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Old 20th February 2009, 15:15   #181
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I dont think that i mentioned anywhere that the question was for a huge amp..did i? my question was for a regular amp. But now that you have made that suggestion i have a question, how do you define a huge amp?

[/quote]
Put another bigger capacity alternator or avoid putting such huge amplifiers and give some rest to ear drums and brain cells.[/quote]
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Old 20th February 2009, 15:32   #182
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Originally Posted by KSM-Vtec View Post
I dont think that i mentioned anywhere that the question was for a huge amp..did i? my question was for a regular amp. But now that you have made that suggestion i have a question, how do you define a huge amp?
Put another bigger capacity alternator or avoid putting such huge amplifiers and give some rest to ear drums and brain cells.[/quote][/quote]

Theory applies to amp. of any capacity , one can have his own definition of huge but something which drains the battery and more then capacity of alternator is huge for that car.
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Old 20th February 2009, 15:33   #183
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Kaushik, chill yaar, nothing at you, Ice is a good example to use. the same applies when we put those multiple headlamps.
huge amplifier are one which can demand more power than the capacity of the car electrical system. like Baleno has a alternator rated at 50-60amps. stock battery is 35amph. if the car is idling it takes 10A without any accessories. so for me a huge amplifier is anything above 30A continuous load.
my amplifier has a Current Consumption (+B = 12.0 V, 4 Ω, 10 % THD) of 53 A on peak. I consider it huge but it is nothing if you see whats in other member ICE here in showoff section.
If i try this stuns without the battery connected i will be buying another alternator. When i was replacing mine i did try to source a higher capacity but didnt get.

Last edited by gigy : 20th February 2009 at 15:43.
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Old 20th February 2009, 15:35   #184
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Originally Posted by amitk26 View Post

Theory applies to amp. of any capacity , one can have his own definition of huge but something which drains the battery and more then capacity of alternator is huge for that car.
Sorry to ask but, what kind of an amp would be huge for an OHC?
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Old 20th February 2009, 15:45   #185
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Originally Posted by KSM-Vtec View Post
Sorry to ask but, what kind of an amp would be huge for an OHC?
It depends on how much can your OHC alternator put out.
For example lets say you have a 80A alternator.
Now lets say you have 2 headlights of 100W each which comes to 200W
Thus your headlights will draw Approx 17A of current.
Add another 50W for your parking lights etc., and you are looking at 5A more current.
This gives you around 22A of current need for lights. Lets make it 25A misc.
Now your car AC fan will draw another 20A of current, and then add around 20A for the Engine fan
this comes to 40A more.
So your total peak current draw is 60A approx.
This is peak usage, now you want that your ICE system should not draw more than 250W.
You may say "Wow most amps are 1000W!".
Well thats PMPO. On an average you will have these amps draw around 15A, and give another 5 to your HU.

To sum it all up, buy an amp which does not consume more than 20A or 250W average power(not PMPO). Its on the spec sheet of amp. Also note that I am talking about current at max volume, if you are planning to use low volume, you can get a bigger amp if you are listening loud music occasionally.
For example in LBMs car when sub is turned on, the lights used to dim with each note. If he kept that for long time, he and his entire city will go deaf, and then his car battery will also completely drain. IIRC, he got a bigger capacity alternator for the solution. Howerver this is the wrong thread to be discussing that. There is a very good thread in the ICE section which talks about effect of "heavy" ICE on car electrical systems. Do a search, it will turn up.

Last edited by tsk1979 : 20th February 2009 at 15:47.
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Old 20th February 2009, 15:46   #186
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you will have to find out whats the OHC alternator continuous current capacity.(may not exceed 70amps). Dont include how big battery you have in calculating. bigger the battery, alternator has to work more time to restore is capacity. that itself becomes another load.

Last edited by gigy : 20th February 2009 at 15:47.
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Old 20th February 2009, 15:55   #187
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Originally Posted by tsk1979 View Post
It depends on how much can your OHC alternator put out.
For example lets say you have a 80A alternator.
Now lets say you have 2 headlights of 100W each which comes to 200W
Thus your headlights will draw Approx 17A of current.
Add another 50W for your parking lights etc., and you are looking at 5A more current.
This gives you around 22A of current need for lights. Lets make it 25A misc.
Now your car AC fan will draw another 20A of current, and then add around 20A for the Engine fan
this comes to 40A more.
So your total peak current draw is 60A approx.
This is peak usage, now you want that your ICE system should not draw more than 250W.
You may say "Wow most amps are 1000W!".
Well thats PMPO. On an average you will have these amps draw around 15A, and give another 5 to your HU.

To sum it all up, buy an amp which does not consume more than 20A or 250W average power(not PMPO). Its on the spec sheet of amp. Also note that I am talking about current at max volume, if you are planning to use low volume, you can get a bigger amp if you are listening loud music occasionally.
For example in LBMs car when sub is turned on, the lights used to dim with each note. If he kept that for long time, he and his entire city will go deaf, and then his car battery will also completely drain. IIRC, he got a bigger capacity alternator for the solution. Howerver this is the wrong thread to be discussing that. There is a very good thread in the ICE section which talks about effect of "heavy" ICE on car electrical systems. Do a search, it will turn up.
Thanks a lot for the inputs..it was very helpful. Will look for the thread.

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Originally Posted by gigy View Post
you will have to find out whats the OHC alternator continuous current capacity.(may not exceed 70amps). Dont include how big battery you have in calculating. bigger the battery, alternator has to work more time to restore is capacity. that itself becomes another load.
Ya we need to include this also in the above calc by tsk.
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Old 20th February 2009, 16:07   #188
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gigy/KSM, if your alternator gives current greater than the total drain, for example if your alternator is 80A and your drain is 50A normally(After all you drive in day also, not just in night), then you will see that your battery always has near full charge. So whether your battery is large capacity or small capacity does not matter.
However if you forget to turn of the lights at night, and in the morning you find battery dead, a 65Ah battery will take longer to get near full charge than a 45Ah battery.
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Old 20th February 2009, 16:21   #189
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Ok i have a question here..how long does the 45Ah battery take to go upto full charge from zero??

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Originally Posted by tsk1979 View Post
gigy/KSM, if your alternator gives current greater than the total drain, for example if your alternator is 80A and your drain is 50A normally(After all you drive in day also, not just in night), then you will see that your battery always has near full charge. So whether your battery is large capacity or small capacity does not matter.
However if you forget to turn of the lights at night, and in the morning you find battery dead, a 65Ah battery will take longer to get near full charge than a 45Ah battery.
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Old 20th February 2009, 16:29   #190
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Originally Posted by KSM-Vtec View Post
Ok i have a question here..how long does the 45Ah battery take to go upto full charge from zero??
The answer again depends on the alternator you have , Suppose alternator rating is 45 Amp 14.4 V then it should take exactly one hour for an 45Ah battery in theory but add to it some small loads required for normal running of car and losses and it would be bit more then 1 hour. similarly a 90 Amp alternator should take little more then 30 mts taking in to account losses and other load.

Last edited by amitk26 : 20th February 2009 at 16:30.
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Old 20th February 2009, 17:02   #191
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Originally Posted by KSM-Vtec View Post
Ya we need to include this also in the above calc by tsk.
LOL, and also include another big margin due to the fact that TSK's calculation did not take into account the substantial power lost to producing HEAT in the amplifier's heat sinks!
A typical amplifier works at a conversion efficiency of 70% at it's best! Usually far lower.
TSK's example used output power ratings as the basis for the calculations. In real life, the amp will demand about 30% more power at the power input!

However, these are theoretical calculations based on sine waves. In practice, music makes FAR smaller demands, power-wise!
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Old 20th February 2009, 21:38   #192
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Originally Posted by sujaylahiri View Post
I believe that none of the modern cars can run without a(n) ....alternator disconnected.
With an alternator disconnected, any modern car will run till the battery is completely drained.

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A cutout allows you to take current directly from the battery and run the extra lights/ horns installed on a motorcycle.
My bike has a cutout installed for the Roots Vibrosonics.
No extra light fixtures on my bike.
Quote:
Originally Posted by KSM-Vtec View Post
I have noticed in some cars that the ICE setup(amps) is directly connected to the battery. In such a case -

1. What will be the source for supply? Battery right?
2. If its the battery then what would be the impact of this kind of a setup on the health of the battery?
3. If it is the battery and if it is not healthy for it then - is there a better way of powering the ICE?
Connecting directly to the battery, as in running another wire to the batt terminal to connect the ICE, is a wierd concept among some car electricians, who think an intervening fuse, or the car's existing wiring, has resistance, and won't supply enough power to the ICE.

An "unhealthy" batt won't run the ICE well if the voltage drops (such as, if a cell is weak). But a running engine and good alt WILL run the ICE fine even if the batt is not in perfect condition.

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Which cutout(this slang term actually means a relay or contactor) are all talking about here?
The term cutout generally used in market is for headlights. its a thicker wire connected to battery through fuse, goes to a relay or two as per design and then powers the 90/100 and above headlights. The relay is controlled by stock headlight switch.
This is used to prevent the stock wiring of car from getting damaged as it is designed by law to carry only a 50/60w power. there is nothing like smooth flow or other theories. You can use 90/100 directly also but soon the weakest part of the stock car wiring will give way, first thing to go is the bulb holder.
Perfect explanation for what car electricians call a "cutout".
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Old 20th February 2009, 23:08   #193
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Another difference in cars sold in cold countries is that the cabin heaters are electrical. In India, most cars have heaters that work off the engine coolant!
They take forever to warm the cabin at the start of the day!
Not true with all cars. I have used more than one car in US (Colorado) where -20C is common.

Only very high end luxury cars have electric heaters, others still run on heat from the engine, thats why they run the engine for 20 mins to heat the engine and the cabin, otherwise it will be very cold plastic and leathers you have to face.

Also one more fact is that alternator by itself cannot produce any power by itself. It also needs to be started by the battery. There is a rotor coil or a field coil that induces current in the stator coils of the alternator. If initially no voltage is applied across the field coil no power will ever be produced by the alternator no matter how fast you rotate them. However once the alternator has started to produce power it can power the field coil by itself. From then on the current through the field coil is controlled to control the power produced by the alternator.

Last edited by arunmur : 20th February 2009 at 23:15.
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Old 21st February 2009, 09:14   #194
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Hey just a plain simple explanation to the thread title:

Yes, a petrol car MAY run with the battery disconnected, BUT not for a long time. It can be used for emergency situations.

Running a car with battery disconnected for 20 km or so will result in the alternator's elements going bust.

Before anyone jumps the gun on me, kindly try it in your petrol car. It does not matter whether car is MPFi or Carburettor.

Old School diesel vehicle, can run indefinitely with the battery removed. [I am referring to the Diesel vehicles that have a decompressor lever to switch off the vehicle]

Modern diesels with ECUs may NOT run with the battery disconnected. This may differ with vehicle to vehicle and I have not tried this!


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Old 21st February 2009, 15:24   #195
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Originally Posted by headers View Post
Running a car with battery disconnected for 20 km or so will result in the alternator's elements going bust.
This is going in endless loop You may repeat this statement multiple times but at least once give a logical reason what will go bust in alternator and why? FYI my 1998 M 800 I have run from Whitefield to Koromangla in night (more then 20 KM ) with out battery few years back.

By the way you belive that alternator in only petrol car would go bust ? What is difference between alternator of petrol and diesel car ?

I posted detailed explanation on why battery has no role to play in rectifier going bust. There is a Baleno circuit diagram which does not show any regulator. Can you please look at the alternator of you petrol car first and find if there is anything which can be called regulator ?
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