Do AGM Batteries Lose Water?

AGM batteries do not lose water and are maintenance free. You should not add water to them because it will cause damage.

  • Flooded lead-acid batteries – contain water and require adding water
  • AGM batteries – sealed and never require watering
  • Gel battery – never add water


The AGM battery “Absorbed Glass Matte” is a type of lead-acid battery. It has a fiberglass separator fitted between the battery wrappers and the lead plates. This fiberglass separator holds the electrolyte in the battery, resulting in a rigid physical bond between them.

In the same way, water will soak upwards when one side of a towel is placed in the bathtub, the AGM battery capillary action is responsible for holding the electrolyte in the glass matting in place. This is the reason why AGM batteries are 100% spillproof even when exposed.


The AGM batteries have the most significant impact resistance capacity among all the lead-acid batteries, mainly due to their tightly packed content but with the least internal resistance. The low internal enhances the battery’s efficiency by reducing the charging time, increasing the output voltage, and reducing the internal power losses in the form of heat as the power flows through a low resistance system.

As the overall best lead-acid batteries, AGM batteries do not require any form of maintenance. These premium batteries, as mentioned above, feature a technology that helps re-combine the internally formed gases back into the liquid “electrolyte.”


The recombination process is a continuous chemical process that doesn’t require your efforts, and this is what makes these AGM batteries maintenance-free. You aren’t needed to add any water into an AGM battery whatsoever. AGM batteries have no acid leak, no charging issues.

Indeed, charging an AGM battery is straightforward; plug in the terminals and leave it alone. They can power anything that the flooded batteries can power, and even better.


Will adding water to an AGM battery help?

You know that regular maintenance of your equipment is the best way of staying ahead of problems and having complete control over the issues and not just the other way round. Although this is very admirable, not all situations will demand you regular maintenance efforts.

An excellent example of an area that doesn’t require maintenance efforts is the AGM batteries. These batteries feature an advanced battery technology that prevents water loss when used, unlike the typical flooded-lead-acid and GEL batteries.

Typically, flooded-lead -acid batteries require that the users checkup the water levels frequently, after one or two months, as a maintenance requirement, but this is not the case with AGM batteries.


AGM batteries retain water through the mechanism of an ingenious catalytic cap. As mentioned earlier, the innovative fiberglass catalytic cap helps combine the two gases produced, i.e., Oxygen and Hydrogen, to form water.

The water is then soaked into the cells via the fiberglass separator through capillary action; hence no water is lost. AGM batteries are maintenance-free, so you won’t have to add water. So unless you’re replacing an old AGM battery, then you don’t have anything else to do about it.


Should you add water?

Despite the clear warning label on the battery caps, “DO NOT OPEN,” the folks goes ahead to open the vents and gush plenty quantities of water into all the cells. Things change when he start charging the battery. The excess electrolyte began spilling out of each cap, so intensely like an active volcano.

The spills also contain concentrated sulfuric acid, and this can result in corrosion of your car tray. Rinse off the acid on your car trays immediately and start planning how you will replace the battery since you diluted its electrocute down such that it won’t charge effectively. AGM batteries will cost you more than ordinary batteries, and that’s why you shouldn’t add water.


Why my AGM battery does loses charge?

Typically, a full charge AGM battery should have a voltage reading of over 12.8V – 13V; otherwise, your battery has an issue. For instance, an AGM battery reading 20 % and below the voltage reading of a fully charged battery, then consider replacing it.

It could be as a result of damage from frequently under/overcharging the battery or battery age. Besides, adding water into your AGM battery will result in diluting down the electrolyte to the extent that it won’t hold charges for long. Sulfation is also a common cause of battery discharging, but the good news is that you can use a desulfation device to rectify this issue.


If your AGM battery has a good voltage reading once you fully charge it, but within a few minutes, the voltage drops to below 11V, it can indicate faulty cells that need replacement. Excess vibration from driving over ridges with inadequate shock absorbers can damage your car’s battery cells, thus discharging within a short duration.


Leaving your battery in the storage for quite some time without a formal charge or connected to a load drawing charges until its voltage drops below 10V, there is nothing you can do to bring your battery back to life other than replacing it.


Can you add water to get the battery back to life?

Unless you want to ruin your battery completely, adding water into your AGM battery can only mess up with it more. Besides, you risk getting into contact with the highly corrosive sulfuric acid, which can leave your skin charred. Unlike the plates you saw in the flooded lead-acid batteries, the AGM batteries include glass mats for absorbing electrolytes, keeping the batter spill-free.

Adding water will only mess with the sulfuric acid concentration, i.e., diluting it below the recommended point, which will make it not hold charges for long.


Can the AGM battery be reconditioned after adding water?

Please never attempt to add water to your AGM battery whatsoever! Doing so means damaging your battery utterly such that it will never rejuvenate nor maneuver. Adding water can only ruin the internal unit system by exposing the internal components to undesired external oxygen.