What are the effects if a car battery gets soaked in water?

[McEliza]

It can cause engine failure, circuit short circuits, damage to the driving system, and other effects. If a car battery is soaked in water and not treated promptly, it may become unusable. Although there is water inside the battery, it is different from ordinary water. The water inside the battery is usually distilled or high-purity water, with very low conductivity and is essentially non-conductive. However, the water commonly encountered in daily life contains various metals and trace elements, making it conductive. Therefore, water ingress can lead to phenomena such as short circuits in the battery. What to do if a car battery is discharged: A discharged car battery can cause sulfation. If the discharge is severe, it may even render the battery unusable. A discharged battery means deep discharge, where the voltage drops below 10.50V, and sulfuric acid reacts with the lead plates to form lead sulfate. If not recharged promptly, the lead sulfate can crystallize. Prolonged crystallization makes it difficult to decompose during recharging, a condition known as sulfation. After a car battery is discharged, it should be recharged immediately using a battery charger. If a regular charger fails to recharge it, a repair device with high-resistance repair should be used to raise the voltage above 10V to enable successful charging.

[JadeDella]

Last time after driving through water in the rain, my battery got soaked - what a headache! Water seeps into the gaps around the terminals, and over time it'll definitely rust and form that green copper corrosion. That's exactly what happened to me when I didn't deal with the accumulated water under the battery cover - a week later the engine struggled to start. The worst scenario is if the battery case has cracks, as the electrolyte mixing with water can cause leakage current and overheating. Quickly remove the battery, dry the casing thoroughly, especially cleaning any oxide from the terminals, then let it air dry for two days before reinstalling. If you notice the battery getting hot or small bubbles forming, don't force charge it - you must replace it! This isn't something to take lightly, as it could potentially fry your car's computer.

[DeOlivia]

When dealing with a water-soaked battery, the first step is to disconnect the power. I often use a multimeter to measure voltage. Even if a water-soaked battery can start the engine, its capacity will shrink by more than 30%. Electrode corrosion increases resistance, and the system voltage can drop below 11 volts after ignition. After drying the gaps in the terminals with a heat gun, apply specialized anti-corrosion grease. Pay special attention to the battery's inspection hole—if the liquid inside is cloudy or white, it indicates a short circuit in the plates. Even if such a battery works now, it will definitely fail in winter. It's advisable to keep an emergency jump starter on hand; you'll realize its importance when your car suddenly won't start one day.

[DeBrody]

I can totally relate! Two years ago during a typhoon, my garage got flooded and the battery was half submerged. The tow truck driver used an endoscope to check and found the electrode plates were frosted over, saying the active material had fallen off, causing it to lose charge. At the time, the charger kept tripping the overheating protection, and the positive and negative terminals felt scalding to the touch. The mechanic disassembled it and found the separator had deformed, causing a short circuit, and the electrolyte had leaked to only half its original level. The longer it soaked, the worse the sulfation became, and the charging process gave off a particularly pungent acidic smell. This kind of damage is irreversible, and in the end, I had to spend over 700 yuan to replace it with an AGM battery before I felt at ease.

[VonJonathan]

The water level is crucial when a battery gets submerged. The most dangerous scenario is when the water rises above the vent caps, as it dilutes the electrolyte density. I've encountered cases where customers forcibly charged waterlogged batteries, resulting in swollen and deformed casings. If water enters the lead-acid battery's vents, it generates hydrogen gas, posing a combustion risk! For emergency handling, disconnect the negative terminal and neutralize acid stains on electrodes with baking soda solution. If the internal resistance exceeds 20 milliohms after drying, the battery is beyond recovery. Nowadays, many car batteries located in the trunk are safer, whereas older Japanese models with batteries near the wheel arches are more prone to water damage.

[LeCamilla]

A waterlogged battery is like a diseased lung—it may look fine on the surface, but the internal damage is fatal. Water accumulation corrodes the internal lead plates, and when sulfation crystals block the micropores, it shows a full charge after just ten minutes of charging, but it's actually a false voltage. I recommend replacing it immediately if it's been submerged for over two hours, as continued use can overload the alternator. In emergencies, you can remove the battery and drain the water by turning it upside down, but avoid shaking it to prevent plate detachment. The most reliable approach is to take it to a professional shop for charge-discharge testing—those who claim drying it in the sun will work are simply misleading.