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

[Frank Lee]

didnt motorcycles use magnetos to run the lights back in the day?

Yup, still do. They have high rpms at cruise vs cars though. Still, should be possible.

[Jorge89]

I've been thinking about removing my car's alternator to save on fuel. I only drive about 15 miles a day and I wouldn't mind charging the battery at home every night. I also have a 72 watt solar panel I built which I could use to keep the battery from discharging too fast. The parking lots at my school and work don't have any shade and I'd get about 10 hours of sun every day so I'm sure that would help. I just want to know if having to start the car 3 times a day and driving 15 miles with the solar panel would be too much. If so, would adding another battery help?

[California98Civic]

Originally Posted by Jorge89

I've been thinking about removing my car's alternator to save on fuel. I only drive about 15 miles a day and I wouldn't mind charging the battery at home every night. I also have a 72 watt solar panel I built which I could use to keep the battery from discharging too fast. The parking lots at my school and work don't have any shade and I'd get about 10 hours of sun every day so I'm sure that would help. I just want to know if having to start the car 3 times a day and driving 15 miles with the solar panel would be too much. If so, would adding another battery help?

You needn't remove it to get the benefit. Put it on an on/off switch if you can. When the field windings can't power up, the belt/pulley alone puts very very little drag on the engine. But with an on/off switch, you always have easy instant access to the alternator generating ability if you need it. That's my set up. Works very well for me. The solar panel will help a little, but only very little. I plug my deep-cycle battery in at night. More details are available on my car's page, including links and battery brands and such.

Good luck! Keep us all posted. I'd love to see your solar panel results if you try it.

james

[flying kurmaster]

On my KURBMASTER camper I have wired all my interior lights and accesories to a deep cycle battery and was planning on keeping the starter battery as it is still good which is not deep cycle. I bought a marine switch with four position dial, off- 1- both- 2 . I plan on dash mounting it. I was thinking that this would be ideal as I could use the altenator to charge the house battery when I was on the move (one of these days I will get solar panels as well) I read most of this thread and it seems that I will able to save some fuel if I turn it to off. My question/concern... is there any chance that I can damage my altenator by switching while engine is running. The van is a 1986 so no ECU but it has electronic ignition. no electric fan, water pump or gaz pump. Also should I avoid charging them both at the same time as they are different types of batteries and could I do this if they were both deep cycle. Thanks....

[Frank Lee]

Keep in mind that auto generated electricity is about 5x more cost than wall-outlet electricity.

[California98Civic]

Originally Posted by flying kurmaster

is there any chance that I can damage my altenator by switching while engine is running.

Sometimes, I switch the alt on/off while driving at night, when the headlights pull enough power that I feel better if I run the alt a little for any significant driving. I'll keep the alt off as I accelerate and when I reach something close to cruise speed I'll turn it on. Then off again when I cut engine at coasting speed. I keep the alt off until I decide to boost voltage again on a later acceleration pulse. I use this kind of strategy especially when I know I am about to climb steep hills.

No problems have occurred with my alternator and my only vehicle problems have been strictly with mechanical parts like bearings, no electronics per se.

The switch is also nice because I can choose to just turn the alt on at night and not bother with monitoring voltage.

I hope that helps... your experience may vary, of course, so consider your vehicle and choose your strategy...

Originally Posted by Frank Lee

Keep in mind that auto generated electricity is about 5x more cost than wall-outlet electricity.

Agreed.

[flying kurmaster]

Originally Posted by Frank Lee

Keep in mind that auto generated electricity is about 5x more cost than wall-outlet electricity.

Thanks guys...Yeah I get that, the thing is that when in North America I live in the van off the grid, so I would have to plug into someone elses electric bill which might be pushing my luck. All this off grid stuff is part and parcel of the overall plan for the rig. Anyways looking forward to doing more ecomoding on the van again this coming summer, will be over there mid May hope it warms up by then. I have a bunch of parts, plans and ideas to see if I can improve my gaz mileage and living conditions. Also planning on doing the Trans Labrador highway in July/ August which should be a good shake down cruise and testing run, anyone done it??

[Night_Sailor]

Originally Posted by MetroMPG

For this approach to make sense financially, you would neither either (or both) of:

1) fuel that is much more expensive than it is now;

2) a supply of free or cheap batteries.

Fortunately, I've found (2).

Today, with two 6v "junk" batteries (from the forklift company) in series to make 12v, then in parallel with the existing 12v starting battery, I did a 46 mile / 74 km alternator-less round trip.

Starting voltage: 12.68
Ending voltage: 12.40 (batteries resting for 1 hour)

11.7v is "empty", so I used 26% pack capacity in that trip, with light accessory load: wipers occasionally; heater fan occasionally; lights; occasionally; plus engine overhead, turn signals & brake lights.

Assuming similar electrical loads, my total range to 100% depth of discharge is about 177 miles / 285 km.

This is how you kill batteries. You do not want to deeply discharge them.


You should increase your battery bank size and discharge only 20% for max battery life. That means a larger battery bank which means more weight. I suppose lithium batteries would be an option, albeit an expensive one.

[Night_Sailor]

Originally Posted by flying kurmaster

On my KURBMASTER camper I have wired all my interior lights and accesories to a deep cycle battery and was planning on keeping the starter battery as it is still good which is not deep cycle. I bought a marine switch with four position dial, off- 1- both- 2 . I plan on dash mounting it. I was thinking that this would be ideal as I could use the altenator to charge the house battery when I was on the move (one of these days I will get solar panels as well) I read most of this thread and it seems that I will able to save some fuel if I turn it to off. My question/concern... is there any chance that I can damage my altenator by switching while engine is running. The van is a 1986 so no ECU but it has electronic ignition. no electric fan, water pump or gaz pump. Also should I avoid charging them both at the same time as they are different types of batteries and could I do this if they were both deep cycle. Thanks....

A surge could blow the diodes in the alternator.

[MetroMPG]

Originally Posted by Night_Sailor

This is how you kill batteries. You do not want to deeply discharge them.

Agreed 100%!

Thus the advice that for this to be financially workable in most cases, "a supply of free or cheap batteries" is required.