Testing A Battery - On Vehicle, or Pull It?

[barlowc]

Earlier this week, I had to replace the battery in my Nissan which was four years old. It got me to thinking about the battery in our Saturn which is over five years old. I don't really want to replace a battery that still has years of life left in it, but I also don't want to get stranded someplace because it dies.

I had it tested at AutoZone back in December. They came out to the parking lot, popped the hood, hooked up their tester, and said it was good. I'm thinking about having it checked again before we take the vehicle on any of the upcoming family trips.

What's the best way to get the battery tested? Pull it, take it up to the auto parts store, and have them test it on the counter cold? Or drive the car up and have them pop the hood and test it on the vehicle, which would be warm at that point? Does it matter?

 

[exranger06]

It doesn't matter. I test batteries all the time at work, both in and out of the vehicles.

 

[sasilverbullet]

I would drive it to Autozone or o'reillys and have them run the test on the battery with engine off. Then start engine and have them run the charging test. Make sure you turn on high beams, A/C, radio to load it down.

If it all checks out, press on and enjoy it!

 

[Tegger]

How to test the battery while it's still installed in the car, ignition OFF, key OUT...
1) turn headlights ON, and wait 5 minutes.
2) turn headlights OFF again, and wait another 5 minutes.
3) using a DVOM, measure for voltage across the battery's terminals.

Once you have your reading, go here: http://batteryfaq.org/
and download the Excel file under the link entitled, Temperature Compensated Battery State-of-Charge (SoC) Table.

If the reading you get is NOT one of the acceptable readings shown in Bill Darden's file, then the battery is unable to hold a full-charge, or the alternator is not operating correctly.

 

[typ901]

Solid post Tegger.. Thanks.

 

[eljefino]

The Midtronics tester they use compensates for battery temp; it has a little IR thing one points at the battery case.

It doesn't actually load test, but rather send a high frequency current through the battery and tests its internal resistance, from which it infers CCA. It also allows a "system test" which one just follows the directions on the screen; it watches voltage dip during starting, tells you when to rev the motor, when to turn on accessories-- very cool and idiot proof.

The "pass point" is 50-60% of rated CCA. Don't be alarmed if you're down some.

 

[Bgallagher]

Originally Posted By: Tegger
How to test the battery while it's still installed in the car, ignition OFF, key OUT...
1) turn headlights ON, and wait 5 minutes.
2) turn headlights OFF again, and wait another 5 minutes.
3) using a DVOM, measure for voltage across the battery's terminals.

Once you have your reading, go here: http://batteryfaq.org/
and download the Excel file under the link entitled, Temperature Compensated Battery State-of-Charge (SoC) Table.

If the reading you get is NOT one of the acceptable readings shown in Bill Darden's file, then the battery is unable to hold a full-charge, or the alternator is not operating correctly.


Perfect

 

[mechtech2]

Waiting 5 minutes with the headlights on is excessive. All you want to do is remove the surface charge, to get a decent rest voltage.
A load tester is great, properly used.
And don't forget the old hygrometer to check each individual cell for specific gravity.

 

[Donald]

Originally Posted By: Tegger
How to test the battery while it's still installed in the car, ignition OFF, key OUT...
1) turn headlights ON, and wait 5 minutes.
2) turn headlights OFF again, and wait another 5 minutes.
3) using a DVOM, measure for voltage across the battery's terminals.

Once you have your reading, go here: http://batteryfaq.org/
and download the Excel file under the link entitled, Temperature Compensated Battery State-of-Charge (SoC) Table.

If the reading you get is NOT one of the acceptable readings shown in Bill Darden's file, then the battery is unable to hold a full-charge, or the alternator is not operating correctly.


This will work, but you need a pretty accurate DVM. NOT the free one at HF.

 

[Tegger]

I've been following the five-and-five method for surface-charge-removal for years with good results, but it appears the famous Bill Darden has a better method, where you let it sit TEN minutes after turning the headlights on for five.

Go here: http://www.batteryfaq.org/

On that page, click on: Car and Deep Cycle Battery Frequently Asked Questions (FAQ) 2012
Then click on: 4. HOW DO I TEST A BATTERY?
Item 4.3 tells how to remove the surface charge.

And my $25 iEquus Innova DVOM is plenty accurate for this test.