Whilst being well aware of the recommended protocols relevant to jump-starting between the donor vehicle and the vehicle with the discharged battery, is it practicable to undertake the procedure when one of the vehicles is diesel powered and the other vehicle is petrol driven. I'm sure I have read somewhere in the distant past that this should be avoided?
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the only thing i can think of is a large diesel engine may put too much demand on a smaller petrol engined cars battery
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the only thing i can think of is a large diesel engine may put too much demand on a smaller petrol engined cars battery
Should be OK for one start if the battery is healthy.
The donor car should not be running though, swithed off and key out, modern electrics can be damaged when the receiving car starts and it's alternator whacks a charge back up the jump leads.
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Ah, but what if its bio-diesel..?
Although in theory there's a chance voltage spikes as the leads are connected may damage something, in practice over at least 30 years of using jump leads - including on some high-tech cars after they've stood with auxilliary equipment working for extended periods with the engine idling - its never done so for me, in practice.
As long as they're both the same voltage and connected pos to pos and neg to neg (away from the battery as the final connection) I can't see any reason why there'd be any problem, if the charged battery (or the running alternator) have sufficient capacity to provide the current required - and even if it didn't, it would just 'not start' not damage it?
N
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Whilst being well aware of the recommended protocols relevant to jump-starting between the donor vehicle and the vehicle with the discharged battery,
>>
I have carefully RTFM as I am not aware of "the recommended protocols"
There appears to be no consistant information across manufacturers.
e.g. some say do not turn on lights,.some say turn on the HRW before disconnecting the jump leads.
There are previous threads discussing this.
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I must disagree. My (admittedly pretty unqualified, although I'm in the 3rd year of a physics degree...) advice is that the donor vehicle's engine is running, and at a fast idle to provide the necessary power. The high current will be isolated from sensitive electronics anyway, and the voltage regulator will take care of any voltage spikes.
The car's ECU will be supplied with power regardless of ignition switch position, they're constantly updating their thermal models of the engine, and will be linked into central locking and alarm systems too.
I would be surprised if any car is damaged through running as a donor, and I reckon anything that's happened in the past is more likely to be due to careless handling of the jump leads.
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Re my original post on this topic and my reference to 'recommended protocols'....the following is an extract from an article in Auto Express magazine dated 30 August 2006 and headed 'the right way to jump-start a car?"
1. Use the red jump lead to connect the positive terminal of the donor vehicle's good battery to the positive terminal on the flat one
2. Use the black lead to connect the negative terminal of the good battery to a suitable earthing point on the engine or chassis of the other car. This earthing point must be away from the battery and the fuel system.
3. Voltages will equalise in three minutes.
4. Start the donor vehicle's engine, let it settle for a minute, then start the other car's motor and leave both running at a fast idle for 10 minutes.
5. Don't remove the jump leads while the engines are running as this can cause serious damage to the electronics on either or both vehicles.
6. Turn off the ignition on both cars and then disconnect the leads carefully in the reverse order to the way that they were connected.
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Will ten minutes give a really dead battery enough urge to cope with a re-start on its own straight away?
I've personally never had a problem taking the leads off while the engines are running.
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One relevant point is the quality of the jump leads. Good ones, ie thick copper and metal croc clips make it a lot easier.
As all the things I've jump started in the last few years have been petrol engined and not that big, whereas my Landrover is diesel and has a battery big enough for a moderate battle ship, the donor vehicle is connected, gives 5 mins charge to the failed one, and is then switched off, and the failed one then started. Removes most worries about electronics fighting, as I certainly do not want to replace the alternator on the Landrover as it is an expensive one.
But you'll never do this with cheap leads.
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I must disagree. My (admittedly pretty unqualified, although I'm in the 3rd year of a physics degree...) advice is that the donor vehicle's engine is running, and at a fast idle to provide the necessary power. The high current will be isolated from sensitive electronics anyway, and the voltage regulator will take care of any voltage spikes.
Perhaps you are right though I have been advised on numerous occasions NOT to have the donor car's engine running because the voltage regulator etc can be damaged.
Aside from this if the donor car's battery is healthy and the receiving car is healthy apart from a flat battery then there is noi need to have the engine running, the battery will only take the same drain as it would on on a normal start up cycle on it's own vehicle.
The car's ECU will be supplied with power regardless of ignition switch position, >>
To a degree though eeproms and similar will be inactive.
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You can get those cables that go from one cigarette lighter to another. Then you don't have to worry about leads etc.
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You can get those cables that go from one cigarette lighter to another. Then you don't have to worry about leads etc.
But with those don't you have to wait awhile, whereas with jump leads it's pretty much instant.
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SOrry but if you try to send a current for a starter motor through a lighter socket, it won't happne. The current will burn out the fuses or wiring or both.
I have started largeish diesles (2 lites) from a 1.1 petrol and vice versa with no problems. Connect cables when neither is running, start donor and let it idle and then rev to 2000rpm and start dead vehicle. Switch off donor , disconnect cables (no current flow now so safe, and leave dead vehicle to idle.
Once dead vehicle has warmed up a bit, load on starter will be MUCH less if you stop and restart so driving it is safe providing you drive 3-4 miles without all lights etc on .
Over 20 years never had a problem.. and usually once evry winter it is required.
A running engine plus fully charged battery should be enough to start almost any car..
madf
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The lighter socket things are controlled and give something around the 20 amp mark which slowly brings the flat battery up, in a safe fashion for the donor car.
It's idiot proof, which is no bad thing.
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If mine is the donor car, I never start the engine or have ignition on. It always works fine without, I don't usually have another engine running when I start my car normally, not neccessary, yet doing so introduces risk of damage (expensive abeit small)
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