In this column -Is it dangerous to jump start a dead battery - Cecil verifies that connecting directly to both battery posts of the dead car battery may cause an explosion due to leaking hydrogen gas from the battery.
I was hoping our brave leader would comment on the some changes in battery design.
Compared to years ago many car batteries are sealed instead of open. They neither require the addition of water nor do they appear to have the ability to vent hydrogen gas.
So what’s the scoop?
Also, it looks like someone (certainly not our brave leader, I’m sure) is falling down on the job.
I’m sure Cecil will be looking into who is undermining him, and inserting extra words in an attempt to make him look bad.
My girlfriend’s battery died the other day, and I attempted to jump it using my car. I connected + to + and - to her engine block. It wouldn’t start. Then somebody else came along, connected + to + and - to - and voila! Car started! So what happened there? Why didn’t he blow up and why wasn’t I the hero?
Incidentally, I am one of those who follows the instructions – meaning in particular that I attach the last negative connection to something other than the car battery – and I have never had a problem getting a car started in this fashion.
Did he disconnect everything and reconnect it all again? It could be that he just managed to connect it to the terminals better. Sometimes I’ve had to disconnect the cables and try again in a slightly different spot on the battery terminal in order to get it to work. It also could’ve been that you juiced the car up a little bit, but not for long enough. Either way, you still went home with the girl - right? 
While my wife was just about finished gassing up her convertible (with the top down) at a gas station, a truck was being jumped at the pump island across from her car.
When the battery exploded (which is quite loud), the two people (presumably incorrectly) performing the jump ran away. Their injuries are not known.
My wife finished up quickly and drove off, not really sure what had happened.
Later than day the damage from the exploding acid was obvious. She had slight red welts on her exposed skin, her clothes developed burn holes, the car leather was speckled and “burned through”, the paint was speckled and pitted. Because we couldn’t provide the other drivers license plate, we ended up paying our full insurance deductable, and it cost the insurance a few thousand dollars to replace the leather and re-paint.
I once mildly electrocuted myself jumping a car in the rain with only a vague idea how to do it.
But people I know seem to be usually pretty big on the “last connection to the engine block,” so the idea is out there.
I’m glad Cecil finally got around to answering this one. There was a GQ thread some years ago discussing it. Everyone claimed putting the cables on in the correct order (and places) was crucially important, but everyone had a different procedure. Every post refuted the previous one with, “No, my god, you’ll kill yourself.” Amusing in a scary sort of way.
After having about 10 cars in my life, ranging from utter crap to used-but-acceptable, I finally bought a car that was pretty close to what I really wanted: a BMW M3. OK, so I bought a 10 year old one, but still I’m happy. I was really enjoying this, except for the part about only really driving it for commuting back and forth to work, which on 101 near San Francisco doesn’t really allow for any challenging/fast driving very often. (On the weekends, we drive the 13 year old Acura because the baby seat fits in it 
).
Anyhow, I actually stopped commuting in it because I found the train was fairly convenient and allowed me to catch up on my reading to and fro, so it was sitting out front without being driven for quite a while, which inevitably caused a semi-dead battery. And then of course, one day, I was bound to oversleep and miss the train… (although actually it was waking up to about 1000 ants swarming some leftovers, but that’s kind of distracting.)
So I pull the wife’s car alongside mine, get out the jumpers, and life both hoods. Uh, where’s the battery on the BMW? WTF? I’m looking all over, there’s something that looks like it COULD be the battery, but it’s totally enclosed. Sure, I’ve got the manual… somewhere, but I gotta get to work. This has to be possible.
Now, growing up in Detroit, you learn to jump cars when you’re a wee one. I’ve done this a zillion times in the past. But there were always two pretty clear batteries! And yeah, actually, we’d usually TRY to attach one negative clip to someplace on the engine, but 90% of the time give up and connect the two batteries directly. But this was a new one.
So after a little more inspection, I noticed on the passenger side of the engine compartment there’s a small box labeled “+”. Open it up, sure enough, there’s a lone electrical post, about the size of a battery terminal. OK, that’ll work. I guess on this side, we’re definitely going for engine block as the other connection. And hey, whaddya know, there’s a really nice large metal flange (I believe actually used to hoist out the engine) right on top. Done. Perfect. Started right up. So still, I don’t understand why the Germans have hidden Das Battery underneath a bunch of screws, but they actually did make jumping it pretty easy.
Oh, and I had to do it a couple more times too, before realizing that the glove compartment switch wasn’t working, and was keeping the bulb in there, on all the time. Gah.
The battery is actually in the trunk, in order to improve the car’s weight distribution by counterbalancing the heavy engine.
They put that positive terminal in the engine bay precisely for jump-starting.
I’ve jumped a number of cars in my life and, other than being unable to start the ‘dead’ car, I’ve never had a problem.
I was witness to a problem. I was over my girlfriend’s house and her father was attempting to jump start a car. The cars were parked facing each other but they were far enough apart that when the jumper cables were connected, they didn’t touch the ground.
It turns out her father had made a mistake and hooked up the cables so that the batteries were wired in series (+ to - and - to +) instead of parallel. This caused the cables to get very hot, very fast. I remember seeing some movement and turning just in time to see the insulation melt off the cables and drop to the ground.
I’m a pretty methodical person. I always hook up the cables + to + first. Then - on the starting car and somewhere on the body of the ‘dead’ car. Because of paint, grease, and whatnot sometimes it’s hard to find a good connection on the body. I’ve always tried to avoid connecting directly to the dead battery because I was taught, sealed or not, batteries can vent flammable gas. Can anyone confirm or deny this?
People keep posting about making the connection to the “engine block”. Maybe I’m being to literal but I don’t think I could reach my engine block with a cable clamp. In my experience there’s usually a wire running off of the negative battery cable that attaches to the body as a ground. I thought that the last connection could be made to any part electrically connected to that ground.
Actually, sealed batteries sometimes do need water added, but in most there is no way to do so. A sealed battery does have the ability to vent hydrogen, because if it didn’t, it would blow up.
The negative clamp probably was attached to some part of the engine that wasn’t grounded. Bolts on the shock towers work well, or any piece of unpainted metal on the body.
Here’s a link
to a site that tells you everything you wanted to know about car batteries but don’t know what to ask.
Years ago, the battery in my car froze. It blew up when I tried a jump start. By the next day my parka was full of holes.
Back before the world was round, you could jump-start a car with only one cable if the metal bumpers were touching.
On General Motors front-drive vehicles, there is at least one dogbone-shaped engine stabilzer–a sort of auxilliary motor mount.
The bolt holding the dogbone MOUNT to the radiator support is an excelent ground. When jumping GM to GM, I’ve had excellent results connecting bolt-to-bolt and not touching either negative battery post.
The “bone” itself has rubber grommets at each end and is therefore no good for jumping.
My dad was an auto mechanic. Sort of still is, because I don’t think it’s something you stop doing, it’s just something you stop getting paid for.
He taught me to attach the clamps in the Cecil-specified order, with the last one on some bare-metal part of the body. Just as Cecil sez, this was to prevent explosions. And my father saw enough explosions in his time from causes many and various (including one which he claims blew the wedding band off his friend’s finger – my father never wore one himself. Then again, maybe it was just an excuse…).
I’ve always followed the Rules even though modern batteries are less prone to exploding thanks to their sealed design. How much less prone, though, seems unclear, and I’m happy enough being safe.
But I’ve found, in the last decade or so, that finding a bare metal body part under the hood is getting to be a problem. There just aren’t any these days. Time was the engine sat in this massive open compartment surrounded by struts and guylines and whirligigs and hoozits – plenty of rusty stuff to clamp a negative onto. Now my minivan’s engine compartment looks like a nuclear submarine made entirely of plastic. I can’t even tell the positive terminal from the negative half the time – and let me tell you how quickly a cheap set of jumper cables melts if you crosswire to a live battery: VERY QUICKLY.
So lately I’ve been forced to jump using the Impure Method. Luckily, these days there are also hardly any sparks, because cars just aren’t as MANLY as they used to be. We’re all driving metrosexual autos today.
It’s almost sad. But for the short time I owned a MANLY car – a 1969 Olds 98 convertible – let me tell you, I missed things like, you know, seat belts. Radio knobs you could reach without mounting an expedition. Door handles you could see on a clear day. FM.
So it’s sad, but not so sad.
– Chris.
No mention has been made of the danger of frying engine computers if the booster cables are accidentally hooked up positive to negative. It’ll cost a million dollars, except when jumping old six-volt Fords, which you have to hook up positive to negative — unless you’re jump-starting a six-volt Ford with another six-volt Ford — because they have positive ground.
Don’t know about blowing a wedding band up, but you could melt one through PDQ. I’ve seen a picture in a model aircraft mag of the results of shorting out a nice big NiCd with a gold ring, as well as the burn that went with it. With a lead-acid battery, you can possibly do even better. Figure that the “resistance” of the ring is a small fraction of an ohm, and the battery will provide a lot of current for a brief while. :eek:
Just weighing in that I’m not using my car very often either and sometimes have to jump-start it. A few weeks ago I bought a portably battery with clamps and an air pump included, among others, that can be used to start a car. It’s manual also said to use the Cecil specified method. I did it, and it worked flawlessly. I guess my car (Alfa 155) is still one of the manly kind, because there was a nice bit of metal frame to attach the minus to.
Thanks Foaming Cleanser.
You answered my original question. I’m going to take a closer look at my “sealed” battery to see where the vents are located.
My Bro’s an eye doctor - he’s told me enough horror stories to make me extremely wary when jumping cars. He suggests a simple safety addition - get a decent pair of protective goggles, keep them in your trunk, and put them on when you perform the jump start.
I also bought one of these, and I can’t reccommend it highly enough. I never have to worry about finding someone to give me a jump when I run low, this works every time. And when someone else needs a jump, I just give this to them and tell them to hang on to it for a day in case the battery has gone bad. It saved one a buddy of mine once, who ended up needing use it three times in the day I loaned it to him. They should put these in all cars as a standard, like the spare tire.
A tow truck driver I spoke with recently gave a different reason for the baroque method described of jump starting a car. Apparently some high-end vehicles (certain BMW’s & Jaguars) are very sensitive to voltage spikes, such that the electronic computer on the cars in question are easy to blow and hugely expensive to replace. And if they do, you won’t even be able to open the car door because of the electronic locks.
The electrical load-bearing instructions are designed to minimize the possible voltage surge. In his experience, he turns on the headlights of the dead car when initially connecting the jumpers for this very reason.
Food for thought,
Dallas Hodgson
Cupertino, CA
-djh