Jump start a car?

[rudds1 102]

I've always connected battery to battery like yourself.

 

The problem with doing it like that is the defective battery can absorb some of the currant from the slave battery so you don't get the full ampage or power going to the starter of the car being jumped

[El Cid 221]

Most TVR's actually have an anderson connector for jump starting.

 

 

When driving vans, the battery tends to be in the cab, Renault Masters, there is a red main wire near the front panel, mechanics have used that when jump starting.

 

---------- Post added 07-01-2016 at 18:05 ----------

 

The problem with doing it like that is the defective battery can absorb some of the currant from the slave battery so you don't get the full ampage or power going to the starter of the car being jumped

 

Surely you want the dead battery to absorb power? Cars always running when connecting, so does it really matter?

[peak4 287]

My understanding is that, for -ve earth vehicles, as almost are these days, the reason is to prevent an accidental short circuit.

Put the +ve on first, as that is going onto the smallest target, i.e. the battery post. if you fumble the connection, or drop the cable, it doesn't matter as the circuit is not complete.

Put the -ve on next, , ideally onto the engine block in case the engine earth to the battery on the dead vehicle is corroded.

That way round if you drop the final connection, it doesn't really matter, as it's heading for the the vehicle bodywork/engine/-ve terminal anyway.

You would have to be spectacularly unlucky or inept to short it onto the +ve battery terminal.

Consider it the other way round; connect the earths (-ve) up first and then drop the +ve jump lead, or let it slip whilst trying to connect it to the battery, and you would have to be very fortunate indeed not to short it to earth.

A full short on a charged lead acid battery may well weld the jump leads to something, and then you get the scenario of an exploding battery, which really isn't something you want to witness at close quarters.

I've seen it on film and it's quite spectacular.

[Obelix 11]

All a bit too "elf and safety". Jus get on with it but don't touch the two clamps together.

 

Right up to the point when the battery explodes and blow sulphuric acid in your face....

 

Always make the last connection at least 2 feet away from the battery. Look for a lifting eye on the engine block, or a clean bolt on the bodywork. Many cars have earth points now specifically for jumping a car.

 

---------- Post added 07-01-2016 at 18:42 ----------

 

When driving vans, the battery tends to be in the cab, Renault Masters, there is a red main wire near the front panel, mechanics have used that when jump starting.

 

---------- Post added 07-01-2016 at 18:05 ----------

 

 

Surely you want the dead battery to absorb power? Cars always running when connecting, so does it really matter?

 

You will never start a car down a jump lead they cant deliver the current. As you say, the idea of jump leads is to start charging the flat battery, that's why you wait a short while with the other car running on a fast idle...

[ANGELFIRE1 10]

Wow, I am a lucky guy then. I have been doing it wrong for for close on 50 years. You are never too old to learn new tricks.

 

Angel1.

[max 13]

I didn't see it mentioned but once connected start the 'good' car first before attempting to start the other. I've seen someone try to start the 'dead' car before the other has started and managed to drain the other battery.

[alchresearch 215]

Not sure if its been mentioned, but an electrical spike can sometimes upset or damage the ECU.

[PeteMorris 10]

I might be wrong, but isn't there on 'some' cars a sort of safety cutout, which prevents jump starting?...Maybe stopping the fuel flow?...Or I might have dreamed it. I thought it had something to do with the ECU 'detecting' something amiss, and effectively shutting down the car.

[TimmyR 10]

The problem with doing it like that is the defective battery can absorb some of the currant from the slave battery so you don't get the full ampage or power going to the starter of the car being jumped

 

You don't want that dried fruit being used up.

 

---------- Post added 08-01-2016 at 12:40 ----------

 

I might be wrong, but isn't there on 'some' cars a sort of safety cutout, which prevents jump starting?...Maybe stopping the fuel flow?...Or I might have dreamed it. I thought it had something to do with the ECU 'detecting' something amiss, and effectively shutting down the car.

 

Yes i wouldn't be surprised if modern cars don't allow this sort of thing. They're no fun anymore.

[alchresearch 215]

I might be wrong, but isn't there on 'some' cars a sort of safety cutout, which prevents jump starting?...Maybe stopping the fuel flow?...Or I might have dreamed it. I thought it had something to do with the ECU 'detecting' something amiss, and effectively shutting down the car.

 

There certainly is for some cars which have those AdBlue additive tanks. When it runs empty the car won't start.

 

Do not ignore the AdBlue® Warning Light. Remember to refill AdBlue® on time. If the tank runs out the vehicle can’t be restarted after the engine has been switched off.

 

To enable the engine to restart a minimum of 3.8 litres of AdBlue® must be added.

[truman 10]

The problem with doing it like that is the defective battery can absorb some of the currant from the slave battery so you don't get the full ampage or power going to the starter of the car being jumped

 

The battery is usually connected directly to the bodywork anyway..so in effect (and practice) you are connecting straight to the bodywork.. if you attach to the body you're just connecting to the end of an "extended" -ve post..no difference..I stand to be corrected though..

[peak4 287]

The battery is usually connected directly to the bodywork anyway..so in effect (and practice) you are connecting straight to the bodywork.. if you attach to the body you're just connecting to the end of an "extended" -ve post..no difference..I stand to be corrected though..

 

In the ideal world yes, but not if the engine/body earth is corroded, and thus high resistance, hence my comment about adding the -ve jump lead to the engine on the dead vehicle.

Edited January 8, 2016 by peak4