Re: Which battery lead to disconnect first

[Robert Wilkinson <wilk@domain.elided>]

Regarding Mr. Johnson's post (see below; this might bring us up to 80%!):

The (unsealed type) battery outgasses from the vents, not the terminal(s).
Moreover, there are six cells distributed between the terminals.  A spark
arising from either terminal might well contact vented hydrogen from any
cell.  This is always a possibility, particularly if the battery is
supplying current.  Thus, although unrelated to the discussion of which
terminal to disconnect, one should not load the battery while it is being
disconnected.

Another tip, also unrelated to the thread but brought up obliquely in the
post, is the proper method of "jumping" a car.  It is sometimes argued that
one should connect the positive jumper cable first at both ends (assuming
negative ground), then connect one end of the negative cable to either
battery, then complete the circuit by connecting the other end of the
negative cable to the other car's frame AWAY from its battery.  Thus the
spark (inevitable in this case because the dead battery will draw current
from the good one) will occur away from either battery. Note that the
grounded side is connected last--whether positive or negative ground.

Bob Wilkinson
72 Spider 

Date: Tue, 14 Jan 2003 03:44:23 -0600
From: Johnson David-QA2282 <David.R.Johnson@domain.elided>
Subject: RE: Which battery lead to disconnect first

.....The key point which no-one mentioned is that the flammable gas
(actually hydrogen, which is about as flammable as they come) is emitted
only at the positive terminal of a lead-acid automotive battery.--
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