Packard Forum Index » Pre-War (1899-1942)

Quote:

If the battery needs to be charged in order to test it, they may want to keep it and charge it. If you can charge it first it they can just run the test. Some of the testers will give the result that you should charge the battery and retest.

Static resting voltage of a fully charged 6 volt battery should be about 6.6 volts. That's charged and at rest....not tested immediately after charging.
During cranking you should NOT see a 2volt or more drop. If you do, something is amiss. Incorrect size cables, corrosion at terminals and even crawling in the copper cable itself, abnormal resistance somewhere (mag switch or starter solenoid, or bad armature,etc.)
test fully charged battery at rest with carbon pile tester at ONE-HALF CCA's...2 volt or more drop battery needs replaced
test fully charged at rest with a electronic digital tester for "state of charge" "pass" or "fail" etc. if the battery has been charged and it tells you to charge and retest, battery is bad.
Cables should be AT LEAST 0 awg.on a 6 volt system. I use 00 awg. because that's what I have in stock..and a T&B crimper..Please use a GOOD crimper when making cables, the crimp is very important, as is the use of heat shrink tubing over cable and terminal.
Finally, the GROUND is as IMPORTANT as the FEED. Do not neglect the ground cable or grounding point. PB

It is well understood that, subject to some variance, a fully charged 6V battery is 6.4V and a discharged one is 5.8V, with no load. A typical cranking current is given right in the service manual (Specifications section) and it's basically 200 amps for every 50's I8 except about 10% higher on the high compression '54 engines. Considering a modern 2E battery is 650 CCA, a good battery should have no problem cranking over. The CCA rating is the maximum current draw that you can crank for 30 seconds at 32F without dropping below 7.2V (for a 12V battery) which is equivalent to a 2.7V drop on a 6V battery.

FYI, you can measure current draw by taking a careful resistance measurement of a battery cable with a milliohm meter, then measuring the drop with a voltmeter while it is in use. This would require calibration of the leads of the meter, etc. and is not something that most people have lying around, but it is possible.

Therefore you shouldn't be too close to that amount of drop unless the battery is going out. As the battery wears out, it develops more internal resistance, causing a larger voltage drop across the terminals for the same current output. In this example, a 2.3V drop on a 200A load doesn't make sense for a healthy 650CCA battery.

It looks like I'm right on the borderline on voltage drop at the starter end. I'll check the cranking voltage at the battery posts after leaving the battery on a 3 A smart charger overnight, and I need to check that the ground cable attachment at the frame is clean and tight. I think I have a 24" battery cable with an "eye" at each end. Putting that between the ground point on the frame to a handy bolt on the engine or transmission can't hurt.