Battery Resistance testing Temperature

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Aug 29, 2009
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I have a Digital Harbor Freight Battery tester that gives resistance reading based on the CCA value you put in based on your battery. Does the Temperature at the time of the test affect the estimated CCA that the battery has at the time? What ambient temp do I use to test? I have seen the voltage table vs temp to rough guess a state of charge. I know there are more accurate testing equipment out there. Thanks
 
Yes it does. The Midtronics tester takes the battery temp via an infared thermometer. The HF does not have this feature. I would assume it's calibrated for room temp, so readings below 68'F will show the battery in worse shape than it really is.

The manual makes no mention of temp.
 
Technically speaking, in most cases when measuring at ambient temp, it should be CA instead of CCA.

In practicality, it is more of a pass-fail test. So if it still have a Amp-acity beyong a certain percentage then the battery is good or operational.
How good, it depends on the percentage value which when it is closer to the lower threshold then you may want to consider buying a new battery especially when the temperature gets colder.
 
yes, cranking amps drops when temperature drops. That's because amps are a function of voltage over resistance.

That being said, I noticed with Project farm testing batteries that he measured increased resistance at very low temperatures aswell, so that's a double whammy
 
Getting a correct impedance value is an art and takes much more specialized equipment than an HF sensor or a midtronics unit.

Impedance varies with temperature and SOC, as well as ageing.
 
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Last year I had an intermittent battery warning light advising to turn on the vehicle cause the battery was too low to run radio etc. I replaced the battery after bad load testing and such. 9 months later I got the warning again on a cold morning after not driving it for a few days. I brought out the Noco 3500 and put it on battery for 6-8 hours each over several days. The green light still never goes completely out on the charger, but should be getting closer. The HF tester showed around 12.3 volts at around 30 degrees and 687 out of 1045 rated CCA. I'm sure the CCA would be higher closer to 78-80 degrees.
 
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The HF carbon pile tester has an analog meter and a couple of scales on the voltmeter so you can read using the one closest to the actual temp of the battery. While the battery must be fully charged to do a proper test, its a better test than the conductive test done by a Midtronics.
 
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