12 Ways to Extend Your AGM Batterys Life


1. Charge to full as often as possible; this point cannot be over emphasized.

2. Get back to at least 80- to 85-percent state of charge (full capacity) with each charge cycle, and get to 100-percent state of charge as soon as you can thereafter.

3. Do not regularly discharge your bank below 50-percent state of charge.

4. Size your most powerful charge source, usually an alternator or inverter-charger, for a minimum of 20 percent of bank capacity. Odyssey TPPL AGMs prefer 40 percent of amp-hour capacity as minimum charge current.

5. Use smart chargers. Not all chargers that claim to be smart are in fact smart.

6. Use temperature-compensated charging for all charging sources.

7. Use smart solar controllers. Some solar controllers start each day at a new absorption voltage charging cycle. This is not healthy for AGM batteries that have low self-discharge and minimal parasitic loads when left unattended on-the-hook. Smarter controllers have a voltage trigger to pop them out of float mode. If they don’t drop to the trigger voltage, they remain in float.

8. Using the correct float voltages is a critical aspect of AGM batteries. Chargers that use dip switches for programming often lack the correct voltages for both absorption and float settings.

9. Use an alternator temperature sensor and external regulator, if possible. AGM batteries can demand a lot from an alternator, and the heat created can shorten its life or cause premature failure.

10. For the best charging performance, minimize the voltage drop in system wiring. Even a 3-percent voltage drop at 14.4 volts means just 13.96 volts at the battery terminals. Incorrect voltage sensing robs you of the fastest charging potential, especially during short duration, high current charging events.

11. Know your correct state of charge at all times, even if this means investing in a battery-monitoring device. It will help in overall cycle life. If you are using voltage to determine state of charge, be sure you are getting it as accurate as possible.

12. Avoid installations in engine rooms or hot areas of the boat. Heat shortens battery life.

Practical Sailor has been independently testing and reporting on sailboats and sailing gear for more than 45 years. Supported entirely by subscribers, Practical Sailor accepts no advertising. Its independent tests are carried out by experienced sailors and marine industry professionals dedicated to providing objective evaluation and reporting about boats, gear, and the skills required to cross oceans. Practical Sailor is edited by Darrell Nicholson, a long-time liveaboard sailor and trans-Pacific cruiser who has been director of Belvoir Media Group's marine division since 2005. He holds a U.S. Coast Guard 100-ton Master license, has logged tens of thousands of miles in three oceans, and has skippered everything from pilot boats to day charter cats. His weekly blog Inside Practical Sailor offers an inside look at current research and gear tests at Practical Sailor, while his award-winning column,"Rhumb Lines," tracks boating trends and reflects upon the sailing life. He sails a Sparkman & Stephens-designed Yankee 30 out of St. Petersburg, Florida.


Please enter your comment!
Please enter your name here