OPTIMA Batteries are among the most-trusted and popular automotive batteries on the market. One of the great things about OPTIMA’s AGM-style batteries is their extremely low internal resistance. This allows very high amperage output enabling the battery to power your accessories longer and deeper than a traditional battery while discharging it at the same time.

But even the best batteries can fail, especially when starting batteries are used for deep-cycling applications (learn more about choosing a battery here and here). In many cases, though, OPTIMA batteries that are pronounced “dead” are actually just deeply discharged. According to OPTIMA, these AGM-style batteries can be resuscitated and saved using three different methods. Before you send your battery to the car parts graveyard, give one of these solutions a try:

1. Use a AGM-Specific Charger

An AGM battery can stump car guys because it doesn’t work like a traditional flooded lead-acid battery. They may hook a seemingly bad OPTIMA battery to the old tried-and-true battery charger and get no signs of life.

Here’s the problem.

Most battery chargers have built-in safety features which prevent them from recharging deeply discharged batteries. If a traditional battery is at 10.5 volts or less, an analog charger will remain off because the battery is seen a defective. The charger will remain off because charging a “bad” battery could create an unsafe scenario. The AGM battery may be just fine, but has slipped below the minimum voltage threshold of the charger to turn on.

That’s why it’s important to purchase a modern, AGM-specific charger for your AGM-style battery.

AGM-specific battery chargers have special 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, too. They have the additional capability of doubling as a battery maintainer for batteries in storage. OPTIMA offers a Digital 1200 12V Performance Battery Charger and maintainer that enhances the performance of OPTIMA and other AGM batteries, recovers deeply discharged batteries, and extends battery life.

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

2. Try the DIY Solution

Want to stick to the charger already in your garage?

OPTIMA offers an alternative that tricks your traditional charger into charging the deeply discharged AGM battery. According to OPTIMA, 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.)
  • The seemingly dead, deeply discharged AGM battery
  • A voltage meter
  • A watch or timer

Start by hooking up the good battery and deeply discharged AGM battery in parallel — positive to positive and negative to negative. Next, hook up the good battery to the charger and 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 charging for an hour, check to see if the AGM 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.

IMPORTANT: Discontinue charging immediately if the battery is hot to the touch or if you hear the battery “gassing” — a hissing sound coming from the safety valves.

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. Once it reaches the 10.5-volt threshold, disconnect the charger from the wall outlet and remove the good battery from the charger. Now, connect only the deeply discharged AGM battery 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.

3. Get Professional Help

You can always take your battery to a professional battery specialist who knows AGM technology. Most auto parts stores use conductance testers that don’t provide correct readings, so we’d recommend a battery specialist like Interstate Batteries or other independent battery distributors. Most of these places are willing to provide “charge and check” procedures free or for a small fee and can determine if your battery is recoverable.


Author: David Fuller

David Fuller is OnAllCylinders' managing editor. During his 20-year career in the auto industry, he has covered a variety of races, shows, and industry events and has authored articles for multiple magazines. He has also partnered with mainstream and trade publications on a wide range of editorial projects. In 2012, he helped establish OnAllCylinders, where he enjoys covering all facets of hot rodding and racing.