wargo@sdcsla.UUCP (Dave Wargo) (01/30/85)
I read an article about how some guy invented a box that cuts out his alternator most of the time thus saving gas by not having the device under a load when not needed. The article goes on to say that the alternator only comes on when either the break lights come on or the batt. level is low. There is only a minimal level of friction from the now free spinning alternators. A couple of questions. First would this work? How would one go about making the box "know" when the batt level is low and turning on the juice? Any ideas? Dave Wargo U.C.S.D.
gvcormack@watdaisy.UUCP (Gordon V. Cormack) (02/02/85)
> I read an article about how some guy invented a box that cuts out > his alternator most of the time thus saving gas by not having the > device under a load when not needed. > > Dave Wargo > U.C.S.D. The regulator that comes with the car does this. The field strength is varied depending on how much output is required from the alternator. The output from the alternator goes directly (actually through some rectifiers) to the battery without any further regulation. Aside from the friction of the alternator the energy consumed by the alternator is proportional to that required. The regulator can easily sense when more output is required. The voltage at the battery terminals is maintained at 13.5 volts. If the battery is discharged (or there are a lot of accessories to drive) it will require a lot of current to bring the voltage to 13.5. If the battery is fully charged, it will require almost none. This method of control was the major advance of alternators over the generators found in cars until the mid-60s. Generators have permanent field magnets and therefore the output cannot be adjusted. The regulator has to discard some of the output of the generator. This also can be done without appreciable power loss by making and breaking the connection between the generator and the battery, but this control circuitry must switch very high currents. -- Gordon V. Cormack CS Department, University of Waterloo gvcormack@watdaisy.uucp gvcormack%watdaisy@waterloo.csnet
fowler@uw-beaver (Rob Fowler) (02/02/85)
> > I read an article about how some guy invented a box that cuts out > his alternator most of the time thus saving gas by not having the > device under a load when not needed. > That's strange. I always thought that your regulator did that. As I recall the Delco transistorized regulator in my Scout II connects the alternator only when certain conditions occur such as some obscure reference voltage (related to the state of the battery) being too low and the alternator being able to charge it up. If those conditions do not obtain then the alternator continues to spin, but no electrical energy is taken from it. It would really surprise me if using a mechanical clutch would save enough energy to be worth the addtional complexity and maintenance hassles. I guess that if you were racing that not having that added mass being accellerated all the time might give you the smallest iota of an advantage, but that seems pretty unlikely. About that damned transistorized regulator: The reference voltage is measured across a 1 to 3 ohm resistance wire from the back of the alternator to the ammeter. It goes through the firewall as part of a huge cable that has a bulkhead connector there. Get a little water and salt in it and it corrodes, changes the resistance, and presto!! the aternator is permanently on, even when the engine is off. This happened to me on an all night drive through a blizzard in Falling Rocks, Montana. I long for the days when it was possible to do reasonable, temporary roadside repairs. -- Rob Fowler
moroney@jon.DEC (02/03/85)
>I read an article about how some guy invented a box that cuts out >his alternator most of the time thus saving gas by not having the >device under a load when not needed. > >The article goes on to say that the alternator only comes on when >either the break lights come on or the batt. level is low. > >There is only a minimal level of friction from the now free spinning >alternators. > >A couple of questions. First would this work? How would one go about >making the box "know" when the batt level is low and turning on the >juice? > >Any ideas? I have been toying with the exact same idea for the last several years but I never got around to building such a device. It would improve gas mileage and performance somewhat because the alternator places a load on the engine only when the brakes are on. As far as making the "box" know whether the battery needs to be charged, that is a standard voltage regulator which every car has (If it didn't, your battery would overcharge and go KABOOM!). This "box" is really a modified voltage regulator which has an extra input which goes to the brake lights. Instead of the normal voltage regulator function (charge only if battery voltage < x) this box works on the principle is (charge battery only if (battery voltage < x) or (brakes on and x <= battery voltage < y)). I have seen similar devices for sale which cut out the air conditioning when the car is accellerated (sp?) hard. The car I was experimenting with had a large change in engine RPM when it was idling when I overrode the voltage regulator and manually turned on/off the alternator. "There's a madness to my method." Mike Moroney ..decwrl!rhea!jon!moroney
mag@whuxlm.UUCP (Gray Michael A) (02/03/85)
> > I read an article about how some guy invented a box that cuts out > his alternator most of the time thus saving gas by not having the > device under a load when not needed. > > The article goes on to say that the alternator only comes on when > either the break lights come on or the batt. level is low. > > There is only a minimal level of friction from the now free spinning > alternators. > > A couple of questions. First would this work? How would one go about > making the box "know" when the batt level is low and turning on the > juice? > > Any ideas? > > Dave Wargo > U.C.S.D. Sure it would work! It called a voltage regulator and every car I ever heard of has one. Some are better than others, but they all sense battery level and only charge when it is low. If you charged when the battery is not low, you'd blow it up. Incidentally, are several ways to know when the battery level is low. A hard way is to measure the specific gravity of the electrolyte. An easy way is to apply a controlled charging voltage briefly and see how much current it draws. A fully charged battery will draw about an amp at 14 volts. Another way is to draw a controlled current out of the battery and check the voltage at its terminals. The voltage at current X will decline as the charge of the battery does. (Both of these methods are basically measuring the internal resistance of the battery, which, for lead-acid batteries, increases as the charge is lowered.) Alternator output is controlled by the level of current in the field coils. As the field coil current(a small current) goes up, so does alternator output. Also, so does the mechanical load on the engine. Besides preventing the battery from blowing up, accurate control of alternator output saves a little bit of gas, and a fair amount of wear on the alternator bearings. This guy may have invented an improved voltage regulator, but he hasn't exactly done anything earthshaking. Mike Gray, BTL WH
tggsu@resonex.UUCP (Tom Gulvin Root) (02/05/85)
> >I read an article about how some guy invented a box that cuts out > >his alternator most of the time thus saving gas by not having the > >device under a load when not needed. > > > >The article goes on to say that the alternator only comes on when > >either the break lights come on or the batt. level is low. > > > >There is only a minimal level of friction from the now free spinning > >alternators. > > > >A couple of questions. First would this work? How would one go about > >making the box "know" when the batt level is low and turning on the > >juice? If I remember right, the new honda CRX has a similar idea - the battery voltage is maintained at ~11.5 volts during cruise and only goes to 13.5 during idle, coast, etc. Makes you wonder if it's all worth it - I'll be surprised if it saves more than .1 mpg. Tom Gulvin - Resonex, Inc. - Sunnyvale CA
mikey@trsvax.UUCP (02/06/85)
Most non-solid state regulators keep a small charge to the battery under most conditions and kick to a high charge under certain conditions. The problem with cutting out your alternator for highway cruising is that it can ruin your battery, unless you have a "marine" battery, or also called a deep cycle battery. Regular lead-acid car batteries can be damaged it they are discharged past a certain point and left there with even a small load. Putting an extra switch under the gas pedal to cut out he AC and alternator is a great idea for short burst of ultimate go power, but I would not recommend that you run just the battery for a cruise. Best idea is to replace the alternator and regulator with the new solid state designs that have a variable field regulator. Then the alternator only puts out whats needed to run the car plus a SMALL extra kick to keep the battery up. mikey at trsvax