We Weren't Kidding! This Stuff Works...How to Charge a Dead Battery

Dead Batteries...The Joy of Children

It was my turn to take my son to school today. As we prepared to get in our red Subaru Legacy my son asks, "Dad, did you charge the battery yet?" I had completely forgotten to do so. The battery went dead the prior week after our youngest daughter found an unlocked door and managed to flip every switch, turn every dial, and twist every lever. Needless to say, the lights and everything else that draws power were left on without us noticing.

I had a PulseTech Xtreme charger in the garage and connected it to the terminals. Nothing. The charger indicated it was connected to AC power and that it was not connected to a battery. Of course, being the 'smart' man that I am, I figured the charger was wrong or at the very least the clamps slipped off.  So I held the clamps directly on the auto post avoiding any corrosion and...nothing. Nada. Zilch. Deader than a door nob. The charger would not register that there was a battery connected, meaning the voltage was lower than this smart chargers safety threshold.

We tell customers how to fix or overcome this issue all the time. It really is rather simple and not a big deal especially since I have the tools and knowledge in how to revive 'dead' batteries. And yet, my natural thought process went something like this, "That Jiffy place sold me a crappy battery! There is no way this battery could be this dead..." Don't take this the wrong way customers, but I was thinking just like many of you. But those thoughts were nothing more than my own pride and male ego flaring up in response to a frustrating situation. Nonetheless, I certainly will have more empathy the next time a call comes in for a dead battery, cause it sucks.

Back to the story...

Knowing I needed to create a parallel connection with a good 12V battery I began to ponder how I could accomplish the task at hand. After thinking for a moment and blindly searching the garage for ideas I discovered where the jumper cables were hidden and remembered our push mower had a tiny (And I am talking tiny... measures 3.82 x 1.69 x 2.28" and is only 1.3 amps!) SLA battery used for starting. Luckily, the lawn mower battery still registered high enough voltage even though this 'smart' battery professional failed to leave the mower connected to a charger since last October.

OK I have to pause the story again. It is important to point out at this juncture that I DO NOT recommend using a battery this small to complete this test.  To help place it in visual perspective, one of the jumper cable clamps was bigger than the battery I was attempting to use. I was in a pinch and was prepared for the worst and indeed sparked or perhaps it would be better to say welded with the little battery since the terminals were so dang small in relation to the cables...Besides, I knew where I could get a replacement battery at a great low price.

The Story Continues...

It took about 20 minutes for the car battery to have enough surface voltage before I could disconnect the smaller battery and simply attach the charger leads directly on the car battery terminals. Sure enough, the charger recognized the battery and began the charging process.

Normally, I recommend leaving the battery connected until the charger says it has completed its charge profile, but being the impatient 'smart' battery professional that I am, I tried starting the car about 2 hours later--it barely turned over.  But it did turn over! Elated, I figured I should follow my own advice and connect the charger back up and leave it until it finished charging.  At this point it read 25% charged.

STEP by STEP Charging Instructions

1. If you discover your battery did not 'take a charge' or the charger indicator lights say 'no battery moron' (or something to that effect) then you most likely have a battery that has voltage of less than 8 volts. Most smart chargers, as a safety feature, will not allow charging of such a battery to prevent users from trying to charge things they are not suppose to charge.
2. Get over the fact that you feel insulted and have worked with batteries your whole life; your a mechanic...yada yada yada... it happens to the best of us get over it!
3. Find a set of jumper cables and a similar sized battery of the same type that you know to be of adequate voltage. In a pinch and if you know what you are doing and are aware of the potential consequences you can substitute a different size battery or type, but not a different voltage.
4. Be careful when connecting the batteries in a parallel configuration (positive to positive and negative to negative) to attach the positive cable first to avoid sparking. I must confess though, I spark them often for fun. however, if you feel as though you have started welding, you have done something wrong.
5. Connect the [properly sized] smart charger to either battery and leave it alone. After a few hours, or perhaps 30 minutes if the charge current to battery ratio is just right the 'dead' battery should have enough surface voltage that you could disconnect the parallel configuration and simply finish charging with the charger directly connected to the bad battery.

Does the Battery Really Require A Warranty?

You would be surprised how many battery owners experience a dead battery and assume the battery is bad or defective. Over the years we have tracked the number of battery related warranty calls received to those that actually truly need a warranty and those that simply had a 'dead' or depleted battery. Nearly 45% of those calls did not require a warranty and revived their battery. About 5% go off the deep end and cry bloody murder when we suggest such a tactic as parallel charging (if this is you, please refer to step two). The other half lied to us about their findings and received a warranty...just kidding. ☺

In short, this stuff really works.  It is not some crazy voodoo or magical potion, it is just science and a matter of fact.