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

[teoman]

Int that the same as cutting the alternator wire? Making sure the ecu does not command the alternator to draw any current?
Or the belt the item that creates the resistance irrespective of alternator load.

Ill have to test his out sometime once i find a Clamp type Multimeter.

[oil pan 4]

The alternator is driven 3 times crank speed.
That's where most of the engine power it gobbles up does, just beating up air.

[teoman]

Hnm, ok

So using capacitors that are charged from a battery will have close to no benefit.

Thanks.

[RedDevil]

Maybe a not too big supercap bank combined with a small BMS protected lithium iron phosphate battery, but split by a resistor.
The supercaps generate the amps to crank the starter motor, the battery keeps them charged over time.
The resistor prevents high currents to or from the battery so it won't get killed by high recharging after starting up in the cold.
That would be lighter than straight lead acid and not have the overcharging losses.

[oil pan 4]

The super capacitor thing seems good of you are trying to save weight by going with a much smaller battery than normal.

To float charge a car battery at system voltage only takes around an amp when fully charged.

[Daox]

If you're electrically minded, it might be better to come up with your own programmable logic controller for controlling the alternator output. A bunch of OEMs have done this in recent years for a small bump in fuel economy.

[teoman]

I have a whole bunch of titles which claim i should know a bit about electricity. I also teach microcontrollers, embedded systems and robotics.

I have arranged a test with a renault megane diesel.

First measure the output amps of the alternator and record the fuel consumption (the car switches to showing l/hour when stationary).

Then disconnect the alternator cables to see what it shows as fuel
May also try disconnecting the belt if it is easy.



Then start charging the battery of the car from ac to see if alternator current drops to 0 and there is a decrease in liters per hour.


Usually the fuel consuption is 1l/h or there abouts. If this drops by 0.3l then i would be saving about 0.6l per day as i am stuck in traffic for atleast 2 hours a day.

Any/all recommendations are welcome.

[Daox]

Sounds like a great place to start. Let us know what happens.

[bandit86]

So put the alternator on a pto clutch like the air conditioner compressor, hook it up to the brake or a switch some whenever you brake or coast you charge your battery.

[teoman]

From talking to semi knowledgeable people in the auto-industrial lot over here, they say that the alternaotr is already fairly low drag when not under load.

Assuming that the cars own electricity management module cuts the load on the alternator:
What i could do is, have a minimum sized capacitor bank that is charged from an aux batter. Whenever i detect brakes being applied over canbus on the car (or throttle at 0 and not neutral gear or not clutch pressed and still moving) stop charging the capacitor so the alternator takes over charging it. Or stop charging it and divert power over to the aux battery.


Cars i will be working on will probably be post 2010