nick49

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.

Dave Howerdel

I'd say the battery has a bad cell and needs to be replaced. Take it to be tested.

Gary Gaukler

I agree. Take it to an auto parts store and have the battery checked. My (stock) battery died last week, and I was able to recharge it to 12.6V, but it would self-discharge quickly and would barely produce enough amps to crank the starter over.

I bought a new battery at Walmart (is this heresy?), and everything works again. By the way, the Walmart battery is 10lbs lighter than the stock battery (36lb vs. 46lb), at the same rating. I think I've read that the Optima is 26lb?

Gary

nick49

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.

cas951

You already have all the tools to check the battery. Charge your battery till it's fully charged. Place your voltmeter on the battery and measure your voltage. You should have 12 ~ volts. Now you need to put a load on it by trying to start the car. The battery voltage should hold and drop slowly to 11 to 10 volts and a little lower if the battery is weak. If it drops quickly to 9 volts or or less you probaly have a bad cell and will need to replace. Once the car is running your volatge should be anywhere from 13 to 14.5 volts. Anything higher your charging system is overcharging.