Marine Battery Charging Instructions

by Anthony Smith

Overview

Boating can be an expensive hobby, and boat owners often need to take measures to cut unnecessary costs. One area in which more money is spent than need be is in the replacement of marine batteries. Marine batteries are often charged and discharged incorrectly, causing premature failure and early replacement costs. Following a few basic guidelines on proper charging can save a boat owner significant money in the long run.
Use a Quality Battery Charger

Marine batteries are different than the type of battery with which most people are familiar, the car battery. Thus, they also have different charging requirements. It is important that you use an automatic "smart" battery charger specifically designed for charging marine batteries. A good charger will charge a marine battery in three phases: bulk, acceptance and float. This will prevent overcharging, which is a killer to batteries. Those marine batteries constructed using flooded lead acid will also need a charger that can include an equalization phase. Finally, your charger should have adequate amperage to do the charging job. Use a charger that is rated to at least the equal the sum of the DC loads, plus 10 percent of the amp-hour capacity of the batteries.

When and How to Charge

Charge your marine batteries well before they are fully discharged. Running a battery down to the end of its capacity is known as a deep discharge, and continual deep discharging will shorten the life of the battery. Instead, charge the battery when it reaches a discharge state of about 50 to 85 percent of its capacity. Do not interrupt a charge cycle until it is complete, as this can lead to decreased battery performance and life.
Other Charging Tips

There are some tips that will also be beneficial in regards to charging. For instance, when you are running marine batteries together, it is best not to mix old batteries with new ones. Do not leave a battery in storage while it is discharged. When you bring it out of storage, it is likely you will never get the battery back to full capacity. Charge batteries fully before storing, and then check them regularly, charging as necessary. An even better solution is to keep the stored battery hooked up to a "smart" charger while it is not being used.