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Discussion Starter #1
Okay so my 2012 Focus S. Has just a tad over 42k on the odometer. This winter I've noticed something quite annoying. We have a jeep that's just easier to drive in the winter so we drive it occasionally. So the focus sits for 2-3days at time. Well in that time the battery goes dead. And I have to jump start it. I have no extra accessories other than what came factory on it.

Is it quite possible I'm already due for a new battery? I first thought it had to do with the cold snap we had right after Christmas. But its still doing it and it's been 30-40* for weeks.

Any thoughts, thanks. Just hoping I'm not missing some sort of TSB or what not.
 

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Rebecca
2016 Focus ST
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You're not under warranty by chance are you? Probably a bad cell in the battery. I had that happen to a Mustang GT and the dealer replaced it under warranty.
 

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Discussion Starter #3
36k bumper to bumper and 60k drivetrain.
 

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The battery should be covered under bumper to bumper. If you are familiar with batteries and how to inspect them, I would suggest checking fluid level in the battery before hand, so that it is not dismissed as "warranty voided due to neglect."
 

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Premium Member
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Really can't guess without testing.

Some batteries gave up early, some may not be quite as good at 3 years old - some cars have had more static drain than normal.

Easiest to get the battery checked first after charging it up to see if that's the problem.

Assume it's clean & dry with terminals in good condition.
 

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How dead is dead?

My battery voltage (after the car has been off and resting for a few hours/days) has been ~11.7V for well over a year (the first time I checked it). It hasn't given me a single problem starting.

Should I replace the battery anyway? I wasn't planning on it, but I guess it could be causing some wear on my alternator or something.

EDIT: That's via the dash TEST MODE menu - so maybe it's just not that accurate? I haven't checked it with a multimeter yet. Obviously, that's something I'll do before shelling out the money for a new battery that might not be necessary.
 

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Premium Member
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It needs to maintain over 9.6 v while cranking, if it can do that it'll work OK.

(3 second full load standard, normal cranking requires less output)
 

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Focus Addict
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My battery voltage (after the car has been off and resting for a few hours/days) has been ~11.7V for well over a year (the first time I checked it). It hasn't given me a single problem starting.

Should I replace the battery anyway? I wasn't planning on it, but I guess it could be causing some wear on my alternator or something.

EDIT: That's via the dash TEST MODE menu - so maybe it's just not that accurate? I haven't checked it with a multimeter yet. Obviously, that's something I'll do before shelling out the money for a new battery that might not be necessary.
It's not accurate as it's about 1v less than actual, I've had the battery in the ST reading around 11.7 or so in test mode but when I hooked up a multi meter and probed the terminals it came back as 12.7+V. Obviously it puts a load on the battery to run the car with the engine off to take the reading but 1.0 V exactly idk.
 

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It's not accurate as it's about 1v less than actual, I've had the battery in the ST reading around 11.7 or so in test mode but when I hooked up a multi meter and probed the terminals it came back as 12.7+V. Obviously it puts a load on the battery to run the car with the engine off to take the reading but 1.0 V exactly idk.
Thanks for the info!

I'll have to check the battery with a multimeter to compare (which also has its own range of accuracy). I'll disconnect the terminals to rule out anything that might be using voltage (the screens, parking lights, modules, etc.)
 

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Premium Member
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Ah, the rest of the story.

suss got it, standard numbers are as measured directly at the battery.
 

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__________/\__
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My battery voltage (after the car has been off and resting for a few hours/days) has been ~11.7V for well over a year (the first time I checked it). It hasn't given me a single problem starting.

Should I replace the battery anyway? I wasn't planning on it, but I guess it could be causing some wear on my alternator or something.

EDIT: That's via the dash TEST MODE menu - so maybe it's just not that accurate? I haven't checked it with a multimeter yet. Obviously, that's something I'll do before shelling out the money for a new battery that might not be necessary.
I have a voltmeter plugged in to my console power port and it also reads low(about 11.9 volts) before I start the car.

The only reading you can trust is at the battery terminals and only after you drain the surface charge off; otherwise, you will receive an artificially high reading of voltage:

"Lead acid batteries are sluggish and cannot convert lead sulfate to lead and lead dioxide quickly enough during charge. As a result, most of the charge activities occur on the plate surfaces. This induces a higher state-of-charge on the outside than in the inner plate. A battery with surface charge has a slightly elevated voltage. To normalize the condition, switch on electrical loads to remove about one percent of the battery’s capacity, or allow the battery to rest for a few hours. Surface charge is not a battery defect but a reversible condition resulting from charging."

http://batteryuniversity.com/learn/article/water_loss_acid_stratification_and_surface_charge
 

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Discussion Starter #12
Battery and charging system passed. So I'm not sure what else it could be. The battery is showing good on the little "view" bubble on top.
 

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My battery voltage (after the car has been off and resting for a few hours/days) has been ~11.7V for well over a year (the first time I checked it). It hasn't given me a single problem starting.

Should I replace the battery anyway? I wasn't planning on it, but I guess it could be causing some wear on my alternator or something.

EDIT: That's via the dash TEST MODE menu - so maybe it's just not that accurate? I haven't checked it with a multimeter yet. Obviously, that's something I'll do before shelling out the money for a new battery that might not be necessary.
Hi PratoN,

Have you had a chance to talk to your dealer about this? I want to see how I can jump start this situation. ;) Let me know when you have an appointment set up, along with your mileage.

Meagan
 

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Focus Preacher
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It's not accurate as it's about 1v less than actual, I've had the battery in the ST reading around 11.7 or so in test mode but when I hooked up a multi meter and probed the terminals it came back as 12.7+V. Obviously it puts a load on the battery to run the car with the engine off to take the reading but 1.0 V exactly idk.
Nope, it's just a simple voltage reading at the PCM power pins. You get near 1V of drop-out voltage because of the wire resistance (small wires) in the harness.

Best way to measure REAL voltage of the 12V battery is to let the voltage stabilize (+/- 120 mins) before taking the reading and use a voltmeter directly at the battery terminal. (Don't use TEST MODE)



12.8V 100% (higher than that you need to wait before taking measurement)

12.4V 75%

12.2V 50%

12V 25%

11.8V = Completely discharged (BAD)

LESS THAN 11V... your battery is shot sorry (you may be able to charge it but won't hold charge for long)!

Other precise test is with an hydrometer but nobody do that anymore ! :)
 

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Okay so my 2012 Focus S. Has just a tad over 42k on the odometer. This winter I've noticed something quite annoying. We have a jeep that's just easier to drive in the winter so we drive it occasionally. So the focus sits for 2-3days at time. Well in that time the battery goes dead. And I have to jump start it. I have no extra accessories other than what came factory on it.

Is it quite possible I'm already due for a new battery? I first thought it had to do with the cold snap we had right after Christmas. But its still doing it and it's been 30-40* for weeks.

Any thoughts, thanks. Just hoping I'm not missing some sort of TSB or what not.
Hi there,

I recommend setting up an appointment with your dealer to have this diagnosed. Once you do, please let me know so I can see how to best assist.

Meagan
 

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Discussion Starter #16
Nope, it's just a simple voltage reading at the PCM power pins. You get near 1V of drop-out voltage because of the wire resistance (small wires) in the harness.

Best way to measure REAL voltage of the 12V battery is to let the voltage stabilize (+/- 120 mins) before taking the reading.



12.8V 100% (higher than that you need to wait before taking measurement)

12.4V 75%

12.2V 50%

12V 25%

11.8V = Completely discharged (BAD)

LESS THAN 11V... your battery is shot sorry (you may be able to charge it but won't hold charge for long)!

Other precise test is with an hydrometer but nobody do that anymore ! :)
Car running or turned off?
 

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Focus Preacher
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Car running or turned off?
OFF (and wait 2-3 hours before measuring voltage) ....

When it's running, you should at least have 13V (for alternator charging troubleshooting)
 

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Discussion Starter #18
I believe my alternator was 15.1v high if u ask me. But it said passed. I'll my battery again
 

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The ImpoSTer
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2,285 Posts
My battery went bad on my 2012 before I hit 60k.
 

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Focus Preacher
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My battery went bad on my 2012 before I hit 60k.
Battery dying factor is well... depending on so many factors!

Short trips?
High prolonged load?
Bad alternator?
Car not moving alot?
ACC used often when car not running?
Impurities when mixing DI water with acid?
Accessories not turning off with Ignition?
Quality of the battery batch?
Battery maintenance done?
Has been completely depleted before?

For example:

My previous Golf mk3 '96 had the battery replaced in 2003 (Motomaster brand) and still going strong in -40F winters today!

My dad's PT Cruiser 2005 had OEM battery failed in less than 3 years!
 
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