What does a low battery really mean?

My 2001 Chevy Tracker would not turnover, all the lights & radio came on, NO SOUNDS, then it dies. Everyone says its the starter, the online searches say its the starter. I get the starter replaced this morning and the service tech tells me the battery (which I just bought in April) is very low and needs to be replaced. I ask can I wait til Saturday, he says I’m taking a big risk. Is it possible the alternator was the real problem?

The charging system should be tested as a normal proctocol when changing the battery, but if the battery is shot it’s likely the source of the problems…and if it’s the original battery it’s lived a full life. It’s time.

A “low battery” as in this scenerio means the plates have lost their ability to retain a charge.

Did you check the battery before changing the starter?

If the battery was purchased in Apr 09, it should be covered under warranty. Take it back to where you purchased it, and let them load test it for you.

Before telling you the battery is bad, the tech should have also done the alternator charging system test, to narrow down what exactly was bad.

unfortunately in an attempt to save money i had a friend change the battery for me. it was the original battery and i was being told that the sluggishness of my car was most likely due to a 9 year old battery. so i went with the persons advice and had them change the battery for me, which i purchased at a local auto store.

see my note below. The warranty should be good, since it has been six weeks or less since the purchase. Round up the store receipt, have them verify how good/bad the battery is, and you should walk out with a new battery at no additional charge, if the battery fails the load test.

Apologies. I missed that statement that you’d put a new battery in.

Yes, the slternator I’d consider suspect. Follow Jayhawk’s advice to get the charging system checked.

thanks for the info. finally got a call back from the service station, i’m going to bring the car back so a test on the alternator can be done.

Always charge a new battery before installing it in your car. Failure to charge a battery MAY cause an alternator failure (depending on how long the battery has been sitting on the shelf).

From experience I find that the chance of a new battery killing your alternator is about one in ten.

wow, thank’s for that. would not have even known to do that.

The water pail analogy is usually a good one to get the basic concepts down.

Imagine that your battery is a large water pail.
There is a full line near the rim. This is your pail’s POTENTIAL.
When it’s new, you can fill the pail to the line and it holds 1 gallon of water. This is your pail’s CAPACITY= 1 gallon.

Over time, you add rocks to the pail. This simulates what happens to your battery as it ages.
The rocks displace water such that you can still fill the pail to the full line but there is less and less water in the pail. Your pail’s CAPACITY has dimished but it can still achieve the same POTENTIAL.

Your alternator is the device that replenishes the pail with water. It will only fill up to the POTENTIAL line. It has no knowledge of your battery’s CAPACITY only when it is up to its full potential.

When you have a problem like you describe, the first thing to verify is whether or not the alternator is doing its job and supplying energy back to the battery.

Your starter motor is one of, if not the most, demanding load on your battery in terms of its capacity. Any weakness in the battery capacity will manifest itself when you attempt to start the engine. So replacing a starter motor at the first sign of cranking difficulty is a mistake. First, they should check the alternator to insure it can produce the desired battery potential+charging voltage. If the alternator is OK, then they should perform a load test on the battery. This tests the battery’s capacity. Only when both of those tests are complete should they consider diagnosing the starter motor circuit. And that diagnosis checks all sorts of possible problems before the motor itself is considered. Things like corroded connections, bad solenoid and so on.

As mentioned, your battery is at the age where it is suspect. But the proper diagnosis is easy to perform and insures that the right parts are replaced without undue expense and repeat visits.

Hope this was helpful and best of luck to you.

Never in 35 years of professional auto mechanics (and electrical was my speciality) have I ever experienced this had a co-worker experience this or had a customer experience this.

I have been exposed to the water pail analogy used to explain AC theory, you are bailing out buckets of heat.

When I first started turning wrenches, I was trained to perform a complete electrical check whenever there was a problem related to vehicle electrics. The customer is billed .5 an hour for the entire thing and that’s pretty cheap IMHO for covering all of the bases at once.

Battery on charger for a minimum of half an hour.
Load test battery.
Alternator output test.
Starter current draw test.
Parasitic current draw test. (Does not include tracing down to the nth degree where a problem lies; only that one exists and that it exists in a certain circuit.)