Alt kill switch planning (help)

[3dplane]

Originally Posted by drmiller100

barna, making the wire longer just wastes energy. it will still try to get to the desired voltage, but will waste a bunch of energy doing it.

i'm a little puzzled about the whole alternator kill idea. how much energy are we really saving?

I might be wrong but I can't agree with that right now here is why! Even though some energy will go to waste heat,the end result is reduced torque required to turn the alternator and your battery still gets charged given enough time to replenish used amp hours. Instead of it going to full output trying to recharge instantly. Not a fair comparison but people fine tune windmills this way when needed if the alternator is "too powerful" for the rotor blades/wind conditions and not letting the prop blades get up to a more efficient rpm. They add "line resistance" (longer cables) to allow lower wind speed operation. I know there are totally different factors involved with the propellers but I'm talking about the same electrical principal.
Not trying to argue here,we are just talking
Apologies to the OP if we're off topic!
Barna

[pete c]

I would be hesitant to do this as well for a few reasons.

What kind of energy savings are we looking at?

What is the risk of blowing expensive ECUs?

How much of a life reduction is there to a battery which is being cycled much more than it would be normally.

Seems to me that the best way to lower alternator drag is to do everything you can to lower it's load. Minimize HVAC use, radio, etc. if you do a good deal of driving in the dark, look into LED lighting. It is starting to be used and the efficiency gains over incandescent is enormous.

[California98Civic]

Originally Posted by pete c

I would be hesitant to do this as well for a few reasons.

What kind of energy savings are we looking at?

What is the risk of blowing expensive ECUs?

Here are MetroMPG's results and discussion: Plug-in Blackfly: going alternator optional nets +10% mpg - MetroMPG.com. My own "non-scientific" results seem to be at about a 5% FE difference when I run the alt plugged in, versus running without it. My ECU is fine after months unplugging the alt. My deep-cycle battery is fine too. I've been away at Yosemite for Christmas, and can return to this... thanks for input all.

[deathtrain]

Also the alternator output usually goes to the battery and then on the the ecm and load center. The battery takes that on rush of current and voltage and acts as a buffer.

Civic are your ~5% gain with the belt still on and you just using your field kill switch?

[California98Civic]

Originally Posted by deathtrain

Civic are your ~5% gain with the belt still on and you just using your field kill switch?

This rough figure is with the alt unplugged but the belt still on. I have not had the time to attempt to complete the switch yet: ripping-up the master bedroom carpet and jackhammering the front path!!

[BrianAbington]

I am likely buying a 97 DX coupe in the not to distant future. This thread has peaked my interest.

[California98Civic]

Originally Posted by drmiller100

There are only really two wires needed for the alternator to work.

The main battery lead (big wire) from battery to alternator I leave alone. If you unhook the Yellow/black which goes from the key switch to the alternator, and start the car, the alternator will not charge.

If you then give power to the yellow/black, the alternator will start charging. I have not tested to see if you shut the power off to the yellow black if the alternator will keep charging.

Following this theory of what wires do what, I attempted (finally) drmiller's recommended test procedure. I made connecting wires for each of the 4P connections so that I could plug all four in and remove them one at a time. Before I give you the results, a point of clarity: if I leave the thick white power line from the alt to the battery connected and unplug the 4P connector, the alt does not charge (I have a voltmeter mounted on my dash).

Results: no matter which individual connector of the four I disconnected, one at a time, the alt continued to charge at 14.2 or 14.3 volts. Is it possible that when one wire is disconnected the others somehow back it up? It seems very unlikely that there is a sufficient residual charge in the field windings because if I unplug all four, the alt immediately stops charging.

What's the solution? Is an alt delete impossible on my car? Do I really need four switches? Is there a switch I could use that could cut all four at once?

james

[deathtrain]

I would start with unplugging two at a time.

[California98Civic]

Originally Posted by deathtrain

I would start with unplugging two at a time.

Thanks for this. I had wondered that too. Your confirmation sent me back to test it. I unplugged the best suspects first: the yel/blk that must be the field winding power wire and the wht/blu which is the wire to the charging light on the dash. When these are unplugged, the car shows 12.5 volts while running. Bingo. So you were right. Knowing that now, I look at the wiring diagram below and I think I could remove the charging light lightbulb and break the one circuit and then install my switch on the yel/blk line and be fine. Sound correct?

[deathtrain]

yes that sounds correct but what does it do when you plug everything in and remove that 7.5a fuse No. 15?