Jump cables mix-up

[Balaur]

Hello all,

This thread on Reddit is quite interesting. It shows what happens when you mess up the jump cables' connection to the battery.
http://www.reddit.com/r/pics/comments/ls9in/a_friend_of_mine_was_helping_a_girl_jump_her/

The red car was the jumpee and the gray car was supposed to help it start.

More pictures here:
http://imgur.com/a/JSntv
 

[david77]

Poor Golf   ,

Ok, I never really understood this: Why do you not connect the negative jump lead directly to the negative pole of the flat battery but to the engine block? I and everybody I know have done this wrong for years until I read about it somewhere.

My car wouldn't start last monday, I did not jump start it but decided to pump 10A from the lab PSU into the battery for 10 minutes, did the trick  .

[elliott]

Ok, I never really understood this: Why do you not connect the negative jump lead directly to the negative pole of the flat battery but to the engine block? I and everybody I know have done this wrong for years until I read about it somewhere.

So you aren't creating sparks near the battery, lead acid batteries give off hydrogen gas. Always make that connection last.

[david77]

Ah. So I take it the newer "maintenance free" types are safer then. I suppose they are of the "gel" type, like the smaller types found in UPS's and such?

[ejeffrey]

AFAIK, the main reason is explosion safety.  A lead acid battery can produce hydrogen gas.  There is a slim chance that enough of it can accumulate so that the spark from completing the circuit can ignite it and cause an explosion.  It is low probability, but connecting to the chassis reduces the chances.  On many modern cars there will be very little exposed metal to make good contact, so you may have no choice but to connect directly to the battery terminals.

[alm]

Another advantage of connecting the negative lead to the engine block is that less current is wasted trying to charge the battery, and more is going to the starter motor.

[elliott]

Ah. So I take it the newer "maintenance free" types are safer then. I suppose they are of the "gel" type, like the smaller types found in UPS's and such?

No, maintenance free batteries are still vented, I think the maintenance free part is a chemistry difference that makes them consume less water. There are gel cell batteries and totally sealed ones on the market, but they are typically more expensive and aren't that common to find.

[david77]

Thanks for clearing that up Elliot  .

[Uncle Vernon]

Poor Golf   , 

little sympathy when it's self inflicted.

OK, I never really understood this: Why do you not connect the negative jump lead directly to the negative pole of the flat battery but to the engine block? I and everybody I know have done this wrong for years until I read about it somewhere.

charging batteries are likely to gas at any time. you have a potential difference between a charged and uncharged battery and a near zero ohm circuit, the current and the sparks can be substantial.
The other reason for connecting to the engine block (on the stranded vehicle only) is to effect the best possible current path to the needy starter.

If your jumper cables are bargain specials save everything a whole lot of stress by waiting a few minutes after connecting and starting the dinar vehicle before trying to crank the dead one particularly if it's already had 25 attempts to start on a dead battery.

My car wouldn't start last Monday, I did not jump start it but decided to pump 10A from the lab PSU into the battery for 10 minutes, did the trick  .

Same precautions apply, but you may just want to switch off the lab supply before cranking unless it has good overload protection. The starter on even a shopping car can easily put a couple of hundred amps peak particularly at low volts.

[david77]

little sympathy when it's self inflicted.

The car's not to blame for the users stupidity.

Same precautions apply, but you may just want to switch off the lab supply before cranking unless it has good overload protection. The starter on even a shopping car can easily put a couple of hundred amps peak particularly at low volts.

I did think about that and disconnected the PSU before turning the key  . I was stressed enough at that point, wrecking my good PSU would've been a bit much on that particular morning. Some joker had also left the air out of one of the front tyres. Good thing I own a compressor and a long hose to go with it.

[Joshua]

We have made some jumper cables from 00 welding leads. Best jumper cables you've ever laid your eyes on.

[elliott]

We have made some jumper cables from 00 welding leads. Best jumper cables you've ever laid your eyes on.

I have some 0ga ones that are probably 30 years old, they were used to jump heavy equipment. It is hard to find anything heavier than 4ga unless you make them yourself.

[sonicj]

it would be nice if all cars came with a Anderson connector for boosting the battery...
-sj

[elliott]

it would be nice if all cars came with a Anderson connector for boosting the battery...
-sj

Those are pretty common in race cars.

[rr100]

My car is too complicated for its own good ("standby" current too high) and the battery is rather old. And the cold season is coming on a collision course. I really don't want to replace the battery if I don't have to (although it would be very good for peace of mind). However I can't wait the morning (most likely a Monday morning) when the car won't start. I have a 60A bench power supply and everything else needed prepared: color coded thick (and short) cables with impressive clamps, grounding point identified and cleaned up. And a 50m extension cord just in case.

[david77]

I've dug out my old jump leads from the back of the garden shed this morning and they are in an appalling condition, I think it's time to get a new set the old ones are at least 30 years old, I'd guess. They have been in our family as long as I can think.
Problem is to find a proper set. The crap they sell in hardware stores is just not worth considering.
100% plastic clamps with a tiny strip of bent metall in the "jaws". One of the clamps broke while I was looking at the things in the store. I left them hanging there and scarpered.
At the auto parts place they have a good quality set but the price is a joke: 129,00 Euros, that's taking the piss.
So I want to make up a set myself. Anybody know a good source for proper high current clamps? Otherwise I'll have to refurbish the old ones. Suitable wire is not a problem.

[Psi]

Anybody know a good source for proper high current clamps? Otherwise I'll have to refurbish the old ones. Suitable wire is not a problem.

Welding stores will have really solid metal clamps but they will be all exposed metal (for earthing things).
So i think you'd have to cover them in some sort of rubber or heat shrink

I'm not sure if the jaws will work for cars though, welding clamps tend to have a flat jaw.
But its probably worth having a look.

If your building some yourself it's a good idea to put a large bi-direction TVS diode across it so spikes don't damage things.
If you wanted to get even more custom you could add some 200A relays to connect only if the polarity is correct.

[Balaur]

Personally, I'm using a battery jump box instead of cables. I keep that in my truck and it's very useful during the winter.
Much easier to use on any car without troubles.

[sonicj]

Anybody know a good source for proper high current clamps? Otherwise I'll have to refurbish the old ones. Suitable wire is not a problem.

check these: [urlhttp://shop.genuinedealz.com/Items/Item.aspx?SKU=gim-06137-38/pr&caSKU=gim-06137-38/pr&caTitle=Parrot%20Jaw%20Booster%20Cable%20Clamps%20-%20One%20Pair]Parrot Jaw Booster Cable Clamps[/url]
&
east penn booster paraphernalia: link

[SgtRock]

Greetings EEVBees:

--In order to screw up royally, you do not necessarily need the jumper cables. I have a Nautical friend, the kind who wears a Captains hat when he is not at the Law Office or a political party meeting. He rang my bell the other night; I do not get out of bed for my cell phone; I am retired. Anyway, he had a lot of little red spots on his face, and some holes in his monogrammed shirt the kind with the ship's wheel embroidered on the pocket. Turns out, he wanted me to help him with the yacht (30 footer, lots of teak, very nice). It seems his engine space lights were out, and instead of checking for a blown fuse, after having started the inboard Cummins-Onan generator, he decided to have a look at his batteries using a cigarette lighter.

--Now, I am pretty sure you boffins, bodgers, gaffers and itinerant hook up fellows can guess what happened next, Bob's your nuncle. I shut down everything, and taking due care, sprayed all of the bulkheads and the floor with dilute soda water, and flushed with clean water, repeating several times. I hand cleaned all plastic covers using the same. All metal parts were cleaned repeatedly with WD40. I then personally checked the bilge for fumes, and reassured myself that the sniffer and the pump had not been mucked with. I then replaced the fuse for the engine room lights and then the blown battery (only one of three was destroyed, ($400 deep cycle") and reconnected all. And, Em's your auntie, all was copacetic.

--End result: $250 and three quarters of a a bottle of acid stained Yamakazi 18 Yr scotch, with missing top. Can small amounts of sulfuric acid kill a person? Please answer quickly, as I may need to call the Medics. 

"I happen to have discovered a direct relation between magnetism and light, also electricity and light, and the field it opens is so large and I think rich." Michael Faraday 1791 1867

Best Regards
Clear Ether

[IanB]

Can small amounts of sulfuric acid kill a person?

Only if you breathe it in. It may irritate the delicate membranes and cause a fluid build up in the lungs. But normally you would choke on the fumes before you inhaled enough of it to matter. If you are not coughing and choking you are fine.

Incidentally "soda water" (the fizzy stuff you add to Scotch) is not the right thing to clean up acid spills. If you actually used a bicarb or washing soda solution then you are good to go.

[SgtRock]

Dear EEVBees:

--Dear IanB:

--Indeed, I did use the Bicarb for washing the acid off of the bulkheads and floors. I took the Yamakasi scotch neat except for the occasional drop of H2SO4. Not being a scotch drinker, all I can say is; Smooooth, at least till I get a taste of the Suntory Oaken Cask Bonded 200 Years in the Hokido Vaults stuff. Duh, Hik.

"If it moves, tax it. If it keeps moving, regulate it. And if it stops moving, subsidize it." Ronald Reagan

Best Regards
Clear Ether

[rr100]

HURRAY!!!!!!!!!!

My battery survived the winter 2011-2012 without incident.
Then 2012-2013.

But TODAY (technically spring 2013, although temperatures around 0C) it did not start! I left it for like 2 days only but probably some previous short trips took the toll (also the voltage cut-off is really low, charging usually at around 60% I guess, it did not bother me before so I didn't investigate). Also surprising as this winter I left the car even for 2 weeks and it started then at -20C.

Anyway, today it started to rotate the engine and it died!!! Luckily I was parked rather close so I could even use a shorter extension cord (the 50m one, scroll up, I found later on). Set the (60A) power supply to 15.6V and some lower current, connected to battery and then slowly increased the current. It started at 40+A, then went down to something like 25A. Let it there for something like 1-2min, giving a surface charge to the battery and also most likely heating it up. Then it started from the first try!

Before, when planning for this, I was debating with myself if I should try starting with the power supply connected or not; I'm sure charging 10 min at 20A would give me enough charge to start without any drama and without the power supply connected. However having a very shallow charge and the power supply connected seemed a nice touch for an almost instant jumpstart. 60A extra is nothing to sneeze at and also having the current available for glowing sparks (it's a diesel) and the few other amps needed for whatever else (basically still charging the battery all the time with tens of amps instead of draining it) was a nice touch. Pretty pleased with the results today :-)

[G7PSK]

That sort of trouble ( blown out batteries) used to be fairly common when car manufacturers first started to make negative earth cars, it was quite common in those days to park the donor car bumper to bumper with the car needing a boost and just connect one lead for the battery well you know the result when the car needing the boost is positive earth and the donor car is negative as was often the case.

The car I have now has special contacts for jump start leads as the battery is tucked away so you need to take half the car to bits to change it.

[tom66]

I have two 12V, 98A server power supplies. I've often wondered if one, or both, could start a car...  I've heard some smaller engines need "only" 60A or so.