Need new batteries...
 

long story short but all 3 of my current batteries are bad. They are the batteries that came with the boat a few years ago. The cranking battery is an Interstate MT-34 (700 CCA) and the other two that are wired together are Exide Orbital deep cycle marine (750 CCA). They are all wired to a perko switch and I usually run it on "all"

My question is what is the best bang for my buck? Also, should I go with all the same deep cycle marine battery? Any and all advice is greatly appreciated as I am no battery guru. I have a WS Syn 4 running two rev 10s, and two other amps running a sub and my in boats. Also, some LEDs throughout. My boat is a 99 SAN with the GT40, just FYi.

I run XS Power XP3000's. I will not have another battery run my system ever. Spend the money and do it right the first time. Then you don't spend more when you get something you don't like.

I run 3 interstate 29s. 115Ah and $115 a piece.

I run two Interstates, (1) 27M-XHD for starting and (1) SRM-29 for the stereo. I run a small, simple system and the 29 is more than enough to run the two small amps.

Some of the best bang for the buck out there.

I also run the 27m-xhd for starting highest MCA rating for a group size 27 that i could find. For the stereo I have 4 interstate GC2-XHD golf cart batteries.

I've been satisfied with the group 27 dual purpose pair I got from Costco, 115 ah each!

First question; "should all of my battery's be the same" Absolutely
They should also all be the same age. don't buy 2 this month and then add another battery months/years later they all need or should be all new and fresh when u get them. Make sure they all have the same "born on date" on them.
Group 31 battery's are a the largest most common boat battery's I have come across most group 31s are 130 amp hrs each
So 3 group 31s should give you a pretty good run time.
As far as bang for buck you can't get cheaper battery's them Flooded lead acid.
Check out the Trojan 30Hsx for FLA battery's $200 a pop.
More expencive option would be a gell or AGM Then your in the $250-$275 range

I have a similar stereo and battery setup to yours. I have 3 batteries, all group 24 size. 1 deep cycle for starting that I got from Walmart, can't remember the exact brand. Then two for stereo are interstate deep cycle. I've played my music on full blast for 3-4 hours at the beach and the boat still started on that battery bank. I can't imagine how long the more expensive/larger batteries can play for but that is my experience with the standard lead acid deep cycle batteries. Might wanna look into an onboard charger as well. It's good peace of mind but it will also help your batteries last longer.

I'm running 3 full river DC115-12 BATTS group size is 31. With a big system and I can run all day and they don't go dead. I'd recommend not going cheap on batteries and also I'd get a on board charger so u can plug them in and let them charge when u Park your boat.

In the past couple years I have learned quite a bit about battery wiring. Wiring batteries in parallel when done without extreme attention to detail can kill batteries in a year or two. I had 6V batteries wired in series with no issues for a couple years then when I switched to 12V batteries in parallel I started killing batteries about once every 2 years. The key is to make sure they are wired in such a way that they all see EXACTLY the same voltage. This requires you to hook one end of the array to the positive connection and the opposite end of the array to the negative terminal. The puts all of the batteries at exactly the same voltage. This allows them to charge at the same rate and discharge at the same rate. If you just hook them together and wire the closest one to the load and the charger you will always be cycling that closest batter deeper than the others. Both Grant and I have seen it happen in the boats we work on. Generally it's easier to wire two 6V batteries for a house bank versus two 12V batteries.

I'm going to order 4 Trojan J305G-AC to replace 6 of my smaller 12v's that came in the boat.
Question is, can I put all 4 6v on 2 bank and a g31 on the other bank of my perko so it's isolated for starting?

Ran 2 Kinetic 2000's on a perk switch. They are 12v deep cycle audio comp batteries.Used both as starting and audio batteries. Sealed, Gel, powerful, no maintenance, lasted from 2007 til 2 months ago. New they are around $400 each, well worth it. If you do some searching, you can find them for around $300 each. I replaced both of my batteries 2 months ago because one went bad, the other was still good (but as Grant mentioned above, all your batteries should be matching). This time I decided to give a pair of slightly used/refurbished sealed gel 12v deep cycle batteries, same as the Kinetics, but were from a battery bank for a generator or solar powered system. They were 1 year old, tested as new, and were only $80 each with a 6 month warranty.

I will report back... hopefully in 7 years, that they are still working well.

I'm guessing my batteries have been in the boat since around the 07 mark as well. They seem to be losing their juice quite fast now with the strain on them. Using the calculators online, I'm looking to need around 600ah for my stereo. I'm pulling right around 7k rms