Rick's Free Auto Repair Advice

Revive a dead car battery

Can you really revive a dead car battery?

I know you want to save some money and try to revive a dead car battery by following all the really crazy advice on the internet, but let me save you some time and effort. It won’t work. I’ll explain why.

First, is it really dead or just discharged?

All car batteries, just like every other type of battery, self-discharge when they sit unused for long periods. In addition to self-discharge, your car’s computer draws a very small (<50mA) current at all times to keep the computer memory intact.

Two things happen as the battery discharges

First, sulfate crystals start growing on the plates. If caught early and recharged, the crystal formation can be reversed. However, the longer the battery sits in a discharged state, the more the crystals harden. Hard Sulfate crystal formation can’t be reversed. Since hard sulfate crystals are non-conductive, the battery develops high internal resistance, making it impossible to recharge.

Second, as a battery sits unused the 63% water/37% car battery acid stratificationacid solution starts to separate. Since sulfuric acid is heavier than water, it falls to the bottom of the battery, causing acid stratification. The 100% sulfuric acid solution eats away at the battery plates, causing irreversible damage. None of the battery revival techniques posted on the internet can reverse plate damage caused by acid stratification.

If you’ve tried recharging the battery with a de-sulfating charger and the battery still fails a resistance, capacitance, and load test, there is no way to revive it. None. The battery is dead and it will stay dead.

Why reviving a dead car battery with chemicals doesn’t work

Here’s how the “revive a dead car battery” routines are supposed to work.

Add distilled water to a dead battery

As a battery is discharged and recharged, the battery can lose water. If the solution is above the battery plates, adding more water to get it up to the recommended level won’t hurt, but it also won’t do anything to get the battery going. Replacing the lost water with distilled water will not create more power. In fact, if you pop off a vent cap and plates aren’t submerged in the solution, don’t even bother adding distilled water because the battery is already destroyed!

Drain the battery acid, add baking soda solution and then an Epsom salt solution

In this routine, people suggest dumping the acid/water from the battery and refilling it with a 2:1 mixture of baking soda and water. The baking soda solution neutralizes battery acid. You’re supposed to shake the battery containing this solution for about one minute and then dump out the solution.

Next, they want you to fill the battery with a 1:3 ratio of Epsom salt-to-water. Epsom salt and water produces a strong acid electrolyte. This procedure just might produce enough power to get your engine started one time. But it will not reverse the damage that’s been done from acid stratification and sulfate crystal formation.

Adding crushed aspirin/water to each battery cell

Aspirin is acetylsalicylic acid, so you’re pretty much adding more acid to the cell, just like in the Epsom salt example above. It might produce enough power to get you started. But don’t kid yourself, it won’t revive your car battery.

Summary

If the battery won’t fully recharge with a de-sulfating battery charger, none of these car battery revival hacks will revive a dead car battery. So don’t waste your time and effort.

©, 2020 Rick Muscoplat

Posted on by Rick Muscoplat

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