Adding Water to a Car Battery

If your battery’s power is reduced, your vehicle is hard to start, slow cranking & won’t recharge properly, look for dimming lights, an alternator, or a battery light flickering on along with
corrosion built up on the terminal post due to the absence of water inside the battery adding H2O to your car battery could bring it back to life. How do you add water to a car battery?


  • Open up the battery cell 
  • Measure each hole
  • The lead plates inside the battery have to be covered with water
  • Fill with Distilled Water
  • Don’t overfill the holes in the battery as this will may also cause trouble.
  • You can recharge the battery with a trickle charger or replace it in the vehicle to recharge
  • After you fill the battery close up the holes.


Overcharging a car battery is the main reason why the water level in the battery is responsible for the charging properties of the battery once the cells run dry the battery can’t recharge.


How Do you Know When Your Car Battery Needs Water


Lead acid batteries consist of flat lead plates immersed in a pool of electrolytes consisting of water and sulfuric acid, the size of the battery plates and the amount of electrolyte determines the amount of charge lead acid batteries can store or how many hours of use.

Water is a key part of how a lead battery functions. During the recharging process, the water is converted to gases hydrogen and oxygen which is lost over a period of time and needs to be refilled.

The liquid in your car battery is an electrolyte which is a mix of H2O and sulfuric acid that allows the ions to move between the positive and negative plates of the battery’s cells when the battery is being charged or discharged.

Matenence-free car batteries are sealed and shouldn’t be open for water to be checked or refilled completely sealed and should never be opened. Batteries that require regular water service often have service instructions and warning labels clearly visible. Normally older type vehicles still have batteries that need to be serviced.


  • You will notice that the car or truck will be hard to start.
  • Open up the caps on the top of the battery to see the level of the water inside
  • Some batteries that require refilling will have an ‘upper-level’ & lower-level visual guide printed on the outside of the battery
  • Do a visual inspection of the individual cells by removing the caps from the cells and make a visual inspection of the water level. When your car battery is fully charged the water level should be level to the bottom of the tube. It is imperative that the H2O level covers the plates inside the cell.


How to Refill Battery Water for Car

There should be knobs or plastic screws on top of your battery to open and refill water to the inside of the battery. For a normal 12-volt battery there will be 6 holes to open. Open up the caps with a flathead screwdriver and with a flashlight look for a level of water for each hole.

If you can’t see water then you probably let it go too long but still go ahead and fill each hole to the right level.

  • While you are working on the battery clean the battery post with a piece of sandpaper (300-400 grid)
  • Used Distilled Water
  • The lead plates inside the batter have to be covered with water
  • You can recharge the battery with a trickle charger or replace it in the vehicle to recharge
  • Don’t overfill the holes in the battery as this will may also cause trouble.
  • After you fill the batter close up the holes.


Adding Water to Scrambled Eggs

For more great articles on the science of adding water stay here at MyWaterEarth&Sky-I love scrambled eggs especially when I am camping not only for breakfast but anytime during the day and have acquired a taste for them after learning the secret to ……………………….… Continue reading



JimGalloway Author/Editor

References: Crown Battery-Watering Your Lead Acid Battery: The Basics


Recent Posts