Is an isolator needed?
 

I just bought two new Deka DC31DT batteries for my boat. Do I need an isolator for them? I know what it does and how to hook it up, I'm not looking for that. I just want to know if it is needed with two identical batteries that are both brand new. Thanks.

not "necessary" - but highlyl recommended. Automates the separation of the batteries and ensure each gets the charge it needs from the alt.

It depends on your install. Did you wire them in parallel just to have more capacity ? Or is one foe accessories and the other for starting?

I plan to wire them in parallel. They will both be used for everything.

use an ACR

Acr?

Automatic Charging Relay this one seems to be the most common:

http://bluesea.com/category/2/productline/overview/387

It is the same type product as the SurePower 1304?

John, do you mean that you are going to have only the 2 batteries hooked together in parallel and no separate battery for starting? Be careful using the term isolator. When you say isolator most people will think that you are talking about a diode style isolator which does not give priority and has a voltage drop of 1v. I think you are asking about a sure power style separator/combiner. They could also be considered and ACR or voltage sensative relay. As far as the blue sea one goes I think it separates the batteries when off and combines them when you start the boat and it is running. The downfall I see to this is it doesn't provide priority charging to your starting battery. The surepower is cheaper and does provide priority charging to your starting battery.

Now if you strictly planning on leaving the batteries in parallel as a single bank then you don't need a separator but I wouldn't recommend that. What will happen is you will drain the 2 batteries when listening to the stereo with the boat off. It is going to be hard on your starting and charging system as well as the electronics in the boat. It also may leave you with no way to start your boat if the bank is drained.

If I was you I would wire both Deka's in parallel and use as a stereo bank and put the surepower 1314 between the stereo bank and a starting battery. This will give you the added AH of having 2 stereo batteries. If you wire it with one of the batteries as stereo battery and one as a starting battery with the surepower between them you are fine for everything other than you won't have as long of play time on you stereo when the boat is turned off. Which is not a big deal if you don't listen a bunch at high volumes with the boat off.

I am sure you have seen David mention it but an onboard battery charger is an absolute must unless you absolutely have no way to plug one in. This will be the key to extending battery life.

Brett - I didnt know about the 1V drop from using the surepower. Are you sure about that? Where did you find this info, I dont remember reading that in the manual... thanks

I think I'm going to pick up another battery, Deka DC24?, for starting. Then use a surepower to disconnect my two DC31DTs. Does this sound like the best route?

Derek, a surepower 1314 is not an isolator per say. This is what I am referring to when I say isolator.


http://www.pplmotorhomes.com/parts/r...a-isolator.jpg

John, I wouldn't do a Deep Cycle battery as your starting battery. Do the dual purpose(dp24 or dp27) or get an actual starting battery. The DP24 has 550 CCA which is probably about the minimum you want to have.

if you have 2 batteries in parallel, with out an isolator or ACR

the lower voltage battery will drain the other one

I'm going to get the starting battery today. There is a Deka distributor nearby that has GREAT prices. Which one would you go with? DP24 or the 24M5? Something else?

I would go with the 24M6 or 24M7 if you are going to get a true starting battery. The 24M5 has the same CCA rating as the DP24 so I would go with the DP24 if those were the 2 batteries I was looking at. The 24M6 or 24M7 will give you a better CCA but if you drain it down too many times for whatever reason it will die on you pretty quick. The DP24 will last longer if it is drained but still provide a solid CCA.

I looked it up and the 5.7 indmar manual says to have a minimum of 650CCA and 700MCA. I bet you would be fine with the DP24 but you may consider the DP27. It shouldn't be much more than the DP24 and is similar in size to the DC31's you bought.

Picked up the 24M7. Now I need the 1204 and wire. Is 4ga plenty?

Brett,

I really like your idea of going with a dual-purpose starting battery because its predictable that the starting battery will be frequently depleted deeper than a normal starting function as its combined with one or two discharged stereo batteries in combination with an operational stereo. It seems like the right compromise to sacrifice a bit of ultimate cranking power for reliablity and longevity.

Alot of people run deep cycles in their boat on the starting side also. If boating is a warm-weather activity or at least done in a warm season or climate, how important is it to have a pure starting-type battery?

David
Earmark Marine

Where were you two hours ago? I already spent the $$ now. :) I'm sure I would be happy with either.

How will I need to handle charging after this? Will I need to disconnect the starting battery before I charge? all batteries?

Also, do I need to run the neg terminal from each batt to the 1314, or is the ground on it just for the relay?

Im goIng to try to post a wire diagram of how I think I need to hook this up, unless some one already has one they could post, just to make sure I'm not leaving anything out.

Good point David. Most people are probably fine running the Deep Cycle versions of the Deka's at least. I know their CCA rating is measured at 0 degree F. So by their specs which are usually underrated in my experience a group 24 deep cycle has a CCA of 500 and an MCA(32 degree F) of 625. The DC27 has a CCA of 575 and an MCA of 715. The DC31DT has a CCA of 650 an MCA of 810. Seeing how most people probably aren't ever going to start their boat in anything close to 32 you would probably be fine with a single group 24 deep cycle for starting a 350 chev motor.

At this point you could match all batteries, using all deep cycle batteries which isn't a bad thing.

John, go exchange the starting battery for a Deep Cycle or dual purpose. It will be slighty more expensive though.

John, David has some good thoughts on a way to disconnect the batteries for charging using a dual bank charger using a standard perko. The other thing you could do is just ad a simple battery disconnect switch between the positive of the starting battery and the 1314. When you hook up the charger just disconnect the power. I mentioned putting it between the starting battery and the 1314 because this way the 1314 won't sense the charger and try and activate. Another thing I thought would work but David has said sure power doesn't like the idea is to install a simple 2 position rocker of toggle switch inline with the negative terminal on the 1314. When you want to hook up the charger just flip the switch. The only problem besides whatever sure power says is that you have to remember to flip it back when you go boating or your stereo battery is a stand alone battery and not going to get any amps.

John, the 1314 is really easy to hook up. Your main starting positive and negative cables will run to the starting battery like you only had a single battery. Then run a cable, sure power has recommendations in their directions about sizing the cable, from the positive of the starting battery to the correct terminal on the 1314(or you would run to a battery disconnect switch then the 1314). From the other large terminal on the 1314 run the same size cable to the positive of the stereo/2nd batter/bank. Next run similar sized cable across all the negative terminals of the batteries like you are hooking them all up in parallel. The last thing you need to hookup is a 14 gauge wire from the small negative spade terminal on the 1314 to a negative source somewhere. I would just run it to the negative screw terminal of the starting battery. Then you are done unless you want to add the 2 options the 1314 has. These options are to have an indicator light run to your dash and a manual combine switch to your dash.

The simple way of saying this is run both batteries in parallel(positive to positive and negative to negative) with th e1314 in between the 2 on the positive side.

If I add the switch to the pos side of the starting battery can I use a standard battery charger?

If by standard battery charger you mean a single out put charger I would just leave the 1314 with no switch. That way once the starting battery is charged to 13.2v it will activate and start charging all batteries. You are better off having a 2 bank charger and charging them as 2 completely separate banks as the battery(s) on the stereo side will have been used differently than the starting battery.

Yes, single output.

The way this system will be set up, there should not be a reason for me to but the starting battery on the charger is there?

In theory, I guess you would be fine unless something is causing your starting battery to discharge or not fully charge before the end of the day. If the 1314 is disconnected when you hook up the charger to the stereo bank then it won't ever combine, just charging the stereo bank. If it is activated when you put the charger on it won't disconnect until you turn the charger off. This means the 1314 may stay activated for days or weeks. I am not sure how good that is for the 1314? It has a continuous amp rating of 100 amps.

I need a switch between my stereo batts and the 1314.

I am starting to get confused now. It goes to show you there could be a million possibilties on how to correctly wire this stuff.

To answer this question and the question before. You could, but don't need to put in the switch between the starting battery and the 1314 on the positive side. This means your charger would never charge the starting battery if the switch is disconnected which in theory should be ok because you should always have a fully charged starting battery. Then if at any point you upgraded to a dual bank charger you wouldn't need to change anything.

Crude, but what I had in mind.

http://img337.imageshack.us/img337/1323/scanb.jpg

Looks ok. I would move the disconnect switch to the other side of the 1314. Also connect the negative on one of the stereo batteries to the negative of the starting battery.

All grounds will be connected together and run to the block. If I move the switch, won't the 1314 make contact durring charging? Is it NO or NC?

No, because the 1314 only senses off battery 1.

john, with this setup, will the alternator charge both banks?

If it doesn't, I might just do that on my boat, just to make sure my 65amp alternator doen't get toasted charging those big batteries, while listening to music.

Jonathan, I am guess you didn't read the thread because it is kind of explained. The 1314 will connect and disconnect the 2 banks automatically to charge the stereo bank in stages so your alternator isn't getting fried. If you had a battery disconnect switch in between the 2 banks you could manually disconnect and just leave your stereo bank as a stand alone bank then.