Go Back   Team-BHP > Under the Hood > Technical Stuff


Reply
 
Thread Tools Search this Thread
Old 19th February 2009, 08:54   #121
BHPian
 
Join Date: Apr 2006
Location: North America
Posts: 960
Thanked: 3 Times
Default

I believe that none of the modern cars can run without a battery or alternator disconnected.

The alternator only supplies so much voltage to charge the battery, however, your car's electricals might have different voltage and current requirements and hence won't run. Also I don't think there's a circuit which goes straight from the alternator to the main circuit of the car, unless you hard wire it physically.

Last edited by sujaylahiri : 19th February 2009 at 09:00.
sujaylahiri is offline   Reply With Quote
Old 19th February 2009, 09:20   #122
Senior - BHPian
 
Join Date: Sep 2007
Location: New Delhi
Posts: 3,083
Thanked: 252 Times
Default

Quote:
Originally Posted by sujaylahiri View Post
I believe that none of the modern cars can run without a battery or alternator disconnected.

The alternator only supplies so much voltage to charge the battery, however, your car's electricals might have different voltage and current requirements and hence won't run. Also I don't think there's a circuit which goes straight from the alternator to the main circuit of the car, unless you hard wire it physically.
Sujay, you are defeating the very purpose of this thread!

Please do read ALL the posts and you will be a changed man!
anupmathur is offline   Reply With Quote
Old 19th February 2009, 09:41   #123
Senior - BHPian
 
suman's Avatar
 
Join Date: Sep 2005
Location: Gurgaon
Posts: 4,589
Thanked: 257 Times
Default

Quote:
Originally Posted by DirtyDan View Post
Diesels often have 2 batteries OEM for easier starts particularly in cold weather on larger motors such as the merc. One battery may be enough to turn the motor over slowly but not fast enough to start the "heat cycle" that is the ignition system of a diesel. I found this out the hard way a couple times when one of my 2 batteries died. The single remaining battery would not crank the motor fast eough to catch. Also both of my batteries died once. A single battery jump attempt from another vehicle also failed to crank the motor hard enough to catch.
Dan, I think you've given a very logical & likely reason, thanks!

Quote:
Originally Posted by headers View Post
Sir, please remove your battery physically from your car [wagon R] I'd presume, run it for a day maybe without battery. You'd get all your answers..or read my post above:
Vikram, give it up man. Anup will not try it for 20 minutes or a day because he knows it will run that long. So he doesn't want to waste his time.

Right Anup?

Last edited by suman : 19th February 2009 at 09:42.
suman is offline   Reply With Quote
Old 19th February 2009, 09:51   #124
Senior - BHPian
 
Join Date: Sep 2007
Location: New Delhi
Posts: 3,083
Thanked: 252 Times
Default

Quote:
Originally Posted by suman View Post
Vikram, give it up man. Anup will not try it for 20 minutes or a day because he knows it will run that long. So he doesn't want to waste his time.

Right Anup?
Not quite, Suman!
That it will run is of no consequence to me other than having the confidence that, if needed, it could be done. Academic!
My reason for not wanting to try any of this is simpler: As I said before, I do not intend to plan/make any trip without all stock components of the car being in good order!
anupmathur is offline   Reply With Quote
Old 19th February 2009, 09:59   #125
Senior - BHPian
 
suman's Avatar
 
Join Date: Sep 2005
Location: Gurgaon
Posts: 4,589
Thanked: 257 Times
Default

Quote:
Originally Posted by anupmathur View Post
My reason for not wanting to try any of this is simpler: As I said before, I do not intend to plan/make any trip without all stock components of the car being in good order!
True, that's one hell of a valid point!
suman is offline   Reply With Quote
Old 19th February 2009, 10:55   #126
BANNED
 
Join Date: Nov 2004
Location: Bangalore / Madras
Posts: 1,980
Thanked: 14 Times
Default

Will / should a petrol car engine idle with the battery disconnected?
hrag is offline   Reply With Quote
Old 19th February 2009, 11:00   #127
Senior - BHPian
 
Join Date: Sep 2007
Location: New Delhi
Posts: 3,083
Thanked: 252 Times
Default

Quote:
Originally Posted by hrag View Post
Will / should a petrol car engine idle with the battery disconnected?
Yes, hrag. If it does not, chances are that one or more windings/rectifier diodes in the inverter are gone.
Of course, it is presumed that no un-necessary electrical loads are kept on at idle with only the alternator supplying the car.

Re-connecting the battery terminal should be done with the engine turned off!



Quote:
Originally Posted by headers View Post
The Alternator is a pure charging device, It cannot take the dynamic loads of the cars electrical system and will surely bust the regulator.
Hahaha, headers, is that supposed to be a joke?
Please bear in mind that these might just get taken seriously by some people!

Last edited by anupmathur : 19th February 2009 at 11:04.
anupmathur is offline   Reply With Quote
Old 19th February 2009, 11:14   #128
BANNED
 
Join Date: Nov 2004
Location: Bangalore / Madras
Posts: 1,980
Thanked: 14 Times
Default

Quote:
Originally Posted by anupmathur View Post
Yes, hrag. If it does not, chances are that one or more windings/rectifier diodes in the inverter are gone.
Of course, it is presumed that no un-necessary electrical loads are kept on at idle with only the alternator supplying the car.
And this is irrespective of ECU sophistication and alternator rating? Assuming the alternator is in good condition.
hrag is offline   Reply With Quote
Old 19th February 2009, 11:20   #129
Senior - BHPian
 
Join Date: Sep 2007
Location: New Delhi
Posts: 3,083
Thanked: 252 Times
Default

Quote:
Originally Posted by hrag View Post
And this is irrespective of ECU sophistication and alternator rating? Assuming the alternator is in good condition.
Hrag, I am not here to challenge/encourage everyone to try this experiment.
The purpose of the thread was rather different!
Those who wish to gain some knowledge from it are welcome to do so, but I am not issuing any challenge, nor am I instituting any prizes!
I hope that makes it clear!

Quote:
Originally Posted by tsk1979 View Post
If you disconnect battery after starting the car, it will keep running, thats what I observed in Indica and the Safari.
However if your alternator is not working, and you remove the battery terminal, engine dies in the indica. So you need someone generating power, either it has to come from battery or it has to come from alternator.
Once on a long trip, my alternator died, and the battery drained. Car stalled. with new battery it would run.
After alternator replacmenet, the mechanic started car, and then disconnected battery to see if engine dies. since it did not die, it was a crude way of checking that new alternator is okay. Later I used to multimeter to properly verify this.
anupmathur is offline   Reply With Quote
Old 19th February 2009, 11:26   #130
BHPian
 
Join Date: Apr 2006
Location: North America
Posts: 960
Thanked: 3 Times
Default

Quote:
Originally Posted by anupmathur View Post
Sujay, you are defeating the very purpose of this thread!

Please do read ALL the posts and you will be a changed man!
Quote:
We're talking alternators, not dynamos! The idle rpm can be left where the maker set it. An alternator will even charge the battery at idle!
Hi Anup

I did read through the whole thread and had a few comments myself.
  • Firstly, the alternator does NOT charge the battery at idle rpm. This is coming from personal experience as in Northern Alberta during the winter, we sometimes leave our cars idling for 15-20 mins before getting in and if the battery was previously not charged up fully, it is still in the same state. I usually find that out during gearshifts (manual transmission) whereby when I depress the clutch, the daytime running lights or the headlights get slightly dimmer, for the first 10-15 mins of driving. Once the battery is fully charged up, it doesn't occur anymore. And other people have also had a similar experience.
  • Secondly, the alternator is not the only primary source of power. Recently when I got an engine block heater installed in the Mitsubishi dealership, they forgot to connect the alternator back and I lasted about 175 kms before everything died on me. Now I don't know if the battery runs on a parallel circuit with the alternator, or does it just serve as a conduit for the current from the alternator.
I guess I can always ask some electrical engineers from work, since this is not exactly my area of expertise.

Last edited by sujaylahiri : 19th February 2009 at 11:34.
sujaylahiri is offline   Reply With Quote
Old 19th February 2009, 11:36   #131
Senior - BHPian
 
Join Date: Sep 2007
Location: New Delhi
Posts: 3,083
Thanked: 252 Times
Default

Quote:
Originally Posted by sujaylahiri View Post
  • Now I don't know if the battery runs on a parallel circuit with the alternator, or does it just serve as a conduit for the current from the alternator.
I guess I can always ask some electrical engineers from work, since this is not exactly my area of expertise.
Sujay, the alternator and the battery run in a parallel circuit. Someone has even posted a diagram earlier in the thread.
The source with the higher instantaneous voltage feeds the electricals of the car. It is conceivable that there might be points where both sources are able to feed in parallel.
I wouldn't want to argue about ALL cars in Alberta or anywhere. Suffice is it to say that most cars' alternators will manage to charge the battery even at idle, provided there are no retro fitted loads being kept on.

Oh, and may I suggest that it might be that your alternator is not working at full efficiency?

In case of any doubts, it would be helpful for all of us if you could verify with the engineers at your place of work.

Last edited by anupmathur : 19th February 2009 at 11:39.
anupmathur is offline   Reply With Quote
Old 19th February 2009, 11:51   #132
BANNED
 
Join Date: Nov 2004
Location: Bangalore / Madras
Posts: 1,980
Thanked: 14 Times
Default

Quote:
Originally Posted by anupmathur View Post
Hrag, I am not here to challenge/encourage everyone to try this experiment.
The purpose of the thread was rather different!
Those who wish to gain some knowledge from it are welcome to do so, but I am not issuing any challenge, nor am I instituting any prizes!
I hope that makes it clear!
In my experience with the petrol Indica, the engine died after a few minutes of idling after the battery was disconnected. It may have been a sign of imminent alternator trouble since the regulator failed ~ 3 months after that day (back in 2006). tsk1979 is talking about his diesel Indica that didn't come with an ECU.

I'm also given to understand that there are some ECUs which bump up the idling rpm in such scenarios (the ECU of my 2003 Indica is definitely not one of them).

star_aqua pointed out that this would also depend on the alternator rating. I am only trying to understand this whole business - not challenging you or anybody else.
hrag is offline   Reply With Quote
Old 19th February 2009, 12:15   #133
Team-BHP Support
 
tsk1979's Avatar
 
Join Date: Feb 2005
Location: New Delhi
Posts: 22,953
Thanked: 15,645 Times
Default

Quote:
Originally Posted by hrag View Post
tsk1979 is talking about his diesel Indica that didn't come with an ECU.
I am also talking about my safari which does come with a ECU. It remains started with battery disconnected.
From this thread I think the safe conclusion is that not all cars are made same. Some will run with battery disconnected, and some will not. However the why and how of this I am not aware. From what I learned in my engineering, all cars should run with battery disconnected if alternator is fine, since battery is just parallel to the circuit.
However electronics are a funny thing, and there are many checks/controls/nuances etc., which may not allow this to happen.
So the only thing I can conclude with confidence is that if your alternator is fine, an older engine will run without problem with battery disconnected.
If you have a very very old diesel engine which has everything mechanical including the Fuel Pump, it will probably run without alternator battery. Case in point, the vintage diesel engine at our farm used for pumping water when electricity is not available.
Its hand crank and does not have battery, and the flywheel is connected to water pump.

Last edited by tsk1979 : 19th February 2009 at 12:20.
tsk1979 is offline   Reply With Quote
Old 19th February 2009, 12:45   #134
Senior - BHPian
 
suman's Avatar
 
Join Date: Sep 2005
Location: Gurgaon
Posts: 4,589
Thanked: 257 Times
Default

Quote:
Originally Posted by tsk1979 View Post
I am also talking about my safari which does come with a ECU. It remains started with battery disconnected.
I would not continue this experiment long term, not sure if there's anything else that's getting screwed up in the process
suman is offline   Reply With Quote
Old 19th February 2009, 12:58   #135
Team-BHP Support
 
tsk1979's Avatar
 
Join Date: Feb 2005
Location: New Delhi
Posts: 22,953
Thanked: 15,645 Times
Default

Quote:
Originally Posted by suman View Post
I would not continue this experiment long term, not sure if there's anything else that's getting screwed up in the process
This was no experiment, but necessity. The battery was completely dead. Started car on another battery. disconnected battery, and then reconnected battery terminals on the original battery. Let her idle for 30 minutes, the fully dead battery had enough charge to start the car after that. After running car for few hours now, the battery is in its fully charged state.
Now how did I end up with a fully discharged battery on the Safari... thats another long story
tsk1979 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Battery / Alternator / Voltage Regulator problem? babe_on_wheels Technical Stuff 108 20th October 2017 10:23
Battery Not charging light on - Alternator giving 14+ !! What is it ? karizma_devil Technical Stuff 90 30th August 2012 21:00
Battery / Alternator problem in Ambassador Diesel adrian Technical Stuff 5 11th December 2009 14:25
M800 - Vaporizer tube disconnected eternalck Technical Stuff 5 14th July 2009 13:39
MP3 Player gets Disconnected navdeep Technical Stuff 11 18th January 2007 16:56


All times are GMT +5.5. The time now is 04:42.

Copyright 2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks