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That's a good point, though I didn't suggest it because I don't know a normal voltage drop under load conditions, and it varies a bit by battery and car.

All batteries have internal resistance, you can visualize as a voltage source (like a power supply) in series with a small resistance. The internal resistance increases slowly but permanently with age (and excessive heat), and temporarily from discharge (and cold temperatures). This is why a battery is considered discharged at like 11½ volts instead of 0... because the resistance gets so high that there is not much power available. (An axiom of battery power is that the maximum power available under an optimal circumstance is V^2/R where R is the internal resistance. As R goes up, power drops.) This is why, even though you could crank over a car just fine on a charged up 11V battery (if there were such a thing), you would have no chance if you have a 12V battery reading 11V.

So that's why, given the engine won't turn over, a simple voltage reading is useful on its own. 12V batteries go roughly from 12.6V full charge to 11.6V empty. So if you read a voltage of like 11.7V then probably you have a charging system issue and ran the battery dead. If it's like 12.1V and still won't start then the battery is toast.

To be clear, nothing of what Howard said is wrong, I just wanted to explain the slightly different path of reasoning that I like to use.

G'day ErikT,
Very nice looking Packard. to PackardInfo, wish you well in getting your Packard Convertible to start again.

And, I invite you to include your Packard Convertible in PackardInfo's Packard Vehicle Registry.

Hello all, I may be somewhat oldfashioned but I actually carry a spare 6V Optima battery when I take any of my old cars out (not one for each of course). I have used it on the odd occasion, maybe six times in 20 years, but always on someone else's vehicle. It certainly sounded like a supply problem such as a loose terminal, etc. to grind to a halt so suddenly. Even if the battery is dead, the generator will provide the ignition voltage. It is why you can bump start a generator vehicle when an alternator vehicle will not as the generator vehicle does not need exciter current to generate voltage. Peter T

Hello all, I may be somewhat oldfashioned but I actually carry a spare 6V Optima battery when I take any of my old cars out (not one for each of course). I have used it on the odd occasion, maybe six times in 20 years, but always on someone else's vehicle. It certainly sounded like a supply problem such as a loose terminal, etc. to grind to a halt so suddenly. Even if the battery is dead, the generator will provide the ignition voltage. It is why you can bump start a generator vehicle when an alternator vehicle will not as the generator vehicle does not need exciter current to generate voltage. Peter T