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Old 17th February 2009, 20:38   #46
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Originally Posted by headers View Post
... we can start the car and disconnect the battery and keep running. Only your horns, Headlights, Taillamps, indicators etc will not work..does it really matter. The battery should also last more than 10 years then.
Wrong. Your headlamps etc... will work! If the rpm is not increased to maintain sufficient generation, then the engine will stop.



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I do agree with your point, but my friend anup tells me that a car can be run without the battery. Else I have misunderstood the issue completely

The only issue i disagree with my friend anup is "whether a battery is required in a petrol vehicle to run the car - OR NOT" A dead battery still completes the circuit.
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Originally Posted by anupmathur View Post
Headers, the only occasion I had to TEST this out was when a friend's Baleno battery got fully discharged due to using the stereo and the blower too long in the parked car.
With no jump start cables, I had to take the battery out from a Zen and plonk it in the Baleno.
The Baleno was started and then the battery was disconnected and put back in the Zen. Did the Baleno engine stop while this was done? No, Sir!

And you do not have to believe my theories. There are many other sources that will tell you the correct answers. One such source I have posted above, but you have obviously not read the article.
With a car running, yes it is the alternator that supplies the electricals.
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BUT, anup informs us that a battery is NOT required in running of the car and that is blowing my wits out!
Headers, maybe the example I had given above, which is a real life case of a car (Baleno) with an ECU, will help!
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Old 17th February 2009, 20:41   #47
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If anybody is in doubt still, just read below the experience I had about a month before.

As my Exide battery conked off after faithful service of about five years, I decided to replace it with a Prestolite. Called up the shop, and they sent the new battery over. I did the replacement myself, and to my surprise, the car won't start now! Measured the battery voltage, it was very close to zero (just a few mV). I was baffled, but didn't remove the battery from the car.

Called the shop again. This time two guys came in a scooter with another service battery and cables. This battery was connected in parallel to the prestolite using the cables, and the engine started when I turned the ignition key. They asked me to drive the car to the shop so that they will check what is the problem with the Prestolite battery. I asked with some concern "will the car stop on the way?" to which they replied "don't worry, since the engine is now running the battery will charge very fast..it won't stop".

I followed those guys to the battery shop (about 2 km away) and the car didn't stop in between. The battery was inspected at the shop, and it was found that there was not a drop of electrolyte in it!! It was completely dry!! Without a word the owner gave me another new battery (with electrolyte inside of course) and I drove back home.

A Lead-Acid battery with no electrolyte is the perfect dead battery. So my car (Fiat Uno, fuel injection type) was running solely on the Alternator for those 2 km, once it was started by the service battery.

cheers,
Reji
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Old 17th February 2009, 20:45   #48
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Sorry, forgot to add in the previous post that mine is a 2003 model petrol car..

Reji
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Old 17th February 2009, 20:48   #49
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Originally Posted by anupmathur View Post
Wrong. Your headlamps etc... will work! If the rpm is not increased to maintain sufficient generation, then the engine will stop.
Do you mean the alternator will generate more than 14V? Or can you explain the above statement?
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Old 17th February 2009, 20:51   #50
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Originally Posted by headers View Post
Do you mean the alternator will generate more than 14V? Or can you explain the above statement?
The alt normally generates between 13.8 to 14.4V. All auto electricals are tested at a standard 14.4 volts, some up to a max of 15v, not 12V as most may think.

Rgds,
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Old 17th February 2009, 20:52   #51
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@anup, I have had the exact same situation in exactly the same car (Baleno). My OE battery died and the Maruti Onroad Service tech came and jum started my car. They then disconnected a terminal (I dont remember which) and said that the alternator was fine, just that the battery was dead. The engine was running (idling) while he did so. He then stopped the car and connected the terminal back on, jumped it again and told me to run it for 10 mins
So, yes the car will run with battery disconnected. Dont know if lights, horn or other things will work. Also, dont know for how long the engine will run like this.
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Old 17th February 2009, 20:53   #52
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Originally Posted by headers View Post
Do you mean the alternator will generate more than 14V? Or can you explain the above statement?
No headers, the alternator will not generate more than 14 volts, but it might be unable to produce the required current at a low rpm. This will cause the generated voltage to drop, and if this drops to less than about 11 volts, the whole system will shut down.

Last edited by anupmathur : 17th February 2009 at 20:54.
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Old 17th February 2009, 20:55   #53
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Thanks Hrishi, guess you have tried running the car without a battery!
Not exactly. This was at a battery dealer when getting my battery checked. The engine was started and then the battery was disconnected. The engine died in a few minutes. My understanding after this episode was that the alternator needs to supply the load demanded by the ignition system, fuel injection system and the fuel pump (approx. 10 A).

Since the alternator cannot do this without a DC supply, the voltage drops - the ECU cuts the engine when the alternator voltage drops below a threshold.
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Old 17th February 2009, 20:55   #54
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Originally Posted by srijit View Post
@anup, I have had the exact same situation in exactly the same car (Baleno). My OE battery died and the Maruti Onroad Service tech came and jum started my car. They then disconnected a terminal (I dont remember which) and said that the alternator was fine, just that the battery was dead. The engine was running (idling) while he did so. He then stopped the car and connected the terminal back on, jumped it again and told me to run it for 10 mins
So, yes the car will run with battery disconnected. Dont know if lights, horn or other things will work. Also, dont know for how long the engine will run like this.
What the Maruti chaps did was a trifle risky. It may work with some cars. I'd advise all not to disconnect the battery when the engine is running.

There are scientific and refined ways of testing the alternator. Disconnecting the battery when the engine is running is not one of them.

Rgds,
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Old 17th February 2009, 21:01   #55
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Quote:
Originally Posted by srijit View Post
@anup, I have had the exact same situation in exactly the same car (Baleno). My OE battery died and the Maruti Onroad Service tech came and jum started my car. They then disconnected a terminal (I dont remember which) and said that the alternator was fine, just that the battery was dead. The engine was running (idling) while he did so. He then stopped the car and connected the terminal back on, jumped it again and told me to run it for 10 mins
Srijit, what a lovely co-incidence!
Please note the bold text above. This was done because most of the local mechanics have learnt the hard way that reconnecting on a running (ECU based) car can be a very expensive mistake! As I have posted earlier, best to turn off the engine for the reconnection!



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There are scientific and refined ways of testing the alternator. Disconnecting the battery when the engine is running is not one of them.
R2D2, you are right, but these advanced means are NOT available to the humble local machanic!

Repeatedly through this thread, it has been mentioned that the practice may not be safe. But for the local chaps this is the only recourse to verify the alternator.

Last edited by anupmathur : 17th February 2009 at 21:05.
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Old 17th February 2009, 21:16   #56
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Originally Posted by anupmathur View Post
R2D2, you are right, but these advanced means are NOT available to the humble local machanic!

Repeatedly through this thread, it has been mentioned that the practice may not be safe. But for the local chaps this is the only recourse to verify the alternator.
Thanks Anup. It is for the owner to decide what is right for him.

An alt can be tested at a local Exide or Amaron dealer. They are quite widespread. Also, another good testing outfit is the Bosch service centre. No need to rely on mickey mouse outfits.

Rgds,
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Old 17th February 2009, 21:29   #57
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An alt can be tested at a local Exide or Amaron dealer. They are quite widespread. Also, another good testing outfit is the Bosch service centre. No need to rely on mickey mouse outfits.
LOL, perfectly correct!
My little incident about the Baleno happened at 2330 hrs at Kasol! This is a small hamlet in the Tirthan Valley in Himachal Pradesh! We were miles from any 'good practice' engineering support!
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Old 17th February 2009, 22:36   #58
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I can recollect that I had a Mahindra CJ500D diesel Jeep , with the MD2350 International engine.It was very crude for a diesel, the crudest ever. The engine NVH levels were the highest ever for any Indian automobile (sorry the Jawa/Yezdi 250 competes with the CJ500D). But the jeep was very, very dependable. Parts were available anywhere , even in the rural areas and any mechanic would repair it well.
This vehicle is unique and is made to run without any battery support.It had a Lucas dynamo (alternator used to be fitted in the CJ 3B/ CJ 4A's) for recharging the battery.Now whenever my battery conked off, the jeep could be either jump started or pushed for the start.Being in a rural area, it could be a few days before I could go to get a new battery.On chilly mornings the start would be a tedious process as the heater would'nt function.Petrol jeeps (CJ 3B and CJ 4A) when push started take hardly any effort much like petrol cars.
And believe me , the CJ 500D would run for hundreds of kms without any battery. It just does'nt need one to aid the diesel ignition process.The horn, indicators,lights and the heater did not work.So just like many modern bikes, where the battery backs up the self , indicators and horn (the headlights are magneto powered) the CJ 500D would run tirelessly.Even the Royal Enfield Bullet engine cannot run minus a battery as the DC current aids the ignition process. The CJ 500D's engine noise was so prominent that seldom any horn was needed.Night driving would have to be avoided.
The 540DP that replaced the CJ500D had a rotary fuel pump for the 2112cc Peugeot 540DP engine and this fuel pump needed the battery. So no liberties could be taken on the new jeep.There is nothing to beat the CJ 500D for rural duties in India.Its a MULE and needs very little care if at all.

Last edited by anjan_c2007 : 17th February 2009 at 22:41.
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Old 17th February 2009, 23:30   #59
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OK guys read this thread an hour ago and thought it would be a good idea to check my alternator by conducting a small experiment, here is what i did - Started my 2000 OHC Vtec and then disconnected the battery, drove around for more than a 2 kms and nothing went wrong. is that good enough??
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Old 17th February 2009, 23:51   #60
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Cars which dont have electronic fuel control (carburetor type)can be push started and run without battery, there is no need for battery, you just need an assistant to push it every time you want to start it and keep him along for next start.
Modern cars ecu are looking into various sensor output to start and run the car, so a battery is needed to run the ecu where electronic ignition(distributor less) is involved like in a baleno. you can also push it till the alternator is rotating to produce a voltage to power the ignition but it is not a recommended procedure. if there is no power to ignition the car will not start no matter how fast you move it.( if you want to try remove the wire off the alternator and try pushing it to start without a battery). once started the alternator is the main power source, he supplies all the electrical load in car including fuel control, electronic steering, lights, fans, heaters, ICE, wipers, fuel and water pump,charging the battery. the battery cannot supply any load at this time.
only when the alternator is loaded more than its capacity because of ICE or too many lights (or electrical problem)the battery will come in as soon as alternator voltage falls below battery. this becomes evident by poor headlight intensity, low horn volume etc. the car will soon stop if load is not removed. in such situation remove all possible loads and keep the car running till you reach a workshop. nothing will go wrong if your alternator has good voltage regulator

Last edited by gigy : 17th February 2009 at 23:55.
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