In the winter my 98 sits in the garage and generally I will need to charge the battery to get it started and normally this is not a problem. However this time I charged the battery and the car started but I noticed the voltage jumping from 13 down to 8. First thought is the alternator but this happened so quickly I was wondering if something else could be causing this, the car has 30K miles and had been treated very nice. Also the battery was dead after I turned the car off during the voltage fluctuation episode.

 

How did you go about charging the battery? Were the cables removed?

 

First I'd get your battery checked and if good and voltage is still jumping around that much and if you have a DVOM I'd do a quick voltage drop check of your charging system...also a good idea to do a parasitic draw test.

 

no i did not but just decided to try that before I saw your post could that be the problem

 

As previously mentioned have your battery load tested, measure battery voltage with a DVM with the car running. Many times the cables at the starter solenoid have become loose and corroded, this is where the alternator output cable is connected to the battery. I would buy a good trickle charger if the car is not started every two weeks or so .

 

Try what ??

 

What type battery is it? Acid, AGM etc.

 

charge the battery with the cables removed

 

it is a red top optima

 

If it is below 10.5 volts and you are not using an AGM charger it is not taking a charge.

The battery has a diode that needs stimulated to take the charge.

Here is the proper charging for an AGM batter from Optima. Follow this and you should be ok if not then the battery may be bad. Most times people don’t follow the instructions which are different vs acid batteries.


Optima proper charging.


In time, AGM batteries, including OPTIMA® batteries, may fail. Failures are often caused when a starting battery is used in a cycling application, for which a deep-cycle battery is the better choice.

OK, so you have a seemingly bad AGM battery, you attach it to your charger and…CLICK. The charger won't even charge it or it begins charging, but shuts off after a short period of time and displays a fault code. "It must be a bad battery!" you exclaim, or is it? In many cases, OPTIMA batteries that are assumed to be bad may actually be perfectly fine, just deeply discharged.

The great thing about AGM batteries, including OPTIMA REDTOP® BLUETOP® and YELLOWTOP® batteries, is that they have very low internal resistance. This allows very high amperage output so that the battery can power your accessories longer and deeper than a traditional battery, but at the same time deeply discharging it.

An AGM battery with its low internal resistance may stump car guys because sometimes it doesn't work like a traditional flooded lead-acid battery.

Here's the problem: Most battery chargers have built-in safety features that may prevent chargers from recharging deeply discharged batteries. A traditional battery that's at 10.5 volts or less is seen as defective, having either a short, a bad cell or some other defect. Most analog chargers are binary and are either on or off. If they don’t come on, it may be because the charger thinks the battery is “bad.” Turning on to charge a “bad” battery could create an unsafe scenario. But the fact is that the AGM battery may be just fine; it has simply slipped below the minimum voltage threshold of the charger to turn on, and the charger doesn't know what to do with the battery, so it does nothing or charges briefly and then shuts off.

Here are three options for bringing that deeply discharged AGM battery back to peak operational performance.

RECOVERY OPTION #1: THE BEST SOLUTION – AGM-SPECIFIC CHARGERS

The best method for recharging a deeply discharged AGM battery is to purchase a modern charger that has kept up with battery technology. Many chargers now have AGM-specific settings and desulfation steps that help recondition and recover deeply discharged AGM batteries. These are becoming more common, and they work well for all lead-acid batteries. They have the additional capability of doubling as a battery "maintainer" for batteries in storage. Some come with additional ring terminals to permanently attach to your battery leads so you can charge the battery externally with an accessible charger or maintainer. This makes it easy to hook up when you store your car, truck, boat or RV.

The OPTIMA Chargers Digital 1200 12V Performance Battery Charger and Maintainer enhances the performance of OPTIMA and other AGM batteries, recovers deeply discharged batteries and extends battery life. The OPTIMA Chargers Digital 1200 12V Performance Battery Charger and Maintainer is optimized when used with high-performance AGM batteries, but has enhanced charging capabilities that can also be used with all traditional types of automotive batteries.

This is the preferred method of charging a deeply discharged battery.

RECOVERY OPTION #2: THE DIY SOLUTION FOR CHARGING A DEEPLY DISCHARGED BATTERY

This is a recovery method for the do-it-yourselfer using the equipment you've got in the garage. With this option, you're going to trick your traditional charger into charging the deeply discharged AGM battery.

Here's what you need:

• Battery charger (under 15 amps)
• Jumper cables
• A good battery, preferably above 12.2 volts. (It can be an AGM or flooded battery - it doesn't matter.)
• The seemingly dead, deeply discharged AGM battery
• A voltage meter
• A watch or timer

Now, here's what you do:

Hook up the good battery and deeply discharged AGM battery in parallel – positive to positive and negative to negative. Do not have the charger connected to the battery or turned on at this stage.

Now, hook up the deeply discharged battery to the charger. Turn on the charger. The charger will "see" the voltage of the good battery (hooked up in parallel), and start providing a charge.

After the batteries have been hooked up for about an hour, check to see if the deeply discharged battery is slightly warm or hot to the touch. Batteries naturally become warm during charging, but excessive heat may be an indication that there really is something wrong with the battery. Discontinue charging immediately if the battery is hot to the touch. Also discontinue the process if you hear the battery "gassing" — a hissing sound coming from the safety valves. If it's hot or gassing, STOP CHARGING IMMEDIATELY!

With your voltage meter, check back often to see if the AGM battery has charged to 10.5 volts or above. This generally takes less than two hours with a 10-amp charger. If it has, disconnect the charger from the wall outlet and remove the good battery from the deeply discharged battery. Now, only the deeply discharged AGM battery should be connected to the charger. Turn on the charger and continue until the AGM battery reaches a full charge, or until the automatic charger completes the charge process. In most cases, the AGM battery will be recovered.



RECOVERY OPTION #3: ENLIST THE PROFESSIONALS

If you don't own a battery charger, you don't want to make the investment or you're not the do-it-yourself kind of person, this is the option for you.

Take the battery to a professional battery specialist who knows AGM technology. Most specialists are willing to provide "charge and check" procedures free or for a small fee. Auto parts stores are typically not capable of accurately determining an AGM battery's condition and many use conductance testers that don't provide correct readings. Battery specialists (such as Interstate Batteries and other independent battery distributors) are experts who can help determine if your battery is recoverable or not.

 

Thanks, working fine now after overnight charging with battery disconnected from car First time I ever had to disconnect the battery from car while charging will place on trickle charger now for the winter

 

Optima batteries are a bit different and like most AGM will do odd things below 10.5.

I would say many people toss are not really bad. I have recovered a few.

 

Not all trickle chargers are created equal so get a good brand like Battery Tender and make sure it is compatible with AGM batteries. I kept my street rod (Chevy 350) on a battery tender when not driving and my battery was 13 years when I finally had to replace it last year..