You should have no problem starting diesel to petrol - the other way round and you need heavy duty cables, and the petrol battery will struggle to provide enough current to crank the diesel fast enough. Don't forget to connect the earth lead (LAST!) to the chassis of the flat car rather than direct to the battery. This avoids getting any sparks in the location of the battery where there might be hydrogen gas present.
Richard
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>Don't forget to connect the earth lead (LAST!)
Ooops, should have said negative lead....
Richard
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Richard
No, you were right first time - connect the earth lead last, a statement which applies to both positive and negative earth cars!
Regards
John S
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You are probably safe, but look up earlier threads about possible damage to management systems of either car caused by sudden voltage fluctuations as the high current is turned on and off.
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Cliff has raised this key point about disconnecting leads.
RTFM. It may well give you the answers. Haynes may not agree with your manual. I was amazed at what is required these days as I run old cars so well pleased to learn about it in advance. It is possibly even worth keeping details in the car in case you need to jump start again.
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RTFM
very true, jump starting is one of those operations that seem so straight forward that i didn't think to look in the manual, thinking that it wouldn't covered. i'll look tonight
Thanks for the advice
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Safest but not the quickest way is to connect the batteries together and change the flat battery by holding the engine at a couple of thousand or so for a good 10 mins then turn the engine off disconnect and try to start the duff one. If that fails then OK jump start but Never, Never let the duff car start whilst your engine is running, always turn the good system off completely. Regards Peter
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My old Xantia developed a fault in its radio. A (very!) knowledgeable friend tracked the problem down to corrupted software in a processor. He replaced it for me and all was well.
When I asked him what might have caused the problem, he thought it might have been a voltage surge - possibly while using the Xantia to jump start other cars. I've never jump started anyone off my car since!
Now that I've got the C5, I wouldn't even think about it!!!
Graeme
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>> When I asked him what might have caused the problem, he thought it might have been a voltage surge - possibly while using the Xantia to jump start other cars.
Surely if you connect batteries in series (which you do when jump starting) the maximum voltage cannot exceed the value of the highest: 12v nominal.
The max. current will, however, be the sum of the two batteries.
The starter motor will only draw the current it needs.
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When jump starting, my BMW handbook advises that you switch on several major electrical items (on the car with the duff battery) such as headlights and rear window demister BEFORE disconnecting the cables, so as to avoid a damaging surge. Incidentally, the Haynes workshop manual for the BMW doesn't mention this.
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Connect it up, rev the donor car while starting the other to give it more power, and drive off into the sunset. PS do not connect the batteries in series as that will give you 24 volts. Parallel is what the doctor ordered.
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Mare. You are right to be cautious and check out modern procedures to protect sensitive electronics.
Dizzy. Well noted. I total agree. The Focus handbook has similar advice and it is not the obvious things to do.
Haynes Focus manual gives similar advice.
Richard Turpin. Your first suggestion may well be fine for old cars pre engine electronics etc. but I suggest it is very iffy advice for newer cars. I accept what the manufacturers recommend on this subject.
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There are accessories which plug into the lighter socket in both cars - the one end has a number of LEDs which give some idea of the progress. I understand they current limit, and are more controlled than jumper leads.
I have one, and have used it without grief.
Comments, anyone?
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>> PS do not connect the batteries in series as that will give you 24 volts. Parallel is what the doctor ordered.
You are quite right Richard.
Slip of the pen?
I meant connect in parallel, sorry.
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No No No do not run the donor engine when jump starting the laod on the alternator may well blow a couple of diodes in the rectifier pack and your management system may go down the tube. The starter is looking for a 100 amps or so, so just run donor for 5 mins or so to put some life in the duff battery then turn it off and start the other car. Good jump leads are the real requirement here not your alternators contribution. Regards Peter
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Doc, yes I thought it was just a slip.
Peter D, I accept it's better to be safe than sorry, but i don't understand why revving the donor engine can do damage. Surely the donee battery will soak up any excess voltage and anyway, when a normal car is revved, why does that not cause damage to it's own systems?
As for the cigarette socket charge system, this only works if you have an hour or so to spare as the 30 amp standard fuse in these sockets severely limits the current that can pass through. ie, it's just a system for charging, not jump starting. The one they sell in Halfords is very misleading in the blurb on the box.
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The hour it took to sufficiently charge a flat battery on a 2.5 litre 4 cylinder Peugeot diesel lump using the cigarette socket was worth it for me.
There was no damage to SWMBOs Skoda..
The glow plugs alone take more than the average "jump leads" can manage, never mind 300~400 amps cranking.
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If the battery on the Almeira is flat due to mishap (lights left on etc) then either charge the battery off the car (ideal) or from your octavia in preference to just connecting up and jumping it. If the battery has gone flat of its' own accord and is 3 years old or more, replace it. If it is finished it wont take a charge properly and if you try and crank the engine with a low battery the cranking amps go up as the voltage comes down and damage may result. From experience modern batteries dont take to being deeply discharged.
Andrew
Happiness is a T70 at full chat!
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Don't know if this is relevant but I once managed to jump start a diesel mercedes sprinter van from a 15 year old 1.1 litre renault 5 without any problem!
I'm a loser, baby....so why don't you kill me?!
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I have had one of those power pack ni-cad units for a couple of years now - very handy for a 'jump-start' and you recharge via the mains ready for the next time.
Popular with the neighbours if they spot you using it! Costs between £20-50 for essentially the same thing, depends where you buy it.
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Richard,
The reason for not running the donnor engine is simply. When you start a car from its own battery the alternator is contributing but when jump starting the heavy load of the flat battery and the starter motor is straight across the donner alternator and battery, the alternator rectifier pack is rated at a nominal 60/65 amps your alternator is at risk when running your engine other than to get some charge into the flat battery. I hope you understand that. Regards Peter
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Peter D
it is recommended to run the engine on the donor car, when jump starting. you say
'When you start a car from its own battery the alternator is contributing '
sorry but until the engine is turning/running all the energy is from the battery, the alternator replenishes the battery after starting.
As for the alternator diode pack being at risk, both the donor battery and the alternator are effectively in parallel, the alternator out put should be controlled/limited by the alternator regulator.
Finally i have jumped started cars with the engine running, and would be very reluctant to do otherwise, putting the charge of the donor battery at risk.
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what have i started!!
i read the manual. it said connect in order:
plus on dead battery
plus on good battery
neg on good battery
lastly connect to part of car body or engine block on dead car
run engine for 10 minutes on donor and start dead car. Worked ok Saturday. Almera battery was completely dead Sunday morning, did it again and got it replaced at Halfords on Sunday. No ill effects on radio or immobiliser.
By the way, on top of the Octavia battery were 4 wires in a box, in addition to the main leads - any idea what trhese would be. Also it was difficult to get a grip onto the positve terminal on the Octavia because of the plastic surround - basic design issue - i would have thought (can we get to the terminal??)
Thanks all for advice
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Jud, Well stotted, sorry a type, not contributing is what i meant. I have seen several alternators fail during jump starting or soon afterwards due to the alternator hitting the current limit which it does not do under any other cirumstaces at the internal resistance of a battery increases as the charge state falls so it you start a car with a very low battery the mas current is about 25 amps initially unlike then you are jumping another starter motor you are pulling enough current from your battery to drop the voltage to 9 volrs or less and your alternator attempts to keep the voltage up to 14.2 or so therefore a lot of current, max in fact. Your risk your bill, I don't go there. Regards Peter
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I jump started a car for someone. They turned their engine over for ages before it started whilst I revved away. Two days later I had to change my alternator until this moment I had never given it a thought. I am quite cheesed off now as I did not really want to use my car for this purpose but I did not know how to say no.
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Don't rev the engine just let it idle.
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Thanks Carl2 a fine example. Jud tick over will not help run it a couple of K for 5/10 10 mins then turn it completely off and start the flat car. Sorry about your alternator Carl, you do someone a favour and thats the price you pay. Safest way is to couple the batteries together for 10 mins then disconnect and bump start the other car.
Regards
Peter
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Please don't 'BumpStart' anything with a cat, fitted.
You can do ££££££££ to it, without even knowing!
VB
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Cheaper than the Clio ECU which was destroyed in a case of "helping" I came across in the carpark at work.
( I didn't manage to find out exactly what they did. )
I tried a new 20Amp fuse, but that vapourised when the ignition was switched on.
The very nice man from the AA couldn't sort it, either.
ISTR the bill was approaching UKP 1000.... yes, 3 zeros.
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