When to Replace Battery?

[HorseThief]

Originally Posted By: TheLoneRanger
I read that a battery should be replaced when the voltage drops to 12.4v on a fully charged battery.
Is this true?

No... there's a lot more to it than that - like if the battery is dropping to 12.4V (with no load), is it REALLY fully charged? Automatic/smart chargers will almost never FULLY charge a lead acid battery - nor will your alternator. Put it on a manual charger @ 2-6 amp mode for about 8hrs and THEN see what the voltage holds at. Otherwise, if the battery is still dropping down below 12.5 (again - with NO LOAD) then the plates have likely shed too much lead sulfate and there's no way to put it back and make it part of the battery again. Go easy on the manual charging though - if your specific gravity goes too far north of 1.27ish (about 12.65-12.7 resting voltage) you start increasing rate of corrosion due to higher acid concentration (either from charging or evaporation/electrolysis)

otherwise, all batteries fail eventually. Getting a battery load test is a good indicator of health though. Forget about the small electronic testers - they're only a best guess. If you want to test a battery for cranking amps AND capacity you need to do a full 15 second load test at 50% of the battery's rated CCA. Anything else (aside from the fancy electronic bench testers at AZ and similar stores) is just an indication of it's ability to start the car IF the battery is fully charged - which, big fudgin deal, I can figure that out by turning the key. I wanna know if it's gonna hold it's charge parked overnight.

Finally, if your battery is dropping to 12.4 installed in the vehicle, then that's acceptable. I'd be more interested in a reading after 24 hours of sitting.

 

[i_hate_autofraud]

Remember, the meter you use to measure 12.4V may not be that accurate - load test the battery, if it passes,
keep using it until you get a slow crank.

Good batteries can fail if the alternator is on the way out.

Measure the battery voltage - engine off.

Start the engine - battery voltage will jump up to over 13V, if not you have an alternator issue!

 

[Rolla07]

When it dies. LOL

 

[92saturnsl2]

I replace mine when I notice slow cranks. There is usually ample warning between the first slow crank I notice and when the battery leaves me stranded. I've never been stranded due to a battery issue [knock on wood], I've always been able to catch them in time.

I don't trust the chain store battery testers. I once installed a brand new battery into a pickup I owned- the same day my girlfriend took the truck to return a loan-a-tool to Advanced Auto and the truck wouldn't start. The guy at Advanced Auto got his fancy tester, and pronounced my brand new battery (that I bought at Autozone) DEAD. He proceeds to tell my girlfriend that Autozone batteries are the worst you can buy, and tries to sell her a new one. (both store brands are likely made by Johnson Controls and are exact same battery.)

I had to meet her at the store and discovered the battery terminal was loose-- tightened it up and that "DEAD" battery lasted me years until I sold the truck.

A few months ago my Odyssey minivan was in for an airbag recall. Their 99 point whatever inspection determined the battery tested at less than 25% of its rating. They said it would soon leave us stranded and attempted to sell us a new one. Months later, it is still working fine, including taking a cross country trip recently, including lots of time with the ignition in the ACC position without the engine running (charging phones, playing stereo, etc.) The van also has power doors which are a huge drain on the battery and our 4 kids use them constantly.

I typically get 5-6 years out of a battery. I once had a '00 Pontiac Bonneville where the battery was located under the rear seat cushion. It still had the OEM battery at the 10 year mark, and I never changed it in the few years I owned the car.

 

[blupupher]

< than 12.4 v after a day of no use or < 9.6 v while starting.


Or 5 years.

I usually never get that far, but my mom's NAPA battery was right at 5 years and was 12.6v and 9.9 starting when I replaced it 2 weeks ago.
Sold that battery for $25 instead of returning it for the $15 core.

 

[Vikas]

Quote:
Be cautious using those types of testers, I have seen lots of batteries did shortly after using them, of course the battery was on the edge anyway but those thing will put the final nail in the coffin.


Isn't that true of almost any type of "true and direct testing"? I mean if the doctor puts me on the stress test and my heart might just say "I had enough"

BUT, I am with you; I too would NOT recommend the old style carbon tester because the newer inductive digital testers seems to be good and cheap enough these days.

 

[HorseThief]

Originally Posted By: Vikas
Quote:
Be cautious using those types of testers, I have seen lots of batteries did shortly after using them, of course the battery was on the edge anyway but those thing will put the final nail in the coffin.


Isn't that true of almost any type of "true and direct testing"? I mean if the doctor puts me on the stress test and my heart might just say "I had enough"

BUT, I am with you; I too would NOT recommend the old style carbon tester because the newer inductive digital testers seems to be good and cheap enough these days.


the trouble is that they often fail to properly ID a bad battery in the case of a single bad/marginal cell. A carbon pile load test tells so much about a battery in one fool-proof simple test that every automotive battery is built to handle without any detrimental effects.

Ask ANYONE with a 2010+ equinox or similar gm platform and also smaller cars if they noticed any slower cranking pr had any indication the battery was failing before it just died completely - the batteries crank the vehicle just fine and may even report as good on a conductance (cca) tester, but they're shot for capacity due to being cycled constantly by the infotainment system, security, and lighting. They really should spec AGM batteries, but the longevity gains would be minimal and they would just push their "smart" charging systems further. The battery in my parent's car still tested at 80% of it's rated cranking amps with a midtronics tester, but dropped like a rock after 8 to 10 seconds on a load tester. This was on a 3.5yr old battery of a vehicle that was regularly driven.

And speaking as someone who has used a variety of load testers and capacity testers -from carbon pile 1000A to midtronics, ancel, and solar brand testers of varying models and levels of complexity. Except for the bench testers that actually do put a drain on the battery, everything else is just an educated guess.

 

[TheLoneRanger]

What exactly constitutes an overcharged battery?

My new AGM showed 13.3v after being left on a BatteryTender charger for a couple days. (It reverts to a float charger automatically and turns off when it senses a full charge.)

This is more volts than my flooded batteries have shown even when new. Is it common for an AGM to hold this much voltage?

Thanks.

 

[bbhero]

AGM batteries hold a higher charge level when fully charged vs a flooded battery. Your 13.3 is quite likely a normal expected number for a charged AGM battery.

 

[circuitsmith]

Originally Posted By: billt460
Out here batteries don't give you signals or warnings. They just drop dead. Like a retiree on a golf course.


Back in August 2001 I drove out to Tucson to visit an old friend (and others along the way).
We went out in the desert in his pickup, mid-day, to look at some property he bought to build a house on.
Got back in the truck to head back and... nothing. No crank, dim dome light.
2 1/2 year old battery.
We stupidly brought no water with us, no sign of civilization in sight.
It was on an incline and it was a stickshift so we tried to roll-start it, rolling backward: no good.
Luckily a nice lady in a Cadillac came along after about 1/2 hour and went and got a pickup with jumper cables.
Drove back with the AC cranking.
When he pulled in the driveway as soon as he turned off the AC the engine stalled.
I had been basically running with an open battery.

 

[George Bynum]

Originally Posted By: HorseThief
Ask ANYONE with a 2010+ equinox or similar gm platform and also smaller cars if they noticed any slower cranking pr had any indication the battery was failing before it just died completely - the batteries crank the vehicle just fine and may even report as good on a conductance (cca) tester, but they're shot for capacity due to being cycled constantly by the infotainment system, security, and lighting. They really should spec AGM batteries, but the longevity gains would be minimal and they would just push their "smart" charging systems further.


We have a 2013 Equinox, 4 cylinder on the original #47 battery. I'd noted slightly longer cranking (my wife didn't, and it's her car) for about 6 months. 3 weeks ago, she said there was a power steering problem message on the dash. It has electric power steering; I told her it was probably the battery. She then realized that she had observed slower cranking too.

New (size #48) battery and all is well.