What Can Replace Battery Electrolyte?

Sports drinks, like Gatorade, do not have what batteries crave. They contain electrolytes, but that isn't the same as battery electrolyte. Hans Neleman / DigitalVision / Getty

My battery went dead at the absolute worst possible time. I was able to get a friend to help me put a new one in, and he told me that the electrolyte in the old one was too low. I don’t really know what that means, but it got me thinking later that if I had filled it with some other electrolyte, maybe it wouldn’t have gone dead on me and left me stranded. So I was thinking back to science class and wondering if I had put some Gatorade, salt water, baking soda, or some other kind of electrolyte in the battery if it might not have gone dead.

Although Gatorade contains electrolytes, salt water can act as an electrolyte, and baking soda, or sodium bicarbonate, can break down into electrolytes, you should never put any of these things in a battery. If your battery electrolyte is low, the only thing you should ever add is straight water. There are some very specific circumstances where sulfuric acid can be added, such as if the battery tipped over and leaked, but never, ever add anything else.

What Does it Mean When Battery Electrolyte is Low?

When your friend told you that the electrolyte in your old battery was low, he meant that the fluid level in one or more of the battery cells had dropped below the top of the lead plates. Car batteries are composed of a series of lead plates submerged in a bath of water and sulfuric acid, which acts as an electrolyte, and it’s pretty important to make sure that the level never drops below the top of the plates.

If the electrolyte in a battery does drop below the top of the plates, and they are exposed to air, sulfation starts to take place. This process can drastically shorten the life of a battery, as it interferes with the normal operation of the cells, wherein the sulfuric acid in the electrolyte is absorbed into the lead plates as the battery discharges and then released back into the electrolyte when the battery is charged.

Adding the Right Kind of Electrolyte to a Battery

Gatorade might have the right kind of electrolytes to replenish your body after a workout, but it doesn’t have what batteries crave. The electrolytes in Gatorade and other similar sports drinks are primarily sodium and potassium, with smaller amounts of magnesium, calcium, and chloride. The other substances you mentioned, saltwater and baking soda, also contain the wrong kind of electrolytes. In the case of saltwater, the electrolyte is sodium chloride. Baking soda, on the other hand, is made up of sodium bicarbonate.​

Adding anything but water to a battery can instantly damage it, but some substances are worse than others. For instance, baking soda can act to neutralize the sulfuric acid present in battery electrolyte. In fact, a mixture or paste of baking soda and water is one of the best ways to clean corrosion from battery terminals and cables. Another example of an acid reacting to a base in a similar method is the baking soda and vinegar volcano experiment.

How Can Water Be an Electrolyte?

You may remember from science class that water, by itself, isn’t an electrolyte, so adding water to battery electrolyte might seem like a bad idea. At first glance, it seems like you would just water down the existing electrolyte. The water can only be an electrolyte in the first place when mixed with sulfuric acid, so it stands to reason that you would have to top off a battery with a mixture of sulfuric acid and water instead of straight water.

The reason that you can add straight water to a battery to top off low cells is that when a lead acid battery loses water, it doesn’t lose sulfuric acid. Water is naturally lost during the process of electrolysis, and it can also be lost due to evaporation—especially in hot weather—while the sulfuric acid content doesn’t go anywhere, or is lost at a much slower rate.

Prolonging Car Battery Life By Filling Electrolyte

Although you can prolong the life of a lead acid battery by keeping it topped off, the situation was probably far too gone by the time that the battery actually left you stranded. Assuming that your friend tried to charge the battery, and that it wouldn’t accept or hold a charge, the probable culprit is the sulfation that takes place when the lead plates in a battery are exposed to air.

The best way to prevent this type of situation from happening is to keep the electrolyte topped off as part of a regular battery maintenance schedule. Cold comfort when a dead battery has already left you stranded in less than ideal conditions, but at least you stand a chance of avoiding the same fate again in the future.