Reviving A Dead Optima Red Top Battery

I stupidly left the key on in my 323 for over a month. I don’t know how quickly the battery drained but it wasn’t completely done – the trunk light was still dimly lit but nothing else. 

This was a brand-new Optima Red Top and I wasn’t about to spend $150+ on a replacement. Unfortunately, neither of my chargers was having any success. Fortunately, the Optima website is very consumer-friendly and not only did it explain why my chargers didn’t work, it had fantastic instructions for reviving a spent battery.

My off-the-shelf, generic chargers have their own logic that will abandon the charging process if it detects battery voltage to be below a certain threshold. My dead Red Top was down to 1.5v according to my multimeter. The charger will give it a hearty try but call it a lost cause if the voltage can’t be maintained above X.Xv. 

The Optima website gave three options:

1. buy the correct charger for an AGM battery that will not give up
2. use the Optima as a slave to a good battery as the master (and keep the master charged)
3. bring it to a professional shop who will do either 1 or 2

I opted for #2 because I can’t turn down an opportunity to learn a new skill. I bought a set of jumper cables (always good to have those anyway) and connected my Honda battery to the Optima. Right away I had 10.2v at the Optima. 

Then I connected my strongest charger to the Honda battery. I checked voltage every 15 minutes and in under an hour I had 13.4v on the Optima!

I then disconnected the jumper cables and put the trickle charger back on the Red Top and let it do its thing. After two hours it was still going! I had infused enough electrons into the Red Top that the charger’s fuzzy logic accepted. I let the charger work overnight and it continued to put out over 13.5v the next morning. I drove the 323 to work that day with no issues and the voltage gauge reading over 13v the whole time (between 12-14 and closer to 14).

I guess you can say “I’m charged up!”