Alternator v. no alternator - 10% gain @ 70 km/h

[rh77]

BMW's Electronically Controlled Alternator and Regenerative System.

[repete86]

I've thought about removing the alternator and throwing a few deep cycle batteries in the trunk along with adding solar panels to the car once I add a plexiglass shell over the back part of the car. How long do your batteries last at night with your headlights on?

[rh77]

Originally Posted by repete86

I've thought about removing the alternator and throwing a few deep cycle batteries in the trunk along with adding solar panels to the car once I add a plexiglass shell over the back part of the car. How long do your batteries last at night with your headlights on?

Here's an Electrical Load Test Randy performed.

You also have to consider the vehicle's electrical demand from the ignition/spark system. In an additional thread, a calcuation was attempted to see if solar panels could charge batteries, and IIRC, there's just too much amperage required. You could charge them overnight with the grid, but the implication of too much weight is also a factor.

I'd like to find a balance in the equation. As technology progresses, perhaps.

[BeeUU]

Several years ago on a long trip, the alternator quit on my car. A new one was not available at the city I was trapped in....so we drove home on batteries alone. We bought a couple and drove till the car started to run poorly and then dropped in the spare. The fuel mileage was significantly higher and the batteries seemed to last a couple of hundred miles during constant speed freeway driving in the daylight, I used hazards only when it was dusk. I am not sure of the state of charge of the purchased batteries, your mileage may vary.

[Maillemann]

Of all the ideas tossed around here, I have to say that the idea of using a thermopile appeals most to me - recovery of waste heat to create energy, no extra batteries, no moving parts. Of course, it'd be expensive. A quick search shows an entry on Halfbakery.com about it, which includes a link showing a 1kW installation on a Mack truck. The product brochure page for the HZ-14 modules they used in that project even states under possible applications: "WASTE HEAT RECOVERY - Engine exhaust powered Alternator Replacement"

Cost? At $124 each, seventy-two of those HZ-14s would run $8,928!

That's a lot of batteries...

[VetteOwner]

hmm i have no idea if its been thrown up at all BUT! what about a electric clutch much like that on an AC compressor to be retrofitted to an alternater shaft? that way you could just "disconnect" the alternator but when you needed a charge you could just flip a switch and re-enguage the alternator. since the AC clutch pulley is relatively frictionless (you give the pulley a spin and it stays spinning for several minutes) i think it would probably work. you would have to change the pullies on your car to compensate for the larger diameter pulley on the alternator(doubt they make a clutch that small)but those you can find all over the place depending on the car.

[MetroMPG]

I wonder what the electric clutch would draw, though. You'd want to determine what's more efficient:

- leaving the alternator spinning while disconnecting it electrically when you want to run altnernator-less, or,

- the additional energy the electric clutch consumes when you want to run with the alternator.

[VetteOwner]

well depends mostly on the car i would assume

[landspeed]

Has anyone tested just disconnecting the alternator electronically rather than mechanically?. If it is as good (or nearly as good), which couldn't you:

(1) Using relays, make a switch that lets you switch between either
a) Using the standard battery and the alternator charging it
b) Using a spare battery pack, with alternator electronically disconnected.

The spare battery pack could be used until it is almost completely discharged, and then removed and charged up at home. You would also try to reduce electrical load as much as possible (mainly by fitting LED lights, HID headlights if legal in your area, and not using the fan / radio etc when using alternator-off mode).

The batteries could be D-Cell Nimh Batteries (11Ah each) - 11 of these would give 13.2V, which is similiar to alternator voltage, and would last for one hour at 145 watts, or 1/2 hour at 290 watts. You could use two sets in parallel to double these times. As most repeated car journeys are short, you would rarely have to use the alternator!. The car would crank from the original battery which would also get charged overnight when the car is parked outside your house (or you can charge with the alternator in emergencies).

Any thoughts on this?

[Bill in Houston]

Originally Posted by landspeed

Has anyone tested just disconnecting the alternator electronically rather than mechanically?<snip> Any thoughts on this?

I like the idea. If you had a switch on the dash to turn it off and on, and a voltmeter reading on the dash, then you could leave the alternator disconnected until you needed to recharge the batteries. And, this would let you drive long trips, after dark, etc w/o worrying about getting too discharged.

Not sure about using D-cells as a second battery pack.