Alternator modifications

[ECONORAM]

Originally Posted by George Tyler

as that document shows, the diodes are a big loss at high currents, at low current there is the magnetic losses and also the fan etc. I have been thinking of doing the mosfet rectifier thing , but using an international rectifier chip that does the same thing.
de-energising the alternator removes the magnetic losses, but the windage losses are still there. Some cars now have electromagnetic clutches on their alternators, they would not do this if it did not reduce consumption. Failing this, how about removing the alternator fan and using a controlled electric fan instead, and also disconnecting the feild winding when it would help?

Perhaps getting better shaped fan blades will help. From what I recall, alt fan blades are often stamped steel flaps, not propeller style blades...

Originally Posted by George Tyler

that's great for the bottom diodes, what will you do for the top ones? I can't see an easy way of doing that with this chip.

How difficult is this to do? [edit] What I really mean is how difficult is it to assemble this more efficient item and install? I'm running an underdrive pulley on my truck, and if I could also increase alternator efficiency, that'd be double good...

[t vago]

Looking again at oil pan 4's work, I have stumbled upon this old thread.

In the course of some 5 years, state of the art has advanced, and it is apparently now possible to purchase an ideal diode controller chip that can be coupled with your ordinary high-current MOSFET. For a total of $50 or so, I can make a circuit that will replace the existing rectifier.

The circuit will shave off about 1/4 HP from the alternator during normal operation, I figure. Estimated fuel consumption will go down by about 0.4 gallon per tankful, with a little over 2.2% savings. Smaller engines will see a bigger percentage.

[ConnClark]

I have looked at the "ideal diodes" too. It would save a lot of work. I may look at this again in more detail.

[oil pan 4]

Anything else new as far as smart diodes go?
The problem with those solar diodes is they are only good for 15 amps per phase, which limits the size alt they can go on.

[t vago]

Originally Posted by oil pan 4

Anything else new as far as smart diodes go?
The problem with those solar diodes is they are only good for 15 amps per phase, which limits the size alt they can go on.

Texas Instruments also manufactures a chip that contains only the brains, as it were, of the smart diodes -> LM74610-Q1 Zero IQ Reverse Polarity Protection Smart Diode Controller

The major benefits are

• You can use any N-channel MOSFET with it. I plan on using MOSFETs that have a maximum steady-state current of 195 A.
• As there is a charge pump onboard the chip, it has no need for either a dedicated voltage drain (ground) or a supply. Therefore, you can plug it into a circuit just like a normal diode.

The voltage drop of 0.07 V(rms) at conduction in a leg of a full rectifier is much more attractive than the 0.4 V(rms) of a Schottky diode, as is the "reverse polarity" behavior.

[serialk11r]

If someone else wants to build active rectifiers I would happily pay for one even though I don't have a car to throw it on for now, assuming it looks nice and tidy unlike my personal crap electrical work. I've realized that my DIY skills are not really up to par :P

[George Tyler]

Originally Posted by t vago

Looking again at oil pan 4's work, I have stumbled upon this old thread.....
The circuit will shave off about 1/4 HP from the alternator during normal operation, I figure. Estimated fuel consumption will go down by about 0.4 gallon per tankful, with a little over 2.2% savings. Smaller engines will see a bigger percentage.......

Are you calculating on the alternator supplying it's rate output whenever it is running? the average load will be quite low.

[t vago]

Originally Posted by George Tyler

Are you calculating on the alternator supplying it's rate output whenever it is running? the average load will be quite low.

Actually, I calculated using 14 VDC and 90 A of load.

I estimated 30 A for the PCM, injectors, ignition coils, ASD relay, fuel pump relay, O2 heaters, and fuel pump. I estimated another 15 A for the TCM, relay, and transmission solenoids. I estimated another 20 A for the instrument cluster, radio, and body control computer. Finally, I estimated another 25 A to account for the blower motor, lighting, turn signals, and the electric engine cooling fan.

The engine and transmission loads will be quite steady. The body loads will be a bit more variable due to radio output, but will be more steady than the last group of loads.

[George Tyler]

seems excessive to me, guess I need to measure it. My Prius draws 250W, mainly in the computers, and I was complaining about that!

[serialk11r]

Yea that is abnormally high, a car without lights or radio on consumes maybe 25A. Standard car audio can't be more than in the low hundreds of watts.