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Old 21-11-2021, 14:44   #1
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Mixing AGM Batteries

The batter bank on my Jeanneau 349 is pretty inadequate. I want to add 1-2 more AGM batteries to my house bank. Was going to go lithium but my current batteries are new and seems that you can draw down AGM to 20-40% without too much harm (to the point Iíd rather do that for a couple years and do LIFPO4 later). My standard batteries are Exide EP600 70A which I canít find for the life of me in the states. Is there any reason I canít wire with them 2x group 24 west marine AGM batteries 79a to the bank? Age and cycle wise is minimal differences as Iíve only had the boat since September with weekend usage only.
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Old 21-11-2021, 15:34   #2
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Re: Mixing AGM Batteries

i'm no expert, and there are folk here with far more knowledge of batteries than me, however in my experience you can happily mix batteries of different brand and size in a bank - PROVIDED that all batteries are of the same chemistry, and they are wired in parallel (not in series)

but i'd wait for some other comments before going ahead !

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Old 21-11-2021, 19:34   #3
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Re: Mixing AGM Batteries

Quote:
Originally Posted by chrisr View Post
i'm no expert, and there are folk here with far more knowledge of batteries than me, however in my experience you can happily mix batteries of different brand and size in a bank - PROVIDED that all batteries are of the same chemistry, and they are wired in parallel (not in series)

but i'd wait for some other comments before going ahead !

cheers,
Thatís my understanding as well but Iíll wait for others to chime in.
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Old 21-11-2021, 20:17   #4
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Re: Mixing AGM Batteries

Quote:
Originally Posted by Letterkenny View Post
The batter bank on my Jeanneau 349 is pretty inadequate. I want to add 1-2 more AGM batteries to my house bank. Was going to go lithium but my current batteries are new and seems that you can draw down AGM to 20-40% without too much harm (to the point I’d rather do that for a couple years and do LIFPO4 later). My standard batteries are Exide EP600 70A which I can’t find for the life of me in the states. Is there any reason I can’t wire with them 2x group 24 west marine AGM batteries 79a to the bank? Age and cycle wise is minimal differences as I’ve only had the boat since September with weekend usage only.
Exide is standard battery in EU you can buy order almost in all marine shop. very expensive battery for 70A.
buy this lithium battery is cheaper of exide agm.

https://www.aliexpress.com/item/1005...:%223339%22%7D

https://www.aliexpress.com/item/1005...c00s8FX7w&mp=1
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Old 21-11-2021, 21:14   #5
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Re: Mixing AGM Batteries

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Originally Posted by more View Post
Exide is standard battery in EU you can buy order almost in all marine shop. very expensive battery for 70A.
buy this lithium battery is cheaper of exide agm.

https://www.aliexpress.com/item/1005...:%223339%22%7D

https://www.aliexpress.com/item/1005...c00s8FX7w&mp=1
I am in the U.S. and literally canít find them. The one website I found doesnít ship to California. Lithium is the second option Iím considering.
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Old 21-11-2021, 22:15   #6
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Re: Mixing AGM Batteries

Quote:
Originally Posted by Letterkenny View Post
The batter bank on my Jeanneau 349 is pretty inadequate. I want to add 1-2 more AGM batteries to my house bank. Was going to go lithium but my current batteries are new and seems that you can draw down AGM to 20-40% without too much harm (to the point Iíd rather do that for a couple years and do LIFPO4 later). My standard batteries are Exide EP600 70A which I canít find for the life of me in the states. Is there any reason I canít wire with them 2x group 24 west marine AGM batteries 79a to the bank? Age and cycle wise is minimal differences as Iíve only had the boat since September with weekend usage only.
Any particular reason you want to remain with a 70 amp hour battery? I have three AGMís. One separate starter and the second bank consists of two AGMís. All are 105 amp hour group 31ís.
Iíll look into lithium when it comes time for replacement in a few years. The prices are just coming down and dependability is rising to a level Iíd be comfortable with.
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Old 22-11-2021, 07:27   #7
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Re: Mixing AGM Batteries

We have been running a lithium / lead acid battery mix this summer without any issues. 120Ah drop in lithium and Trojan TMX 24, 85 Ah battery. In use the lead acid doesn't do much, lithium does all the work unless we drop below 12.5v or so. However, that lead acid remains on charge via solar all the time running the bilge pump etc whist the lithium is isolated when we leave the boat. It also means if the BSM turns the lithium off, well there is something still running the chart plotter and VHF etc.

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Old 22-11-2021, 07:35   #8
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Re: Mixing AGM Batteries

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Originally Posted by Orion Jim View Post
Any particular reason you want to remain with a 70 amp hour battery? I have three AGMís. One separate starter and the second bank consists of two AGMís. All are 105 amp hour group 31ís.
Iíll look into lithium when it comes time for replacement in a few years. The prices are just coming down and dependability is rising to a level Iíd be comfortable with.
A couple reasons. First, the space where they are is for 3x group 24s. The second is that these batteries are 3 months old. Given the amount of new chargers and wiring Iíd have to do for a LIFEPO4 conversion to make sure the alternator keeps charging them and how new they are, I feel like adding 1-2 more group 24 AGMs might be the best plan and then in 3-5 years do LIFEPO4.
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