Date: Wed, 12 Oct 94 11:57:33 MDT
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: jackr@starfleet.scs.ag.gov
Subject: Re: Cold Start
> 3) A proper jump means several things, done correctly:
> 3.1) The recipiant battery needs to have correct electrolyte level,
> be clean, well connected, etc.
> 3.2) Connect negative to negative first, at the battery terminals.
> 3.3) Start the donor car, if it is not already running and
> get it idling.
> 3.4) Connect the postive termnials, battery to battery,
> 3.5) WAIT. Let the donor charge-up the recipiant's battery for a while.
There are two things I would disagree with you about.
One is where to hook up the cables and in what order.
The positives should be hooked up first, then the negative on the receiving car. Then the
negative cable on the donor car should be hooked to a good ground point away from the battery.
Granted, the ground point is not as good as the battery post at conveying the full charge of the
battery/alternator combo. But if everything is good and tight with no corrosion between the
battery negative strap and the body losses should be minimal. These losses of course make more
and more difference the colder it is and/or the state of the receiving vehicles electrical system, etc.
This is done to prevent sparking at the battery connections since the hydrogen gas given off by
any lead-acid battery is highly flammable and can cause all kinds of nasty explosions 8-O.
The other item is when to start the donor car. After the cables have been hooked up is the point that
the donor should be started. Otherwise a much fatter spike is delivered to the receiving car when the
cables are initially hooked up. Also, the two batteries in parallel make for a much larger "capacitor"
between the donor's alternator and the receiver's electrical system (computer, etc.). Granted, this
then puts a bigger load on the donor car's starting system, but normally the donor would be nice and
warm and should start easily anyway.
Jack
jackr@starfleet.scs.ag.gov
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