How do I Jump Start a Dead Car Battery

WLM21

I've been asked to help an elderly neighbour jump-start her car tomorrow, but just want clarification of the correct way ... I haven't done it for quite a while
Different web sites show different ways, in other words the order of the various connections

Let's assume the connections are as follows ..
GOOD BATTERY +     GOOD BATTERY -     BAD BATTERY +     BAD BATTERY -
1      3      2      4   <<<< that's the order I should make the connections, to the above 4 battery terminals  **
2       3     1       4
2       3      1       4

So what's the correct order please ?

** last connection can be to bare part of dead car, or battery negative if nowhere else

daveyjp

https://youtu.be/hyLwfthYjKw

Just be prepared for the flat battery to be completely dead and not take much charge.

EssexExile

I've never found it to be that critical, as long as you go + to + and - to - all should be well. Start the car with the good battery before you try to start the duff one.

Marktheshark

just connect them up, start your car and leave it running with the ignition off in the flat car for a good 10 minutes.

Then crank the flat car with the clutch pressed in.

pallyman

Just tell them you will order them a new battery,much easier as it sounds like it is dead,try Tanya,always found them Fab.

Elmer_BeFuddled

Marktheshark said:

just connect them up, start your car and leave it running with the ignition off in the flat car for a good 10 minutes.

Then crank the flat car with the clutch pressed in.

But disconnect the cars from each other before trying to start the dead one.

neilmcl

Connect the cables from the working car, positive first then negative to an earthing point or bare metal in the engine bay of the dead car (don't connect to the negative terminal of the flat battery). Let it sit for a few minutes then start the working car and let run, again for a few minutes. Attempt to start the flat car and when running let both idle for 10 minutes. Remove the cable in reverse order, negative first.

Also, make sure that things like radio, aircon etc are turned off on both cars.

neilmcl

Elmer_BeFuddled said:

Marktheshark said:

just connect them up, start your car and leave it running with the ignition off in the flat car for a good 10 minutes.

Then crank the flat car with the clutch pressed in.

But disconnect the cars from each other before trying to start the dead one.

No, that's not going to work.

facade

If it is one of those poorly engineered foreign cars, Mercedes and Renault spring to mind, the dodgy electrics will fail if another car is connected and started, due to "high voltages". No I don't believe that, it is just poor engineering.

Safest is to jumpstart it from a good battery that is removed from a vehicle.

(Well, actually safest is to let someone else do it )

neilmcl

facade said:

If it is one of those poorly engineered foreign cars, Mercedes and Renault spring to mind, the dodgy electrics will fail if another car is connected and started, due to "high voltages". No I don't believe that, it is just poor engineering.

Safest is to jumpstart it from a good battery that is removed from a vehicle.

(Well, actually safest is to let someone else do it )

If it's a modern car with all that new-fangled electrickery start/stop stuff then there maybe separate charging posts away from the battery to allow the car to be jump started. For example, my BMW has a positive and negative charging post under the bonnet whereas the battery is in the boot and the manual clearly states that you should never connect chargers or boosters directly to the battery.

GrumpyDil

The issue that Facade is referring to is that having the vehicles connected when the car with the flat battery is started risks damaging the delicate electronics on the car providing the jump start. Far safer if possible to use a jump start pack or spare charged battery.