on/off switch for alternator? (Looking for directions / help / how-to)

[MetroMPG]

Negligible gains? AutoMc - you may want to read up on this one a bit more.

Of all the mods I've done, going alternatorless offered one of the single largest MPG gains (10% boost at 70 km/h). It's right up there with the full boattail (15% @ 90 km/h). Almost all the other mods I've done are in the 2% improvement range. Others can provide similar alternator success stories.

But the operator has to know when/how to use this mod to get significant gains. Simply turning it on/off at various times while driving won't net much (could actually make MPG worse.)

Fuel economy gains will only come from depleting the battery while driving, then recharging from the grid (or other source) at the end of the trip.

Side-effects can be managed. It's not without problems, but it can provide big returns.

[Automcdonough]

If you've reduced all other losses to the extent that you're seeing over 80mpg, then yes it becomes a larger % of the losses. I'm sure that the measured 288W while running @ 14.4V was way less than 200W @ 11.5V. Perhaps null point if that loss is being taken out of the equation but you can reduce this loss while retaining functionality.

Spinning an unloaded alternator by hand is easy, that belt is not very significant. What is would be reducing the loads. The best method is explained in that article, switching the regulator voltage. Think about what happened there.
-You cut the voltage going to the spark plugs (possibly reducing MPG). Ideally you would want to keep this one up there as a weaker spark is less effective as plugs wear.
-slowed down the fuel pump. Unless it's mechanical pump or a fancy PWM controlled one instead of the old on/off+FPR setup. It's possible that downsizing this could help.
-cut the lights and resistive losses drastically. Do you think if those were all LED's you would have seen nearly 10% difference?

To be honest I am shocked to see that chopping 1/2HP would yield such a result in that test. That would mean the motor is only operating at 5HP?? Not very inclusive of a typical drive if the gains are totally swamped by a single acceleration.

Sorry to be so dismissive about this but I feel that it's a pretty important part to keep on there. From the perspective of running at a loss to recharge at home I can see the benefit, but outside of that it seems like you'd be putting yourself in a position to constantly fret about reliability in range and restarting.

[EdKiefer]

Originally Posted by Automcdonough

If you've reduced all other losses to the extent that you're seeing over 80mpg, then yes it becomes a larger % of the losses. I'm sure that the measured 288W while running @ 14.4V was way less than 200W @ 11.5V. Perhaps null point if that loss is being taken out of the equation but you can reduce this loss while retaining functionality.

Spinning an unloaded alternator by hand is easy, that belt is not very significant. What is would be reducing the loads. The best method is explained in that article, switching the regulator voltage. Think about what happened there.
-You cut the voltage going to the spark plugs (possibly reducing MPG). Ideally you would want to keep this one up there as a weaker spark is less effective as plugs wear.
-slowed down the fuel pump. Unless it's mechanical pump or a fancy PWM controlled one instead of the old on/off+FPR setup. It's possible that downsizing this could help.
-cut the lights and resistive losses drastically. Do you think if those were all LED's you would have seen nearly 10% difference?

To be honest I am shocked to see that chopping 1/2HP would yield such a result in that test. That would mean the motor is only operating at 5HP?? Not very inclusive of a typical drive if the gains are totally swamped by a single acceleration.

Sorry to be so dismissive about this but I feel that it's a pretty important part to keep on there. From the perspective of running at a loss to recharge at home I can see the benefit, but outside of that it seems like you'd be putting yourself in a position to constantly fret about reliability in range and restarting.

You could install a dual load alternator like Honda uses, which voltage output changes according to load .

Also what about switch to high output phase when you hit brakes , that might help and not hinder mpg .

[busypaws]

Make sure you label the switch for your wife. I've gotten 2 really nasty calls from my wife when she has taken the truck and couldn't get it started to drive home.
I use mine as a poor mans power boost. Making a left at a light or accelerating uphill, merging etc... I turn off the field wires (and A/C if its running). I have a small solar panel on the dash so on the way to the airport I turn off the alternator and then recharge the battery while truck sits at the airport for a couple of days.

[MetroMPG]

Originally Posted by Automcdonough

From the perspective of running at a loss to recharge at home I can see the benefit

And under those conditions, I have consistently seen a significant, measurable improvement in fuel consumption in real world driving (vs. that as-controlled-as-possible steady speed testing).

but outside of that it seems like you'd be putting yourself in a position to constantly fret about reliability in range and restarting.

AKA range anxiety. Once you understand how much energy is available, and learn to monitor consumption (voltage, simply), it can be managed.

I also drive an EV. I understand this. It doesn't cause me to fret.

I'll be the first to say disabling the alternator is a complicated and not particularly user-friendly mod. I don't usually recommend it to people who aren't willing to put in the effort required to reap the gains. It's definitely not a "set it and forget it" situation.

EDIT: Also, you need to do the math. If your goal is financial savings, it could be a wash, since you'll be burning through and replacing batteries at a faster rate. (I have a source of cheap/free used batteries - not an issue to me.)