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Old 13-09-2015, 18:44   #1
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Converting Batteries from 8D

So I have two 8D batteries that are 5 years old at the moment. They are flooded batteries. I've been wanting to go to AGM batteries, but I think I would have to upgrade my whole charging system to do it. I already had a few big upgrades this year, so I am avoiding that all together.

Looking at finding two 8D batteries on the internet, I find out the literal insane price to ship those things. So I am now thinking of doing two banks of three Group 31 batteries. (I think that is the correct size?) and try to wire them together.

Anything I should be aware of? Will it work the same?
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Old 13-09-2015, 20:21   #2
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Re: Converting Batteries from 8D

3 grp 24 are usually the same size as an 8D; if these are house batteries you might consider moving to Golf Carts; a smidgen higher but might work
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Old 13-09-2015, 21:51   #3
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Re: Converting Batteries from 8D

Where are you located that you would need to ship the batteries to and from? Your bio says mahantan beach California. If you are there I would just go to batteries plus and purchase the new 8d batteries there are two locations near you in Culver city.
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Old 13-09-2015, 22:17   #4
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Re: Converting Batteries from 8D

Yeah I will give them a call to see how much it cost. Another reason is that the 8D batteries are extremely heavy.

Moving smaller batteries sounds a lot safer for me.
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Old 13-09-2015, 22:41   #5
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Re: Converting Batteries from 8D

Quote:
Originally Posted by Scott Berg View Post
3 grp 24 are usually the same size as an 8D; if these are house batteries you might consider moving to Golf Carts; a smidgen higher but might work
S
+1

Good luck!
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Old 14-09-2015, 08:59   #6
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Re: Converting Batteries from 8D

Switching each of my 8 D's to 4-Deka Pro Master 6 volt golf cart batteries. Only 64 lbs each, slightly larger imprint-approx. 29 inchs long by 11 inches wide if turned sideways compared to 20 1/2 by 11 inches. But you get twice the reserve ampacity.
Sticking with the wet cels as we only use the boat for 3-4 months straight then it sits till the following year without any use. The batteries get charged monthly but can't see the cost of going to gels for my usage. It would probably be different if I lived aboard. But having the boat sit in the Florida heat in the water for 8 months I can't see using more expensive batteries.
Good luck!
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Old 14-09-2015, 09:13   #7
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Re: Converting Batteries from 8D

We don't know how you use your boat, what your charging system is, whether or not you have shorepower or solar, or whether you cruise or just daysail.

That said, GCs have been shown to be the best bang for the buck and AGMs have inherent issues related to the first sentence above.

Like thesez;

AGM Battery Issues (from Maine Sail)
AGM Batteries - Making The Choice - SailboatOwners.com

AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
Darn AGM Batteries - SailboatOwners.com

Good luck, happy hunting.

Your boat has an active owners association. You might want to check with them, too.
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Old 14-09-2015, 09:21   #8
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Re: Converting Batteries from 8D

Quote:
Originally Posted by dkchen View Post
Yeah I will give them a call to see how much it cost. Another reason is that the 8D batteries are extremely heavy.

Moving smaller batteries sounds a lot safer for me.
I wouldn't say extremely heavy just heavy. My dad is 91 and just replaced his 2 8D dyno batteries by him self on his Spencer use dock carts and lift with knees not your back .
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Old 14-09-2015, 09:51   #9
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Re: Converting Batteries from 8D

Lifeline 8 d are 150lb. I recently replaced 5 8DS With 12 6 volt golf cart batteries. Some of my battery boxes would take 3 6 volt batteries others would only hold 2. I hope never to have to lift those big ass batteries again
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Old 14-09-2015, 09:59   #10
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Re: Converting Batteries from 8D

Go with four golf carts which will give you the same capacity as two 8Ds. Stick with wet cell. AGM is only a benefit to people who either live aboard or are more regular users PLUS keep their boat plugged in at a dock. AGM likes to be charged to 100% which is rarely possible for boats anchored or moored unless they have plenty of solar.
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Old 14-09-2015, 10:10   #11
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Re: Converting Batteries from 8D

Auto Zone the car parts place has a good selection of batteries including AGM GP31 at good prices and warranted.
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Old 14-09-2015, 10:32   #12
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Re: Converting Batteries from 8D

AGM's are a great idea if you plug in to a dock regularly or have enough solar panel to fully top them up every few days. Otherwise, stick with deep-cycle flooded. As mentioned, there are lots of good flooded deep cycle options that are lighter than 8D's.

Sam's Club usually has great prices on high quality batteries.

If you do go with more batteries, have the connecting cables made up professionally. I've used Genuine Dealz. You buy the wire, fittings, and shrink tubing from him (excellent quality and prices) , he will make up the cables to your measurements for about $2 an end.

2 AWG Custom Battery Cables Marine Grade by the foot Genuinedealz.com
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Old 14-09-2015, 10:32   #13
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Re: Converting Batteries from 8D

Quote:
Originally Posted by Stu Jackson View Post
We don't know how you use your boat, what your charging system is, whether or not you have shorepower or solar, or whether you cruise or just daysail.

That said, GCs have been shown to be the best bang for the buck and AGMs have inherent issues related to the first sentence above.

Like thesez;

AGM Battery Issues (from Maine Sail)
AGM Batteries - Making The Choice - SailboatOwners.com

AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
Darn AGM Batteries - SailboatOwners.com

Good luck, happy hunting.

Your boat has an active owners association. You might want to check with them, too.
Thanks for some of the tidbits there. My boat is basically always on shore power. When I make some trips to Catalina is when I need those batteries the most. My last trip, the batteries literally died on me over night. The vessel assist guy told me that he recommends the AGM batteries over the Gel batteries, which seems like the latter one would need new hardware to install.

Anyways, I am leaning towards just normal wet cell batteries. I am going to give a call to some local places to see the price of 8D batteries and some Group 24's.
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Old 14-09-2015, 10:34   #14
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Re: Converting Batteries from 8D

If you decide on going back with 8Ds it might pay to find a locate supplier to truck freight people? Not the local retailer?
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Old 14-09-2015, 14:36   #15
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Re: Converting Batteries from 8D

I just went with a 660 Amp AGM bank, but had to due to sizing constraints with my battery box but truly it goes something like this.
6 GC-2 batteries at Sams Club, $84 ea, total $504
6 AGM batteries $300 ea, total $1,800, plus you need a BIG alt to take advantage of them, >$1,000 plus a three stage charger with AGM voltages, $200?, oh and a shore power charger, a BIG one for the high absorption rate, maybe another $500?
That's roughly $500 vs $3,500?

Now check my numbers, as I sort of pulled them out of the air, but the point is AGM is WAY more expensive as you have to treat them as a system and have ALL the parts, or they will die prematurely, but even if they last twice as long, I can't make the "numbers" on them work, if I could have put Sams Club GC-2's in, I would have. I upgraded my alt and shore power charger anyway though as mine were very old and just killed batteries.


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