Jim,

To my way of thinking, the alternator is running with the engine RPM so the power generated is relative to the RPM. This can't be changed unless you disconnect the alternator.

 

The alternator charges the battery - which in turn runs the accessories.

 

So no savings can be made unless you disconnect the alternator.

 

So turning off things does little - it only saves the battery charge which is being recharged whether you like it or not.

Unless you put a clutch on the alternator.

 

So no savings of HP or fuel.

 

In some cases, systems like to have a continuous drain on the battery, like the Harleys. That's why they run around with their lights on - so they don't overheat the battery.  The chaps who select 'lights on' rather than the hard wired factory systems, always have battery problems. 

George ( down under)

 

It doesn't matter what is generating the electricity, a generator, alternator or battery it takes at least 1 HP to make 746 watts of electricity. That is the conversion factor under ideal conditions with an efficiency of 1. Of course in the real world there are losses that reduce the amount of electricity or increase the horsepower necessary. Alternators are probably more efficient than generators but then there are losses in the rectifier and regulator circuits. The laws of physics dictate that there is no free lunch. Energy can neither be created or destroyed, only converted from one form to another (mechanical,electrical,chemical etc.), and always with losses in the conversion process. So turning off electrical devices will reduce the load on the engine by whatever amount they draw plus what ever losses are required in the conversion. Jim --- On Thu, 3/19/09, Ben Baltrusaitis <expressben@verizon.net> wrote: From: Ben Baltrusaitis <expressben@verizon.net> Subject: [FlyRotary] Alternator (Off topic) To: "Rotary motors in aircraft" <flyrotary@lancaironline.net> Date: Thursday, March 19, 2009, 9:08 AM Since it's quiet:   When I was a kid a guy at the parts store demonstrated to my Dad that when electrical power was needed, a generator put a load on the engine. After that, my Dad was careful not to run lights, radio, heater fan, or other non-essentials when he was trying to get good gas mileage.   I have continued that tradition, however, I have seen it stated that electrical draw on an alternator doesn't increase the mechanical load.   When low on fuel will it help to turn off electrical components not needed for flight?   Is it true of an alternator; an electrical power demand doesn't cause an increased mechanical load?   Or, does keeping headlights on during the day decrease gas mileage?   Thanks! Ben