> From: jtc@ccwf.cc.utexas.edu (James TenCate)
>
> The TR8 has a nasty design flaw: the starter always seems to get
> cooked by the catalytic converter (causes hard starting when hot,
> especially here in TX). Sooo, I'm always interested in batteries
> with lots of "juice." Can anyone tell me what's new and great
> about these new "high heat" batteries I'm beginning to see? Do
> they give you more cranking amps than a normal battery when it's
> hot out?
Um, ... *all* batteries provide more current when hot. (It's a chemical
reaction, and, as you remember from chemistry classes, chemical reactions
work "faster" at higher temperatures.) Those "high heat" batteries are
most likely just constructed more durably, as the high temps also hasten
the deterioration of the lead dioxide anode and the sponge lead cathode.
> (I can use all the amps I can get :-)
I beg to differ with you, James. For the starter to crank slowly when hot,
it's either binding (yuck!), or, more likely, it's wound with too light a
gauge of copper wire, so that the internal resistance goes up intolerably.
(You could determine which of these is the case by measuring the "cold" start
current with a current clamp, then comparing this to the "hot" starting
current:
if (cold < hot) {
mechanical_binding
} else if (hot < cold) {
high_resistance
}
;-)
In the first case, more current available from the battery will just tend to
cook the starter more; you should try to find out which is the case before
you go get a "stronger" battery! (Again, the second case is more likely,
especially if the starter is slowly being roasted by the cataclysmic
converter. Realize that the internal resistance of the starter (including
the field windings, the brushes, and the armature windings) only needs to
increase from ~5 *milli*ohms to ~10 *milli*ohms to cut the power delivered
to starting the engine by a third.)
Pat Vilbrandt
(From Seattle, where today it's 60 degrees and raining!)
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