Maybe you ran a few too many passes at the drag strip. And maybe that Optima battery under the hood of your alternator-free drag car was a Red Top starting battery instead of a Yellow Top deep cycle battery. Or maybe you just left your lights on. At the airport while you were on a two week vacation. However you did it, you killed that Optima dead. Deader than ska music. Deader than Bob Dole’s presidential hopes. Deader than the bird in that amazing Monty Python sketch. But like some kind of walking, breathing defibrillator (in more ways than one), you can bring it back to life.
Here’s the issue. Your normal, parts store battery charger won’t recognize a truly, utterly, dandelion-in-winter dead AGM battery. If a flooded, lead-acid battery registers as having fewer than 10.5 volts, it’s considered a lost cause, by the industry and the battery chargers they make, since lead acid batteries so deeply discharged rarely recover. The charger will switch to a default off mode.
But this never gives your AGM battery a chance to show its stuff. AGM batteries, like Optima batteries, can recover from a much lower state of voltage and go on to lead happy, productive lives. The trick to getting them charged is tricking the charger. Here’s how to do it.
What you’ll need:
- That annoying charger that won’t charge your Optima.
- Your Optima
- Some jumper cables. If you can find some with an extended “flat tooth” extension on the clamps, use them.
- Another battery, fully charged. You can borrow the one in your mom’s Accord if you want to. It doesn’t have to be an Optima.
Start in a well-ventilated area. Charging can create hydrogen gas, and we all knew where we were when the Hindenburg blew up. Hook up the charged battery to the Optima using the jumper cables.
Red to red, black to black. Don’t mess that bit up. Next, attach the charger to the good battery and turn it on, being sure to use the right setting for the type of battery. If you’re using a lead-acid battery, use that setting. Again, make sure you get the polarity right. Black is negative, red is positive.
If all goes well, the charger should recognize the voltage of the living battery and start bringing the dead one back to life. It’s sortof like the scene at the end of (SPOILER ALERT:) Terminator: Salvation, when the one guy does the one thing to keep the other guy going. Except that the good battery will still be good, so…that was a bad analogy. Worse if you haven’t seen that movie.
Within a couple of hours, the Optima battery should be charged to above 10.5 volts, which you can test with a multimeter, and you can remove your multi-battery apparatus and just charge the Optima with the charger. And put your mom’s battery back in the Accord. And reset her dash clock.
Safety things to consider: Don’t get the polarity wrong. Yes, we mentioned that twice already, but don’t get the polarity wrong. That’s four. That should be enough.
Also, keep this process monitored. If the batteries start getting excessively hot, or if the lead acid battery starts gassing, indicated by a hiss from the safety valve, unplug and disconnect everything immediately.
Of course, an Optima charger will jump through all these hoops for you and charge up your AGM battery just fine. But if you don’t have one on hand, give this a shot.
Looking to upgrade your battery to a long-life, stable, Optima battery? Want to skip all this jumper cable hacking and just get a proper Optima charger? Check out our Optima page for all you need to know to find the right one.