blacky

It is not true that charging system is eliminated because engine runs after jump. The engine will run fine on 13 V. A fully charged battery without load shows about 12.75 V.

If it is easy to jump, and if charging system is putting out something around 14.5 V, then it is almost certain battery is at fault. (If it jump starts ok, but only after considerable charging, then the battery is even more suspect.)

Cranking with a fully charged battery is a valid load test. Folks load test their batteries every day when they crank and start their cars.

db/sb

I don't buy the second part of that one. I've had batteries in the past that would start the car if you started it and ran it every day but if you waited say two or three days it became somewhat iffy. Basically a weak cell in the process of becoming worse........

whopper

x2!

blacky

There are many things that could account for the symptoms you describe above.

Suppose there is a 200 mA drain but the battery is fine - it just runs down after a few days. And if that happens too many times the battery really will be shot. The nice man at the load testing place will sell you a new battery. And you would start the process all over again.//

The OP has a multi-meter and knows how to use it. Therefore, a good way to begin is to measure the charging voltage. If anyone disagrees with that, then just say so, and explain.

Corroded battery connections might be the next place to look if charging voltage is adequate; people have replaced batteries thinking they fixed the problem with a new battery, but actually all they did was clean up the connections in the process. A hydrometer test is another next step.

As I keep saying, assuming all else is ok, the voltage across battery should not go down excessively under load. The really big load is starting. The "missing" voltage under load is due to internal battery resistance - when 12.75 V with no load drops to 11.9 V under load, the missing .85 V is the voltage drop across the battery's internal resistance.

If it takes 200 A to crank, then at 12 V the total circuit resistance can't be higher than 12/200 = .05 ohm. If it is, cranking will be slow to non-existent.

db/sb

True...but I told you what was wrong which was solved by replacing the battery (after testing with a load tester...as I said, I have one and have had it for years). I'm not trying to argue with you so you needen't start by directing your response towards me. Some of the things you mention, i.e., checking the cleanliness/integrity of the connections, etc. are among the first things I would check. You know, Occam's Razor, easiest things first. Parasitic drain would be farther down the list. It was just a personal observation based on experience; something else for the OP to consider.

blacky

I think we agree that our focus should be on providing OP with a hand diagnosing HIS observations.

I'm not sure that OP is even with us at this point.