Battery issue?

[Drew99GT]

My mom's 2007 Impala has been cranking slow since the weather turned cold. I went to 2 different parts stores to have the battery tested and both it and the alternator checked out OK at both stores, but the battery was low on charge. It had about 410 CCA when it's rated at 600 (factory AC Delco battery). Both guys at the parts stores said charge it and it should be fine, so that's what I did. Now it does start better. My question is, why isn't the alternator keeping it fully charged even when both it and the battery are still good? One guy at the parts store said it's normal for that to happen as the alternator will keep the battery charged at the batteries current capacity or something to that effect. He made it sound like the battery can develop a memory.

Thanks for any input guys.

 

[Kuato]

When batteries get old, they cannot charge as much as when they are new. Some batteries have "memory" while others just have reduced capacity as the chemicals inside are depleted.

The alternator and charging system send charging voltage to the battery until the charge rate is reduced to a certain amount, at which time charging voltage is no longer sent to the battery. This protects the battery from overcharge.

I'd bet your battery is the original one; in my experience factory batteries last 4 years or less.

 

[AuthorEditor]

I agree that you probably need a new battery--I generally figure 3 to 5 years max. However, you could also have dirty and corroded connectors, or they could be loose. Clean and tighten everything up and see how it does.

 

[Bluestream]

have a look at the plates to see what condition they are in. Look for separation, and dark colored acid.

 

[SrDriver]

I understand that the batteries sold by Wal-Mart get high marks.

 

[wrcsixeight]

Lead acid car batteries have no Memory effect.

A battery must be fully charged for a Load tester to give an accurate reading. Load testing a partially charged battery will not give good results.

Basically, any new battery is beginning to decline in capacity, right off the assembly line.

The best way to make a battery last a long time is to keep it at, or as near to fully charged it's entire life.

If a car does a bunch of short trip, at night with the blower motor on, the alternator might not get a chance to fully charge the battery.

If a car sits for a while in between use, some parasitic draws like the computer and stereo memory, along with the wireless door locks are always drawing down the battery slightly.

Once again short drives might not be enough to fully charge the battery.

As the battery ages, the resistance within increases, making it even harder to truly fully charge the battery.

When a battery sits below 80% charged, the plates are building sulfates on them. The longer these sulfates sit, the harder they become. The more sulfates that form, the less capacity of the battery.

YOu can try regular overnight charges. You might be able to dissolve some of the sulfation back into the electrolyte and restore a little capacity, but with winter coming/here, that battery can fail on the coldest, worst moment possible.

So you can hope the battery lasts the winter and then some, or you could preemptively replace it. Your call.

Without you putting a voltmeter on the battery terminals with the car running, we cannot tell you if the charging system is working to it's potential. But it likely is and you are just expecting too much from an old battery and your alternator and charging circuit.

 

[rshunter]

Originally Posted By: SrDriver
I understand that the batteries sold by Wal-Mart get high marks.

I've had excellent luck with them. Plus, you can't beat being able to pick up a battery at 3am, which is usually when you find yourself stuck needing one.

 

[Steve S]

Originally Posted By: wrcsixeight
Lead acid car batteries have no Memory effect.

A battery must be fully charged for a Load tester to give an accurate reading. Load testing a partially charged battery will not give good results.

Basically, any new battery is beginning to decline in capacity, right off the assembly line.

The best way to make a battery last a long time is to keep it at, or as near to fully charged it's entire life.

If a car does a bunch of short trip, at night with the blower motor on, the alternator might not get a chance to fully charge the battery.

If a car sits for a while in between use, some parasitic draws like the computer and stereo memory, along with the wireless door locks are always drawing down the battery slightly.

Once again short drives might not be enough to fully charge the battery.

As the battery ages, the resistance within increases, making it even harder to truly fully charge the battery.

When a battery sits below 80% charged, the plates are building sulfates on them. The longer these sulfates sit, the harder they become. The more sulfates that form, the less capacity of the battery.

YOu can try regular overnight charges. You might be able to dissolve some of the sulfation back into the electrolyte and restore a little capacity, but with winter coming/here, that battery can fail on the coldest, worst moment possible.

So you can hope the battery lasts the winter and then some, or you could preemptively replace it. Your call.

Without you putting a voltmeter on the battery terminals with the car running, we cannot tell you if the charging system is working to it's potential. But it likely is and you are just expecting too much from an old battery and your alternator and charging circuit.
especially when cold!!!

 

[Whimsey]

My 9 year old F150 has it's original battery. I'm in "cold" NJ so it sits outside all the time winter to winter. So far it starts on the on the first crank. All of my Ford factory battery's have been great. I know I'm on borrowed time. But it seems a waste to replace a good acting battery. I work within 10 miles of home so if "acts" up I can replace it easily. There is an Advanced Auto Parts across the street from work if worse becomes worse.

Whimsey

 

[scott1966]

heat is what shortens battery life, cold is fine for a battery (less self discharge). 0w oils and electronic fuel injection along with electronic ignition , you can go out and start your car at -40 with out much cranking!