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<p>Here's what I'm not getting: When you go to buy a car battery,
what are the numbers you check first? OK, price, but then you
look at: warranty--usually given in months (72, 84, etc.), and
cold cranking amps (CCA). We all know the warranty doesn't
guarantee how long the battery will last, but how much of a
pro-rated 'refund'--usually a credit towards purchase of another
battery of the same brand--you'll get if the battery expires
before the warranty period ends. CCA gives a rough/reasonable
approximation of how much current--i.e. 'power'--the battery has
to supply in the burst necessary to wake a starter and turn an
engine over in freezing weather (more should be available in
warmer temps). Depending on application, you're gonna want at
least 500 CCA for any car battery, esp. an older car without a
geared reduction starter, and more is better (a typical,
non-geared starter in good nick pulls, I think, about 200-300 amps
for a split second--until the inductive load builds--and you want
a margin). The AGM battery I bought recently for my BJ8 has,
IIRC, 800 CCA.<br>
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<p>These 'pocket' jump-starters typically give their 'power' in
milliamp-hours, or mAh. This is a number usually given for a
power source that is expected to maintain a minimal current over a
period of time; i.e. hours. Further--I'm not an EE or battery
expert, don't play on TV and haven't stayed in a Holiday Inn for
years, so FWIW--to my knowledge Li-Ion batteries are known for
just that; supplying a steady current over time (like in your
cellphone or Tesla). I'd be interested in how many CCA these
jump-starters promise; I don't really care if it'll power my
iPhone for 100hours. <br>
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<p>The problem, I'm surmising--if you're a battery expert please
chime in--is that if you're attempting to jump-start a car with a
totally dead battery the dead battery will sink a bunch of the
current from the starter battery, hence that current won't be
available to rotate the starter armature. Which reinforces my
experience that, if you're attempting to jump-start a marginal
battery these might get you over the top, but if you've got a
completely discharged battery--and it's cold--well, good luck
(which begs the question: Should you disconnect your dead battery
and attempt to jump directly to the disconnected cables?).<br>
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<p>Also, if you've bought jumper cables you've found that the good
ones--with, for instance 'double-ought' (00) gauge wires--cost
significantly more than the cheapies, which might be #2 gauge.
With cheap jumper cables, you're going to put as much energy into
heating the cables--and probably get a drop of a volt or two--as
you are into the starter. The pocket jump-starters I've seen all
have really wimpy cables, which can cause a significant voltage
drop.</p>
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<p>Bob<br>
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<div class="moz-cite-prefix">On 4/29/2018 6:43 AM, White, Stephen
wrote:<br>
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<p><span>I got the "Viking compact power pack" from harbor
freight - worthless. Never did have punch for car battery,
won't even do a motorcycle now. (a year later - used only
for attempted 4 jumps) listed as 12V 12000mAh.</span><br>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt"
face="Calibri, sans-serif" color="#000000"><b>From:</b>
Healeys <a class="moz-txt-link-rfc2396E" href="mailto:healeys-bounces@autox.team.net"><healeys-bounces@autox.team.net></a> on behalf
of John Spaur <a class="moz-txt-link-rfc2396E" href="mailto:jmsdarch@sbcglobal.net"><jmsdarch@sbcglobal.net></a><br>
<b>Sent:</b> Saturday, April 28, 2018 1:25 PM<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:healeys@autox.team.net">healeys@autox.team.net</a><br>
<b>Subject:</b> [Healeys] Portable battery jump starter</font>
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I would like to get a portable battery powered jump
starter. They range in price from cheap to expensive.
Any recommendations?</p>
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TIA,</p>
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John Spaur</p>
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font-family: "Calibri", sans-serif;">
San Jose, CA</p>
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