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A road-car's battery is constantly topped up by a device connected to the engine called an 'Alternator'. Basically transfers movement within your engine to electrical power in the battery. This costs you about 2-4% of your total engine power. On current cars it is always connected. Your car is constantly
recharging or trying the recharge the battery no matter what its state, even if it's full.
When the engine is on, the alternator charges the battery FASTER then your car can use that power.
My idea is simple. A small electronic sensor and motor, that disconnects the alternator when the battery is 90% full or more, and doesn't reconnect until it's down to 30% .
Enjoy the 2-4% extra power as you drive for a while (a few hours) .. It's costing you no extra petrol .. its free. Your battery will be 100% fine without being recharged for a while. The car will feel like its got an extra 40BHP, without drinking more petrol! (trust me!). This power constantly drained by the alternator is precisely why formula 1 cars do not have them!
I honestly have no idea why the alternator is currently connected 100% of the time .. probably cheaper manufacturing or some lame excuse.
(?) A bit about the alternator's functionality
http://www.curricst...harginginfopage.htm
"The alternator does not constantly produce electricity, rather it cycles on and off as the system demand goes up and down..." [half, Oct 05 2004, last modified Oct 17 2004]
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once again, I don't feel qualified to confirm or deny this [britboy] idea, but if true then +. |
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The alternator generally provides the power for the sparks as well. You'd get a better power saving by disconnecting the air-con compressor (in the UK).
Formula 1 cars don't have starter motors - they do have alternators. |
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I stand corrected with regards to Formula 1 cars... |
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The voltage regulator effectively turns the alternator "on" and "off" (actually, some levels in between as well) in terms of generating electrical energy by varying the current applied to the rotor. (If it didn't work this way, your battery would be toast in no time at all.) |
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However, when there is no demand, you are still driving the belt and spinning the rotor. |
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The way I read your idea, it is much like the clutch on an automotive air-conditioner compressor. |
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I don't know exactly how much power it takes to spin an alternator that isn't producing electricity, but it isn't much. They will spin fairly freely when spun by hand. Most of the drag in non-charging mode must be caused by the belt/pulleys. Do you propose to somehow disengage the belt? This is a tricky task as it will likely result in fried belts when attempting to mechanically disengage and reengage at as frequently as an alternator would need to do. |
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First off, why is 2-4% result in 40 BHP. How many street cars have 1,000 or more HP? |
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Second, the voltage regulator will decrease the streagth of the field windings when less electrical power is needed. This decreases the force that the alternator requires. |
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May I officially take this opportunity to hang my head in shame .. and quietly scuttle back to the drawing board!! |
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Not a silly idea at all britboy, although as mentioned an alternator is easy to spin with you fingers it would suck considerable horsepower to spin at the 10 thousand rpm or so that it does when then engine is at cruise speed, the aerodynamic drag must be quite considerable. |
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If you idea was a mechanical clutch then you would see a reasonable saving but this depends on the initial assumption that generally the alternator is not charging. I think if you were to monitor most alternators they are always putting out something, the headlights, heater/air con internal fan(s), heated seats, heated rear windows, windscreen wipers, mega watt stereo are all sucking from the electrical system. |
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However, if I may be so bold as to modify your suggestion and suggest a simple baffle that cut the air flow off to the alternator while it was not charging that would be easy to do and would reduce the drag. |
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[britboy] Your question is a good one
though - "why the alternator always
connected?" |
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I believe some manufacturers are
looking to combine the flywheel-
starter-alternator as some motorbikes
already do. This would remove one belt
and the weight of both items (almost). |
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The fact that car makers do not do this
already is an example of the hide-
bound narrow to closed-mindedness of
the automobile industry. |
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//The fact that car makers do not do this already is an example of the hide- bound narrow to closed-mindedness of the automobile industry.// |
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Or it might be due to the fact that a constantly running alternator needs airflow to cool it and under the engine (where it might get oil in it) is no place for an electrical device with lots of gaps in the case. Ever noticed that a starter motor is sealed with no air gaps? Or, it could be so that when the alternator bearings seize, it doesn't destroy the flywheel and tear the engine apart? |
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Also, are you sure that the motorbikes don't have a starter-generator? AFAIK, an alternator cannot be used as a DC motor. For one thing, there is no way to supply alternating current to the windings. Don't forget that an electrical motor needs to have the current alternate in order for it to spin. There would have to be a commutator and brushes in the alternator-starter in order for it to be used as a motor. And in order to get enough torque to start an engine, the windings would have to be made much heavier. |
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Another problem is that the gear ratio between a starter and the engine is much higher than the belt ratio between the alternator and the engine. (Take a look at a flywheel diameter vs the crankshaft pully sometime.) So now the starter/alternator is spinning even faster. Faster spinning means even more drag on the engine and more likelyhood of bearing failure. Motorcycles can probably get away with this because the torque requirements for motorcycles are much less than car engines. |
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Perhaps if you took the alternator out of the belt loop completely and powered it with an electric motor... |
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Perhaps if you just stayed home... |
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Why not use waste engine heat to power the alternator. 50% of fuel is lost as heat. Recover it and power as many items as possible with electricity. |
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Someone (an individual, not a
company) once built an engine
that recycled waste heat - I think it
was ceramic. In any case, it got
something like 300HP and 45
mpg. It's still sitting in his garage
on the bench, because none of the
car companies will buy it. They're
all pork-barreling with the oil
companies, I know it. |
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That sounds like an urban legend to me... |
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Combined alternator Starter motor setups are or atleast where in production. They will probably be part of the switch to 48V car electrics rather than th eusual 12V. |
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Guys, drag racers and hot rodders alike have been doing this since before I was born. Putting the alternator on a switch is a good way to shave .01 of a second off your quarter mile time, doesent sound like much, but in drag racing that's an eternity. |
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I won't say all, but most gm alternators (and most other manufacturers) from say 1960 to 1985 had an energize point to start charging. This means the alternator would have to be excited, which meant revving the engine over 1800-2000 rpm. If the aternator wasn't excited (engine started and left idleing for an hour) the battery would die and the engine would shut off. No one would leave there engine idleing for that long so it wasn't a problem. The thing is, once the alternator was excited, it would continue to charge 12 volts even if the rpm fell under the energize point. The voltage regulator is a series of switches that keeps the alternator producing voltage in a range of +12 - +14.4 volts. If the alternator "switched off" under normal driving conditions the voltage from the battery would drop to 10v or less, most likley killing the radio and dimming the head lights pretty bad (<good way to tell that your aternator is bad). Another thing is that would happen is the battery would go dead after about 30-45 minutes, unless it was a deep cycle marine battery which has a reserve of a couple of hours. Normal batteries only have about 30 minutes of reserve capacity. Meaning if there's a load of more than 6 volts it will only last for 30 minutes. |
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One more thing, alternators DO have brushes, and make very good electric motors with very little modification. Starters are sealed for two reasons one they do not spin 100% of the time and dont need the extra cooling, and 2, Most starters sit low on the engine, closer to water puddles and road debris, both of which are bad on the brushes and windings. A good example of a sarter/alternator combo setup is gasoline golf carts, like the older harley davidson and kawasaki 2 strokes. They use a belt driven electric motor to start the engine and keep the battery charged when it's running. |
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Good idea britboy, but it pretty much only works for drag racing where every thing happens at a few seconds at a time. |
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NOTE: Car batteries will be destroyed if regularly discharged 30% (70% remaining). However, there would still be a good power savings if the clutch kicked off at 85% or more of full charge. |
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A simple electromagnetic clutch similar to the air conditioner compressor clutch would work great. |
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At 55M PH, I can see a 2% savings in HP, and probably 2-3 MPG fuel savings. At current fuel prices, that's not trivial. |
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This is one of those ideas where the fishbones are out of proportion to the annotations. Is there something sinister in this? |
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This already exists. New cars disengange the alternator (the belt runs more or less freely) at full throttle. |
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How about control the alternator so that it only charges when breaks or when the battery is too low? |
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An alternator essentially converts mechanical energy into electrical. When you use the lights, or the fan, they get its energy from the battery and the voltage drops. The alternator then produces the energy that's
been used AND NO MORE. That's what the regulators are for. Try turning the lights on and off with the engine at idle, you'll see how the revs go down when you turn them on and only then, because when the alternator is working its drag slows slightly the engine.
What happens when you switch off the alternator
when drag racing is that the little power needed
for vital functions like the spark is then draw from the battery, not from the engine, but you can't do that all the time without sucking the battery dry.
Resuming : no. |
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I read somewhere that water cooled alternators are the coming thing. Seems to me that this would eliminate most of mechanical energy consumed in cooling the alternator. Kiwijohn's idea of a baffle is good if it were done right. Disengaging the alternator is not worth the trouble IMHO. |
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lots of energy ideas lately. i wonder why |
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There is a way to use the electricity
from the alternator continuously to
provide more fuel - namely hydrogen
from water. Connect the battery to an
electrolysis device which separates
water into hydrogen and oxygen, and
introduce them both into the cylinders
along with the fuel-air mixture. When
the spark ignites, the hydrogen will
recombine with the oxygen, thus
giving more of a "bang" in the cylinder
than if the hydrogen-oxygen mixture
had not been introduced into the
cylinder along with the
fuel-air mixture. This will give greater
fuel economy for the same speed or
greater speed for the same fuel
consumption. |
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I think hybrid cars like the Prius use the
engine/battery system in such a way as to
save battery power when it's not charged
and then save petrol by using the battery
to assist the engine. I don't know if this
means the alternator becomes a motor at
some point in the process, but it seems
like more of a 'solution' than this idea. I
think battery/engine hybrid systems will
get more popular now. |
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'better to leave the car in the Sun, light providing Electrons, from Body, in say Panels, x 32 x 54 cm's to topple of, and off.-set 'losses0' pending next drive. |
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[sirau], that was almost understandable. Have you
been drinking? |
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