Can a bad battery do other damage or throw other symptoms?

[Rtheriaque]

I have an '89 325i.

The other day, the car wouldn't start. Dead battery. A quick jump got her running.

Today, same thing. She had a long run the day before, so it was down to bad battery, fault in the charging system, or a drain.

I did some tests. Per Bentley, the car should have 13.5-14.2V at the battery with the engine running at 1500 RPM. I got 13.52. As I buttoned up, I noticed the battery was covered in condensation. No rain had touched the car. With a manufacturing date of 4/97, I think the battery was my bingo, but I load tested anyway. It passed easily. Hmmm...

I threw the new battery from my '73 2002 into the car. I now get 13.7V at the battery with the motor running at 1500 RPM.

So... I'm leaning toward the E30's battery as being bad. Any other opinions?

[IRON-E]

Your Alternator could be draining the battery. Take the battery to a local shop, to be tested and charged and go from there.

[Rtheriaque]

Like I said, original battery was load tested and passed. Unlike the alternator check, which barely passed, I got a go/no-go from the battery test. No idea if it was a strong pass or a barely pass.

The fact the alternator was putting out more juice to one battery than the other feels like a clue to me.

[jlevie]

Put a new battery in and see what happens. It does sound like the one have is bad.

[george graves]

What's your voltage after sitting overnight on the old battery?

[atldohc]

if you already have another battery why not throw it in and try starting it again the next morning. then youll know if its the battery or a parasitic draw somewhere