erspert@athena.mit.edu (Ellen R. Spertus) (10/05/90)
I saw a car battery recharger for $60 in the Rand McNally map catalog. If your battery is dead, you plug this into your cigarette lighter, and it recharges the battery (enough to start) from a D battery. It seems like a neat idea. I have a few questions: 1. Has anyone used one of these? Any comments? 2. Can I build one of these myself? I've built computers, etc., before, and I have access to lab equipment. Anyone know where I could get plans? Thanks. Please direct follow-ups to the appropriate group or email me. Ellen
damian@wshb.csms.com ( WSHB employee) (10/05/90)
In article <1990Oct4.222556.20668@athena.mit.edu>, erspert@athena.mit.edu (Ellen R. Spertus) writes: > I saw a car battery recharger for $60 in the Rand McNally map catalog. > If your battery is dead, you plug this into your cigarette lighter, and > it recharges the battery (enough to start) from a D battery. It seems > like a neat idea. I have a few questions: > > 1. Has anyone used one of these? Any comments? I've heard of using a 9 volt battery plugged in the cigarette lighter to hold the data in the computer. But I've never heard of a "D" cell to start your car. First a D cell is only 1.5 volts all modern cars are 12 Volts DC. Even if you did hook up 8 d cells it would not carry enough current to start your car under perfect conditions. Second even if it did would the fuses and wire running to the cigarette lighter are far too light to carry the currents required to start a car. It just goes to show you the old addage "Buyer beware" > > 2. Can I build one of these myself? I've built computers, etc., > before, and I have access to lab equipment. Anyone know where I could > get plans? > With a properly maintained car there is no need for such a device provided you aren't prone to leaving you lights on. > Thanks. Please direct follow-ups to the appropriate group or email > me. > > Ellen -- Damian L. Centgraf II | "Take the key unlock the door" WSHB-Broadcast Engineer | "See what your fate might have in store" ...damian@wshb.csms.com | "Come explore your dreams creation" It's only impossible until it's not!| "Enter this world of imagination" - Rush
weverka@boulder.colorado.edu (Robert T. Weverka) (10/05/90)
A D battery has about 2 amp-hours at 1.5 volts. If you put this into your car battery most efficiently, and could retreave it without loss you would get about 7 amp-minutes at 12 volts. Your starter motor draws on the order of 100 amps(depends on the car). At best you could get a few seconds of cranking power.
jgd@rsiatl.UUCP (John G. DeArmond) (10/06/90)
erspert@athena.mit.edu (Ellen R. Spertus) writes: >I saw a car battery recharger for $60 in the Rand McNally map catalog. >If your battery is dead, you plug this into your cigarette lighter, and >it recharges the battery (enough to start) from a D battery. It seems >like a neat idea. I have a few questions: >1. Has anyone used one of these? Any comments? No, but I do have some comments :-) >2. Can I build one of these myself? I've built computers, etc., >before, and I have access to lab equipment. Anyone know where I could >get plans? The math does not add up. A typical D cell battery has between 4 and 6 amp-hours capacity if discharged to total exhaustion which you could not do easily in this application. Be generous and give the charging process 60% efficiency. Now ask the question, "would 2 to 4 amphours of charge in a 60 to 100 amp-hour battery make much difference?" Probably not except under ideal circumstances, which is how the product is tested. Plus you've got to assure that the dry cells are in good shape. If you've got enough presence of mind to do this over the long term, you could probably put that effort in to keeping the battery in good shape to begin with and remember to turn the lights off. A much better solution to this problem is to get one of these new batteries that are actually 2 batteries on one with a switch on top. run one down and flip the switch for the other. Or you could just install 2 batteries. That is my solution. Get a charging bridge from any RV shop and install a battery transfer switch to select which one is connected to the starter. Easy, straightforward and stone cold reliable. BTW, several racing component companies are now selling compact, dry batteries that consist of the GATES starved acid cells of the X capacity strapped together in a nice package. High surge capability, low weight and no acid to deal with. And it will relieve you of about $200 or so. John Pl -- John De Armond, WD4OQC | We can no more blame our loss of freedom on congress Radiation Systems, Inc. | than we can prostitution on pimps. Both simply Atlanta, Ga | provide broker services for their customers. {emory,uunet}!rsiatl!jgd| - Dr. W Williams | **I am the NRA**
phil@brahms.amd.com (Phil Ngai) (10/06/90)
In article <1990Oct4.222556.20668@athena.mit.edu> erspert@athena.mit.edu (Ellen R. Spertus) writes: |If your battery is dead, you plug this into your cigarette lighter, and |it recharges the battery (enough to start) from a D battery. It seems |like a neat idea. I have a few questions: Yow! Better yet, why not *replace* your car battery with a D cell. It'd be a lot cheaper, weigh less, etc. :-) -- Disposable diapers reduce diaper rash.
cs161fhn@sdcc10.ucsd.edu (Dennis Lou) (10/06/90)
In article <4179@rsiatl.UUCP> jgd@rsiatl.UUCP (John G. DeArmond) writes: >erspert@athena.mit.edu (Ellen R. Spertus) writes: >and flip the switch for the other. Or you could just install 2 batteries. But that's an extra 15 (?) or so pounds. On a Lotus Super Seven which only weighs 1100 pounds to begin with, that's a 1.5% weight increase (now that I think about it, there's really no place to put a 2nd battery anyway on a Super Seven :-) >BTW, several racing component companies are now selling compact, >dry batteries that consist of the GATES starved acid cells of the >X capacity strapped together in a nice package. High surge >capability, low weight and no acid to deal with. And it will >relieve you of about $200 or so. You can get Gates sealed 2 volt gel cells from Halted, Haltek or Gateway for really cheap. Is there a way to rig those up? -- Dennis Lou | dlou@ucsd.edu | "But Yossarian, what if everyone thought that way?" [backbone]!ucsd!dlou | "Then I'd be crazy to think any other way!"
larry@kitty.UUCP (Larry Lippman) (10/07/90)
In article <870@wshb.csms.com>, damian@wshb.csms.com ( WSHB employee) writes: > > If your battery is dead, you plug this into your cigarette lighter, and > > it recharges the battery (enough to start) from a D battery. It seems > > like a neat idea. > > First a D cell is only 1.5 volts all modern cars are 12 Volts DC. Even > if you did hook up 8 d cells it would not carry enough current to start > your car under perfect conditions. As an interesting aside, I have seen a battery not much larger than two D-cells that *will* start a car with at least 200 amperes of cranking current. Sound far fetched? Not at all - this represents readily achievable energy density for a lithium-thionyl chloride battery. This type of battery is nothing to trifle with, however, since a short circuit can readily result in an explosion. Lithium-thionyl chloride batteries are used in military and aerospace applications, along with some limited use for industrial and implanted medical device applications. One of the pioneer manufacturers of lithium-thionyl chloride batteries, Electrochem Industries, is located not far from my organization in bucolic Clarence, New York. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 {utzoo, uunet}!/ \aerion!larry
atn@cory.Berkeley.EDU (Alan Nishioka) (10/07/90)
Just for the record... The Rand McNally catalog has a picture of the "D" Booster Car Battery Charger. It gives dimensions as 12"x18"x1.5" which is enough space to hold at least 12 D batteries or about 24 amp hours. The idea is to trickle charge your car battery, not to run your car off D cells, so melting wires and internal resistance isn't a problem. So it may work, but still I wouldn't buy it. ----------------------------------------------------------------------------- Alan Nishioka KC6KHV atn@cory.berkeley.edu ...!ucbvax!cory!atn
JXS118@psuvm.psu.edu (Jeff Siegel) (10/07/90)
In article <4179@rsiatl.UUCP>, jgd@rsiatl.UUCP (John G. DeArmond) says: (about car battery chargers:) >A much better solution to this problem is to get one of these new batteries >that are actually 2 batteries on one with a switch on top. run one down >and flip the switch for the other... Anyone use these batteries in their cars? I've wonder how they keep both batteries charged without having both batteries supply current across the output terminals. +-----------------------------------------------------------------------+ | Jeff Siegel | "Never, never turn the brightness & | | 24 Atherton Hall | contrast up all the way on an HDS | | 862-5124 | terminal in inverse video mode.... | | JXS118 @ PSUVM.BITNET | POOF! | +-------------------------------+---------------------------------------+
willie@iuvax.cs.indiana.edu (william hunt) (10/08/90)
erspert@athena.mit.edu (Ellen R. Spertus) writes: >I saw a car battery recharger for $60 in the Rand McNally map catalog. >If your battery is dead, you plug this into your cigarette lighter, and >it recharges the battery (enough to start) from a D battery. It seems >like a neat idea. I have a few questions: >1. Has anyone used one of these? Any comments? >2. Can I build one of these myself? I've built computers, etc., >before, and I have access to lab equipment. Anyone know where I could >get plans? >Thanks. Please direct follow-ups to the appropriate group or email >me. > Ellen Do not waste your money or time on anything that runs on batteries to charge a car battery. The energy storage of a car battery is many times that of a D-cell. Most recharging devices that plug into cigarette lighter are a joke. These devices can not transfer enough power quickly enough to get a car started without waiting a long time. Users are tricked into thinking these devices work well when actually the car battery itself recovered charge simply by letting it sit for 15 minutes. There are 2 exceptions to the cigarette lighter devices. Low Amp battery chargers that are used over night, and solar panels that are used on the dash during the day. The key with these devices is that they charge the car battery for many hours. My suggestion is to get a good pair of jumper cables for emergency situations. Get a pair with 4 or 2 guage copper wire, copper jaws, strong springs, two different color wires, and a least 15 to 20 feet long (batteries are always on opposite sides of the cars. Murphy's Law). The concern that most people have that hydrogen from the batterys can explode is not true. I have talked to battery engineers about that. What causes a car battery to explode is when the jumper cables are hooked up backwards. Do not be fooled by the colors of the wires in the car, always check the + and - marks on the battery or use a volt meter. I hope this info is useful. Willie Hunt
erspert@athena.mit.edu (Ellen R. Spertus) (10/08/90)
Oops. I messed up pretty thoroughly on that one. I guess I should admit what should be obvious to all of you, that I only know digitial electronics. Like most CS types, I took my analog pass-fail. :-) For those who are interested, this is was the ad said, so you can see it without my misparsing and misrememberances: Avoid jumper cables and tow trucks altogether with this 12-Volt "D" Booster Car Battery Charger. Simply plug it into your cigarette lighter and turn on the control switch. It recharges your dead car battery in 10 minutes and you don't even have to get out of the car, let alone open the hood! A must for winter drivers and people who forget to turn lights off. $59.95. I got many intelligent and detailed replies. Although several people told me to expect flames and that they had almost flamed me, nobody did (at least not in email --- I haven't read the groups). Thanks. In addition to electronics details (which I still have go through carefully to understand), I was told the following: - Consumer Reports wrote up these things and said they're no good. While it may get the battery to restart, you will then need to replace the car battery soon. - You should buy one of those car batteries with a reserve power supply. [Good advice, but I just bought a regular car battery.] - Join AAA if you're worried about needing recharges. [I have, but it's always quicker to find someone who'll let you do a jumpstart from their car than to wait for AAA. I have cables and know how to use them.] Since my concern was from leaving my lights on and not cold weather, I am now considering building a device I saw in a popular electronics magazine that buzzes if you leave your lights on. (I don't have the magazine with me but can give details to anyone who wants more information.) Of course, learning to triple-check that I turned off my lights might be easier. Thanks again, everyone, for help and no flames. I'll stick to NAND, etc., gates, and the occasional diode, resistor, or capacitor for a while. Actually, if anyone could recommend a good introductory analog electronics book, I'd appreciate that. Ellen Spertus
bill@videovax.tv.tek.com (William K. McFadden) (10/08/90)
In article <90280.102233JXS118@psuvm.psu.edu> JXS118@psuvm.psu.edu (Jeff Siegel) writes: >In article <4179@rsiatl.UUCP>, jgd@rsiatl.UUCP (John G. DeArmond) says: > >(about car battery chargers:) > >>A much better solution to this problem is to get one of these new batteries >>that are actually 2 batteries on one with a switch on top. run one down >>and flip the switch for the other... > >Anyone use these batteries in their cars? I've wonder how they keep both >batteries charged without having both batteries supply current across the >output terminals. They use diodes. You can buy a little device for charging two batteries from one alternator that keeps them isolated during discharge. The second battery is presumably used to power a secondary system such as an R.V. The advantage of this isolation is you can still start your truck if you accidentally leave the the lights on in your camper. Also, with appropriate switching, you can use the second battery to start your car if you accidentally leave the headlights on. The new 2-in-1 batteries incorporate two separate batteries, isolator, and changeover switch into one convenient package. The secondary battery is generally a lot smaller than the main one. Most allow you to connect both batteries in parallel for that extra oomph on cold mornings (just remember to switch it back, or you'll end up draining both batteries next time you leave your lights on). Consumer Reports recently examined these batteries and found they worked very well but were quite expensive. -- Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077 bill@videovax.tv.tek.com, {hplabs,uw-beaver,decvax}!tektronix!videovax!bill Phone: (503) 627-6920 "The biggest difference between developing a missle component and a toy is the 'cost constraint.'" -- John Anderson, Engineer, TI
hbg6@citek.mcdphx.mot.com (10/09/90)
In article <1990Oct8.150643.9818@athena.mit.edu> erspert@athena.mit.edu (Ellen R. Spertus) writes: > >Since my concern was from leaving my lights on and not cold weather, I >am now considering building a device I saw in a popular electronics >magazine that buzzes if you leave your lights on. (I don't have the >magazine with me but can give details to anyone who wants more In my wifes car, I installed a relay in series with the headlight relay that insures that if the key is off, the headlights are off. Interestingly, our '75 Volkswagen van has this feature built in but it only turns off the headlights, not the running lights. John
roy@phri.nyu.edu (Roy Smith) (10/09/90)
willie@iuvax.cs.indiana.edu (william hunt) writes: > Do not be fooled by the colors of the wires in the car, always check the > + and - marks on the battery or use a volt meter. I emphatically agree that you should not rely on the color of the wires! A few years ago, I watched a friend miss connect some jumper cables; fortunately nobody was seriously hurt (I did burn my hand a little tearing the cables off) but I imagine it could have been a major disaster. Upon questioning my friend as to why he did such a dumb thing, he protested that he hooked the red to the red and the black to the black; and sure enough, he almost had. Turns out that one car was brand new, and had a black insulated positive lead, and a bare copper ground strap. Since new, clean, copper has a reddish look, it's not to hard to see how he confused the two. A horrible example of human interface design, if you ask me! -- Roy Smith, Public Health Research Institute 455 First Avenue, New York, NY 10016 roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy "Arcane? Did you say arcane? It wouldn't be Unix if it wasn't arcane!"
roy@phri.nyu.edu (Roy Smith) (10/09/90)
erspert@athena.mit.edu (Ellen R. Spertus) writes: > Since my concern was from leaving my lights on and not cold weather, I am > now considering building a device I saw [...] Of course, learning to > triple-check that I turned off my lights might be easier. Having done this on at least one or two occassions, I'm sensitive to this issue. I never understood why it is *possible* to do that. Why don't the lights go out automatically when you turn the ignition off? All it would take is moving the feed to the lighting circuit to after the ignition "power on" relay (and maybe putting in a heavier relay to handle the extra load). For those rare times when you really do want to keep your lights on with the motor off, you could have some sort of positive action over-ride (say, requiring you to push or twist the light switch in some unusual way so you don't do it by mistake). -- Roy Smith, Public Health Research Institute 455 First Avenue, New York, NY 10016 roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy "Arcane? Did you say arcane? It wouldn't be Unix if it wasn't arcane!"
horvath@granite.cr.bull.com (John Horvath) (10/09/90)
All Saabs have this wiring, so when
the ignition is turned off && headlights are on
all lights are turned off.
the ignition is turned off && parking lights are on
the parking lights stay on
This is one reason why you will frequently see Saabs with their headlights
on, when the sun is shinning. There is no need to turn them off at
night and you forget about them the next day.ardai@teda.UUCP (Mike Ardai) (10/10/90)
In article <1990Oct8.201401.1742@phri.nyu.edu> roy@phri.nyu.edu (Roy Smith) writes:
[Suggests that the headlights should only run when the ignition is on]
-load). For those rare times when you really do want to keep your lights on
-with the motor off, you could have some sort of positive action over-ride
How about running the headlight relay off a circuit that is hot when the
ignition key is in either the 'on' or 'accessory' position?
/mike
--
\|/ Michael L. Ardai Teradyne EDA East
--- -------------------------------------------------------------------------
/|\ ...!sun!teda!ardai (preferred) or ardai@bu-pub.bu.eduih@udel.edu (Charlie Ih) (10/10/90)
In article <63220@iuvax.cs.indiana.edu> willie@iuvax.cs.indiana.edu (william hunt) writes: >erspert@athena.mit.edu (Ellen R. Spertus) writes: > >>I saw a car battery recharger for $60 in the Rand McNally map catalog. >>If your battery is dead, you plug this into your cigarette lighter, and >>it recharges the battery (enough to start) from a D battery. It seems >>like a neat idea. I have a few questions: > >>1. Has anyone used one of these? Any comments? > >> Ellen > >Do not waste your money or time on anything that runs on batteries to >charge a car battery. The energy storage of a car battery is many >times that of a D-cell. Most recharging devices that plug into >cigarette lighter are a joke. These devices can not transfer enough >power quickly enough to get a car started without waiting a long time. >....... >Willie Hunt Actually this is technically feasible and may well be practical if it is properly designed. By the way, I am in no way connected with any of the vendors. I am a profession teaching electronics. I, like many of you, intuitively feel this is not possible. But let's look the numbers. Let's assume, on the average, you crank the car 3 times at a duration of 5 sec. each to start a car. The cranking current is 250 amp. This is worth 1 Amp-hr of charge. So you can see, you don't need that much energy to start a car! The typical battery capacity for a small or medium size car is 40 Amp-hr. So you need only 2.5% of the capacity to start a car. Believe of not, the capacity of a D-size Alkaline battery is about 15 Amp-hr (see FEDCO Electronics, Inc. catalog/data sheet (1-800-542-9761), I happen to have the data sheet at my hand). Therefore a single D-cell, in theory, has enough energy to start your car (15 amp-hr at the average of 1 volt has more energy than that of 1 amp-hr at 12v). If you use 8 of them, the total voltage is about the same as the car battery. The car battery charging efficiencey is about 80% (charging at 15 v and discharging at 12). The efficiency of the electronic charging/booster circuit (since the two voltages are approximately the same, less than 1:2) can be easily between 80%-90%. Therefore the overall efficiency is between 64% - 72%. Let's say it's 50%. Therefore if you use 8 D-cells, you can transfer 7.5 amp-hr to the car battery (18.8%). If your battery is still has 10% charge left, after charging by the D cells, it almost has 30% capacity. If the battery is healthy, I am sure it can start your car. Even it is completely discharged, 2 sets (16, approx. $16) batteries will start your car. It may take 30 to 60 minutes to charge the battery. (Twice I called AAA, min. waiting time 4 hr.) The charging/booster circuits are widely used in UPS (Uninterruptible- Power-Supply). Many IC circuits with voltage and current liminting feedback for the booster circuits are available (please check the electronic catalogs, don't ask me). This charging circuit can squeeze the last drop of charge out of your D-cell. If you want to build the circuit for fun is OK but not to save money. I cannot count on the reliability of the circuit I built (without endurance tests).
rdb@mtunf.ATT.COM (Ron DeBlock) (10/10/90)
In article <1990Oct8.201401.1742@phri.nyu.edu> roy@phri.nyu.edu (Roy Smith) writes: <erspert@athena.mit.edu (Ellen R. Spertus) writes: <> Since my concern was from leaving my lights on and not cold weather, I am <> now considering building a device I saw [...] Of course, learning to <> triple-check that I turned off my lights might be easier. < < Having done this on at least one or two occassions, I'm sensitive to <this issue. I never understood why it is *possible* to do that. Why don't <the lights go out automatically when you turn the ignition off? All it <-- <Roy Smith, Public Health Research Institute Buy a Volkswagen. The headlights are linked to the ignition switch, but the parking lights stay on. A good battery will run the parking lights all day, and leave you with enough juice to start the car. -- Ron DeBlock N2JSO If God had meant for Man rdb@mtunf.att.com to see the sun rise, He !mtunf!rdb would have scheduled it later in the day.
crick@bnr-rsc.UUCP (Bill Crick) (10/10/90)
In article <1990Oct4.222556.20668@athena.mit.edu> erspert@athena.mit.edu (Ellen R. Spertus) writes: >I saw a car battery recharger for $60 in the Rand McNally map catalog. >If your battery is dead, you plug this into your cigarette lighter, and >it recharges the battery (enough to start) from a D battery. It seems AHAHAHAHAHAHAHAHAHAHAHA! I don't believe a word of it! Like booster cable replacements that plug into the cigarette lighter! Your starter requires somewhere between 80 -400 amps to crank your engine. There is no way you could get this much current out of a D cell, or through the 20gauge wire these boostr cable replacers use!!!! NOTE the current range is a guess, but we once measured a 3/4ton pickup at about 350amps! Bill Crick
roy@phri.nyu.edu (Roy Smith) (10/10/90)
I wrote: > Why don't the lights go out automatically when you turn the ignition off? rdb@mtunf.ATT.COM (Ron DeBlock) replies: > Buy a Volkswagen. The headlights are linked to the ignition switch, but the > parking lights stay on. A good battery will run the parking lights all day, > and leave you with enough juice to start the car. I *have* a Volkswagen (1980 Rabbit diesel, 125k miles). Maybe I had a marginal battery, but one night of running my parking lights in the winter was enough to kill my battery enough to prevent it from starting. The parking lights should be on the relay too. -- Roy Smith, Public Health Research Institute 455 First Avenue, New York, NY 10016 roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy "Arcane? Did you say arcane? It wouldn't be Unix if it wasn't arcane!"
ih@udel.edu (Charlie Ih) (10/12/90)
In article <32908@nigel.ee.udel.edu> ih@udel.edu (Charlie Ih) writes: >In article <63220@iuvax.cs.indiana.edu> willie@iuvax.cs.indiana.edu >(william hunt) writes: >>erspert@athena.mit.edu (Ellen R. Spertus) writes: >> >>>I saw a car battery recharger for $60 in the Rand McNally map catalog. >>>..it recharges the battery (enough to start) from a D battery... > >Actually this is technically feasible and may well be practical if it >is properly designed..... >after charging by the D cells, .... ..it can start your car. >...... >The charging/booster circuits are widely used in UPS (Uninterruptible- >Power-Supply). ... This charging circuit can >squeeze the last drop of charge out of your D-cell. I would like to add a few comments to my original posting. First I want to apologize if I had spoiled the fun of the lively discussions on this subject. The new alkaline batteries can be stored over an extended period (2 - 3 yrs) and still retain 80 - 90% of the charge. I hope the manufacture(s) who makes this devices also includes a simple voltmeter. It can be uaed to monitor the car battery while being charged and to check D cells to see if they need to be replaced. Markings such as "Fully Charged", "Good", "Weak", etc on the voltmeter would be nice so that everybody could understand the meaning of the readings. If someone have bought the unit, please let us know how well (or bad) it works. I believe if it is well designed and engineered, it should work pretty good.
otto@tukki.jyu.fi (Otto J. Makela) (10/15/90)
In article <63220@iuvax.cs.indiana.edu> willie@iuvax.cs.indiana.edu (william hunt) writes:
My suggestion is to get a good pair of jumper cables for emergency
situations. Get a pair with 4 or 2 guage copper wire, copper jaws,
strong springs, two different color wires, and a least 15 to 20 feet
long (batteries are always on opposite sides of the cars. Murphy's
Law). The concern that most people have that hydrogen from the
batterys can explode is not true. I have talked to battery engineers
about that. What causes a car battery to explode is when the jumper
cables are hooked up backwards. Do not be fooled by the colors of the
wires in the car, always check the + and - marks on the battery or use
a volt meter. I hope this info is useful.
A message from Finland, where jumper cables are common stuff (ever try to
start a car with a weak battery in 40 below zero ?).
Very good jumper cables are the ones used in arc-welding. You can actually
jump-start a large diesel truck with these (I know, I've done this). Anything
weaker than that just melts(!) when the kind of load a diesel starter engine
puts on it goes thru it (of course, many trucks have 24V systems, don't try to
jump-start one of these from a 12V car system...)
Caution is advised if you have an electronic ignition system on your car.
Some cheaper models can turn into smoke when jump-starting. Disconnecting
the positive terminal of the helping car should make things safe, but sometimes
you just have to take the risk if your battery voltage/amperage isn't enough to
give the required boost, and you are forced to leave your engine running.
--
/* * * Otto J. Makela <otto@jyu.fi> * * * * * * * * * * * * * * * * * * */
/* Phone: +358 41 613 847, BBS: +358 41 211 562 (CCITT, Bell 24/12/300) */
/* Mail: Kauppakatu 1 B 18, SF-40100 Jyvaskyla, Finland, EUROPE */
/* * * Computers Rule 01001111 01001011 * * * * * * * * * * * * * * * * */otto@tukki.jyu.fi (Otto J. Makela) (10/15/90)
erspert@athena.mit.edu (Ellen R. Spertus) writes: > Since my concern was from leaving my lights on and not cold weather, I am > now considering building a device I saw [...] Of course, learning to > triple-check that I turned off my lights might be easier. Over here in Finland (where the winters are cold, long and dark :-), most new cars come pre-wired so that you get 1/2-beams when you turn the ignition on. This is because even in broad daylight having your lights on will make you much more visible (most roads are 2-lane here, so you better see the guy coming at you when passing other cars...) I can assure you this is a pain when driving in central Europe, where everyone and their kid sister will blink their lights at you because you have your headlights on ;-) -- /* * * Otto J. Makela <otto@jyu.fi> * * * * * * * * * * * * * * * * * * */ /* Phone: +358 41 613 847, BBS: +358 41 211 562 (CCITT, Bell 24/12/300) */ /* Mail: Kauppakatu 1 B 18, SF-40100 Jyvaskyla, Finland, EUROPE */ /* * * Computers Rule 01001111 01001011 * * * * * * * * * * * * * * * * */
wb8foz@mthvax.cs.miami.edu (David Lesher) (10/16/90)
>Caution is advised if you have an electronic ignition system on your car. >Some cheaper models can turn into smoke when jump-starting. Disconnecting >the positive terminal of the helping car should make things safe, It's not clear if he means disconnect the jumper cable, or the *battery* cable. NEVER disconnect the battery on a running car. This is referred to as a "load dump" and generates the worst possible transient voltages. The battery is an essential low impedance element at frequencies above DC. Without it, the inductance of the field is such that the electronics will be history before the voltage regulator can get things down to where they belong. The best way to avoid problems is patience. Hook up the cars. Sit and let the weak one charge for a while. (10 minutes maybe) Once the other car is running, you can let the good car idle down, and maybe if you want, turn on all of its loads: headlights, heater, etc. Them disconnect the cables. For more details on load dumps, see the GE MOV Engineering Handbook. -- A host is a host from coast to coast.....wb8foz@mthvax.cs.miami.edu & no one will talk to a host that's close............(305) 255-RTFM Unless the host (that isn't close)......................pob 570-335 is busy, hung or dead....................................33257-0335
streeter@theory.lcs.mit.edu (Kenneth B. Streeter) (10/16/90)
In article <1990Oct15.202407.13654@mthvax.cs.miami.edu> wb8foz@mthvax.cs.miami.edu (David Lesher) writes: >NEVER disconnect the battery on a running car. This is referred >to as a "load dump" and generates the worst possible transient >voltages. The battery is an essential low impedance element at >frequencies above DC. Without it, the inductance of the field is >such that the electronics will be history before the voltage >regulator can get things down to where they belong. >The best way to avoid problems is patience. Hook up the cars. >Sit and let the weak one charge for a while. (10 minutes maybe) This will give better results, and is practically essential in very cold weather. The jumper cables will simply not carry enough current to start a car -- a typical jump works by charging the "dead" battery somewhat so that the "dead" battery assists in the starting. >Once the other car is running, you can let the good car idle >down, and maybe if you want, turn on all of its loads: headlights, >heater, etc. Then disconnect the cables. It is best to disconnect the jumper cables shortly after the "dead" car has been started. Leaving the jumper cables connected when both cars are running makes the alternators "fight" one another for the correct voltage. This is generally best avoided, but it won't do any harm for short periods. -- Kenneth B. Streeter | ARPA: streeter@im.lcs.mit.edu MIT LCS, Room NE43-350 | UUCP: ...!uunet!im.lcs.mit.edu!streeter 545 Technology Square | (617) 253-2614 (work) Cambridge, MA 02139 | (617) 225-2249 (home)
bmp@cow.ecs.oz (Bruce Paterson) (10/16/90)
In article <13019@sdcc6.ucsd.edu>, cs161fhn@sdcc10.ucsd.edu (Dennis Lou) writes: > In article <4179@rsiatl.UUCP> jgd@rsiatl.UUCP (John G. DeArmond) writes: > >erspert@athena.mit.edu (Ellen R. Spertus) writes: > >and flip the switch for the other. Or you could just install 2 batteries. > I've heard of a setup which (on the flick of a switch) uses a lantern 12V dry battery to run your ignition while either your almost dead car battery slowly cranks the engine (without pulling the volts to the ignition so low that the car would never start anyway) or (if things are really bad) you push the car. The concept of using a dry cell to recharge your car battery enough is extremely hopeful, as a starter motor can draw up to 100 Amps (so that gives you about 1/4 turn rotation of the motor before you've exhausted your amp-hours). -- | /~~~~\ Bruce Paterson VK3TJN Company: Email Electonics | | / | Electronics Engineer ACSnet: bmp@cow.ecs.oz | | /-----/ /~~~~\ / / /~~~~~ /~~~~~/ bmp@ecs.oz | | / | / / / / /-----/ UUCP: ...seismo!munnari! | |/_____/ / /_____/ /_____ /_____ bmp@cow.ecs.oz |
minsky@media-lab.MEDIA.MIT.EDU (Marvin Minsky) (10/16/90)
In article <524@cow.ecs.oz> bmp@cow.ecs.oz (Bruce Paterson) writes: >I've heard of a setup which (on the flick of a switch) uses a lantern 12V >dry battery to run your ignition while either your almost dead car battery >slowly cranks the engine (without pulling the volts to the ignition so low >that the car would never start anyway) or (if things are really bad) you push >the car. Yes. I did this on a Volkswagen bug (6-volt) in the 60s. It worked fine. I used 4 standard D-sez flashlight cells and it worked every time, with a very weak main battery. 5 cells worked even better.
phil@ux1.cso.uiuc.edu (10/20/90)
I just read through this thread in one sitting. What I am curious about is why some people posted arguments that a D-cell cannot supply enough current to charge a car, when it was quite clear that the matter involved a device that charges the car battery over a period of time, in order to give you a few seconds of high current starting power. Think of the car battery as a power reserve. --Phil Howard, KA9WGN-- | Individual CHOICE is fundamental to a free society <phil@ux1.cso.uiuc.edu> | no matter what the particular issue is all about.
ih@udel.edu (Charlie Ih) (10/22/90)
In article <34700033@ux1.cso.uiuc.edu> phil@ux1.cso.uiuc.edu writes: > >........ when it was >quite clear that the matter involved a device that charges the car >battery over a period of time, in order to give you a few seconds >of high current starting power. > ...... Thanks for setting the fact straight. In my previous postings, I calculated that a single alkaline D-cell can transfer 1 amp-hr to the car battery. Modern electronics can do this readily and economically. That is enough to crank an average car (250 A) for 15 second. Since the posting, I timed my cars and it usually takes 2 - 3 second to start. So my previous calculation was very conservative. Of course using a single cell would take too long (appro. one hour). If we use 4, 6 or 8 cells, the charging time can be reduced to 5 - 15 min. The set of D-cell can be used several times. Charles S. Ih, University of Delaware.