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

[njlou]

BMW has been using a system for years that shuts off the alternator.
they claim a few % extra MPG.
The computer shuts off the alternator if battery charge is ~ 80%.
The other 20% kicks in the alternator when braking thus providing charge and some small regenerative / retarding effect.
The system has a name, but it escapes me now.

[redpoint5]

Originally Posted by sregord

Having read this forum, It seems that a cleverly automated or manual switch on the alternator power lead(off up hill&level-on downhill) could be a fuel saver…. 10% would bring this up to- wow -almost 9 mpg.

Unfortunately it doesn't scale like that. Maybe disabling the alternator on a super efficient car like the Honda Insight could improve fuel economy by 10%, but electrical loads represent a smaller portion of total energy use in larger vehicles.

Kinda like how I could tell when my AC kicked on in my old and weak Subaru. AC represented a larger load on that vehicle than, say, my 7,000 lb Dodge Ram 2500 diesel.

That said, seems a worthwhile project since the solar is already installed and available to be utilized.

[sregord]

Thank you... little bits here and there.
I was going down the 65+ Efficiency Mods ...& this one caught my eye.

Been working on my hyper-milling skills too.

Addressing aerodynamics of a big box? there could be some improvements, but not many. Been looking for a stream here that could be scaled up from a van.
So far the rear is "feathered" with the vortex generators, not sure if we've gained any efficiency, but being around semis has definitely improved.

[freebeard]

Addressing aerodynamics of a big box? there could be some improvements, but not many. Been looking for a stream here that could be scaled up from a van.

Like this?

https://www.dfrc.nasa.gov/Gallery/Ph...uck/index.html

I know aerohead has analyzed this in the past, here is one specific thread. ecomodder.com/forum/showthread.php/plan-my-cargo-trailer-30395.html#post453403

Long story short, the brick is the same on the underside. I posted about my design for a semi-rigid boat tail after you posted about the Trucksack in 2020.

[sregord]

Yes,
I have reviewed the NASA historical data.

Not sure this is the right Forum to continue this.
I'll get over to the "Class a motorhomes aerodynamics stream"
..and we can continue..?

[bandit86]

How about adding a super small crankshaft pulley and larger pulleys on both the water pump and alternator, a reverse under drive setup.

[Phase]

Does the alternator work less hard when the 12v battery is fully charged?

[Mark Serva]

at all if batteries are fully charged. However, most generate a little power to keep their "field" charged. It depends on the alternator I'm sure. I doubt maintaining that field is even measurable as a belt driven load.

[Mark Serva]

at all if batteries are fully charged. However, most generate a little power to keep their "field" charged. It depends on the alternator I'm sure. I doubt maintaining that field is even measurable as a belt driven load.

[Mark Serva]

I've tried to read this whole thread yet ran out of time. Am wondering if anybody has addressed, what I recall from my misspent youth, vacuum driven alternator cut-outs.

I remember they had a adjustment screw. Maybe they could be set so low that the alternator would only cut in during idle or braking. I don't know if anybody has experimented with this or can show any real cost benefit. I know many of us like to experiment.

Of course they wouldn't do anything for oil burners yet might deserve a re-boot with us. I've been looking on FleaBay for some NOS vacuum cut-outs yet haven't found any.