The automobile alternator.

zaveri

2) the alternator is always mounted close to the engine, and as the engine continues working, the alternator coils heat up due to the heat of the engine and thus its efficiency drops down to 60%. now in order to avoid this, can the alternator be mounted separately on the chassis, at a safe distance away from the engine and connected to it by a belt drive. is this feasible ? what would be its pros and cons?

isn't the alternator driven by the crankshaft? now, if we have our alternator placed at some X distance away from the engine, we should use a belt to rotate that and the length of the belt would be having a detrimental effect on the efficiency again.

and hey I'm just a noob trying to understand the basics here.

hdnivara

isn't the alternator driven by the crankshaft? now, if we have our alternator placed at some X distance away from the engine, we should use a belt to rotate that and the length of the belt would be having a detrimental effect on the efficiency again.

and hey I'm just a noob trying to understand the basics here.

I appreciate your efforts in wanting to learn more.

Generally, the alternator is driven by the crankshaft, by a belt. now if the distance between the alternator and the engine were increased, and connected by a belt, the increased length of belt wouldn't affect the performance, because belt drives have 70 % efficiency and they are light in weight.

The remaining 30% loss in efficiency can be considered as design compromise or trade-off.

zaveri

1) In any vehicle, the headlights are solely powered by the alternator only, while the rest of the electrical devices like the horn, beepers, signal lights, starter motor, etc are powered by the battery. what is the reason behind this ?

You sure about this?

We can turn on the headlamps of any car even when the engine is not running. And this drains the battery too. So, how can it be solely powered by alternator?

i don't think the headlights are solely powered by the battery. the battery is what turns over the engine, thus causing the engine to run on its own. while the car is running and turned on, the battery powers all the electrical systems. the alternator recharges the battery so it can continue to power all the electrical components in the car.

mechky

You sure about this?

We can turn on the headlamps of any car even when the engine is not running. And this drains the battery too. So, how can it be solely powered by alternator?

This sure is for bikes, but as for cars i am not sure, because i don't own a car, but i can say with confidence, that even in this case, the same thing follows suit.

KZ 259

i don't think the headlights are solely powered by the battery. the battery is what turns over the engine, thus causing the engine to run on its own. while the car is running and turned on, the battery powers all the electrical systems. the alternator recharges the battery so it can continue to power all the electrical components in the car.

To you alone, i would like to ask, how the battery turns on the engine. explain the mechanism in detail.

zaveri

This sure is for bikes, but as for cars i am not sure, because i don't own a car, but i can say with confidence, that even in this case, the same thing follows suit.

For cars I am pretty much sure that headlights are powered by battery. But yes this might not be the case with bikes.
See the problem in bikes is that the battery is much smaller than what is used in cars and the current requirement of a headlight is about 10A. So the battery might not be able to support headlight along with cranking the engine. This might be the reason why headlight is not powered by battery in bikes.

mechky

For cars I am pretty much sure that headlights are powered by battery. But yes this might not be the case with bikes.
See the problem in bikes is that the battery is much smaller than what is used in cars and the current requirement of a headlight is about 10A. So the battery might not be able to support headlight along with cranking the engine. This might be the reason why headlight is not powered by battery in bikes.

I see your point. but at the same time, bike batteries also power horns, and indicator lights.

zaveri

I see your point. but at the same time, bike batteries also power horns, and indicator lights.

True. But as I said, the headlights come next to engine cranking in terms of power consumption. The maximum rating of battery that can be used being limited due to space considerations in case of bikes, and cranking being the utmost necessity, the headlights are powered by alternator after the engine has started mainly to avoid starting problem in bike due to power shortage to engine starter.
Horns, indicator lights have much less power consumption than headlights. Also, it is quite uncommon that a person would be blowing horn or using indicator light while starting the engine. But it is very much common that the headlights might be turned on while starting the engine. So to avoid any shortage of power to starter of engine it is a wise decision to make headlight powered by alternator in case of bikes.
Once the engine has started, the battery has done its job and it becomes fully available to horn, indicators etc.

zaveri

To you alone, i would like to ask, how the battery turns on the engine. explain the mechanism in detail.

when you turn the key, the battery will send a signal to the starter solenoid, from there the power goes to the starter motor, the starter motor has a gear connected to the fly wheel, the fly wheel begins to rotate, and then the engine begins its 4 stroke procedure.

without the battery, none of this happens. i still can not see how you think the alternator is responsible for activating the headlights....

KZ 259

without the battery, none of this happens. i still can not see how you think the alternator is responsible for activating the headlights....

what you said about the engine-starting mechanism, was completely true.

but as for the alternator and headlamps, discussion, you are not able to get me, i believe.

if you own a bike, then try this;

turn on the ignition key, press the horn switch and it blows. turn on the indicator lights, and they flash and beep as well.

but now turn on the headlights, and you will see that they don't work. why ?

now kick start your vehicle, and the headlight comes to life too. twist the throttle, and you will see the light getting brighter.

this will clearly show you that, the headlight is powered only by the alternator, and has no connection with the battery.

the energy transfer is as follows:

engine ---> alternator ---> headlights.

zaveri

what you said about the engine-starting mechanism, was completely true.

but as for the alternator and headlamps, discussion, you are not able to get me, i believe.

if you own a bike, then try this;

turn on the ignition key, press the horn switch and it blows. turn on the indicator lights, and they flash and beep as well.

but now turn on the headlights, and you will see that they don't work. why ?

now kick start your vehicle, and the headlight comes to life too. twist the throttle, and you will see the light getting brighter.

this will clearly show you that, the headlight is powered only by the alternator, and has no connection with the battery.

the energy transfer is as follows:

engine ---> alternator ---> headlights.

a motorcycle and an automobile are not the same. i am specifically speaking about a vehicle. bikes might be different, not a 100% sure on it.

on a car, the headlamps in a car will work, assuming the battery can still hold a charge, regardless if the key is even in the ignition or not. take the battery out, the lights won't turn on.

KZ 259

a motorcycle and an automobile are not the same. i am specifically speaking about a vehicle. bikes might be different, not a 100% sure on it.

on a car, the headlamps in a car will work, assuming the battery can still hold a charge, regardless if the key is even in the ignition or not. take the battery out, the lights won't turn on.

but in my previous post, i was specifically talking about motorcycles.

and yes according to engineering terminology, the word "automobile" has a broader meaning. it not only includes motorcycles, but also man and beast-powered vehicles.

Ya y

mechky

You sure about this?

We can turn on the headlamps of any car even when the engine is not running. And this drains the battery too. So, how can it be solely powered by alternator?

Your are r8 bro we can also open headlights whether the car engine is off.. Batteries. Is charged by alternator its purpose.is only to charge and to supply power to electrical system only when engine is working ...