What's Your Battery Voltage?

Do Optima batteries not store over 12 volts? (this was also posted on the Boxster forum but it relates to my 996 as well which shows less than 12 volts) My wife had to call me a couple of weeks ago because her car, a '99 Boxster with a 2 year old Optima battery, wouldn't start after parking it for less than an hour in a store parking lot. I jumped it and told her it would be fine. Later that evening I put a battery charger on it and charged it at 2 amps for over night. No problems until the car sat for a couple of days without being driven, then it would barely crank and wouldn't start. I now charged the battery at 6 amps for a few hours and then 2 amps until I got a reading of over 12.5 volts after having the charger disconnected for an hour. The car now starts fine but I checked it after sitting for about 18 hours and the voltage is down to 11.87. This is without having trying to start the car or having it running. I checked it against my Carrera this morning which was 11.92 not having been started or running for 14 hours and having a 1.5 year old Optima Red top battery. Experience tells me that the longer these cars sit without being driven, the lower the batter charge will become until it not be enough to start the car. The charging systems are puting out proper current and voltage on both cars and they are being driven enough to hopefully keep the battery charged, but after sitting over night the voltage seems too low to me. Is this a problem with the Optima batteries? I'm curious what other peoples battery voltage is after having the car sit for several hours. I have a Battery Tender but I don't think I should have to use it for a car that sits for less than a week without being driven.

a fully charged battery ought to read above 12 volts - and should be charging at around 13.8. My voltmeter shows a charging rate of 14 volts, the amperage would vary widely.

A two year old battery should be healthy, unless it has had several deep cycles. A deep cycle will destroy as much as 25% or more of a battery's capacity. You should measure the battery's capacity as well as its voltage. Generally if a battery is putting out less than 12 volts, something is wrong with it. Measure the capacity, that will tell you a lot. Last weekend I finally changed the battery in my wife's 2000 A6. It was cranking slow. I measured the output, 10 volts and 9% capacity......that thing had stopped being a healthy battery quite some time ago.

Of course you are correct that " .... the longer these cars sit without being driven, the lower the batter charge will become .... " . The question is, 'how long should they hold a charge sufficient to start the car'? My 2000, with a 4 year old battery, routinely sits a week at a time, and has sat 16 days for several occasions. Upon my return, no problems starting at all. I have a battery tender, but have never even plugged it in. I would say that something is wrong with your battery so that it is not holding a charge. My experience is that the free battery testers at Auto Zone, etc, will reveal if this is the case with a battery. Optima makes a quality battery. No reason it should lose its charge any faster than others.

My gauge shows around 13.8 while driving

This is a hot topic on the 964 board at times also. Not Optima batteries but voltage drain on sitting cars. My 964 holds up well but both of my 928's would drain a battery in a few days. The only way to check is to place a mili-volt meter in line and read the drain. Then start pulling fuses to locate the culprit. Search the 964 board for detailed instructions. Red top Optima batteries are not designed for continued low charge conditions. The yellow top is a deep cycle battery that will hold up under these conditions. I have one we race with and it is run on cars without an alternator and is run to empty all the time. It is 5 years old and still going They do cost more but IMHO well worth it.

I called Optima and got to a CS Rep right away and they verified that the batteries in both my cars were nearly a full volt low. I returned them to the place of purchase with my receipt and got a 100% refund as it had been less than 3 years. I then purchased two new batteries and installed them. Good to go for a few more years.

Who was the idiot that gave you a full 100% refund on two obviously perfectly good batteries, I have some swampland in FL I like to talk to him about. No, sorry, retract that. The poor guy probably felt it best to simply throw in the towel and give you a full refund rather than go through the tedious process of educating you on the overall aspects of vehicular battery use and recharging. What happens to the batteries if you disconnect them while the car is parked for days? It is not a fault of the battery if the car has so much current load when parked that the battery, obviously already not fully charged by the car's system, gets discharged too quickly. The batteries exhibiting a low charge voltage is more likely a result of the car's charging system than the battery being bad. My guess is that your "new" batteries will begin exhibiting the same symptoms as soon as their initial FULL store shelf charge is used up. PS: The battery obviously accepted a full charge, 12.5 volts(?), when you used an external charger...... PSII: After a few days of being parked my 2001 C4 automatically shuts down many of the accessory circuits so as to conserve the battery charge. But after a month or so the battery will still become so completely discharged due to the remaining residual current load that it will not crank, just click the starter solenoid rapidly.

I agree but I am not going to call anyone an idiot Most likely you have a charging system or voltage drain problem and you will know for sure in a few weeks. Keep us posted please. Inquiring minds want to know

The 2nd Optima Battery that I purchased on Nov 1, '06 went junk on Oct 18, '07, so it lasted 11.5 months. I started my car fine 2 days ago and drove it in the morning, later that evening I tried to pull it out of the garage and it turnrd over really slowly a couple of revs and quit. I charged it for an hour and then overnight still nothing. I returned it to Costco today and got a full refund, bought a standard series 48 from them for $70. My cars running again. It will be intersting to see how long this one lasts. BTW my '99 Jeep Cherokee, that has never been in the garage is still on its original factory battery, not bad for 9 years service and still going strong.

Well this battery didn't last that long, 2 1/2 years. It died on Saturday the 20th. I took it back to Costco and they gave me a 100% refund. This time it turned over a little more sluggish than usual for a couple of days, then on Saturday the solenoid just clicked. I looked at it and saw what looked like a glob of cauliflower on the positive terminal. The positive post had a leak around it and the cable clamp was about 25% disolved. Costco has discontinued the series 48 batteries. I shopped around at Pep Boys, Auto Zone, Checker and Interstate. Prices were around $95 to $125 for 2 year free replacement. I ended up buying it at a place that shall remain nameless for $77 with a 3 year free replacement and a liberal return policy. This is the 5th battery in my '99 Cab.