Basic Battery Charging – Whole House Battery Backup

Basic Battery Charging - Whole House Battery Backup

Proper charging of a battery is crucial for a healthy battery bank. There are many different battery manufacturers and the recommended charging voltages may vary slightly from what another manufacturer might recommend for a similar battery.  This makes it important to contact the manufacturer of your specific battery and to read the installation manual thoroughly to understand the proper charging set points. These charging set points are referred to as bulk, absorption, float, and equalization.



Bulk is the initial charging phase. The goal is to give the battery as much current (flow of electricity) as it will accept until it’s about 80% charged.


Absorption is the second phase of charging which brings the battery to a full charge. In the absorption phase the charger holds the voltage (force of electrical movement) steady (typically between 14.4V – 14.8Vdc for a 12Vdc battery), and decreases the current gradually to safely charge the battery to full capacity, or to charge for a programmed amount of time. The amount of time required to fully charge your batteries will vary based on how much battery capacity you have, the state of charge (how full it currently is), and your charger’s capabilities.


The float cycle keeps a battery at full capacity as long as there is a charging source available. This stage comes after the absorption cycle. Content


Equalization is a maintenance tool that can be used to rejuvenate tired batteries or to prevent batteries from becoming tired.  Equalization is a controlled overcharge of the batteries which helps stir up and equalize the electrolytes within a flooded lead acid battery. Be careful, some batteries should never be equalized or they will be damaged. Other batteries require regular equalization, sometimes as often as once a month. This makes it important to thoroughly understand any maintenance requirements of your batteries.

*Important: Some batteries should not be equalized and cannot be without damage, however others will require regular equalization. Make sure you understand your equipment and the manufacturer’s recommendations for care and maintenance.