By on January 4, 2019

Car Battery Jump Start: https://owner.ford.com/support/how-tos/under-the-hood/battery/how-to-jump-start-a-battery.html

TTAC commentator Towncar writes:

I just recently had a dead battery on the Town Car, so learning how to properly jump start a car battery has been on my mind. I’m telling you, there’s a lot to say on this subject once you get into it!

  1. Do you really have to put the negative clamp on some exposed part of the cars body, which will probably be inconveniently located and totally greasy, when the negative battery terminal is sitting right there, handy and probably clean enough to make contact?
  2. What about those things that are supposed to plug into the cigarette lighter and give you a jump that way — will they work or burn the car down?
  3. And those little pocket-size jump boxes — any good?
  4. Can you damage the electronics in a modern car with a jump? (Assuming you don’t reverse the clamps.)
  5. And have you seen those plugs they have in the grilles of some service vehicles — they just stick in a cord, the other end has clamps, and there you are. Why doesn’t every vehicle have a plug like that? A plug-to-plug connection would get around the whole clamp business anyway.
  6. Or why don’t cars just have two batteries?
  7. Or why don’t they all have battery run down protectors? Should you install one of those protector things if your car doesn’t have it?

Sajeev answers:

Talk about a loaded query!  Let’s do this thing:

  1. Yes because a spark can ignite a de-gassing battery. Granted I am SUPER GUILTY of this, but after a bit of Googling I learned my lesson. And all batteries vent, no matter the design? If you don’t have a clean ground, clean your engine and check the condition of your negative battery cable/grounds…killing multiple birds with two stones.
  2. I assume they work, just not with the speed you’d expect. Backfeeding juice is limited by the wire/fuse size, but hey, if I can backfeed power to a hurricane-damaged house with a gas generator wired via the dryer connection…why not?
  3. See #2
  4. Possibly but not likely: that’s what fuses (and fusible links, if equipped) are for.
  5. Cars are too expensive and littered with fail points as it is: no thank you!
  6. See #5 and keep in mind that many modern, fuel/emissions efficient sports sedans weigh not much less than your rather simple Town Car.
  7. Run down protectors are a good idea, but I’d never spend the money or time to install one on an older vehicle.  That’s what jumper cables in the trunk are for.

Final thoughts, Best and Brightest?

[Image: Ford]

Send your queries to [email protected]com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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73 Comments on “Piston Slap: Don’t Jump to Conclusions!...”


  • avatar
    FormerFF

    My father had a 1972 Porsche 911 that had two batteries. It wasn’t for redundancy, it was more a matter of it being easier to fit two smaller batteries rather than one large one, a 911 being a fairly small car.

    I’m not sure how well a reserve battery would fare. With something as large as a town car, there’s plenty of room to store a moderately powerful jump box in the trunk.

    Maybe the better question is why did the battery die? If the car is sitting for long periods of time, you should consider adding a battery disconnect switch. This works well in boats, and they sit unused for weeks at a time.

    • 0 avatar
      multicam

      Boats also use different batteries. They usually have deep cycle marine batteries designed with that in mind. My old Jeep came with one installed… didn’t last long, it was one of the first things I chucked

      • 0 avatar
        FormerFF

        There are both deep cycle and non-deep cycle marine batteries. The non-deep cycle ones are sometime referred to as “starting” batteries, because their primary purpose is to start the engine. These would be found in boats where there are no sleeping arrangements or trolling motors, such as runabouts and pontoon boats. Marine starting batteries are sturdier than are car batteries because of the pounding that a boat takes.

        Deep cycle batteries are designed to be discharged more before they are recharged, and are typically used in boats that have trolling motors or a cabin. Deep cycle batteries also show up in RVs and are used to run the lights and accessories in the living quarters. Many RVs and cruisers have both, a starting battery to start the engine(s) and a deep cycle battery to operate lights and accessories.

      • 0 avatar
        JMII

        Deep cycle batteries are designed for long continuous use, they are not optimized for the short, high amperage draw needed for starting. My boat has 3 batteries: two deep cycle, one starting. In a pinch the deep cycle can be used to start it up but its generally not a good idea.

      • 0 avatar
        Carlson Fan

        “Boats also use different batteries..”

        Not necessarily. Most single engine trailerable cruisers w/2 batteries are set-up from the factory with just dual purpose batteries. That’s what I run in my 250 SeaRay Sundancer. Start the engine or run the refrigerator, lights, vacu-flush head or anything else all night while your on the hook. Start the motor in the morning with the same battery. Much better than a starting and house battery.

    • 0 avatar
      ToddAtlasF1

      The ’72 911 had two batteries to offset the weight of the engine being in the wrong place.

      I visited two auto parts stores this weekend. For some reason, deep cycle marine batteries are about $90. That’s similar to what they were pre-Obama’s EPA, while car batteries the same size(i.e. Group 24) were starting at $120 for the shortest warranties and going up rapidly form there. I was in the business in 2005, and automotive batteries were half the price pre-Obama. Deep cycle batteries used to carry a premium. What makes automotive batteries a greater threat to the environment than marine batteries?

      • 0 avatar
        FormerFF

        A: What makes you think the EPA had anything to do with it?

        B: Now that it’s Trump’s EPA, shouldn’t the prices have gone back to what they were, if indeed the EPA was to blame?

        There were later versions of the 911 that had a single battery up front as well.

        • 0 avatar
          quaquaqua

          Don’t even bother engaging with Todd on anything political. Dude is so far gone it’s almost comical.

        • 0 avatar
          ToddAtlasF1

          A: The same reason lead was so regulated that toys with gas engines were pulled from shelves and small manufacturing was curtailed.

          B: Marxist judges are stopping most efforts to repeal Obama’s unconstitutional noose on our economy.

          The first 911s had lead ballast behind their front bumpers to offset the handling imbalance. Then Porsche lengthened the rear trailing arms to extend the wheelbase and shift the weight balance a bit forward, which allowed them to reduce the ballast to two batteries. Later, they fitted staggered tire sizes to reduce the dangerous handling traits of the 911. More recently stability control has played a role.

    • 0 avatar
      Bellerophon

      My first car was a 1957 MGA. it had a similar setup, but with 2-6 volt batteries in series (parallel?) to make 12 V.

  • avatar
    Lie2me

    I know it’s wrong, but I’ve always put black to black and red to red without issue except once when I was very young and in a hurry I mixed the two and regretted it terribly, a mistake you only make once

  • avatar
    cartime

    I’ve boosted a battery hundreds of times. Always black to black, red to red without issue. 24V, 12V, whatever it may be. I’ve also read not to boost motorcycles from a car but it always worked without harming anything. Some things may be possible, but not probable.

    • 0 avatar
      brn

      I’ve always felt that particular guideline was extremely pessimistic. They tell you this, just in case circumstances are perfect to cause the issue.

      Hundreds?

      • 0 avatar
        cartime

        I work construction in Canada. Quite often there’s a vehicle sitting in the cold that will need a boost. It’s much simpler now having portable booster packs available. Just this week my Wife’s car battery stopped holding a charge and I probably boosted it four or five times before we could get it replaced under warranty. My old truck did the same last year.

    • 0 avatar
      six42

      Re motorcycles. I always boosted mine from a car battery but always with the car off. My bike had external terminals for easy access, too.

    • 0 avatar
      Russycle

      Speaking of motorcycles, I decided to take mine out for a spin yesterday since the thermometer was flirting with 60 degrees. I have it on a battery tender,, but when I tried to start it turned over a couple times then ran out of juice. Put it back on the charger for a couple hours, tried it again, and it fired right up. Any theories as to why?

      • 0 avatar
        SunnyvaleCA

        Russycle,
        Maybe you had it on a normal battery charger? Mine will run for a certain number of hours and then shut off. If that is the case, maybe you put yours on the charger a month ago, it charged everything up, then shut off for the next 29 days, which allowed your motorcycle battery to slowly run down.
        Can you “push start” a motorcycle? Maybe you have enough slant in your driveway to get it going that way.

        • 0 avatar
          Russycle

          It’s a charger/tender, supposed to charge it up then keep a maintenance charge going once it’s full. I suspect it’s less than perfect, so as you say, once the first start attempt knocked down the battery the tender went to “charge” rather than “maintain” mode and charged it up.

          I used to push start my 125cc dirtbike, but haven’t tried a bigger bike. Probably should practice, good skill to have when you need it.

      • 0 avatar
        mason

        Are you sure it wasn’t just a loose connection?
        If your battery was dead it generally takes several hours at .75- 1.25 amps for a battery tender to charge even a small battery. And that’s assuming there is enough voltage in said dead battery. Battery tenders need a sensing voltage or they won’t initiate a charge.

      • 0 avatar
        Erikstrawn

        I’ve been looking into buying a battery maintainer and one of the issues I read about was batteries drying out. If your battery is the unsealed kind, check to ensure it still has water.

        Also, could be a sulfate problem. I just ordered a desulfator to try and revive three Optima batteries.

      • 0 avatar
        carguy67

        How old is your battery? I’ve had batteries perform intermittently–i.e. they work one time, not the next–when they’re at the end of their lifespans. Also, it might have been just a bit warmer on the second attempt, or the first attempt ‘loosened’ up the oil just a bit.

  • avatar
    Jeff S

    I made that same mistake on a riding lawn mower. The battery was toast after that. I will never make that mistake again.

  • avatar
    Land Ark

    My stepdad nearly set our Olds Custom Cruiser alight connecting negative to negative. It worked fine to get it started but he didn’t pull the cables off fast enough and smoke started pouring out of the car.

    I have done it when attaching it to a proper ground wouldn’t work, but I always touch the clamp on the terminal without clamping it and pull it away as soon as it either fires or doesn’t.

  • avatar
    deanst

    Another great reason to have a manual transmission – just push start. But I learned the hard way that it’s very hard to get enough momentum on snow covered roads!

    On a related note, anyone have any idea why a battery terminal would quickly attract layers of corrosion on the terminal? After installing a new battery, I’ve got lots of corrosion within weeks…..

    • 0 avatar
      multicam

      I’m not sure why, but one preventative measure you could take is to put a thin layer of dielectric grease on the terminal. It should help.

    • 0 avatar
      FormerFF

      It’s really hard to push start a car when you are by yourself, and most bystanders aren’t really willing to get involved.

    • 0 avatar
      FormerFF

      Corrosion is usually caused by battery acid seeping up the terminal. Did you get a packet of grease from the auto parts store and put it on the terminal?

      • 0 avatar
        JMII

        With modern cars, even manuals, there are so many computer sub systems I’m not sure you could use the old push start / pop clutch method to get one running. If you did get fired up but the battery was still bad (IE: not holding a charge) your dash will turn into a Christmas tree with all the lights from the various electronic systems failing due to low voltage. We learned this when my brother’s VW Golf R died on track due to battery problems.

    • 0 avatar
      dukeisduke

      Batteries, even never ones, don’t usually have a perfect seal between the posts and the case, so you’ll get some vapor or acid leakage around the posts.

      I always use the co-pro felt rings around the posts, and the terminal spray. The spray was usually the red stuff, but the the newer stuff is brown colored, and seems to be oil-based.

    • 0 avatar
      Funky D

      Modern computerized cars require about 10.5V just to run. So no amount of push starting will help you if your battery falls below that. In the old carbureted days, you only needed enough juice to fire the spark plugs (even 8V would suffice for this).

      • 0 avatar
        ToddAtlasF1

        What’s your cutoff for when cars started being modern computerized cars? I had a short in my 2007 Honda’s battery that rendered it so dead that there were zero signs of life prior to me dropping the clutch in second and driving it to the store. When I turned off the ignition, immediately there were no signs of life again. No red light on the dash, no dome light, no radio memory. I drove the car two more times like that before putting in a battery and confirming that it was the only problem.

        • 0 avatar
          Lie2me

          Really? I’m with Funky D in thinking you couldn’t actually push start a modern car. This surprises me

          • 0 avatar
            FormerFF

            I helped bump start a friend’s S2000 a couple of times, where the battery was pretty dead. It seems like if you can get the engine to catch, the car will run unless there’s a dead short in the battery.

          • 0 avatar
            Hummer

            See I thought the same thing, no way you could push start a modern car, tried in my dad’s old 2010 Mazda 3, low and behold it works.

            With push button ignition I highly doubt it’s possible to do it in my SS sedan but it does make me want to try.

          • 0 avatar
            ToddAtlasF1

            The S2000 has a starter button, but it literally just engages the starter. My DD Audi A6 had a start/stop button, which is something else entirely. Unfortunately, when a friend let me drive his S2000, I pushed the starter button to shut off the engine which merely engaged the starter instead. Embarrassing and nasty.

    • 0 avatar
      carguy67

      re: “… After installing a new battery, I’ve got lots of corrosion within weeks…..”

      Corrosion forms when the electrolyte–i.e. sulfuric acid–leaks. Unfortunately, you got a ‘leaker’ off-the-shelf. Most batteries these days are made in Mexico, where the quality/control is, er, suspect (I was told this by a starter/generator rebuilder who is Mexican-American). You can try using one of the ‘battery protector’ sprays–a type of paint–or the red/green absorbent pads that go under the terminals, but your best bet is to get another, esp. if you’re still under warranty.

  • avatar
    Flipper35

    We have one of those booster kids for our 16 year old and it has circuitry to protect you if you happen to reverse the polarity (you know, to save the day laddie). She left the lights on one day at school and drained the battery. My mother in law tried to help her connect it but they couldn’t find a good ground on the truck. Daughter said connect right to the battery but MiL wouldn’t do it. Thing is, had they done that it would have been perfectly safe as it would not create a spark because there is no continuity until you rotate the big switch. I finally got there and did both battery connections, flipped the switch and it started right up. You can keep it topped off in the car with a male-mae 12v cord.

    The TL/DR is they work just fine but you might have to wait a minute or two one you turn it on. When I used it the truck turned over fast enough after about 30 seconds.

  • avatar
    NeilM

    I wouldn’t worry much about direct connecting to the battery terminals as long as the battery is in a well ventilated area of the car. If it’s in a well, such as below the trunk floor where gasses might accumulate, caution says otherwise. However those vehicles — and we’ve had three of them — typically have remote jumper terminals in the engine compartment.

    I have one of those lithium battery emergency battery jumper thingies (Noco Genius Boost GB40, about $100) and they’re a great idea. This is a bigger unit, about 6x3x1-½ inches, that’ll start a car directly, without having to juice up the car’s flat battery first. It gives 1000 amps at 12V and holds its own charge for months. Has a built-in light for locating those elusive terminals in the dark, and automatic polarity protection for those who can’t figure out that red goes to the red.

    Everyone should have one of these.

    • 0 avatar
      FormerFF

      When my daughter takes her car to college I’m going to get her one.

      • 0 avatar
        PrincipalDan

        You reminded me of a former professor I had (way back during my bachelors) who told a story about his daughter having a flat on her VW Beetle while attending Purdue.

        She called him and said: “Dad, I’ve got a flat tire.” (Apparently she had never been taught how to change one.)

        He responded: “Well, last time I checked there are boys on that campus.”

        (Today there wouldn’t be a guarantee to find a young man who knew how to change a tire.)

        • 0 avatar
          Lie2me

          These days just finding the jack and spare is a chore. Then to figure out how the jack works is another chore

          • 0 avatar
            Kyree S. Williams

            Every car I’ve ever seen that includes a spare-tire kit shows you how to use it in the owner’s handbook. If you don’t have the handbook onboard the vehicle, it can likely be found online.

            I think it’s particularly important to consult the handbook when the jack points aren’t well-marked, so that you don’t bend the body trying to hoist the car at the wrong location.

          • 0 avatar
            Lie2me

            Kyree, next time I get a flat I will call you and you can talk me through it

        • 0 avatar
          gtem

          Back when my wife and I were first dating (long distance), she got a flat in her old S60, called a friend to help get the spare on, he couldn’t get the lug nuts loose. Some old timer walking down the street got them off (stood on the wrench I’d imagine). I’m all for being chivalrous and helping females and the infirm, but if I see an able bodied man on the side of the road, assuming the spare isn’t flat, buddy this is a basic life test: figure it out yourself.

        • 0 avatar
          Scoutdude

          As you may remember I’m a coach for a robotics team. I do get a number of “second children” who join the program. A couple of years ago I had the second kid and the mother told me about my former student. Seems she was away at her first year of college and came out to find a flat tire. She said I know how to work tools and that the spare and stuff should be in the back so she got out her owner’s manual and the instructions with the jack and did it.

          Now for my kids who took driver’s ed from the school, as a zero hour class had a homework assignment to change a tire. Don’t know how many parents just signed the form but my kids did it and they always help with the seasonal tire changes for their vehicles.

          • 0 avatar
            PrincipalDan

            @Scoutdude, my grandfather had 4 daughters (no sons). His requirement before he would allow them to take the driver’s test was for each of them to demonstrate proficiency with his 5-speed manual 1st gen Bronco and be able to change a tire unassisted on that same vehicle.

            I thought that was a pretty good standard.

          • 0 avatar
            Kyree S. Williams

            Er…hat’s unfortunate. Parents probably shouldn’t just sign the form saying their kids successfully changed a tire if they didn’t. If a parent knows how, they should teach their child, and if they don’t…the parent and child can learn together, on YouTube or from a neighbor.

            No one taught me how to change a tire. We don’t have an official driver’s ed program in my state that mandated it, so my parents didn’t show me how. They did teach me how to drive, though. I learned how to change a tire when mine busted on the highway, and I didn’t feel like waiting around for roadside assistance.

            Meanwhile, I’m happy that my ’15 Grand Cherokee has a full-size spare. It ain’t pretty, and it’s on a steel wheel, but it’s full-size. Meanwhile, the only other car I owned with such an arrangement was a ’14 Jetta SportWagen.

          • 0 avatar
            Scoutdude

            @Kyree, The driver’s ed classes my kids took were not state mandated curriculum. Yes you must have taken a driver’s ed class, to get your license before age 18. However the fact that my school district offered driver’s ed was not that common and for many the for profit schools are the only choice.

            The fact that changing a tire was part of the class was likely due to the fact that the teacher was a “car guy” in that she drove a not bone stock Miata. There was also a test on identifying the basic underhood service points, dipstick, oil fill, brake fluid ect.

          • 0 avatar
            Lie2me

            Kyree, have actually ever changed a tire? It looks easy on paper, but when you have to get out in 100 degree heat or 10 degree cold, rummage around for the owners manual, dig out the tire and spare… or you could call AAA

          • 0 avatar
            brn

            Last time I had to change a tire, I gave up. It was cold and starting to rain. I was on gravel and the little bottle jack couldn’t get the the car up high enough. Sure, hindsight says keep a 2×4 in the car, but I didn’t have one.

            Wound up paying $100 to a towing company to take care of it. Because it was part of an accident, insurance covered the $100.

        • 0 avatar
          FormerFF

          I’ve never tried to teach my older daughter how to change a tire, although I suppose I should. Her car has a spare, and the wheels aren’t too heavy, so I think she could pull it off.

          There are a lot of cars where most women would have a very hard time changing the tire. My wife’s Explorer has 20 inch wheels and those suckers are way too heavy for her to lift. She might be able to get the donut out of the spare tire well, but there’s no way she’d get the regular wheel and tire back in the luggage area.

    • 0 avatar
      six42

      I think you mean 1000 milliAmps, 1 amp.
      Those things are good if the battery is in good condition and only needs a little bit of a boost. Thick jumper cables are capable of moving far more current.

  • avatar
    sirwired

    Those little jump-boxes are just fine. They are nothing like the doo-dads that plug into your 12V port; they are just like the lead-acid jump boxes, but they use lithium batteries, which can deliver ridiculous amounts of current compared to a lead-acid battery of similar size. They can’t sustain it for very long without melting, but it’s adequate to jump a car. The convenience of the charge lasting for 6 months, and the fact it fits in the glove box is hard to beat.

    As a bonus, you don’t need to worry about finding a clean chassis ground OR reversing the terminals, as the cables don’t complete the circuit when not actively jumping and they have built-in reverse-polarity protection.

    • 0 avatar
      redrum

      Yes, this! I bought a $40 portable unit off Amazon and have used it several times. Easy hook up and always started the dead car right away. SO much more convenient than having to move a car nearby, untangle long cords, and wait for enough juice to flow.

    • 0 avatar
      SPPPP

      I like the little jump boxes, and they have bailed me out! The one thing I would mention is that there’s not a bunch of reserve capacity there, so you may only get one or two tries to start the car if you have a small jump box. You might consider getting the biggest capacity one that fits your space and budget, as Scoutdude said somewhere else on this page.

  • avatar

    What you really need is a mat. With different conclusions on it, that you can *jump* to.

  • avatar
    Jeff Weimer

    Many of the little battery boxes work great. I have two.

    They’re also good for recharging your phones and iPods if necessary and some have a flashlight.

  • avatar
    Kyree S. Williams

    Sidebar: A lot of cars have batteries in unconventional locations. Most BMWs have the batteries in the trunk or cargo area, beneath the cargo floor. My Cruze had the battery in the trunk as well, as did its Cobalt predecessor (I never owned a Cobalt). I’ve also seen some older GM cars, like our 1997 Riviera, that bad the battery under the back seat. My current ride, a late-model Grand Cherokee, has it under the front passenger seat…probably because that platform (on both the FCA and Daimler vehicles) is used in cars with massive engines that don’t leave a lot of space for a battery beneath the hood.

    I get asked all kinds of questions about how jump such a car. But cars whose batteries aren’t under the hood almost always have a positive jump post under the hood, usually marked with a red cover and a big “+” sign. For the negative, you just—yes—attach it to a piece of metal that’s attached to or part of the chassis.

    • 0 avatar
      JMII

      Very true, my ‘Vette has the rear battery setup (weight distribution), so under the hood there is a main red + connection but its hidden behind a plastic panel. As for the ground, you need to find an engine grounding strap, as the car itself is aluminum and composite materials so the “stick anywhere metal” doesn’t work. With all that said the owner’s manual actually tells you to connect directly to the rear battery via the terminals. So as usual RTFM for the best course of action.

      • 0 avatar
        Tele Vision

        My CTS-V has a front battery set-up ( lazy engineering ) and plenty of negative grounds, as nearly the only aluminum thing in it is the engine. I trickle-charged it last Winter using the battery posts and all went well. When the starter hit the mat a good ole’ push start got me to the shop to swap the starter out.

  • avatar
    probert

    The lithium booster packs work great. Do not leave attached to add charge to the battery. Attach the red terminal first, THEN the black, start the car and detach in reverse order.

    One trick a AAA guy showed me is to turn on your headlights and when you have a good jumper connection they will react.

  • avatar
    Scoutdude

    #1 while it is a good idea to use a part of the engine or the supplied tab the likelihood of a problem is low. Modern batteries don’t off gas much and if it is in a well ventilated area the likelihood of a dense enough concentration of H2 that will light is very very low.

    #2 Yes they work but they can blow the fuse as many modern cars have 10a or smaller fuses and small gauge wires thanks to the fact that they are not cigarette lighter sockets any more they are power points.

    #3 Yes the good ones are good, I’ve got a Blue Fuel unit (Napa branded Red Fuel from Schumacher that has started cars immediately that were to the point where the lights barely glowed and you’d just get a click when you tried to start. The bad ones are bad though as the Stanley unit I originally got for my daughter doesn’t cut it. In other words by the ~$100 unit not the ~$50 one.

    #4 Yes you can if you are using a vehicle that has a crappy charging system. Electronics are sensitive to voltage spikes and ripples and older alternators do not do as good of a job at controlling that as the modern ones do, in most cases. Using another car built since the computer age will not be a problem if done right.

    #5 Would be nice but packaging would be a pain as most people don’t want that big thing sticking out of their grill.

    #6 Many vehicles do have multiple batteries but if they are connected in parallel they’ll discharge at the same time and still leave you stranded, it will just take longer to drain 2 instead of 1, assuming the 2 are not significantly smaller than the 1.

    Motorhomes on the other hand have multiple batteries with them separated, with an isolator or dual battery relay, into starting and house batteries and some actually have a self jump start button that can allow the house batteries to be combined with the starting battery while the button is depressed.

    #7 I’m not aware of cars with a auto battery disconnect, but many do have a battery saver function that will turn off lights after a set amount of time. I’m guessing your TC is an older one as Fords have had a battery saver function starting back in the 90’s that includes the dome/reading lights. It has saved my butt as back in the day it was not unusual for my daughter to leave on her reading light.

    I’m with Sajeev in that I wouldn’t install it in an older car unless it was used by someone that has a habit of leaving lights on and running down their battery.

  • avatar
    Funky D

    As to #1, I’ve always gone negative to negative as trying to find a ground in today’s plasticky engine compartments is too much trouble. I always connect the dead battery first, THEN the live one. Never have seen even a little bit of fire.

    And a (maybe obvious tip). Carry a set of cables in EACH car you own, never smaller than 4-gauge and if you own a truck, at least 0-gauge (although those can be heavy and bulky).

  • avatar
    George B

    I’ve used the cigarette lighter plug plus a power supply to trickle charge a battery just a little too discharged to start the car. I don’t own a dedicated battery charger, but I have several different regulated power supplies both at home and at work. Set the power supply voltage to some voltage like 14V that’s safe for an extended time and set the current limit well under the fuse rating for the cigarette lighter circuit like 5A. Do something else for a couple hours and let the battery charge.

    I always end up connecting the jumper cables at the battery. It’s hard to find any other ground connection with a sufficiently low resistance to work other than the battery terminal.

  • avatar
    AlfaRomasochist

    I can’t believe nobody has mentioned this yet – the plug sticking out of the grill on service vehicles / etc is almost certainly an engine block heater. It has nothing to do with jump starting the car, though it makes cranking a lot easier by warming up the oil so you’re not trying to crank an engine filled with oil the viscosity of molasses.

    • 0 avatar
      Hummer

      On the other hand vehicles that have Warn disconnects on the front end can buy quick connect attachs with jumper cables and jump start your car without ever opening the hood or finding connect spots. They sell the quick connect fully built on the Warn site. A lot of vehicles already have the battery to winch end installed.

      But your right I didn’t even notice his comment about the block heater cord.

    • 0 avatar
      Scoutdude

      I don’t think they were referring to the standard 3 prong 15a 110v plug hanging out of the grill.

      My guess is they are thinking about the Anderson SB350 connector that is frequently bolted down and used for plugging in a set of cables to boost other cars. https://powerwerx.com/anderson-sb-connectors-sb350-350amp

  • avatar
    pwrwrench

    The potential problem with jump starting has to do with how low the charge (voltage) is in the battery needing the jump and how old it is. Long ago I worked at a new car dealership. This was the 1970s with the “Energy Crisis” and Malaise/Recession and cars were not selling. Often sitting at the port of entry for months before being transported to the dealers. Many batteries were low and cars would not start so they were rolled off the truck and into the service department. Most of them would start after the battery was charged for 30 minutes or so. Sometimes things got rushed so a fully charged battery was hooked up with jumper cables. The cables were usually left attached to the booster battery which was on wheels. The quick route was usually followed attaching the jumper clamps on the battery terminals of the dead car. More than once an internal spark happened inside the low/dead battery and it would explode. Chunks of plastic battery case and electrolyte (acid) sprayed around. Cars got sent to the body shop to repair damaged paint. One guy got lucky when a battery blew apart. The battery was in the cowl area near the windshield. Reaching over the engine to attach the cables his head was turned away. He would have got acid in his face. As it was we took him outside and rinsed him off with a water hose. His work shirt fell apart and he had some chemical burns on his arm.
    Similar things can happen using a car or truck battery to jump a motorcycle. A car battery has 10 times the amp capability of most motorcycle batteries. If the motorcycle battery is very low and or old the amps going in suddenly can cause the water in the electrolyte to separate into hydrogen and oxygen rather violently forcing the acid out of the battery. This can ruin paint and metal parts quickly.
    Use caution.
    I also like the small, roughly 6x3x1, battery jump units. A few years ago the battery in my van was a little too low to start it. I was at a store. I was just getting ready to call for assistance when a man got out of his truck carrying a little box and offered to help. I was skeptical, but kept quiet. He hooked the box up to my battery and it started the van immediately. I bought one a few days later. It has got me going if the lights got left on for a while and I have started others with it. Well worth the $60 in time saved waiting for AAA.
    Push starting: If the battery is very low or dead it depends on what type of alternator the car has. Some require 6-8V or more to start charging. Others will charge as soon as they reach enough RPM. Most of the time even with a dead battery that will not re-charge, the alternator will supply enough volts to run the electrical system.

  • avatar
    Carlson Fan

    My portable generator has a battery charger built in. But that’s a little big to carry around in a car. Just went to pull the Tahoe out of the garage tonight and the battery was completely dead. Think it hasn’t moved for 3-4 weeks. I just put a battery charger on it for an hour or so to get it started. That’s better/safer/easier than jumping it, just takes longer which no big deal if you got the time. Plus no way I’d jump it with the Volt. It may be OK but I’m not about to test the waters and find out!….LOL

  • avatar
    vladzdor

    I have a VW Phaeton. These all came with a dual battery setup — one for Starting and the other for Electronics, on either side of the trunk. Power is needed from both batteries to start the car, as the Electronics battery supplies the ECU. So if the first starting attempt fails to turn the engine over due to weak batteries, the car will automatically parallel the batteries during the driver’s second attempt to ensure sufficient power to start. So far, this has never failed to work even after months of idle time. In case both batteries are too weak to jump start the car, a chassis ground point and remote battery terminal post are provided under the hood.

    However, *why* is connecting to a chassis ground point safer than connecting to the weak battery’s negative terminal? Is there a lower chance of sparks? If so, why? Seems to me a chassis ground connection could still cause a very weak battery to explode as pwrwrench has described?

    Secondly, every jumper cable clamp I’ve seen has serrated copper jaws. But even with the best of intentions, only a couple of the copper points touch the battery nut. They don’t even manage to grab onto the actual metal battery post but only some nut on the connector attached to the post. Seems to me this will have very high electrical resistance and impede the 100s of amps needed during a jump start. And that should only get worse when connected to a chassis ground that is even further away from the battery post.

    • 0 avatar
      SPPPP

      The reason why the chassis ground point is theoretically safer is that it’s farther away from the battery. Many (most) batteries vent some hydrogen gas over time. Because the connection and disconnection of the final point in the jumper cable circuit can cause a lot of sparks, making the final connection farther away from the battery reduces the chance of a fire.

      Now, sparks inside the battery, I don’t think it would reduce the chance of that.


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