I'm trying to figure out why my battery keeps dying every 3 years, and am wondering if the alternator is misbehaving.

I took some measurements today, and observed the following - with the engine off, the battery voltage is about 12.7V. When I start the engine, it jumps to 14V. So far so good.

Then I tried it later, and saw that the voltage took almost 2 minutes to rise from 12.7V to around 13.9V with the engine running. It was a slow and steady rise, but very different from the other time I started it.

Does this indicate a bad alternator? Can someone suggest a standard technique of diagnosing an alternator, especially if its malfunciton is intermittent?

Leon

 

You can buy a load tool. It's a silver box with battery cable leads and clamps that you can attach to the battery. It can put a load on the battery with engine off or while running to see if the alternator responds in a bad way. You may be able to recreate the condition that way. I think you should be able to get it at a local auto parts store or even maybe borrow one.