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help with car battery charger connections - Page 2

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Posted by Scott Dorsey on August 23, 2009, 12:51 am

if my


If you have a modern car, the negative terminal is grounded.  You can verify
this with a meter or a light bulb; connect it between the positive terminal
and the chassis and the lamp will light.

If you have an MG, Morgan, Kallista, Zil, Lada, or some very old Fiat
models, there is a possibility you have a positive ground.  In that case,
you have plenty of other more serious worries to contend with.

Yes.  Batteries produce explosive gas, and when you make the final connection
there will be a spark.  Your goal is for that spark to be far away from the
battery.  So you connect the positive lead to the battery, then you connect
the negative lead to some chassis point away from the battery.  Likewise
you disconnect the negative lead first.  That way, the spark is not near
the battery.

"C'est un Nagra.  C'est suisse, et tres, tres precis."

Posted by Tim Wescott on August 23, 2009, 6:52 am

On Sun, 23 Aug 2009 02:05:38 +0300, mike wrote:

Nearly all modern cars are negative ground -- I'd say "all", but then
someone would come up with some oddball example.  Certainly any American
or Japanese car built in the last 40 years will be negative ground, 12
volt.  If in doubt, you could measure the voltage between each terminal
and the car chassis -- the ground terminal will show no voltage, the
other terminal will show full voltage.  This is something you could do
with a light bulb if you don't have a meter.


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