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.

Darrell Nicholson, editor of Practical Sailor, grew up boating on Miami’s Biscayne Bay on everything from prams to Morgan ketches. Two years out of Emory University, after a brief stint as a sportswriter, he set out from Miami aboard a 60-year-old wooden William Atkin ketch named Tosca. For 10 years, he and writer-photographer Theresa Gibbons explored the Caribbean, crossed the Pacific, and cruised Southeast Asia aboard Tosca, working along the way as journalists and documenting their adventures for various travel and sailing publications, including Cruising World, Sail, Sailing, Cruising Helmsman, and Sailing World. Upon his return to land life, Darrell became the associate editor, then senior editor at Cruising World magazine, where he worked for five years. Before taking on the editor’s position at Practical Sailor, Darrell was the editor of Offshore magazine, a boating-lifestyle magazine serving the New England area. Darrell has won multiple awards from Boating Writer’s International, including the Monk Farnham award for editorial excellence. He holds a U.S. Coast Guard 100-ton Master license and has worked as a harbor pilot and skippered a variety of commercial charter boats.


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