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Old     (ryand121)      Join Date: Feb 2007       12-13-2012, 12:37 AM Reply   
Boat is an '08 MasterCraft XStar. Referring to the pics, the boat came stock with the START and first STEREO battery on the port side connected to the stock battery disconnect switch. Due to the size and playing time of the stereo, I added the two STEREO batteries on the starboard side. My question is, should I connect all three of the STEREO batteries like the first pic or the second pic? Wouldn't it be more beneficial to wire as in the first pic so all STEREO batteries are drawn down together equally, and also for equal charging while the engine is running? Any other concerns I'm missing? Any help is appreciated!
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Old     (bryce2320)      Join Date: May 2012       12-13-2012, 6:09 AM Reply   
Eathier way there run in parallel which is correct. The 2nd pic saves you a bunch of wire that IMPO, is unnecessary. Others will also chime in the opinions to help u out
Old     (david_e_m)      Join Date: Jul 2008       12-13-2012, 6:22 AM Reply   
No grounds pass through a battery switch.
Illustration One does nothing to solve the equalized resistance issue. The longer the distance the greater the cable gauge must be to keep resistance low. Cable gauge and battery/component location may be the only control you have.
In some cases we have relocated batteries, relocated the switch or changed designations to accomplish the above. And in some cases perfection is going to escape you.

Earmark Marine
Old     (boardman74)      Join Date: Jul 2012       12-13-2012, 11:43 AM Reply   
The 2 figures are the same. Doesn't matter which end of the chain you start the ground at. Just a waste of expensive OO cable(at least).
Old     (tuneman)      Join Date: Mar 2002       12-13-2012, 3:16 PM Reply   
IMHO, you should never parallel more than two batteries together. Use an isolator beyond two. You'll significantly reduce the life of your batteries if you don't.
Old     (david_e_m)      Join Date: Jul 2008       12-13-2012, 3:39 PM Reply   
You might offer a little more clarification as most won't understand whether you are referencing multiple batteries divided into two banks or multiple batteries within the same bank.
Earmark Marine
Old     (polarbill)      Join Date: Jun 2003       12-13-2012, 7:38 PM Reply   
Tuneman, I am not sure I understand what you are talking about. It doesn't matter how many batteries you put in parallel.

I also wouldn't use an "isolator" either. Isolators(if we are talking about diode style isolators) usually have around a 1 volt drop. This means that when your alternator is putting out 14.4 your batteries will only see 13.4. Esentially not charging the batteries to the fullest. This will shorten battery life. I would suggest sticking with just the blue seas on/off/combined switch or keep that switch and add a VSR like a sure power 1314/1315, the blue seas version or something similar.

With just the switch you have I would run the negative battery cable from the engine block straight to the negative terminal of the starting battery. Then connect all 4 batteries together on the negative side with 2/0 cable or a similar sized cable. Then your positive cable from the starter will run to the switch. Then there will be a cable from the switch to the positive of your starting battery and the other terminal on the back of the switch will have a cable running to the postive of one of the 3 batteries you are using for the stereo. You will also use jumpers on the positive of 3 "Stereo" batteries. This will give you a 4 battery, 2 bank battery system.

It is kind of weird having 2 of the stereo batteries on one side and the 3rd on the other but as long as you use correctly sized cables you are fine. Are you batteries up in the observers area? If so I would just put all 4 batteries right next to each other so you don't have to run a bunch of extra expensive battery cable. Sure your boat will be slightly uneven but maybe use a little lead or something else to counterbalance it some. You should only need a couple hundred pounds on the driver's side then to weight the boat evenly.

One concern I would have is if you stereo battery you had before was older it is less than ideal to add 2 new batteries to that same bank. You would be better off selling the old stereo battery and buying 3 brand new batteries that are all the same. Having one old battery and 2 new ones on the same bank may shorten the life of the newer batteries.
Old     (ryand121)      Join Date: Feb 2007       12-14-2012, 12:14 AM Reply   
First of all, thanks for all the replies guys. Just for some more info, all batts were purchased at the same time, and all are Deka 31's. The reason for how the batteries are configured the way they are is because all batts are under the rear bench seat, two on the port side of the transmission, and the other two on the starboard side.

Polarbill, the boat came stock with just the two port batts, the start and the one accessory battery. If I'm not mistaking, those two batteries are already wired as you described. So basically all I did was wire the other two accessory batteries to the first accessory battery in parallel.

Now correct me if I'm wrong, and by all means I'm no pro when it comes to stereo's, but the reason I'm asking these questions is because it seems to me that in the second pic, although drawn incorrectly (thanks David, good catch) it seems that I'm basically pulling down the first accessory battery, and the other two are basically "feeding" it. Whereas in the first pic, it seems like the whole accessory bank is being pulled down at the same time, as one big battery. Or am I just completely way off?
Old     (chpthril)      Join Date: Oct 2007       12-14-2012, 6:19 AM Reply   

When 2 or more batteries are wired together, whether it be parallel like in your scheme or in series like a golf cart, they become 1 large battery. The load (stereo), pulls of the banks equally, rather then one battery, then another. They would also be charged at the same rate when wired together.

In your two schemes above, they are electrically the same. The difference is that in option one, your GRN cable is making a long run to the furthest battery, then daisy-chained back to the original battery location. This only serves to require more cable at a larger gauge. If its a shorter run, I would consider taking the grounds for those two STBD side batteries to the engine block, rather then across the boat back to the original port battery.
Old     (david_e_m)      Join Date: Jul 2008       12-14-2012, 7:34 AM Reply   
Now that we understand that all batteries are under the bench seat and in somewhat of a straight line, the resistive distances would seem to be too minimal to be a factor. The engine block is the ground reference point so as long as you configure the runs with that in mind you're good. In contrast, some boats require that four batteries go in all four corners of the engine compartment. With a switch in one corner the combined front/rear & left/right runs (around the perimeter of the engine compartment) might have more of a resistive impact where you would scheme for this situation. But you have a simple scenario with no concerns provided you use adequate gauge cable and quality terminations.

Earmark Marine
Old     (norcalrider)      Join Date: Jun 2002       12-14-2012, 12:03 PM Reply   
Does anyone here use terminal fuses when wiring batteries in series or parallel?
Old     (david_e_m)      Join Date: Jul 2008       12-14-2012, 12:22 PM Reply   
I think it mostly has to do with the exposure and risk. If batteries are separated by enough distance with connecting runs in a particular location that has an increased risk of incident then I think you have to place a protective breaker or fuse at each end of the run. If there are a number of batteries collected in a tight grouping then I do not see the practical benefit of the additional protection. So it's circumstantial.

Earmark Marine
Old     (polarbill)      Join Date: Jun 2003       12-14-2012, 1:26 PM Reply   
Here is my super ghetto drawing/diagram.
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Old     (ryand121)      Join Date: Feb 2007       12-14-2012, 2:55 PM Reply   
Makes perfect sense now guys, I really appreciate the info and helping me to understand. -Ryan
Old     (polarbill)      Join Date: Jun 2003       12-14-2012, 5:39 PM Reply   
Actually in my diagram it may make more sense to have the ground cable from the block go directly to the negative of the starting battery but I am not sure it really matters.
Old     (bwake)      Join Date: Sep 2009       01-24-2013, 2:29 AM Reply   
quick question about this to those in the know

does moving the batteries to under the passenger seat increase the strain on the alternator, and potentially result in a less effective charge of the batteries due to further distance from the alternator to batteries.

likewise will this make starting the boat harder?

Old     (chpthril)      Join Date: Oct 2007       01-24-2013, 5:48 AM Reply   
Nope. With all the proper sized cable for the load and length, voltage drop and resistance will be minimal.


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