Ultimately the best recommendation for potentially recovering a sulfated battery is to save your money and try using a long, slow charge. If you have a battery charger that has a reconditioning or equalizing charge mode on it, that may be your best bet.
``Is it possible to nearly or fully restore a car battery that has gone dead?'' No. Dead is dead. There is no technology to restore batteries that lost capacity because of sulfated electrodes. Sulfate buildup is the final fate of all lead-acid batteries, if no catastrophic damage occurs to them earlier.
While recharging a dead car battery is possible in many cases, several factors can influence the success of the process. These include the age and condition of the battery, the extent of discharge, and any underlying issues such as sulfation or internal damage.
The simplest way to bring your vehicle back to life is to jump-start the battery. This involves either sharing the electrical power from another automobile through jumper cables or using a portable jump pack to help give you enough juice to start your vehicle.
If you let the battery rest for awhile, the hydrogen gas dissipates and the battery "comes back to life". In any battery, be it an alkaline battery found in a flashlight or a lead acid battery in a car, the same sort of thing can happen.
According to Wehmeyer, adding Epsom salt (magnesium sulfate) to a lead-acid battery will 'artificially' increase the specific gravity reading (SG), but because it does not increase the sulfuric acid concentration, it does nothing to improve battery performance.
One of the most common and effective methods to start a car with a weak battery is jump-starting. To do this, you'll need a set of jumper cables and a functional vehicle with a fully charged battery. Park the donor vehicle close enough to your car so that the jumper cables can reach both batteries.
The short answer to this question is yes, a car battery can be too dead to jump start.
Reviving a Dead Battery in the Cold: Step-by-Step Guide
If you have a dead battery, the only short-term solution is to jump start the battery. To do this, you'll need either a jump starter or a set of jumper cables and someone with a running car who is willing to give you a jump.
Using Epsom salt is another way to recondition a battery that won't hold charge. Epsom salt or magnesium sulfate can help dissolve solid salts that have formed around the battery plates over time. Simply mix one part Epsom salt with three parts distilled water, and pour the solution over the battery cells.
Batteries require a certain amount of time to recharge adequately, especially if they were significantly drained before the jump-start. By driving for at least 15-30 minutes, the battery has a chance to recover and reach an optimal charge level.
Turn off the ignition on both cars. First, clamp one end of the positive cable to the dead battery's positive clamp. Now have a helper connect the other end of that cable to the other battery's positive clamp. Next, connect the negative cable to the negative terminal on the good battery.
Typical Battery Lifespan Unplugged
Typically, you're looking at a lifespan of about 4 weeks to 2 months if your car sits unused. This duration isn't set in stone; it varies depending on several factors, such as the battery's age and whether you've parked your vehicle in extreme temperatures.
Can a dead car battery recharge itself? If your battery has run down completely, your car will fail to turn over, meaning it won't start. If you can't start your car, the alternator can't work, and it won't put any additional energy back into the battery, so it's impossible for a dead battery to charge itself.
Prepare a mixture of baking soda mixed in distilled water and by use of a funnel pour the solution into the cells of the battery. Once they are full, close the lids and shake the battery for a minute or two. The solution will cleanse the inside of the batteries. Once done empty the solution into another clean bucket.
Reviving. If the car is slow to start, then it's definitely time to revive the battery. For this you should connect a commercially available charger to the battery and recharge it. If nothing else helps, you can also try a special device called Megapulse.