Thread:

How many batteries do I need and also a wiring question for my new stereo system

Thanks for the detailed explanation Keith. I like your idea of how to set this up and am gonna give it a shot.

However I'm going to have to skip out on the dual blue tops for now and go with a couple of decent group 27s.

I cant spend $500 on a couple batteries right now.

Originally Posted by Joey805

Thanks for the detailed explanation Keith. I like your idea of how to set this up and am gonna give it a shot.

However I'm going to have to skip out on the dual blue tops for now and go with a couple of decent group 27s.

I cant spend $500 on a couple batteries right now.

In my last boat, a 2003 21' Aftershock, it had to 24 series batteries in it. After the first season i changed them out for 27 series, both deep cycles. I wasnt running a big stereo like you though, i had six 6.5's running off the head unit and one 12" sub off a 1000 watt amp.

On my current boat, a 2005 26' Cobra Razor, it came with a 27 series starting/deep cycle battery on bank #1 and on bank #2 i had a standard 27 series deep cycle. I ended up putting a newer sound system: six 6x9's powered by a 650.4 amp and one 12" powered by a 750.1 mono amp(im about to add two more 6.5's by the driver/passenger seat to hear it at speed).

Long story short, after the new system i added a third 27 series deep cycle to bank #2(or switch #2 if you want to call it that) which is what i run the sound system off when the engine is OFF! Usually if i know im gonna be hanging out any longer then an hour with the engine off i switch the battery switch from ALL to the #2 position to save my starting battery on switch #1.

Optima blue tops are awesome but the price is outragoues for me, for the price of 2 of them i could buy five 27 series Interstate deep cycles. When i put new batteries in my Cobra i spent about $290 FOR ALL 3!!!

BTW, i use Interstate's and they have never let me down in the 7 years i have been using them.

Just some advice cause you said you were new to boating, if someone hasnt told you yet; if you do decide to switch your battery switch like i do when your motor is off remember to turn it back to ALL BEFORE you start your boat....dont ever turn your battery switch while the motor is running, you will blow a fuse. If you forgot to switch it back to all, like i have done several times then remembered once i got underway, i stop the boat, shut the engine off, turn to ALL then off you go...that way your charging ALL your batteries.

Originally Posted by fed4life

In my last boat, a 2003 21' Aftershock, it had to 24 series batteries in it. After the first season i changed them out for 27 series, both deep cycles. I wasnt running a big stereo like you though, i had six 6.5's running off the head unit and one 12" sub off a 1000 watt amp.

On my current boat, a 2005 26' Cobra Razor, it came with a 27 series starting/deep cycle battery on bank #1 and on bank #2 i had a standard 27 series deep cycle. I ended up putting a newer sound system: six 6x9's powered by a 650.4 amp and one 12" powered by a 750.1 mono amp(im about to add two more 6.5's by the driver/passenger seat to hear it at speed).

Long story short, after the new system i added a third 27 series deep cycle to bank #2(or switch #2 if you want to call it that) which is what i run the sound system off when the engine is OFF! Usually if i know im gonna be hanging out any longer then an hour with the engine off i switch the battery switch from ALL to the #2 position to save my starting battery on switch #1.

Optima blue tops are awesome but the price is outragoues for me, for the price of 2 of them i could buy five 27 series Interstate deep cycles. When i put new batteries in my Cobra i spent about $290 FOR ALL 3!!!

BTW, i use Interstate's and they have never let me down in the 7 years i have been using them.

Just some advice cause you said you were new to boating, if someone hasnt told you yet; if you do decide to switch your battery switch like i do when your motor is off remember to turn it back to ALL BEFORE you start your boat....dont ever turn your battery switch while the motor is running, you will blow a fuse. If you forgot to switch it back to all, like i have done several times then remembered once i got underway, i stop the boat, shut the engine off, turn to ALL then off you go...that way your charging ALL your batteries.

Thanks for the heads up on battery switching. I'll be sure never to touch that switch when the motor is running.

I have a question for you on how you wired your system...

Did you use two switches like Keith mentioned above? Or did you just go with one switch and make position #1 your one starting battery and position #2 your two batteries for the stereo?

How long can you run your stereo off the two deep cycles sitting in a cove before you start to run low on juice?

Thanks man!

Originally Posted by Joey805

Thanks for the heads up on battery switching. I'll be sure never to touch that switch when the motor is running.

I have a question for you on how you wired your system...

Did you use two switches like Keith mentioned above? Or did you just go with one switch and make position #1 your one starting battery and position #2 your two batteries for the stereo?

How long can you run your stereo off the two deep cycles sitting in a cove before you start to run low on juice?

Thanks man!

I didnt do what Keith had mentioned, although his idea is sound, solid, and works. I just have one switch, #1 is my starting battery and #2(with 2 deep cycles) is my sound system, this is the way the boat came when i bought it so i just added a third battery to bank #2. It was easy, just put the battery box in with battery, run about a 2ft. length of pos/neg #2 gauge battery cable to the battery that is already on the 2nd bank and your done. When the engine is on i have it switched to ALL to charge all 3 batteries.

I cant tell you how long it will take before it runs out of juice because each sound system uses a different amount of juice. I can tell you though that i have yet to hear the system cut out on me due to low power and thats with playing it for about 5 hours solid at HIGH VOLUME! My amps would actually overheat before anything else which is why im installing fans for the amps in the next week.

If the situation and your surroundings permit, every 2-3 hours i would switch the battery switch to ALL and start the boat for 5-10 minutes to charge up your batteries. Although this short time of running might not charge them fully it will give them a little charge and you will also be able to look at your volt gauge and see where your at. Im sure some people will disagree with me on this, this is just what has worked for me.

Personally if im boating with just me and the lady and no other boats we dont hang out for places longer then 4 hours, we like to explore around. If we do hang longer then 4 hours or so its usually cuz were hanging out with friends and tied up to their boats, in that case we switch on whos plays their system about every two hours, that way were sure nobody is gonna be left without power.

Again, im am no expert on this stuff, im just going off my experience and what has worked for me in the past.

I pulled this from the Interstate website and here is the link to look at the whole chart:
Interstate Batteries


This what i have on bank/switch #1 which is my starting battery, its still a deep cycle but has a much higher cranking/starting rating, CCA is 800, MCA is 1000:

27M

27M-XHD

800

1000

180

24

12-3/4

6-3/4

9-1/2

54

Auto/Stud posts

I have two of these on bank/switch #2 which are the deep cycles, the CCA is 675 and the MCA is 845:

27M

SRM-27B

675

845

180

30

20.4

5.7

3.0

12-3/4

6-3/4

9-1/2

55

Auto/Stud posts

Awesome, thanks for the great info.

Last question, where do you have your amps mounted? One of mine is under the engine hatch and the other one is up front under the stereo but mounted really crappy. I would like to relocate it so they are both under the hatch in back if possible. Think I'll have cooling problems if I do that?

Originally Posted by Joey805

Awesome, thanks for the great info.

Last question, where do you have your amps mounted? One of mine is under the engine hatch and the other one is up front under the stereo but mounted really crappy. I would like to relocate it so they are both under the hatch in back if possible. Think I'll have cooling problems if I do that?

My boat is a mid-cabin so i have them mounted behind the starboard side seat in the cabin. Im having cooling problems now so I'm gonna raise the amps about a 1/4 inch off the deck with some rubber grommets then I'm installing two cooling fans, the cylindrical kind from Stinger to cool them. My problem was I'm working the amps hard with the system i have to make matters worse theres no airflow or a place for the hot air to go THEN add in 100 degree outside temps and BAM, my amps shut down after about an hour of playing them HARD. I talked to my stereo shop who did my system and they recommended what i said above and it should keep them cool.

Your boat is obviously a little different then mine but when i had my 21' Aftershock i had the amp mounted on the passenger side in the foot rest area with it mounted to the side of the boat if that makes sense. My buddies 21' Ultra which is a lot like yours has the amps mounted in the back of the boat in the engine compartment but on the opposite side of the engine compartment and bolted to the interior panel. So basically the amps are between the hull of the boat and the engine compartment panel. Thats the way he bought it so I'm not sure if thats sound and if the engine heat will effect it.

Just a suggestion, if your going to put new amps and stuff with a lot of power, or even if its mild power and you know its in a place thats probably not going to get a lot of airflow, spend $60 bucks and get a couple of fans! There very easy to install and they run off the power of the amp...just two wires. One wire goes to ground on your amp, the other goes to your remote power source connection on the amp. Also, whether you do the install yourself or someone else does, when you mount the amps i wouldn't mount them flat against whatever you mount them too, put some grommets, washers, ect. between the amps and the surface area you mount them to. That way the heat will dissipate better and if you run the fans it will help cool them that much more.

Here is the link for the fans that I'm using:STINGER 12V CROSSFLOW AMP FAN BRAND NEW KEEP AMPS COOL | eBay

Im no expert or anything like that, I'm just going what has and hasn't worked for me and what advice i have received from experts.

Originally Posted by Beer:30

I suggest the "Troll Fury" kit above. Here's the link: Optima Battery Optima Batteries Free Shipping! Best Service! Deep Cycle Batteries Yellow Blue Red Top Optimum Quite a value and mounting case as well. I don't know about you and your new boat, but my engine hatch is ONLY up to get chairs out for the beach or to do maintenance. So, I don't care about billet battery trays.

Next, throw away the Perko switch and use the ACR or similar AUTOMATIC battery isolator. You WILL forget to switch the Perko at one or two points in your boating times. OR, you will tell someone to switch it one way and they will (unknowingly) switch it to the wrong setting. The automatic electric switches are the only way to go. Key on - everything is ONE BIG BATTERY - so it all gets charged. Key off - just your two or three STEREO batteries are active and the starter batt is sequestered. Some switching relays are even smarter and don't need to be wired into the key switch. They ONLY activate ALL batts at 13.8V or higher....meaning, when the alternator is charging. When the engine stops, the voltage goes right to battery voltage which will be 12.8 or so for a freshly topped off (by the alt) battery. Being below the 13.8 threshold, the batts are isolated from the starter batt. Very smart, super easy, FAIL SAFE.

Keep in mind that $400 or $600 here or there to make it RIGHT - is going to last you for 5,6, maybe even 10 years before you have to change anything out. My blue Optimas were put in the boat in late 2005. So, coming into SEVEN YEARS LATER, it was worth-while to spend (then) $320 on two batteries. I would have spent twice that by now on flooded batteries. AGM (Absorbed Glass Matt) batteries (which are NOT GEL) are 300 TIMES more vibration-resistant than flooded batteries. Since everything is spiral-bound and tight - the lead plates can't break during - let's say - rough water in the afternoon. So, a bit of $ now, will keep you safe and playing your stereo for several years to come.

FANS - I also run the horizontal fans, as my amps are being a seat. In the Havasu heat, fans are your friend. I just wire them onto the remote amp trigger. If you want to be trick down the road....there are heat-switches. When temperatures reach the adjustable set-point on the switch.....it turns on whatever they are hooked to. So, it would save some battery power by only coming on when absolutely necessary. Trick stuff.

HOWEVER - you don't need a whole lot of batt power now, as those amps are not near what your amount of speakers require. That being said, they will be running HOT. The trick with boats in hot temps is to run MORE AMP THAN SPEAKER. For instance, each FOUR 6" or 6X9s should have ONE four-channel amp of 75-100 watts PER channel at 4 OHMs. This way, each amp is not stretched out to twice it's limits or more. They will run COOL and have plenty of reserve power. Same with the 12"s ONE classD amp that will run 1000watts RMS at TWO OHMS would be the trick. Everyone wants to run ONE OHM to the subs. This is maximum current through the amp and thus, the most HEAT. 2ohms runs significantly cooler than 1ohm. So when upgrading your amps, pick ones that will run the power levels you want at 4ohms for the highs and 2ohms for the lows.

Just clicked on the link beer:30 sent on the Optima Fury pack; thats actually a pretty sweet deal and pretty good price! Especially cause it includes free shipping and no tax. If i would have know that when i bought all new batteries last year i probably would have bought that set up. For only $100 more then what i spent you can have two optima blue tops in a nice secure case. Pretty legit if you ask me! Gonna have to save the link for the future.