Current reversal in 2 connected car batteries?

saying


Define "standard" when there are several voltage standards on the road.

I'm sorry if you took it that way, but on Usenet, one never knows the ability of one's audience. Do you know for a fact that the OP (who toasted his battery during a jumpstart) didn't accidentally hook it up wrong? If you don't then a misconnect (or a battery mismatch) is a reasonable possibility.
Eric Lucas
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Given he diidn't need a new battery straight away that would seem to be a reasonable assumption.
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wrote:

I've been around Usenet long enough to know that *any* assumption about the reader is unwarranted, foolish and dangerous, not matter how apparently well-founded.
Eric Lucas
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We were somewhere around Barstow, on the edge of the desert, when the
something like:

For this particular episode, 12V neg ground.

Car to car, both fairly ordinary vehicles. At this time in the UK, the only other common higher-voltage use is 24V on heavy trucks. 42/48/50V vehicles are extremely rare. Of course, he could have attempted it from a milk float or forktruck - it wouldn't surprise me.
As for hooking it up wrong; well, that's a possibilty, but he'll be more careful next time.
--

Dave
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saying

That's not a good assumption, considering the new standards that are coming along, plus all of the classic cars that are around from the 1940s - 1960s. My MGB has a 12V-neg gnd system, but through my participation on Usenet rec.auto groups, I've seen warnings about similar sports cars from a similar time period having postive ground, and I think I've even heard of 6V and/or 18V systems, but I can't be certain about that. The driver of the old car with the odd electrical system *might* be aware of what his vehicle has (although, unless he's one who works on his own car, he may not), but it is more likely that the driver of the other car might have no idea that he's dealing with other voltage standards...or even that such things exist. Most people are not very educated about the vehicle they drive. They just know that they feed it gasoline, they get in, they turn the key, they press the pedal and they go. Most know that they also need to have somebody replace the brakes and oil once in a while. Beyond that, it's a black box.

Well, see comments above about the fact that "ordinary vehicles" has a statistically finite chance of not applying.

That's my point. To blindly say "No way could jumpstarting knacker your battery", a statement which, taken on its own at face value is incorrect, does nobody any service, and possibly prevents him from learning the lesson, if indeed it's what needs to happen. Even just adding the condition "if you're talking about two vehicles with healthy 6V-neg gnd systems" at least tells him that there is something more he may need to look into and learn about.
Eric Lucas
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The number of Positive gnd , 6v or 24V Mitsubishi Shoguns is pretty negligible. You're more likely to encounter a dead short than an non 12V neg gnd car which isn't covered in warning signs or driven by someone who knows it.
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We were somewhere around Barstow, on the edge of the desert, when the
something like:

<bored now>
The whole comment I made was predicated on the assumption that the OP wasn't a total idiot and knew that both cars were 12V neg ground. Recall that there was another party involved in the jumpstarting and he, at least, probably had more clue than the OP.
--

Dave
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When I was younger and sometimes today, we still jump 6V (either positive or negative ground) with 12V negative ground equipment. Although all of this equipment uses generators instead of alternators. I would not try this with something that uses an alternator or all. And gosh does a 6V starter turn over an engine really fast with 12V connected to it. Even hard to start engines generally pop off really quickly. :D
--
Bill



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saying something like:

Hahahaha... I knackered my car battery trying to start a semi truck in cold weather. Just simply jumping, my car battery didn't have enough current to turn over the diesel engine. So it had taken me 20 minutes using my car's alternator to charge up four of the huge 12V batteries enough to give it enough boost to finally start the truck.
And I let my car run another 5 minutes after disconnecting to charge my car battery up enough so I could start it later. Well 12 hours later, I went to start it and my battery was dead. Used the truck to now start me up. All was well after that. What a PIA! lol
Oh but I do have a story about jumping someone else that could cost you or someone plenty. My dad and his friend jumped a vehicle and the battery blew up in my dad's friend's face. They had a garden hose right there and thus hosed him down with water and he turned up okay afterwards. Thank goodness. Just some cuts on his face.
I have jumped hundreds of vehicles and I have never seen this ever happen. I have heard these stories though for decades. This was the first time my dad has seen this happen too from hundreds of jumps.
The safe idea though is to connect up the last connection to ground and far enough away from the battery so that the spark doesn't ignite the battery vapors. Although with most things made of plastic and having plastic shell covers on everything. And everything metal is also painted if you can find the real metal, this is getting harder and harder to do on some makes and models. :(
--
Bill



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We were somewhere around Barstow, on the edge of the desert, when the
something like:

Kind of wildly different capacities, doncha think? The damage may have been caused by your initial attempt at a straight jump.

I saw it happen to a workshop manager who was in the habit of jumpstarting a knackered old forktruck every morning with an arc welding set. The silly sod was lucky not to lose his eyesight and part of his face.
That particular morning, he'd asked me to do it - no way, I said, so he set to with a will and it happened. Funnily enough, he never did that again.
--

Dave
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