When you jumpstart a vehicle, why do they say this..

[WildGoose]

Connect from the negative of the booster battery to an earth point of the vehicle to be jumpstarted, rather than direct to the battery?

I always do it battery to battery and never have problems, but the consenus is as above.

Just wondered why?
____________________
So in other words, he stopped you for being flagrantly in posession of a motorcycle in direct contravention of the Hippies, Darkies and People Whose Face I Don't Like The Look of (Police Powers) Act. 1976

[Al]

I think they say to earth it to the same point that the the dead cars starter motor is earthed to, to cut down on power loss or something.

I always just connect to the battery though.
____________________
Yamaha FZR400RR 3tj
My Instagram Thingy

[The Shaggy D.A.]

I thought it was the risk of igniting the gas from the battery - if there's a spark, it won't be right next to the battery vent.
____________________
Chances are quite high you are not in my Monkeysphere, and I don't care about you. Don't take it personally.
Currently : Royal Enfield 350 Meteor
Previously : CB100N > CB250RS > XJ900F > GT550 > GPZ750R/1000RX > AJS M16 > R100RT > Bullet 500 > CB500 > LS650P > Bullet Electra X & YBR125 > Bullet 350 "Superstar" & YBR125 Custom > Royal Enfield Classic 500 Despatch Limited Edition (28 of 200) & CB Two-Fifty Nighthawk > ER5

[10 pence Short]

It's to try to cut down on sparks near the battery, connect reds first then negative to donor battery and then final lead to engine block ideally.
There will be some current flowing through this lead, sparks will probably be created. It is therefore best that these sparks are as far away from the battery as possible to avoid igniting any hydrogen gas created by the battery charging.
Removing the leads in the reverse order also helps prevent this. HTH
____________________
I haven't had a cont all day, drinkstable.

[stinkwheel]

[WildGoose]

Good to know. Thanks peeps.

The transit is somewhat unsubtle in its approach to everything, it does encourage a blase attitude I guess.

I've always had a soft spot for the 406 (605 insert as applicable, they all look the same) after seeing them ragged about in the film 'Ronin'. Glad I never bought one.

I would be wary of helping anyone these days, after all the stories you hear of people claiming damage after being on the recieving end of a snap recovery from a snow drift.
____________________
So in other words, he stopped you for being flagrantly in posession of a motorcycle in direct contravention of the Hippies, Darkies and People Whose Face I Don't Like The Look of (Police Powers) Act. 1976

[Flip]

I jumped my Pug 306 twice, battery to battery when it was bitter cold last week or whatever with no problems. I have since bought a new battery because jump starting sucks.

Although having read stinkwheels ECU story I won't be risking it again.

[WildGoose]

I've bought a new battery as well, it now has more cold cranking amps available than is used to start the trucks at work.

Mechanical simplicity is an advantage in the summer, but a lack of glow plugs or similar in the winter becomes a pain in the arse.
____________________
So in other words, he stopped you for being flagrantly in posession of a motorcycle in direct contravention of the Hippies, Darkies and People Whose Face I Don't Like The Look of (Police Powers) Act. 1976

[Flip]

I think the battery I put in was 80 cranking amps higher then the one I replaced. It was -8 outside when I put it in the car, bugger me it was cold that morning.

[stinkwheel]

Aye. The transit is most amusing on cold days. Even says in the book to crank it over for 20 seconds at a time with your foot to the floor. Then another 10 seconds of cranking with assosciated spluttering, followed by a huge cloud of black smoke as it picks up properly.

I was taking the battery in the house during the latest cold snap. Minus 12 one morning and it was having none of it.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Phoenix]

There's very popular rumours going around Pontiac forums that you should never ever jump start one without using fused jump leads because it'll cause a power surge that will blow the ECU. Now i'm not entirely sure how much a new Pontiac ECU is or how many months and how much import duty it would take to get hold of one but I completely ignore this scary story. The system is no different to any other, wiring diagrams for the car indicate this and therefore I see it as nothing but bunkum. Unless you sit there doing a bit of arc welding with the negative lead I can't see there being a problem, or revving both cars at once may make it unhappy. I've jumped the Pontiac about 6 times and had no issues, if it blows the ECU one day then i'll eat my words but I can't see that happening.

Personally I think most of the stories are from people who have made some dumbass mistake, reversed the polarity or shorted the battery or something and are just trying to cover up their ineptitude. If the car provides jump points use them, if it doesn't use whatever you want. Batteries may produce some gas but I doubt there'll be enough buildup to ignite, chances are probably similar to those of you're house blowing up from accumulated fart methane. I put the negative on a metal area of the engine purely because it's usually easier to clip onto than the battery terminal, in my BMW though the battery is in the boot so there isn't any extra earth point closeby so the battery get's both leads, i'm the one providing the jump though so no sparks if I connect first.

[lozzypop1]

[Wafer_Thin_Ham]

[10 pence Short]

ECU spiking is due to removing the leads with the engine on.

With the leads connected, the vehicle with the flat battery's
alternator is charging a charged battery(donor vehicle connected). When the leads are disconnected the alternator then senses the battery is flat and outputs more voltage causing a spike of high voltage. Alternators can output something like 20V but are regulated down.

Best idea is to run the other vehicle to charge the battery, switch off and disconnect leads, then start up. This won't work if the battery is knackered rather than flat, a good jump start pack is ideal.
____________________
I haven't had a cont all day, drinkstable.