[lapis_lazuli]

Originally Posted by Sutripta

Don't take it otherwise, but your posting a data sheet, mention of poles and zeros etc I feel is a polite probing to see how much the other person knows. I could mumble some jargon like transfer functions, loop gains, stability, etc, but I'd rather reiterate something which I have said it before, and I'll say it again: On this forum of experts, I'm just a layman. And for almost all technical aspects discussed on TBhp, it can be answered by an informed layman, in language which can be understood by other laymen. And understood by other laymen should be the goal. (My posts don't follow this. Those are meant to stir thought. But I do steer clear of jargon.)

Regards
Sutripta

It is and it is not. I disagree, that on all occassions, even a subject matter expert must ALWAYS speak in layman terms. Mildly surprising that the focus is now on jargons (or not) ! The way the discussion headed, it was necessary to point out facts as they are, with published data and rudimentary high school math/physics. Certain explanations, when demanded by not so straight-forward questions, in my opinion, does call for limited use of jargon. Because, that limited target audience, is mature enough to handle the same!

Whatever you choose to disagree, I am willing to clarify again, Sir.

PS: You affirmed your aquaintance with the subject: so what was offensive in the use of jargon? It is not meant to be offensive at all, again, just stir thoughts. I could explain the same, without jargon as well! This subject of power management, is my bread and butter, anyway!

I think I run the risk of a few digits under my avatar, now. So this will be the last post from me. I welcome PMs for a detailed understanding of the subject.

[Jeroen]

Originally Posted by lapis_lazuli

This subject of power management, is my bread and butter, anyway!

As we all seem to agree the current isn't measured/monitored, because there isn't the need to do so, (The way I see it's inherent to the design) could we return to my my original question.

I was wondering if you could shed any light on that one:

It goes back to the often heard/repeated phrase along the lines:

During a jump start it is better to run the donor cars engine at around 2-2.500 RPM. Any thoughts perhaps?

I don't think it makes a material difference for the various reasons I mentioned in earlier posts.

Thanks

Jeroen

[Aroy]

Originally Posted by Jeroen

....

During a jump start it is better to run the donor cars engine at around 2-2.500 RPM. Any thoughts perhaps?

I don't think it makes a material difference for the various reasons I mentioned in earlier posts.

Thanks

Jeroen

In my opinion the only reason for running donor car's engine, is to ensure that the jump start does not drain the donor battery enough to stop it starting, in that case you have two stranded cars instead of one!

OT
Regarding push start, some cars can be, some cannot. I have push started both my Exteem MPFI and the Alto K10, they start easily. In contrast the Honda City does not start at all.

[Jeroen]

Originally Posted by Aroy

[/QUOTE=Jeroen;3954314]....
In my opinion the only reason for running donor car's engine, is to ensure that the jump start does not drain the donor battery enough to stop it starting, in that case you have two stranded cars instead of one!

Why would the donor car battery drain because of a jump start. Unless you have to start for an extended period of time that might come into play.

Jump start from connecting the cable, to starting the car and disconnecting is typically a process that is measured in minutes at best. Unless there is something wrong with the car with the dead battery it should fire up immediately on the first try. If not, you should investigate, before endlessly cranking the engine.


Jeroen

[Sutripta]

Originally Posted by lapis_lazuli

What excites the rotor in the first place?? Is the battery connected? If the rotor has no excitation, even a 12000rpm will not destroy any alternator: robust or not. Except the bearings perhaps. I definitely missed something here.

Missed the third line.

Originally Posted by Sutripta

Re: blown stators: Take a robust old world alternator. Remove the AVR, and connect the rotor (field) across output and ground (ie rail to rail). Connect a battery, and as much load as you want, and spin it up.

Regarding some of your other queries: Should we think of the alternator as a voltage source, or a current source? Or both? If both, which mode when?

Regards
Sutripta

[Aroy]

Originally Posted by Jeroen

Why would the donor car battery drain because of a jump start. Unless you have to start for an extended period of time that might come into play.

Jump start from connecting the cable, to starting the car and disconnecting is typically a process that is measured in minutes at best. Unless there is something wrong with the car with the dead battery it should fire up immediately on the first try. If not, you should investigate, before endlessly cranking the engine.


Jeroen

It may seem a trivial concern, but I have seen the donor battery drained and both cars stranded, when both the owners were not that careful. This happens often when an novice is stranded in a remote location, due to drained batter (caused by a short or by an installed accessory) and a good Samaritan (an equal novice) tries to help. So better be careful rather than sorry.

[Lobogris]

Originally Posted by Jeroen

Why would the donor car battery drain because of a jump start. Unless you have to start for an extended period of time that might come into play.

Jump start from connecting the cable, to starting the car and disconnecting is typically a process that is measured in minutes at best. Unless there is something wrong with the car with the dead battery it should fire up immediately on the first try. If not, you should investigate, before endlessly cranking the engine.


Jeroen

I have often found that a car with a completly drained battery doesn't start immediately after being connected to a donor car. It might just crank a bit initially but won't start. If you leave it connected for about 5 minutes then the car starts and there are no further issues. A car with a partially depleted battery might start instantly on the other hand. Another issue is the question of the power required to turn over the recipient car's engine. Sometimes a bit of extra power is required due to differences in vehicles and a running car can have a little extra amps to spare. In addition, one never knows how much power would be drained by a jump start. What if 3-4 cranks are required and before you know it leads to 5 or 6 and then you can have two dead batteries. Why risk it when you can keep the donor car on?

[Jeroen]

Originally Posted by Aroy

It may seem a trivial concern, but I have seen the donor battery drained and both cars stranded, when both the owners were not that careful. This happens often when an novice is stranded in a remote location, due to drained batter (caused by a short or by an installed accessory) and a good Samaritan (an equal novice) tries to help. So better be careful rather than sorry.

Originally Posted by Lobogris

I have often found that a car with a completly drained battery doesn't start immediately after being connected to a donor car. It might just crank a bit initially but won't start. If you leave it connected for about 5 minutes then the car starts and there are no further issues. A car with a partially depleted battery might start instantly on the other hand. Another issue is the question of the power required to turn over the recipient car's engine. Sometimes a bit of extra power is required due to differences in vehicles and a running car can have a little extra amps to spare. In addition, one never knows how much power would be drained by a jump start. What if 3-4 cranks are required and before you know it leads to 5 or 6 and then you can have two dead batteries. Why risk it when you can keep the donor car on?

Thanks for your replies, but in both cases keeping the engine just idling would solve the problem.

Still no answer on why it's better to rev it up to 2-2.500 RPM.
Maybe the example of the donor car having to little power is a little bit in the right direction? But again, if we go what we discussed earlier along the lines that the additional load the alternator takes at that higher RPM is likely to be not very much, I still don't see the point.

But in general I would say it might be an idea not to attempt to jumpstart a car with a donor car with a seriously smaller capacity battery. As per the discussion on Voltage and current discussion I don't think the current would be a problem as such. At least not on modern alternators. But putting a very (too) high load on a battery could lead to problems of the battery. Maybe modern batteries are not more resilient to quick deep depletion?

I don't see much new insights into this revving thing myth coming. So I think I will consider it as mostly busted, in practice busted.

Jeroen

[Neel]

I just installed a rear sensor on my Brio; Co-incidentally, they battery went dead after about a month. It was 3 years on a stock battery. Is there any reason to believe there could be a leakage?

[Jeroen]

Originally Posted by Neel

I just installed a rear sensor on my Brio; Co-incidentally, they battery went dead after about a month. It was 3 years on a stock battery. Is there any reason to believe there could be a leakage?

If it was fine till you did the modification I would say the modification might be suspect or during the modification a wire or so got nicked, exposed whatever.

Easiest way to check is hook it up with a multimeter and check for leak current. This was discussed before with some very useful links to a YouTube video how to go about it.

It could of course be something else, but as you did or had some electrical work carried out you have a strong suspect I would think.

A well maintained battery should last much more then a month. Even on cars with alarm systems and ignition disables (they draw a constant small current) most systems would easily give you 10-12 weeks problem free standing still and still the ability to start.

Good luck
Jeroen

[Sutripta]

Originally Posted by Jeroen

If I check a few diagrams from say Denzo,

Could you share these with the forum please?

Regards
Sutripta

[Jeroen]

Originally Posted by Sutripta

Could you share these with the forum please?

We are moving house (again) so in the process of packing up all our stuff in various boxes at the moment

But have a look at these as they illustrate my point:

http://densoautoparts.com/alternator...rs/alternators.

http://densoheavyduty.com/alternators/light-duty

This is a bit generic, but it shows the output at say 1000rpm around 65A and at 2000RPM about 100A.

There is no doubt, of course, that the output at higher RPM goes up. If you rev higher it will go even higher.

But let's take your 'average jump start' scenario.

Somebody notices that his/her car doesn't start. No or slow crank, lights are low, pretty good indication the battery is drained. Bring on the donor car! Open the hoods, trunks, wherever the battery sits, you hook up the jumper cables, you start the car and you disconnect the jumper cables. At best you will have the jumper cables attached a mere few minutes.

Irrespective of the actual output of the alternator I don't think the 'additional' output of the donor cars alternator over and above it's battery is going to make a material difference one way or the other.

Leaving the donor car to idle, makes sense, just in case you inadvertently run down the battery of the donor car by long repeated cranking. Say you crank for 2 minutes, that will be a good drain on the battery. Having the donor car alternator run at 1000 or 2000 RPM during those two minutes, what is the measurable difference? There will be some, of course.

I have seen the statement that it is 'better' to rev the donor engine on countless forums. And it certainly isn't bad. I do wonder how much better it really is? For all intents and purposes from a more practical than theoretical point of view I just don't see the point.

Jeroen

[sgiitk]

@Lobogris; As I have stated somewhere earlier, once I had to jump start a totally dead Swift or WagonR from my Brio. The owner had left the lights on for a couple of days. I remember to my surprise the jumper leads (10mm) getting quite warm, and also the donee being able to crank only after some time.

[Jeroen]

Originally Posted by sgiitk

@Lobogris; As I have stated somewhere earlier, once I had to jump start a totally dead Swift or WagonR from my Brio. The owner had left the lights on for a couple of days. I remember to my surprise the jumper leads (10mm) getting quite warm, and also the donee being able to crank only after some time.

I think it was mentioned before, but always try and get the thickest jumper cables money can buy.

If the battery is really dead, it might need a bit of a charge first I imagine Though whether it is 'better' to rev the donor car and send even more amps to those jumper leads and into that dead battery I'm not so sure?

Anybody with real battery experience/insights who can comment on that?

Jeroen

[Ricky_63]

Originally Posted by AstonMartin

Mates, please check out "http://www.batterybhai.com/" before changing the battery from local shops or ASCs. I recently used their service and it was excellent. They come home and fix the new battery for you and take away the old one. The prices are really competitive. This service is available only in large Indian cities.

I second that. I changed my Vento Diesel Highline battery a few months ago. Thru battery bhai.com - great doorstep service & cheaper than regular market rates.