How to Revive a Dead Car Battery

a man starting a car, such an everyday occurrence, made possible by the car battery
Starting the Car is Such an Everyday Thing, but a Dead Car Battery Will Leave You Stranded.

Every time a driver turns the ignition key or presses the “Start” button, the starter motor is expected to crank the engine. This mechanism is caused by the 12-V flooded lead acid car battery, which is standard on virtually every vehicle on the road. Some cars carry a second battery, and trucks and RVs may carry a battery bank, linking several batteries. Similar batteries can be found in tractors, power equipment, motorcycles, powersports machines, snowmobiles, four-wheelers, and solar power backup systems, to name a few.

Car batteries tend to last for several years, but lifespan depends on how they are used. The typical car battery, driven every day, properly charged, and never deep-cycled, could last upwards of 7 years, but that’s a best-case scenario. Most maintenance-free (read: replace on death) car batteries tend to last 4 to 7 years. Short car battery life, less than 3 or 4 years, can be related to several different problems, such as lack of use, corrosion, excessive deep cycling, electrolyte evaporation, damage, or charging problems.

How Does a Car Battery “Die?”

car instrument cluster showing check engine light and battery light, which could mean the car battery is dead
If the Battery Light is Illuminated, it Could Indicate a Problem with the Car Battery or the Charging System.

The are several things that can shorten the life of a car battery, and most of them are preventable. Now, we’re not talking about that “dead battery” that you get when the dome light was left on or the car hasn’t been driven in a month. Usually, a jump start, booster pack, or battery charger is all that’s necessary to revive the car battery and get the car back on the road, but the damage has already been done. It’s the accumulation of damage that leads to the untimely death of the car battery, at which point it simply will not start the car. Car battery death, for the purposes of this article, refers to the battery’s inability to hold a charge, usually caused by sulfation.

At its most basic, a car battery is constructed of alternating plates of dissimilar metals, usually lead and lead oxide (Pb and PbO2), in an electrolyte bath, usually sulfuric acid (H2SO4) in water. When discharging, the “battery acid” facilitates the flow of electrons, from the Pb plate to the PbO2 plate, generating an electric current, which can be used to start the engine or illuminate the headlights, for example. Because of this chemical reaction, both plates become more chemically-similar and converting fully-discharged car battery plates to lead sulfate (PbSO4), wherein lies the problem.​

So-called “soft” battery sulfation occurs practically every time you discharge the battery but, because it is usually immediately recharged, electron flow easily forces the opposite chemical reaction, resulting in dissimilar Pb and PbO2 plates. If the car battery is left discharged for long periods of time, “hard” sulfation occurs, the formation of lead sulfate crystals. As PbSO4 crystals form, they gradually reduce the available surface area for chemical reaction, reducing the capacity to charge and discharge the battery. Eventually, PbSO4 crystal formation spreads, leading to cracks and short circuits within the battery, rendering it useless. 

Ways to Revive a Dead Car Battery

in case of a dead battery, two vehicles and jumper cables come together to get the engine going
Even if the Car Battery Can't be Saved, a Jumpstart Will At Least Get You On the Road to the Autoparts Store or Your Trusted Technician.

Unfortunately, it is impossible to reverse hard sulfation, but it does one good to note, regarding products and services claiming to reverse sulfation, there is no real proof to back up their claims. Still, if you have a dead car battery, there are several things that you can try to get yourself back on the road, even if it’s straight to a repair shop or auto parts store for a new battery. Vehicles started using these methods should not be shut off until a new car battery can be obtained, and a couple of these methods will finish off the battery, anyway.

  • Jumpstart: Jumper cables and a second battery, battery booster, or second vehicle might be enough to jumpstart the vehicle. The dead battery won’t accept a charge, though, so don’t shut the engine off! Note: Do not attempt to jump start a frozen battery, as it could explode. Thaw it out and attempt to charge it, first.
  • Distilled Water: If the electrolyte level is low, adding distilled water might be enough to fully-submerge the plates and enable a bit more reaction area. This might be enough to give the engine a few more turns.
  • Epsom Salt: Epsom salt (magnesium sulfate or MgSO4) can readily be found in grocery stores, home gardening centers, and drug stores. Adding a stronger acid to the electrolyte mix, such as Epsom salt, might be enough to tip the chemical balance, delivering enough charge to start the engine. Dissolve 1 part MgSO4 with 3 parts warm water, then add to each cell until the plates are covered by ¼” to ½” electrolyte.
  • Aspirin: Imagine a vehicle out in the middle of nowhere, a remote camping trip, and all that’s available are a couple bottles of water and aspirin. Believe it, or not, Aspirin (acetylsalicylic acid or C9H8O4) can be used to chemically alter the electrolyte mix. Crush and dissolve 12 Aspirin tablets, 325-mg or 500-mg, in about 6 oz of warm water, and add equal amounts to each cell. Add additional water to make sure the plates are covered.

Prevention is the Best Medicine

the alternator is directly responsible for preventing car battery death
To Prevent Premature Car Battery Failure, Inspect the Charging System Regularly.

It’s always better to prevent damage than repair it, and in the case of the car battery, “replace it.” The only way to deal with car battery hard sulfation is to prevent it in the first place. To ​prevent sulfation and failure, always recharge the battery immediately after use, make sure the vehicle charging system is functioning properly and put an unused car battery on a float charger to maintain full charge.​