1. Home
  2. Car Maintenance
  3. the order of jump lead connections

the order of jump lead connections

I don't know what the conventional wisdom on this is, but the only reason I can think of for doing it this way is that when you make the final connection, a small spark sometimes results. This could ignite hydrogen from around the battery causing an explosion, so this final connection should be somewhere else on the body instead. Since the body is pretty much always negative, this means doing the positive connection first.

In practice, I'm not sure how much of risk there would be in connecting the negative terminals of the two batteries to each other, although hydrogen evolution can be a real problem when charging batteries.

Joe

Reply to
Joe Kelleher
Loading thread data ...

Hi, to hitch up jump leads is this the correct order please?

from good battery positive lead to positive on flat battery. then negative lead on good battery to preferably an earth point on the flat battery car. (or negative on flat battery if you cannot find one).

this is how I think I remember it, but recently saw it written down differently. so am now a bit confused.

is it really that crucial anyway?

thanks for any advice. john west

Reply to
j west +++

The message from "j west +++" contains these words:

Not really, but I usually use the engine as negative on the recipient car 'cos it's got a more solid connection to the starter motor.

What we shall all do when cars move to higher voltages I don't know.

Reply to
Guy King

The order is correct.

With a ECU laden modern car yes. It wil cost you dearly if you fry something- connect correctly.

Allow the donor car to run at fast tickover (1500rpm is plenty) for a minute or two. More revs does not mean more power, contrary to some popular belief!

When you have started the car with the weak battery, allow both to return to natural idle then turn on power consuming appliances on both- heater fan, HRW, which will absorb any surge as the jump leads are removed, in reverse order.

Tim..

Reply to
Tim (Remove NOSPAM.

That's the argument, probably more of an issue when disconnecting & you moght as well attach the earth lead to the engine & save the volt drop down the batery lead.

Reply to
DuncanWood

It is recommended that the black/negative/earth lead is connected last and removed first. If you connect the negative lead first and then go on to connect the positive, and accidentally touch anything metal other than the positive battery terminal on the way, then you get a lovely shower of sparks/burnt metal/spot-weld. Connecting the negative lead last and removing it first avoids this.

Reply to
Richard C

What if one of the vehicles is positive earth and the other is negative? (I do own one vehicle which is negative earth).

Reply to
Howard Neil

... will be shown in your car handbook.

The normal rule is "disconnect earth lead first, reconnect last"

Reply to
Richard Murphy

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.