Should I add a 3rd battery to my Bu?
 

Next Tuesday I'm having a stereo over haul done to my boat. I'm having one pair of Rev 10s installed to the tower powered by a syn 4. 2 pairs of XS650s and 1 kicker solo baric subwoofer (about 500 Watts rms) all powered by a syn 6. Right now i currently have two interstate 24M-XHD 800CCA 1000MCA.

will i be ok with just two batteries or should i add another interstate to the power plant??

add an on board charger if you have power. I would add a battery just to have the extra if needed. I bet you will be fine with 2 but i have 3 syn 4s and 1 jl 600.1 and i think they are so efficient that you can really crank on the system and not kill the battery. i have had other systems and would kill battery time, but have found the top end amps really save on play time. hope this helps

I don't have an on board charger but i do connect them to a trickle charger after a day on the water and leave them connected till the next time I go out. Hopefully that helps the longevity of the batteries life.

I run 2 pro 80's, 4 6.5 JL components, 4 wetsounds free air 10's a syn 6 and syn 1. I use two batteries one cranking battery and one deep cycle. My boat automatically switches to the deep cycle when the engine is not running and the key is turned to power the accesories. I have never had a problem. My voltage while idling with the system cranking is about 13.5V.

How may batteries/amp hours you need will depend on how long you want play the system with the engine off.

At a minimum, i would swap one of the cranking batteries for a deep cycle.

My suggestion for what your running would be to atleast off the stereo bank 24m and add a minimum of a pro27.... that will increase play time substantially... Now if your gonna crank it for hours at the sandbar, then add another pro27 and a on board charger... then youl be set for over 6 hours of playtime at rest rocking.... thats the proper set up.. if ya want though.. you can keep the 24m and add a pro27 to it, untill the 24m takes a crap, then switch it out for another pro27.... if you dont crank it (the stereo)while the key is off, I see no issue just leaving it alone and throwing it on a charger every once in awhile to keep the batts topped off... this is just a get by solution though...

I dont know the stereo lingo like some of these guys. I have a Malibu, I run 10 wetsounds, 15 inch baric sub, 3 amps all on two batteries and I have never had battery problems. I installed a Perko switch to isolate the stereo battery, so I can play music and not have to worry that i just killed the battery and wont be able to start up the boat. Then when i start the boat back up, this switch automatically recharges the stereo battery.

On another note, I highly recommend, if you are buying a new deck, to look into the Aquatic AV's. Mine came with a wireless remote, so I installed a IR in the rear by the blower and my rider can change the song, turn the music up et cetera. Its pretty sick if you ask me. Chicks dig it to :)

i have 570 total amp hours and still dont feel like i have enough.

Ditch one of the starting batteries and add a single group 31/29 dual purpose or deep cycle battery. Either that or get serious and go to one starting battery and add 2 golf carts for the stereo.

Sorry guys, i should have stated the amount of time i intend to run my stereo with the keys off, beached, really cranking it up etc. MAYBE 1 hour if that. We generally wakeboard surf and what not. The most sitting the boat does with the stereo on and the boat off is in between sets, setting up sacs for surfing or wakeboarding, or at the dock to let girls run to the bathroom (for number 2). So... What do you guys still think?

Honestly, based on this, you are fine with only 2 batteries if your batteries are isolated with a dual-battery switch.

You are probably fine with just 2 batteries but I would ditch one of the starting batteries and put in a deep cycle or dual purpose group 27/29/30.

I concur with both^^^

The question should be should I upgrade my alternator to a 200 amp output?.. When the engine is running, the alternator should have sufficient output to handle the complete load of the systems on board.. Including the sound system..

Batteries are simply there for party cove and starting..

What is the output of your alternator?.. If it is less than the total amp requirement, it will run WFO pegged and will burn out in no time..

Thx for all the insight guys! Yes i do have a perko switch setup for my two batteries. I like the idea of switching the engine starter battery to a deep cycle interstate. Of those couple you listed, which is best? Another question if my audio battery goes out, what's another good intrastate battery to get the job done?

Keep one of your starting batteries that will be designated specifically as your starting battery and if you like interstate buy an srm24(probably use the same battery box as you are now) or get an srm-29(will have to buy a bigger box but they are only $10a or so). Hook up all(i mean all) stereo gear ti this battery.

I'll check and see what kind of alternator i have And its output. Thx for that advisory too!

Overkill going to a 200amp alternator unless you plan on upgrading to more amps and gear.. If your running a syn4 syn6 combo your perfectly fine running 1 24 ( your current battery) as a dedicated start battery then running a pro27 (interstate) or higher (29/31) as the stereo bank.. This will give you ample buffer to the charging system for what you say you normally run ( 1 hour maybe at stop, the rest while driving) .. You will not be cranking it as much while driving and frequent low volume playing, so it won't be at WOT that long... Thus it will give your charging system a nice "buffer" to not pull hard from the alternator.. Now upgrading the alternator is always good when doing big pulling 1000 watt + sub systems... This is what most of your amperage is drawn to... JMO...

When my alternator goes out and or my stereo battery no longer holds a charge, i wouldn't mind upgrading to a 200 amp and a pro 29 or 31 battery. I crawled into the boat the other day before she left and snapped a photo of the alternator.

http://i1141.photobucket.com/albums/...-35-11_497.jpg

That is a Delco 7si 70 amp unit. As you can see the delco part number is 19020608. In good conditions we have seen them put out close to 90 amps. It is a really good little alternator. If you have a little space around the alternator you can upgrade to a delco 11si which delco rates at 95 amps. IT is a part number 8600002 I believe. You can search around but my guess is you will not find anything over 150 amps in a small frame that will fit your boat. At least not a quality unit that will last and is SAE J1171 marine certified. Balmar makes the only quality unit above 105 amps I have seen and they run about $600+. Grant has installed a Balmar 200 amp unit but it is a much bigger alternator that I can't imagine will fit most of the newer boats with the alternator mounted down low. I also am not sure it is really a marine/gasoline safe alternator either. But that is a different story and Balmar says it is so whatever. I know there are companies that make really high output small frame units for automobiles but outside of Balmar I haven't seen anything quality in a high output marine(gas) setup. You are better off spending money on more batteries for your stereo bank and getting a nice on board charger.

Well i got my boat back and almost everything is perfect with the job they did. Does anybody know the dimensions of the interstate pro 29 or 31? So i can Buy the correct size battery tub for the upgrade

You want the pro series... Good choice :)

PRO-27M. L-12 3⁄4" W-6 3⁄4" H-9 1⁄2"



PRO-29M. L-13" W-6 3⁄4" H-10"

DC,

Battery boxes and trays are typically labeled for the battery they will fit. Example: for a group-24 battery, look for a box or tray that is a group-24 tray/box. A 27 and 29 are the same length and width. Not sure about a 31 as Interstate doesn't offer a marine group-31 lead-acid.

An Interstate Pro 29 is 13Lx6.75Wx10H

Between the pro 27 and pro 29 interstate batteries. Which is a better deep cycle battery?

My guess is they use the same technology. The 27 and 29(I think Interstate's group 29 is the same as most companies group 31 but could be wrong) will have similar if not identical footprints but the 29 will be about an inch taller. Seeing how the 29 will have more lead it will give it a higher reserve capacity/20AH rating so I guess I would pick it. That said I am not sure one is a "better" deep cycle battery than the other. If you want a better deep cycle battery look at the Deka DC27 or DC31. The DC stands for deep cycle. One indication of a better deep cycle battery is the weight. More weight=more lead and thicker plates. Thicker plates=better deep cycle. Another option would be the Deka Seamate group 27 or 31 AGM battery. Most AGM batteries are pretty good deep cycles but they are spendy.

Bigger is better! The Interstate Pro-27 and Pro-29 have about the same foot print, but the Pro-29 is a .25" longer and .5" taller. This allows for more lead surface area which yields a little more Ah, which is whats important when choosing a house battery.

Sweet! Thanks again guys for all the insight! I really do appreciate it!