Liquid lead acid batteries are designed with electrolyte – a mixture of acid and water.  Acid is heavier than water and will settle on the bottom of the battery.  This process is called stratification.  When a high concentration of acid builds up at the bottom of the battery, lead sulfate is produced.  Lead sulfate attaches to the battery plates and reduces the charge storage capacity.   There are some maintenance steps you can take to help prevent battery stratification.

All batteries, regardless of their chemistry, will self-discharge.  The rate of self-discharge for liquid lead acid batteries depends on how the battery is stored, and also on what temperature the battery is operated.  At a temperature of 80-degrees F., a 125-AH (Amperage Hour) lead acid battery will self-discharge at a rate of about 5% per week.  If this 125-AH battery is stored for four months (16 weeks) over the winter without being charged, the battery will lose approximately 80 amps of its 125-AH capacity.  The battery will also have a heavy amount of sulfation that causes additional loss of capacity.  For this reason, it is important to keep the batteries charged even while not in use.

Avoid these common mistakes when maintaining liquid lead acid batteries:

1. Undercharging – This occurs when the battery is not restored to a full charge.  Continually operating a partially charged battery, or storing a partially charged battery, results in the formation of sulfate on the plates.

2. Overcharging – Too much charging can cause accelerated corrosion of the positive plates, added water consumption and damage due to excessive heat.  Units equipped with an inverter will self-charge in three stages - bulk, absorb, float – and this prevents overcharging of the batteries.  If a portable charger is used to charge the RV batteries, closely monitor the process and use a battery hydrometer to test each cell.  Liquid lead acid batteries should be charged after each discharge of more than 50% of the battery’s rated capacity and during storage of 30 days or more.

3. Underwatering – Water is lost in the battery cells during the charge process.  Damage can occur when the electrolyte level is allowed to drop below the top of the plates.  Check the battery level often and replace using distilled water only to cover the top of the plates.

4. Overwatering – Excess water in a battery will cause additional dilution of the electrolyte and reduce battery performance.  Add water to the battery after is it fully charged. 

5. Surface Charging – A high concentration of sulfuric acid around the plates prevents the battery from fully charging by only allowing a surface charge that will quickly diminish.

6. Improper testing – Prior to checking the battery voltage, let the battery sit for two to four hours to allow electrolyte time to distribute throughout the battery.  If you don’t have that much time to perform a battery test, turn the headlights on bright for 3 to 5 minutes and then let the batteries sit at rest for 5 minutes before testing the battery voltage.