Maintenance Free Batteries

Maintenance free battery charge indicator.

We do not typically add water to a maintenance-free battery. It's sealed and contains either a gel or glass fiber mat instead of the liquid solution found in standard batteries.

Instead of vents, they have relief valves that prevent pressure buildup. That's why the manufacturers refer to them as VRLA or valve-regulated lead-acid batteries.

These batteries have a small hydrometer with a sight glass on top of the case. A bright green dot indicates a charged battery. The electrolyte solution is close to (1.265) and heavier than water (1.0).

A dark green or black sight glass indicates that it needs a charge. The electrolyte has undergone a chemical reaction and is now closer to water. Charging a battery with a dark indicator restores the solution's specific gravity to a weight closer to (1.265).

A light yellow or clear sight glass means the electrolyte solution has dropped below the built-in hydrometer. Most battery manufacturers recommend replacing the battery when the level drops below this threshold.