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Old 03-10-2019, 08:05   #1
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Adding agm

I want to replace my three house bank batteries with AGM and leave the starting and windlass batteries as they are. The batteries are charged through a sterling power Prosplit D from alternator and solar.

Can i just add a new AGM-appropriate charger after the Prosplit D.

What is needed.
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Old 03-10-2019, 09:26   #2
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Re: Adding agm

Likly nothing needs to be done. The voltages of agm and flooded batteries overlap. Check the settings of your existing charger and the requirements of the old and new batteries. Only then will you know.
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Old 03-10-2019, 10:06   #3
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Re: Adding agm

More specifically, check the actual Absorb voltage at your current House bank, and compare to the profile specs of the AGMs you are considering.

Odyssey, Lifeline and Northstar being top choices in the NA market for deep cycling.

Do not just order online, nor buy what a convenient automotive, big box or marine retail outlet offers, call the above makers and ask for a list of their dealers nearby.
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Old 03-10-2019, 10:28   #4
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Re: Adding agm

If you don't plug in every night or have a LOT of solar, AGM's are a bad choice for a house bank. My last set of Lifeline AGM's lasted less than 3 years despite careful use (never discharge below 50%, fully recharge overnight at dock whenever possible, occasional 8 hour "conditioning charge")

Regular AGM's are great for start batteries or anything else that will only be slightly discharged and then fully recharged.

While expensive, if you use size 31 batteries the Firefly Batteries are a superior AGM option for most cruisers. They can use the same charger settings as your current batteries

https://oceanplanetenergy.com/advanc...asis-group-31/

Another long life option are gel batteries - but those do require adjusting the charge voltage.
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Old 03-10-2019, 13:13   #5
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Re: Adding agm

I agree, skip AGM for house use.
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Old 03-10-2019, 13:42   #6
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Re: Adding agm

Quote:
Originally Posted by CarlF View Post
If you don't plug in every night or have a LOT of solar, AGM's are a bad choice for a house bank. My last set of Lifeline AGM's lasted less than 3 years despite careful use (never discharge below 50%, fully recharge overnight at dock whenever possible, occasional 8 hour "conditioning charge")

Regular AGM's are great for start batteries or anything else that will only be slightly discharged and then fully recharged.
I agree on most of the points, with one exception. I got over 10 years out of my Lifeline AGM batteries. Technically those batteries are still going to my knowledge, however I sold the boat.

I will look this weekend, however, I believe I'm on 5 years on my current Lifeline AGM batteries.

I find (YMMV) that not dipping down too deep and fully recharging are the key. I typically drop no lower than 12.7/12.8. The key to this is a combination of frugal usage with an oversized bank. I charge them every 12 hours and strive to completely charge if possible.

Disclosure: I only use the boat Th/Fri - Sun 5-6 months of the year, with a stretch of 2-3 weeks during that 5-6 month period. Otherwise the boat is plugged into a dock.
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Old 03-10-2019, 19:39   #7
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Re: Adding agm

Yes even calling 75% SoH as EoL, properly cared for quality AGM should go well over five years, maybe 8-10.

But many setups just "can't" get to 100% Full, or at least buying a new bank more frequently is more cost-effective than putting in the infrastructure required to maximise lifespan.
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