Battery gauge and time to replace battery

Guys Based on the owner's manual it recommends the battery gauge to be between 12 to 16. My car is currently showing 13 and it's about 4 years old and a little over 15k miles, therefore is it time to replace the battery???? Thanks

the battery guage has no measuremnt of battery life. you need to perform a load test to tesst the battery. is your voltmeter at 13 with the car running or the car off?

13 is with car running???

I read that too in the manual..but my battery volt meter reads BELOW 12...it is in the middle of 10 and 12. Yet I have zero problems with the car.... it is a 2001...so maybe its time to change? I swear there is ZERO PROBLEMS...and I have left the car for days at a time etc. I was worried that the batt may be going bad too since it was NOT reading above 12....am I looking for trouble?

if your between 10-12 with the car running your going to be needing an alternator sooner then later

DAYAM...really? I better email the service advisor that performed the PPI and gave the car a gold star and said it was perfect in everyway.

Just to give you an idea about the lack of a link of the battery gauge to battery performance. My OEM battery died a couple of weeks ago. It was reading 14 consistently. One day I got in the car and it wouldn't crank. I recharged and all was fine for 4 days (including the reading on the battery gauge), then it died again and would not hold a charge - time for a new battery and all has been fine since then. Batteries can die slowly, or abruptly.

I wouldn't replace your battery until it dies. I can't think of any reason to do it pre-emptively.

How long do these batteries last? I have an '01 C2 and it still has original battery!

you're usually good for 5 years.... sometimes longer if you're lucky. I had one battery last 8 years.

there is no such thing as a battery guage on your dash is a volt meter it gives an idea of th4e vehcile current power output. with the car off key on the guage should be 11-12 volts give or take if its slightly discharged or freshly charged. With the car running you should see 13.5-14.5 volts on a propelry opeating charging system maybe 13.0 if all loads (accessorys ac radio wipers lights defrost ect) are on.

hmm...ok well then my car's charging system must be off then right? Because is never goes to 12 in my ride. I am above 10 and below 12 all the time.

you should get it chekced

Good battery indications and performance. One day it was just dead and would not accept a charge. It was a three year old battery on a car that had 5k miles, ie little use. Remember, our cars are a little bit of a hassle if the battery is dead and the doors are all closed. You can get in the cabin with the key but remember the trunk and engine lid will not open with the swithches. I say replace it if it's over 4 years old. it's a battery, they don't last forever. The original post may indeed have something else going on too, just talking batteries here.

First, I would sincerely doubt that anyone at Porsche would attest to the accurracy of that voltmeter. BUt more importantly I really have no idea why it's there. IMMHO you should tape it over or learn to ignore it completely. Maybe watch to be sure the voltage doesn't drop significantly when you first switch on the street/parking/HB(***) headlamps, but otherwise.... *** HID LB current draw is too low for a good test. Battery failures are generally the result of metalic debris flaking off the plates during use and then eventually piling up on the bottom high enough to short out a few plates. You may notice that deep cycle batteries have a greater distance between the bottom of the plates and the bottom of the battery container for this very reason. The only reliable method I know of detecting that the battery is on the cusp of failure is to take note of the engine cranking rate.

Well I emaile the service advisor at McKenna in Cerritos that did the PPI on the my car before I took delivery...they also had to replace the MAF because I had a CEL like 2 hours from driving it home. Luckily its a real good friend I bought the car from...so he took care of it. My friend paid for a FULL inspection of the car. They came back saying the car has zero problems and is perfect. So...I sent the email asking about the low voltage readout and see what they say. I also emailed my local Rusnak SA and asked their opinion. I have a feeling I will be spending some money soon....

Guys Thanks for al your input, I think it's a good idea to replace battery every 4 years if our cars are low miles for preventive maintenence. And I assume it's normal that these cars start after maybe three cranks?? Slower start compare to other cars??

What a coincidence, I've been reading this thread and today, I just got a "Warning:Battery/Generator" red light. My car always starts up on first crank, same as usual today. I didn't notice any hesitation, but as soon as the car started, the red light came on. It didn't happen again, just that once. Should I take that as a warning and get a new battery before I get stranded somewhere? My voltmeter shows exactly what 99firehawk says: just a hair below 12v with engine off, and just a hair below 14v when running.

well if the battery light is on the alternator is not putting out enough amperage to charge the battery. ive found the the light come on when there is little to no output. Alternator output degrades over time and the amperage output goes down, once it falls below a specified out put the battery warning comes on. Its not uncommon for the alternaotr ot put out plenlty of voltage ie 14 volts and very little to no amperage. You should deffinalty get it checked

99firehawk: So you think it could likely be the alternator instead of the battery? The light didn't come back on after that, so I'm thinking maybe there wasn't full cranking amps available at that time when I started the car. I'm thinking maybe the battery is weak/old and not holding a good charge, especially when the car sits in the garage 3-4 days a week. Well, I looked at the battery today, and it doesn't look like an OEM battery. It looks new, and doesn't say Porsche anywhere. It has a label on top that says "Auto Life"...sounds cheap to me! The dealer I bought it from must have slapped a cheap one in just to keep it running until it sells. I checked the water levels and they were about an inch down from the top, didn't see any markings so I'm not sure where they're supposed to be. No plates were showing though. Assuming the battery goes, wouldn't any maintenance-free battery be good as long as it fits in the bracket? I'm thinking of replacing it with the yellow Everlast from Walmart (about $80) which is rated very good by Consumer Reports. (Provided they have a compatible/group battery.)

when ever you replace the battery you should have the charging and starting systems checked. Charging and starting systems are not usualy the type of thing that fails in an instant (Not saying it cant but very rare for it to happen) But the alternator output goes down and starter draw goes up. I would get it checked, somemay disagree but thats my professinal opinion

Your volt gauge should read around 14 volts on a properly running alternator with minimum load on battery. If, when turning on the lights, the gauge drops to below 13 volts and stays there, it is a battery problem and nothing else. (barring a short or improper grounding in the lighting sytem). The car runs off the battery and NOT the alternator. An alternator generating greater than 60 is more than enough to maintain a charge a good battery The Bosch alternator in your car is rated at 14 volts and 120 amps. If the alternator were to fall below 70 amps when engine is running, your warning light would come on and stay on until more amps were generated. Therefore, if your alternator is reading 14 volts with engine running and no load, there is nothing wrong with your alternator. The starter is not dependant on the alternator.

199Porsche911: I just checked the manual, and for the light I got "Warning:Battery/Generator" on the dash, it says to pull to the side and stop driving. Have dealer inspect the system. (???) This sounds a little exaggerated, don't you think so? The light came on once immediately after starting, I flicked the switch to dismiss it, and it's never came back on...yet. My cranks at startup seem strong, no signs of a weak battery. Should I be concerned? Or just keep driving and be on the watch out. Also, another question...just to be prepared, if I should get stranded, is it all right to just get any good replacement maintenance-free battery? Depending on whether I'm near a Sears or Walmart... Thanks!

I get my battery replacements from Samsclub for about $48. Last just as long and fits right in. You can get them vented or non vented. Stock is vented and the new battery will connect to the vent hose in the car. I forgot the battery size off the top of my head...maybe 48? Someone else can confirm the size for you. You may have had a belt slip at startup which caused the light to come on and then go off. If it was only that one time, I wouldn't lose any sleep over it.

well all this reading is really making me worry. My gauge reads between 10 and 12 no matter what. At start up, while driving, headlights on or off it doesnt matter. Again...the cranks just fine, starts up perfectly...ZERO signs of any problems. If I hadnt come across this post I would of never thought anything was wrong. I am looking forward to seeing what the service advisor says when I emailed them. I will report back.

The only even slightly reliable test for a battery is a load test. Almost anywhere which sells batteries will do one for free for you. If you are worried about the reading on you gauge I'd do two things - firstly get a load test and secondly measure the actual voltage across the battery terminals with a proper meter (about $20-$40 from RadioShack, or the battery place will probably do this for free as well). Compare this reading with your meter - I'll bet they are different.

Not to be overly picky, but volt meters do not indicate power output. You need to know the current which is flowing at that voltage in order to determine power. To determine power output of a battery, use an ammeter to measure current under load, and a voltmeter to measure the voltage (with the same load), and then multiply them together to get the power output of the battery.