Ford Fiesta - Jump starting?

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Fri 22 Dec 2017 07:38
Ford Fiesta - Jump starting? - fredthefifth
Ages since I've done this and I've got a faint recollection that on modern cars it's possible to mess up the electronics. Mines a 2013 Passat hers is a 2009 Fiesta. I would normally start mine, connect up (do I have to connect positive or negative first?) and go for it.

Any tips please?
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Fri 22 Dec 2017 08:22
Ford Fiesta - Jump starting? - kiss (keep it simple)

Positive to positive first. Then neg to neg. If the flat battery isn't too far gone you don't usually need to start the donor car. The secret is having good sturdy jump leads.

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Fri 22 Dec 2017 08:22
Ford Fiesta - Jump starting? - hardway

It's as you most likely remember it,

But I connect pos to pos first.

then negative on the live car BUT the negative to the dead car connects to good clean engine or gearbox metal.

Reason for this is if you connect to dead cars battery negative terminal your forcing current through the dead battery.

there's a thing called internal resistance which can have a bad effect on the dead battery cells.

Going direct to say the gearbox

which is easy to see and get to the doner vehicles current should get right to the starter.

Your not just jump starting but trying to avoid voltage spikes.

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Fri 22 Dec 2017 10:30
Ford Fiesta - Jump starting? - fredthefifth

Thanks both, turns out the immobiliser light is flashing so could connect the national grid to it and it won't start. Seems to be a common problem.

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Sat 23 Dec 2017 10:34
Ford Fiesta - Jump starting? - kiss (keep it simple)

.

Reason for this is if you connect to dead cars battery negative terminal your forcing current through the dead battery.

I don't quite get that. All you're doing is bypassing the earth strap. Jump starting a car effectively puts the 2 batteries in parallel. There will be a flow of current into the dead battery because the good one will be at a higher voltage, that's why there is usually a spark on connection.

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Sat 23 Dec 2017 12:15
Ford Fiesta - Jump starting? - SteveLee

.

Reason for this is if you connect to dead cars battery negative terminal your forcing current through the dead battery.

I don't quite get that. All you're doing is bypassing the earth strap. Jump starting a car effectively puts the 2 batteries in parallel. There will be a flow of current into the dead battery because the good one will be at a higher voltage, that's why there is usually a spark on connection.

Indeed, you have to have a pretty damn poor battery connections for the voltage to the battery to differ based on where you put the leads! The real reason to make the last (earth) connection away from the battery is in case the battery is venting explosive gas - which batteries can do when they've been put under stress (such as continued cranking to start a car - or forced hi amp charging after connecting the good battery), the spark when attaching the last lead could be enought to ignite the gas - and in some rare cases (where electrolite has been allowed to run low) cause a battery explosion itself. Similarly when taking the leads off - remove the "remote" earth lead first to avoid the sparking>explosion issue..

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