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


Reply
 
Thread Tools Search this Thread
Old 23rd April 2016, 21:08   #181
Distinguished - BHPian
 
Join Date: Jul 2009
Location: Kolkata
Posts: 3,302
Thanked: 1,689 Times
Default Re: Car Battery: Dos and Don'ts!

^^^
We can discuss all these in detail if we have a dedicated alternator thread. As I have said before, there are things to discuss, debate, and differ on! But to do it now will take us off rail. So we'll keep these for another day. Otherwise I feel we are in agreement enough to proceed.

To continue:
So the alternator will have a I-V curve. In fact a family of curves, if we step some parameter, like say RPM.
Now where on the curve will the operating point lie? This will be determined by the load. In case of a simple resistive load, the operating point can be found quite easily, either analytically, or graphically. It will be easier for others to visualise it graphically: the load line will be a straight line. The operating point will be the point of intersection of the two lines.
The battery most certainly is not a simple resistive load.

To emphasise how the nature of the load determines operating point, and its importance, let me use a (very bad) analogy, but which people are familiar with: audio systems. No matter how powerful your amplifier, load (speaker impedence) along with amplifier determines how much power is actually delivered.

Are we still more or less in agreement?

Regards
Sutripta
Sutripta is offline   Reply With Quote
Old 3rd May 2016, 23:11   #182
Distinguished - BHPian
 
Join Date: Jul 2009
Location: Kolkata
Posts: 3,302
Thanked: 1,689 Times
Default Re: Car Battery: Dos and Don'ts!

I thought we would be having a lively give and take interactive session here. Looks like that that is not going to be, so let me put down my thoughts in one final post. More so because I'll be off the grid for sometime now.

Let us start with something all of us on this forum is familiar with: the push start because of a dead battery. Immediately on starting, if one revs the engine, one gets more output (in the form of current) from the alternator than when idling. Substantially more. (To those who think that that is not the case, may I suggest you actually measure, not go by it has to this or that, and so no need to measure etc. And a word about measurement: if one is using one of those el cheapo digital tong tester, make sure you have an AC/DC (Hall effect) instrument. And see to it that the setup gives consistent reproducible readings. It is not as simple as it sounds, given that these meters will give a different reading everytime one snaps shut the jaws. Or how one places the wire in the ~25 sq cm window. And yes, I know wire placement should not matter as long as it is enclosed (Gauss's law) but it does with these meters.)

Now let's come to another part: what happens when one connects a healthy battery in parallel with a dead one.(The situation is the same whether the two batteries are physically in one car, or in two.) There will be substantial current flow from the healthy battery to the dead one, as the healthy one gets discharged trying to charge the dead one.
What happens to the common voltage (Let us call the common voltage the Bus Voltage.) Logically it should be in between that of the two batteries. (Where it actually is depends on the characteristics of the two batteries, esp if one of these is near EoL (which is different from SoC). In fact it can dip so low that the engine will not crank. As the dead battery accepts some charge, the bus voltage rises (even though the healthy battery gets discharged). Hopefully it will rise enough so that the engine cranks. (This phenomenon has been noted and alluded to by some people earlier.)

Now apart from the two batteries, there is another power source connected to the same bus:- the alternator. Its primary purpose is to keep batteries charged. To have it and not use, would in my philosophy, be ridiculous. And its output is more when it is revved!

Jump starting a car is not just about cranking the helpee car. It is about connecting (parallelling) two power sources, which at that point of time have different characteristics, which is never recommended, and hoping for the best.
We do not know the condition of the helpee vehicle. Keeping the engine on of the helper car is insurance, so that the helper does not land up needing help itself. Revving the engine of the helper is to bring into play the third source of power, the alternator, to help in charging the discharged battery, and thereby help with the bus voltage. Not really to supply power to the self starter.

Others might have different philosophies. Including praying to God while cranking, or pummelling the steering wheel while mouthing obscenities. Whatever works for that person!

One point which can give rise to a lot of esoteric hairsplitting: What is a dead battery? I think we'll go with a commonsense* approach: n the not so distant past, this battery was cranking/ starting the car. Now it is not.

* As we have seen just a few posts back, not everything can be answered with just commonsense. Some amount of extra knowledge is needed. But in this particular case, I think this commonsense definition of a "dead battery" will suffice.

Regards
Sutripta
Sutripta is offline   (2) Thanks Reply With Quote
Old 10th May 2016, 19:34   #183
BHPian
 
TheTeacher's Avatar
 
Join Date: Feb 2013
Location: Space-Time
Posts: 473
Thanked: 312 Times
Default Re: Car Battery: Dos and Don'ts!

Most interesting, thank you gentlemen for your erudition!

Somewhat OT: alternators put out alternating current. How / where is it rectified? The AVR?

More OT: Timeline: 1960s, '70s, early '80s. We were always Ambassador owners and did long trips quite often. Batteries would die quickly. There was one auto electrical specialist in Chennai those days, and batteries were sourced from them. They suggested turning on the headlights when on the highway to reduce charge into the battery from the dynamo. This didn't help. They then took to fiddling with the cut-out etc; if I remember right, those were the "esoteric Lucas CV regulators". The driver would take the car to the auto electrical place before the trip; they would make some adjustments; after the trip, the driver would go there again to get things set back to "normal". We never had problems with batteries or dynamos after following this practice.

Last edited by TheTeacher : 10th May 2016 at 19:41.
TheTeacher is offline   (1) Thanks Reply With Quote
Old 16th May 2016, 22:36   #184
Distinguished - BHPian
 
Join Date: Jul 2009
Location: Kolkata
Posts: 3,302
Thanked: 1,689 Times
Default Re: Car Battery: Dos and Don'ts!

Quote:
Originally Posted by TheTeacher View Post
Somewhat OT: alternators put out alternating current. How / where is it rectified? The AVR?
By two sets of three diodes commoned together (diode trio).

Quote:
More OT: Timeline: 1960s, '70s, early '80s. We were always Ambassador owners and did long trips quite often. Batteries would die quickly. There was one auto electrical specialist in Chennai those days, and batteries were sourced from them. They suggested turning on the headlights when on the highway to reduce charge into the battery from the dynamo. This didn't help. They then took to fiddling with the cut-out etc; if I remember right, those were the "esoteric Lucas CV regulators". The driver would take the car to the auto electrical place before the trip; they would make some adjustments; after the trip, the driver would go there again to get things set back to "normal". We never had problems with batteries or dynamos after following this practice.
Discussions about dynamos and its regulators should belong in the vintage and classic car section! However a few point:

The "esoteric cutout" was phased out around the late 60s. It was easily identified by its two coil internal structure, and externally by its rounded cover being held with a wire clamp. It was replaced by the (much better) three coil design.

The "switch on headlights on long runs" was another piece of widely repeated misinformation based on misconception. It had to do with how the ammeter was wired in the Ambassador.

Regards
Sutripta
Sutripta is offline   (1) Thanks Reply With Quote
Old 21st September 2016, 16:09   #185
Senior - BHPian
 
sourabhzen's Avatar
 
Join Date: Jun 2012
Location: GURGAON
Posts: 1,420
Thanked: 1,147 Times
Default Re: Car Battery: Dos and Don'ts!

Help needed - the connectors that are attached to cables and connected to the battery are corroded are are about to break. How do I change them? is it required to take the car to authorized service center for the job?
sourabhzen is offline   Reply With Quote
Old 21st September 2016, 20:10   #186
BHPian
 
Join Date: Mar 2011
Location: Mumbai
Posts: 554
Thanked: 226 Times
Default Re: Car Battery: Dos and Don'ts!

Quote:
Originally Posted by sourabhzen View Post
Help needed - the connectors that are attached to cables and connected to the battery are corroded are are about to break. How do I change them? is it required to take the car to authorized service center for the job?
If you take it to a battery shop, they will have the necessary connectors and will do the job for you. no need to go to the SC.
Mortis is offline   (1) Thanks Reply With Quote
Old 21st September 2016, 20:17   #187
Senior - BHPian
 
R2D2's Avatar
 
Join Date: Oct 2008
Location: Punya Nagari
Posts: 1,361
Thanked: 405 Times
Default Re: Car Battery: Dos and Don'ts!

Quote:
Originally Posted by sourabhzen View Post
Help needed - the connectors that are attached to cables and connected to the battery are corroded are are about to break. How do I change them? is it required to take the car to authorized service center for the job?

If I were you I'd take the car to the ASC and get them replaced. Battery cables are not very expensive. And believe me, OEM cables last heck of a lot longer than the cheapskate cables the roadside battery dealers use.
R2D2 is offline   (1) Thanks Reply With Quote
Old 27th September 2016, 06:16   #188
BHPian
 
KALSANKRPAI's Avatar
 
Join Date: Apr 2012
Location: BANGALORE
Posts: 54
Thanked: 14 Times
Default Re: Car Battery: Dos and Don'ts!

Quote:
Originally Posted by saket77 View Post
Good points, in short, you need to cut down on everything that draw battery power when the engine is not up. You may include this in the list too:
What does a maintenance free battery means?

Last edited by SDP : 27th September 2016 at 13:28. Reason: Fixed broken quote tag
KALSANKRPAI is offline   Reply With Quote
Old 27th September 2016, 10:24   #189
Distinguished - BHPian
 
saket77's Avatar
 
Join Date: Dec 2012
Location: Ranchi
Posts: 2,969
Thanked: 3,061 Times
Default Re: Car Battery: Dos and Don'ts!

Quote:
Originally Posted by KALSANKRPAI View Post
What does a maintenance free battery means?
Well, if you are talking about wet cell batteries used in most cars, then I would say it is more of a marketing gimmick! At the most, an improvement over old technology.

See it like this: if you compare it with older generation wet cell batteries of the 80s and upto mid-90s which were mostly used in Ambys and Premier Padminis of the times, then they required to be topped up with distilled or demineralized water frequently. The water which was used to dilute the sulphuric acid inside was frequently lost during recharge cycles as they were either converted to gases as a chemical reaction, by means of evaporation and by boiling off. Due to these, topping up of water was a frequent affair.
However, the current gen batteries require less frequent top ups as some of the evaporation and boiling off situations are now controlled with better designs, materials and better engineering.
Due to this, they were pitched as 'maintenance free', mainly against the older gen batteries.
Gel/ AGM/ Non spillable etc batteries which do not have liquid electrolytes may be better examples of being 'maintenance-free'.

Regards,
Saket.
saket77 is offline   (2) Thanks Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Honda Civic : Maintenance, Service Costs and Must dos laluks Long-Term Ownership Reviews 7914 16th January 2017 09:57
VW Polo - Maintenance and Service cost and dos/don'ts gaurav_chopra04 Technical Stuff 1182 13th January 2017 01:28
Car battery life - How long did your battery last? shuvc Technical Stuff 781 9th November 2016 11:28
Effective Resume/CV creation ,dos and donts ,suggestions . black12rr Shifting gears 29 26th April 2011 00:55
A challenge - finish this old DOS game ! Hatari Shifting gears 21 12th April 2005 10:37


All times are GMT +5.5. The time now is 03:24.

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