Another Battery Question

[Coach]

Is it me or should HB have an entire section on batteries? :rollside:
On to my question. Trojan makes AMG 31 Marine batteries as well as and 8D-AMG.
The 31 has 110 Amp Hours at 71 lbs
The 8D has 230 Amp hours at 155 lbs
Would 2 31's at 220 Amp hours at 142 lbs be better than 1 8D? Besides price, which at the moment I have know idea about price, would 2 batteries in a bank be better than the one huge battery? Is there other advantages other than price or size restrictions?

[Tom Brown]

...would 2 batteries in a bank be better than the one huge battery?
No.
If the same electrode plate surface area were spread across two batteries, they would be able to store the same amount of power, given the same cathode and anode materials as well as the same specific gravity electrolite.

[Coach]

Tom-
I am confused 2 31's will double the Amp hours correct? If give that there is room an 8D would be a better choice than 2 31's? Thanks for your help

[Tom Brown]

I am confused 2 31's will double the Amp hours correct?
Yes.
If give that there is room an 8D would be a better choice than 2 31's?
There is no tangible difference between having a single cell or two cells.. If those specifications were done exactly the same way, the single 8D would have a tiny amount more power.
The way the batteries are tested, gives a sleight advantage to a larger battery. This advantage is minimal but I would expect a pair of batteries to test just slightly more than double the capacity of a single battery, if you bridged up a pair of identical batts. In other words, there's probably less than 10 Ah or 4.5% difference between the two configuration choices you present.
If there were no other factors, I'd look at a single 8D as opposed to a pair of 31s for reasons of having ever so sleightly higher energy density in a single package and you'll basically eliminate battery interconnect resistance. Those factors are just barely worth considering, if at all.
The group 31 choice might make more sense if you have room for three of them. You could install two now and have the option of adding a third later, if you felt it desireable to have more battery capacity at a later point in time.
I don't think there's a bad choice here, Coach.

[Coach]

Yes.
There is no tangible difference between having a single cell or two cells.. If those specifications were done exactly the same way, the single 8D would have a tiny amount more power.
The way the batteries are tested, gives a sleight advantage to a larger battery. This advantage is minimal but I would expect a pair of batteries to test just slightly more than double the capacity of a single battery, if you bridged up a pair of identical batts. In other words, there's probably less than 10 Ah or 4.5% difference between the two configuration choices you present.
If there were no other factors, I'd look at a single 8D as opposed to a pair of 31s for reasons of having ever so sleightly higher energy density in a single package and you'll basically eliminate battery interconnect resistance. Those factors are just barely worth considering, if at all.
The group 31 choice might make more sense if you have room for three of them. You could install two now and have the option of adding a third later, if you felt it desireable to have more battery capacity at a later point in time.
I don't think there's a bad choice here, Coach.
Thanks Tom, that was a huge help!!!

[Coach]

I just talked with Battery Systems near my house
31-AGM $260 each
8D- AGM $600 each
Looks like for cost and storarge reasons the 31 wins.

[shadow]

I just talked with Battery Systems near my house
31-AGM $260 each
8D- AGM $600 each
Looks like for cost and storarge reasons the 31 wins.
I run 2 of the AGM 8d's in my boat,the only downfall is space and weight.
They will crank my system all weekend and never skip a beat.Fairly big system and i normally have it cranked @ WOT.I'm on my 4th season now with these batteries.I think you should be able to pick these up for about $400 per batteries.
This should be the web site wwwlifelinebatteries.com
there located out by the miller brewing co off i belive the 210
626-969-6886 ask for Andrew or Dave i've dealt with them in the past and
they should be able to hook you up.Don't for get a (true)40amp charger.

[Coach]

Has anyone used the West Marine SeaVolt AGM's?
The 8D is 245 Ah and runs $400
The 31 is 105 Ah and Runs $200