{"id":6353,"date":"2014-11-10T20:53:50","date_gmt":"2014-11-10T20:53:50","guid":{"rendered":"http:\/\/www.oracletutoring.ca\/blog\/?p=6353"},"modified":"2018-01-27T23:16:08","modified_gmt":"2018-01-27T23:16:08","slug":"auto-batteries-part-two-cold-cranking-amps-and-internal-resistance","status":"publish","type":"post","link":"https:\/\/www.oracletutoring.ca\/blog\/auto-batteries-part-two-cold-cranking-amps-and-internal-resistance\/","title":{"rendered":"Auto batteries, part two: cold cranking amps and internal resistance"},"content":{"rendered":"

The tutor continues to explore auto batteries (aka car batteries). \u00a0While this topic is rare during tutoring, it’s probably relevant to virtually everyone at some point….<\/h1>\n

\u00a0
\nI recall, decades ago, a friend of mine bought a new battery for his car. “It’s got 600 cold cranking amps,” he smiled. “No more doubts about starting.”<\/p>\n

I soon learned the meaning of 600 cold cranking amps: his car started perfectly from then on. At the same time, he was impressed by the number because of its technical meaning; being a mechanic, it spoke to him in a more precise way.<\/p>\n

Years went by: I finished my degree, then went back for (of all things) some mechanics training. Today, when events from the past pop in my head, I try to answer questions that I let go at the time.<\/p>\n

So it is with the issue of “cold cranking amps”. The other day I suddenly realized: if a 12-volt battery is pushing 600 amps, its internal resistance must be less than 12\/600=0.02Ω. The obvious question: do car batteries really have internal resistance that low?<\/p>\n

I started searching the net. The answer was harder to find than I’d expected, but here are some numbers:<\/p>\n\n\n\n\n\n
car battery resistance<\/td>\nlink<\/td>\n<\/tr>\n
0.003\u03a9<\/td>\nchiefdelphi.com<\/a><\/td>\n<\/tr>\n
0.01\u03a9<\/td>\ntap.iop.org<\/td>\n<\/tr>\n
0.001\u03a9<\/td>\nfurryelephant.com<\/a><\/td>\n<\/tr>\n<\/table>\n

So I guess it’s true: 600 cold cranking amps – or even more – is possible, based on internal resistance alone.<\/p>\n

I have yet to define “cold cranking amps”; I will do so in a coming post. Cheers:)<\/p>\n

Jack of Oracle Tutoring by Jack and Diane,<\/a> Campbell River, BC.<\/p>\n","protected":false},"excerpt":{"rendered":"

The tutor continues to explore auto batteries (aka car batteries). \u00a0While this topic is rare during tutoring, it’s probably relevant to virtually everyone at some point…. \u00a0 I recall, decades ago, a friend of mine bought a new battery for …<\/p>\n

Auto batteries, part two: cold cranking amps and internal resistance<\/span> Read More »<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[188,11,181,7],"tags":[280,284,283],"class_list":["post-6353","post","type-post","status-publish","format-standard","hentry","category-autos","category-chemistry","category-lifestyle","category-physics","tag-car-battery","tag-internal-resistance-of-auto-battery","tag-internal-resistance-of-car-battery"],"_links":{"self":[{"href":"https:\/\/www.oracletutoring.ca\/blog\/wp-json\/wp\/v2\/posts\/6353","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.oracletutoring.ca\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.oracletutoring.ca\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.oracletutoring.ca\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.oracletutoring.ca\/blog\/wp-json\/wp\/v2\/comments?post=6353"}],"version-history":[{"count":21,"href":"https:\/\/www.oracletutoring.ca\/blog\/wp-json\/wp\/v2\/posts\/6353\/revisions"}],"predecessor-version":[{"id":28854,"href":"https:\/\/www.oracletutoring.ca\/blog\/wp-json\/wp\/v2\/posts\/6353\/revisions\/28854"}],"wp:attachment":[{"href":"https:\/\/www.oracletutoring.ca\/blog\/wp-json\/wp\/v2\/media?parent=6353"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.oracletutoring.ca\/blog\/wp-json\/wp\/v2\/categories?post=6353"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.oracletutoring.ca\/blog\/wp-json\/wp\/v2\/tags?post=6353"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}