The performance and life of your batteries can be greatly extended through the use of a correctly sized quality multistage battery charger.

The construction and chemistry of deep cycle batteries is different to that of regular car cranking batteries. As such, a battery charger intended for car batteries will, in most cases, not be suitable for charging deep cycle batteries.

A correctly configured multistage battery charger is required for sealed and wet-cell lead acid batteries to achieve full charge.

A battery charger should (as a minimum) incorporate the following charging stages:

• BULK charge in which the charger delivers a high current charge which returns the battery to around 80% of full charge.
• ABSORBTION charge where the charger holds the output voltage constant but allows the charge current to reduce. This stage allows the battery to absorb the remaining 20% of it's capacity.
• FLOAT charge where the charger voltage is lowered to maintain the battery at full charge without risk of overcharging.

Note that the battery charger's output voltage levels for the above stages must match those specified by the battery manufacturer.

Gel and AGM batteries are generally charged and floated at slightly lower voltage levels than wet-cell batteries. Incorrect voltage selection can result in undercharging or overcharging of your batteries, both of which will reduce their performance and life.

Larger battery chargers generally incorporate another stage or operating mode called EQUALISATION (or Boost on a CTEK charger). This mode lifts the battery voltage to a higher level, such as 15V for a 12V battery, and holds it there for a period of time.....usually 2 hours.

The Equalise funtion is generally only beneficial for wet-cell batteries, but can help balance some AGM batteries. Check with manufacturer beforehand!

Holding the battery voltage at this higher voltage level causes the electrolyte to bubble vigorously which stirs it up and reduces stratification of the electrolyte. Stratification refers to different acid concentrations at different levels in the battery which reduces performance, affects Specific Gravity readings and can significantly reduce battery life.