My 2005 H44 came with two 200amp-hour AGM batteries. They have been kept pretty well charged by solar panels, but they have been cycled daily for 2 months each summer to about 70%-80% of full-charge keeping the fridge running while the boat has sat at its mooring. In addition they have been cycled for about 30 days each year while cruising, but never below 50%. How much longer can I expect these batteries to last? (We are starting year 4.)
Lifetime for AGM batteries
- Thread starter Larry Jackel
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Look forward to the answer.
I look forward to the answer, myself having installed all AGMs in the spring of 2007. My three Gels were nine years old and still holding a charge when I replaced them. I was leaving on an extended cruise so I installed four new 100Ah AGMs. The starter battery is a three year old 900CCA AGM. If they are as good as the Gels I am looking for ten years out of these batteries.
I look forward to the answer, myself having installed all AGMs in the spring of 2007. My three Gels were nine years old and still holding a charge when I replaced them. I was leaving on an extended cruise so I installed four new 100Ah AGMs. The starter battery is a three year old 900CCA AGM. If they are as good as the Gels I am looking for ten years out of these batteries.
AGM lifespan
I maintain some remote solar installations and have some sites with AGM's that are over 10 years old and still going strong. These sites will cycle to below 50% on occasions when it is extended cloudy weather. Quality AGM's will go a long time if they are not abused. After they are charged 100%, watch the voltage drop when you run a heavy load like a microwave. You will get a idea of what is normal. When you start to see a significant change in voltage they are getting near the end. Use the same load for the same period of time and make sure they are fully charged each time you test them.
I maintain some remote solar installations and have some sites with AGM's that are over 10 years old and still going strong. These sites will cycle to below 50% on occasions when it is extended cloudy weather. Quality AGM's will go a long time if they are not abused. After they are charged 100%, watch the voltage drop when you run a heavy load like a microwave. You will get a idea of what is normal. When you start to see a significant change in voltage they are getting near the end. Use the same load for the same period of time and make sure they are fully charged each time you test them.
Alot depends on re-charge time
Typical AGM's that only discharge to 80 percent of full capacity should expect to see well over 2000 discharge cycles if it was charged back to full capacity. I have seen some numbers in the 3 to 4 thousand cycles for that depth of discharge. There are alot of caveats to that number of cycles like temperature, charge method and time, and certainly load considerations. The boaters demise is usually temperature and re-charge. AGM's usually have a 10 Yr. pro-rated warranty. If you get 10 years you are VERY lucky. I would plan for 7 years and anything over that is a gift.
Typical AGM's that only discharge to 80 percent of full capacity should expect to see well over 2000 discharge cycles if it was charged back to full capacity. I have seen some numbers in the 3 to 4 thousand cycles for that depth of discharge. There are alot of caveats to that number of cycles like temperature, charge method and time, and certainly load considerations. The boaters demise is usually temperature and re-charge. AGM's usually have a 10 Yr. pro-rated warranty. If you get 10 years you are VERY lucky. I would plan for 7 years and anything over that is a gift.
They Don't die.....
They are usually murdered.....aside from religiously avoiding exceeding 50% discharge, I believe you can increase their life by tuning your charging voltages (absorb and float) to precise manufacturers specifications. I installed an inverter/charger that allows you to set these values to a 10th of a volt along with time and frequency and re-float values. I'll get back to you with my success story in about 9,5 years.
They are usually murdered.....aside from religiously avoiding exceeding 50% discharge, I believe you can increase their life by tuning your charging voltages (absorb and float) to precise manufacturers specifications. I installed an inverter/charger that allows you to set these values to a 10th of a volt along with time and frequency and re-float values. I'll get back to you with my success story in about 9,5 years.
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