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I have a clueless car question.


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#1 Norville

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Posted 20 June 2012 - 10:17 PM

I don't drive, so don't know much about cars. Mom's been sick for a while, not up to driving, so she wanted me to run her car a few minutes daily or so, to keep it going. Well, it was... then it began to start with difficulty, and now it won't start at all. It sort of clicks and rattles. I hope this is something as simple as the battery needing to be recharged or replaced, which we thought some daily engine-running would prevent. I suppose running it drained the battery, which could mean the alternator needs fixing. (I wouldn't have damaged the engine by running it without driving it, would I? The Check Engine light goes on, but actually, all the lights go on.) It's a 1989 BMW, quite a good old car for the most part, and I hate to think I may have helped kill it. (The ironic thing is that, in books, I often read the description "killing the engine" when turning the car off, and when I turned it off the other night, I thought, "Killing the engine now... and I hope that's not literal." And it was...)

Yeah, I know, call AAA... I'll do that, but wanted to get some advice first.
"The dew has fallen with a particularly sickening thud this morning."
- Marvin the Paranoid Android, "Hitchhikers Guide to the Galaxy"

Rules for Surviving an Autocracy
Rule#1: Believe the Autocrat.
Rule#2: Do not be taken in by small signs of normality.
Rule#3: Institutions will not save you.
Rule#4: Be outraged.
Rule#5: Don't make compromises.
Rule#6: Remember the future.
- Masha Gessen
http://www.nybooks.c...s-for-survival/

#2 M.E.

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Posted 21 June 2012 - 09:30 PM

The only thing I can think of, Norville, is that you must have left a light on somewhere on/in the vehicle because you are correct.  It will not run the battery low if you just idle the car in park for a few minutes a day. :dontgetit:

#3 offworlder

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    pls don't kick offworlders, we can find a place too

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Posted 22 June 2012 - 10:28 AM

that clicking is the starter not having enough juice to turn over the motor
;)
I have had that many times with a car I leave parked b/c of troubles, and just run it only a lil or not at all; then the battery goes down; rem that idling does not charge the batt; you must drive for at least twenty minutes to give the alternator time to do some charging and then only a bit, not really charge the batt but not let level go more down;
that's why I have a home charger, plug in and clip onto batt terminals, charge it up; any car you don't drive regularly.
:harper:
"(Do you read what they say online?) I check out all these scandalous rumours about me and Elijah Wood having beautiful sex with each other ... (are they true?) About Elijah and me being boyfriend and boyfriend? Absolutely true. We've been together for about nine years. I wooed him. No I just like a lot of stuff - I like that someone says one thing and it becomes fact. It's kind of fun." --Dominic Monaghan in a phone interview with Newsweek while buying DVDs at the store. :D

#4 Norville

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Posted 22 June 2012 - 03:25 PM

Not at all, M. E. -- I didn't leave any lights on.

Uggh... maybe I need to acquire a home charger and learn how to use it!
"The dew has fallen with a particularly sickening thud this morning."
- Marvin the Paranoid Android, "Hitchhikers Guide to the Galaxy"

Rules for Surviving an Autocracy
Rule#1: Believe the Autocrat.
Rule#2: Do not be taken in by small signs of normality.
Rule#3: Institutions will not save you.
Rule#4: Be outraged.
Rule#5: Don't make compromises.
Rule#6: Remember the future.
- Masha Gessen
http://www.nybooks.c...s-for-survival/

#5 Orpheus

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Posted 23 June 2012 - 01:28 PM

Oops. Sorry I was sure that the gearheads would have answered this question quickly and correctly by now.

Starting a car and idling it a few minutes each day will absolutely and inevitably drain the batteries.

Starting it takes a significant fraction of the battery's stored charge. With a strong battery, warm conditions and a well-tuned engine, it may just be 5% of the battery's full charge; in winter with an out of tune engine and weak battery, it may be 1/3 - 1/2 of a "full charge". I've seen batteries, near the end of their life, that could readily start the car once, but if you fiddled and diddled, tentatively starting instead of giving it a full solid go, you'd fritter away that charge and that opportunity. Starting a car can take 100s of amps for up to 20 seconds, at atime whenthe battery is 'cold' and least willing to deliver full power (hence the importance of the Cold Cranking Amps [CCA] rating]

Idling a car may not restore appreciable charge -- maybe just an amp or two over the car's own minimal needs -- to provide more power would be wasteful 99% of the time. Starting an engine and then idling it a few minutes represents a net loss per cycle. Back in the day, they used to say "don't turn off a jumped car until you've driven it around for 20 minutes", but back then engines were bigger and more powerful relative to the power needed to turn the alternator; idle RPM (how fast the engine spins while idling) were a larger fraction of cruise RPM; etc. Today's electrical systems adjust the power being generated by the alternator (which corresponds to mechanical energy being produced by the engine, and hence fuel burned) until it is just an amp or two above what the car's own electronics need -- and modern car electronics need much more -- back in the day you could actually remove the battery from many cars once they started, and they'd keep running. As a result, a good solid drive every month or two becomes more important.

If you take a perfectly healthy car, and  start/idle it a few minutes every day, the battery will be dead in 7-10 days, maybe 2 weeks if you're lucky. Fortunately, this does not *generally* harm much beyond the battery (though todays more sophisticated car electronics carry a certain risk of a glitch or problem every time you jump them -- you may do it dozens of times without problems --or only twice-- before you "catch a glitch, and though fixing that glitch is usually as simple as disconnecting the positive battery terminal overnight (if you even need to do that much), they aren't called glitches for nothing. There's a small possibility of blowing an Engine Control unit or somesuch.

There's a lot more to say, but I'll summarize: when you start the car, drive it for a while. 10-15 minutes on the expressway in the spring/summer is often more than enough, but on some cars that's just a delaying action, but still very worthwhile, meaning that your battery will still end up drained but once every couple of months instead of each week. That's a big difference -- it means 2-3 jumpstarts all "winter" and much less hassle and risk of damage. Start-stop in-town driving may require 20 min or more. That's 20+ min at a single stretch, not "10 minutes to the store, for a quick grocery run, and then 10 min back".

There are many variables to consider, but the biggest ones are :1) how easily does the engine start (temperature and length of storage factor into this); 2) the ize of the engine and alternator (but modern electronics make those simple statistics less important, because they "regulate" the excess power); 3() the condition of the battery (which is damaged slightly each time it fully discharges, which it never does in routine operation) and the quality of the battery to begin with. I could tell you stories about Batteries That Simple Would Not Die (even after being shuffled between several consecutive cars that needed daily jumps until they were finally fixed)  and batteries that Simply Wouldn't Live -- basically feeble pansies that failed on the first overcast day after installation, whatever their warranty.

One tip: get a can of starter spray ($1-2) and learn to use it. This will often save you a jump start. It contains ether and other super-ignitable substances (even explosively ignitable --ether makes gasoline look like baby oil, so treat it with respect!!!), and a 2-3 second spritz into the air intake can often get an engine started if it will turn over at all. Once you get it started, run it until the battery is charged -- recognize that you just got a lucky break (albeit a fairly reliable one) and respect your luck. Don't push it.

If you can, get a trickle charger and plug it into a garage outlet. I've seen these sold for as little as $5. All they do is provide a small safe current that keeps your battery charged between uses, which can be months apart. Honestly, I wouldn't fel at all bad going 2 months between starts, and would forgive myself 3 months, if I drove the car for a solid 20-30 minutes on those rare start-ups. You want to drive it long enough to drive off moisture and volatile organic acids of oxidation which form over time and the change of season. You can't do this forever, but think about it: 4 "seasonal" start-ups and drives adds up to a year. By then, the gas in your tank will be going bad and form "varnish" (a very bizarre  emulsive semi-liquid that must be seen to be believed). You can probably keep a car going for 2-3 years if you add a can of Sta-bil to a less than half-full tank of gas, and then fill'er up with premium to mix it thoroughly in, but seriously, by 2-3 years of storage, you really need a better game plan. At the very least,  take it on some longer drives --a seasonal roadtrip or some such-- because you can start having issues with your tires, belts, gaskets etc. if you go much past a year of total storage

#6 M.E.

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Posted 23 June 2012 - 01:41 PM

Sorry, Norville.

Looks like I was clueless as well.

#7 Norville

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Posted 23 June 2012 - 08:52 PM

Wow, Orpheus, thanks for the thorough reply! I was hoping someone would take some time -- glad you did.
"The dew has fallen with a particularly sickening thud this morning."
- Marvin the Paranoid Android, "Hitchhikers Guide to the Galaxy"

Rules for Surviving an Autocracy
Rule#1: Believe the Autocrat.
Rule#2: Do not be taken in by small signs of normality.
Rule#3: Institutions will not save you.
Rule#4: Be outraged.
Rule#5: Don't make compromises.
Rule#6: Remember the future.
- Masha Gessen
http://www.nybooks.c...s-for-survival/


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