP the car of all non essentials.

I am a cruiser so the extra mass of another battery is literally irrelevant and immesurable on my fuel economy.

however the HUGE difference of removing both the alternator and water pump from the equation should have a pretty large impact on fuel economy.

[JRMichler]

Originally Posted by Nerys

now you city drivers its a different ball game. you want TINY tires to reduce acceleration loads aero is completely irrelevant and mass is EVERYTHING.

Aero counts, even in city driving. I picked up my daughter the other day, starting with a warm engine. Drove there against a strong headwind and got 26 MPG on the Scangauge. Came back with a strong tailwind and got 49 MPG. Maximum speed was 30 MPH. Two miles and three stop signs each way.

[dipstick]

Originally Posted by Nerys

however the HUGE difference of removing both the alternator and water pump from the equation should have a pretty large impact on fuel economy.

How are you going to replace the benefits of the water pump?