how to Boost start a car.

"Charles P" wrote

Either way makes no difference, how do you know that the boosting vehicle doesn't have a leaking battery which will blow up under the right conditions?

You, along with a million other posters on newsgroups, worry too much about boosting techniques. I've been in the trade, working as a licensed technician for over 20 years. I'm located in Canada, so boosting cars is somthing that we do "all" the time during the winter, whether it's our own vehicles, someones vehicle in a parking lot (most people here carry a set of booster cables in the trunk), or boosting dead heads on the lot at work. This is what I do, I will install the cables to the dead vehicle while the boosting vehicle is running....it doesn't matter. I'll then start the dead vehicle. If necessary, I'll get someone to rev up the boosting vehicle so that it is putting out as much amperage as is possible from the donor vehicle. It works, and in 23 odd years, I've never had any problems. So the lights dim when you put a load on the donor vehicle, that's normal, it's probably going to full field on the alternator in order to handle the load....so what, as long as you aren't running it that way for hours on end.....

Hook up the cables in the basic order that you first mentioned..."properly" and you won't have any problems.

Ian

Have you ever heard of a battery blowing up even when all 4 posts are directly connected?. I think it's another urban myth. Whenever i use jumper cables i just hook up pos post to pos post and neg to neg and when i disconnect i first blow real hard on the battery on the million to one chance some H2 is around.

You can do that, and indeed I have done that on cars that don't have a good groud connection, but you really ought to be careful 'cause if you

*do* get a spark...

oh, wait, I forgot who I was responding to. Never mind. Contunue with your present method, it's great.

nate

| |Either way makes no difference, how do you |know that the boosting vehicle doesn't have |a leaking battery which will blow up under |the right conditions?

A battery that is just leaking won't blow up, battery acid is not flammable. Explosions happen when the gasses from charging are ignited. So if it's been sitting with a dead battery, the chances of gasses having accumulated are very low. However, the hazard is when you disconnect at the receiving end first, after it's charged for a few minutes. So I'd say the removal order is the more important, due to the explosion hazard.

So, attach the donor ground last, and remove it first. Rex in Fort Worth

Having followed the instructions and failed to start the car too many times, I don't even bother any more

My order is

1) good (+) 2) bad (+) 3) bad (-) 4) good (-)

If you have a convenient decent ground (not the frame, but perhaps the starter housing, if accessible), I'm told the first method will work.

I start the car with the good battery before connecting the cables. This does require a little bit of care in not getting the cables or body parts caught in moving parts of the engine.

Not really. Perhaps if you jump started cars day in and day out, the additional wear would be a problem, but on an occasional basis you won't notice it.

There's all sorts of surges from a normal car electrical system -- the car's electronics are made to take it. It sometimes helps to open the throttle slightly on the good car, so it idles faster (and thus runs the alternator faster) -- I needed to do that starting up a truck from my Miata.

You could do that, but many times it won't work. And since the dead battery is drawing charge from the good one, and starting the car also discharges the good battery, you risk ending up with TWO dead batteries.

Actually, I *have* seen a battery explode from its *own sparks* from a bad pole connection, but that's another story. Still, it indicates that sparks from making the connections are a slight, but real, hazard. IMO, since they

*do* explode rather well (As in: "That blowed up *real good*!") and they *do* spray sulfuric acid around (Easy enough to get off your skin in a few minutes with only a residual second degree chemical burn, but *very* nasty on the corneas.) when they do, it's a hazard to be avoided.

The real reason you connect the negative remotely from the 'dead' battery is so you get the most power to the car's *starter* and not to the battery. Connecting directly to the battery takes much of the power to recharge it. If you think it doesn't make a difference, try experimenting yourself. You'll find that a ground connection to the engine block (alternator bracket, etc.) or the body will spin the starter faster.

Well, you ought to be real good at *that* part ...

-- C.R. Krieger (Been there; done that)

That would make sense, except the usual instructions are to connect to an unpainted frame member. This, IME, gets decent amounts of power neither to the battery nor the starter. Whether it would get more to the starter than the battery would depend on the ground strap configuration.

Though if I'm jump-starting a Miata, it's a moot point. There's two places to connect the cable; one the negative battery terminal, the other the other end of a ground strap that's connected to the negative terminal. The latter is hard to connect to and is near enough the battery that a spark there would be just as bad in the presence of flammable gases. Perhaps worse, because it's _above_ the battery and the danger is H2.

Instead of going back and forth, wouldn't it be easier and equally safe to make both connections at one car, then do the other car?

E.g., standing at the dead battery, one pair of plus and minus alligator clips in hand, visually confirm that the other pair aren't short circuited. Connect the ones you're holding to the dead battery. Then connect the other pair to the good battery. That's how I do it.

With the "siamesed" jumper cable I have, the paired alligator clips at each end of the cable are always close to each other. If only one is connected, the other can get into mischief when you move the cable to connect the other vehicle.

Years ago I used to make the final connection at a chassis ground away from the battery. Often it was difficult to get a good ground, though. Nowadays I make all four connections at the batteries. As soon as the last one is made, I tell the other driver to crank it. Right after the engine starts I disconnect, in no particular order. The cars are connected for only a few seconds.

I have never run my engine to jump someone, and never had trouble with insufficient juice. On the other hand, I never had someone with a big engine ask for a jump. I'd probably decline, pleading small car and aging battery.

Is explosive gas really a significant hazard in this context? If it were, it seems to me the jumper cable manufacturers would have to take countermeasures to avoid litigation these days. Say, a safety switch in the middle of the cable. Or maybe that's already done. I haven't shopped for jumper cables in years.

You make a good point and I guess the other point is that when you are hooking up one of the cars, the cables could be getting in mischief on the other side and touching each other. Even if you keep an eye on them, you never know what might happen.

Do you generally jump cars of similar size, or just smaller ones?

They put warnings on packaging. There are some more expensive cables that are impossible to connect backwords, the cables detect the polarity and adjust accordingly. They may have a switch in the middle as well.

A good tip I learned, and still do today, is to clip the neg of each end onto the insulation just behind the pos. That way you don't have the "live" ends dangling around and sparking off each other.

My order

1. Clip each neg clamp to the cable.
2. Holding "dead" end in left hand, pos to good battery.
3. Unclip neg clamp, and neg to good battery.
4. Pos to dead battery.
5. Neg to frame of dead car.
6. Start good car, run at idle, and start dead immediately. If it won't start, just wait a few minutes.

Of course, I'll get the chance to put it to a REAL test, when I move to Anchorage this summer.............

Peter

Hmmmm. I hadn't thought of that. Makes sense. Who wrote the comment for you.?

Probably not, because now you've got to make sure the two live ends up the cables don't touch each other or a piece of metal, which can be an issue when you've only got one pair of hands and you're using one of the two to make the connections.

Clamp one connection against the jumper's cable's insulated wire and you won't have to worry about the two touching.

The only thing that matters is that the last connection not be to a battery. It'll generate a spark and if the battery is spewing hydrogen, it's probably a good idea for that spark to be to the car's frame away from the battery.

How to make on large light bulb filament in one easy lesson, clamp the clamp onto the cable insulation.

If the clamp is even half decent, it will eat/cut right through the insulation and the wire will go incandescent.

I have seen that happen several times.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

No urban myth!

I have the scars to prove it too.

I had one blow up in my face once when disconnecting the battery after a highway drive.

The vehicle would discharge overnight so I disconnect the battery every day.

It put pieces right through the hood, pieces sliced me in the cheek and eyebrow and covered me with acid. I was lucky and there was fresh snow to dive into with water only 6' or so away.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Sounds like a great way to damage the cable.

PATH of least resistance. And it actually flows proportionally to the resistance of the path. You implicitly assume that the wiring between ground points has no resistance, which is not true in real cars.

To play safe, CHARGE the battery of the larger car, that is, * connect the cables * start your car and run it at high idle for several minutes thereby CHARGING the other battery * DISCONNECT one end of the NEG cable * start the LARGER car * If it starts, OK. Disconnect all cables and shake hands. * If it doesn't, take the key out of the LARGER car and CHARGE more. * Repeat if necessary.

I've learned this a long time ago, and it DOES work. Alex

Buy any of the dozen or so rechargeable jumper packs available on the market. Red to red, black to black, switch on, start the car, throw the pack back in the trunk and go.