Engine management and using jump leads question

EdGasket

For more info see:

http://electronics.stackexchange.com/questions/24830/why-is-there-risk-of-overvoltage-when-jump-starting-a-vehicle

http://forum.a8parts.co.uk/showthread.php?t=3980

http://www.vwaudiforum.co.uk/forum/showthread.php?51896-Damaged-Ecu-Due-To-Jump-Leads-Spike-
Golf-Mk4


http://forum.difflock.com/viewtopic.php?t=65626&sid=3fffc3dc962af38b676e6387d9df0bda

http://www.dailyrecord.co.uk/authors/the-judge/driver-vents-fury-after-simple-1558512

There are plenty more; just google it.

IamNotAllowedToUseMyName

Jump started Golf Mk4 an excessive number of times, the only ECU problems were related to undercharged batteries causing spurious error codes prior to jump starting.

Jump started Merc C Class numerous times when battery was failing and under-used, no issues.

As long as you are careful, there is no reason electrically why there should be a problem.

If you are really twitchy you can get battery starter packs that charge off the mains and hold their charge for a few months.

Zeitgeist

Although it sounds counter intuitive, turning on your headlights on the dead car is helpful as it helps smooth any electrical spikes when trying to jump start it.

londonTiger

EdGasket wrote: »

Don't jump start modern cars. Remove the battery or disconnect one lead, then charge it. You can get away with jump starting some of the time but it can and does cause expensive damage to ecu's and other modules; sometimes the damage does not manifest itself straight away.

My battery went flat after I left the lights on once. Somethings wrong with me I left the lights on twice and the car unlocked twice in the last 2 months.

Anyway, I just purchased a a car battery charger and just charged it up from mains. It's important to note that a car battery takes about 8 hours of motorway driving to charge from empty to full. Car batteries were never designed to go emtpy (they are designed to stay in the 80%-100% capacity range) and falling below 80% capacity reduces their life cycle.

Additionally. you should give a car battery a full charge every now and then to pronlong the battery.

When you jump start you just get it going for now, but it won't bring the battery up to full capacity you have to drive it for ages to bring the battery up to full charge - an external battery charger is good to have and costs about the same as a pair of jump leads.

Stoke

I've jump started dozens of cars and never fried an ECU. You just need to go about it the right way.

TrickyWicky

Zeitgeist wrote: »

Although it sounds counter intuitive, turning on your headlights on the dead car is helpful as it helps smooth any electrical spikes when trying to jump start it.

Have you ever tried that? - I did ONCE and the remote locking on the car packed up. It did return to life eventually.. six months later.

When using jump leads you turn off EVERYTHING that may draw a current. Shut doors, internal lights / radio / everything else OFF so that the only thing drawing a current *MIGHT* be the alarm.

THEN you jump start it.

Turning on the lights will ensure around 20 lovely amps flows straight into the car which will have virtually no protection against this sudden surge.

Slowly_does_it..

Jumped a friends car many a time, never managed to jump his head into turning lights etc off...

No ill effects to his car, on mine I had one dud cell on my battery that boiled away while the leads were connected and were putting some charge into his. Always thought I would have to replace the battery, but the 12 year old battery outlived the metalwork underneath the car...

Only real damage was caused by getting a jump from a car where negative was red and positive was black, so the leads were connected the wrong way - quick fuse change, and all was good!

colino

If your not sure how to jump start a car. Don't do it.
Leave it to the thousands of traders, techs, apprentices and handy men who do it every day on millions of cars without a problem.
If your handbook states do not jumpstart, suspect the manufacturers faith in their product, not the probability of jumpstarting being a car killer.

Nodding_Donkey

I think it's more likely to be their faith in their customers

TrickyWicky

colino wrote: »

If your handbook states do not jumpstart, suspect the manufacturers faith

Or lack of