Battery Self-Discharge

Some of the most frequently asked questions about lead-acid batteries relate to their rate of discharge.  

All lead-acid batteries will naturally self-discharge, but how long it takes for the charge to deplete is based on a few variables such as storage temperature, length of storage, sulfating, and whether the battery is exposed to dirt and dust. 

Temperature of Storage  

For lead-acid batteries, if the environment it is stored in is warmer, then the self-discharge will increase. For example, a lead-acid battery left in storage at a moderate temperature will self-discharge rate of around 5% per month. At the same time, a battery stored at warmer temperatures will experience higher discharge rates, and anytime the temperature of a battery is increased by 15°F, the self-discharge rate doubles.

Length of Storage

The time a battery stays in storage will also affect the amount of discharge. A battery can typically last six months to one year at mild to average room temperatures. Checking on a sealed lead-acid battery at least every two months is recommended, giving it a periodic charge. 

Sulfation of Battery

A lead-acid battery risks a greater discharge rate if left in storage too long because of a buildup of lead sulfate crystals. Sulfation occurs in lead-acid batteries when they are deprived of a full charge, ultimately impeding recharging.

Exposure to Dirt and Dust

If a lead-acid battery sits in storage in an environment where dirt and dust can reach the battery, it can similarly create a reaction that leads to self-discharge. Prevent this by keeping the top of the battery clean and dry. Wipe it with a soft cloth to reduce the amount of dust and debris build-up while your battery stays in storage.