Electrical system guru's.... battery q

[Tanner]

I was wanting to replace my deep cycle house battery w/ four larger capacity 6V batteries wired into a 12V string. Now this is a 06' 24V that has one deep cycle on the starboard side and my starting battery on the port side. There are 2 individual switch's as well as an isolator.

My concern is that I noticed the two batteries are wired in parallel as well. I was always told NOT to connect a deep cycle and starting battery together. So I am confused why this was done.

But my question is If I re-wire the 6V's back in the way the Deep Cycle House battery was, will I run into problems... remember the 6V's will be set up in a 12 volt string. I also plan on pulling the radio off of the starting battery (why in the world was this ever done?).

[Coach]

I understand the 6V thing I run Trojan T-105's. You should still keep your battery bank linked in parallel but use a perko switch to sperate your bank and starting battery. This way your starting battery will run all of your basic electronics in the boat and your stereo bank is isolated so you never have a starting issue. You can put the switch over to 2 or all if you are having a starting issue as a back up but you should be able to leave it on one. I would add on on board charger to your system that can charge 2 battery banks as well. I am not familiar with isolators even thought I have read about them. I know they make it almost fool proof, but I still think for the money and piece of mind the perko switch is a better option. Isolators will take a beating from the rough ride a boat has vs a car and will at some point fail (must sooner than a perko). You just hope it fails and is switched to your starting battery. I hope this is helping you answer your question.

[Tanner]

Ok so Coach you don't have a problem having the two T-105's paralleled w/ the starting battery? That's my only concern. I realize theroetically the system doesn't know the difference from a single 12V battery from two 6V's wired in series for a 12V load... but I want to be safe.

I'm running the T-145's. And I've managed to squeeze four of the suckers back in my battery compartment on my 24V. Two on the starboard side. Then there's three batteries on my port side... the starting battery and the other two T-145's which will be tied in w/ the other two.


As for the perko switches.... my 06 was actually one of the first run's... and it doesn't have the single switch with 1/2 or both. There are two seperate switches for each battery that only have on/off. And yes... once I yank the radio off the starting battery tomorrow, the starting battery will always be in the off position while sitting listening .

[Coach]

Don't run your starting battery and bank in parallel. Run your T-145s in parallel and complete the circit with a new perko switch. I think they are about $45 at West Marine or anyplace like that.

I understand what your are saying about parallel using the switch, I just don't look at it that way because only in certain cases would I or do I put it on both. I would only do that if my boat was struggling to start and needed more volts. I would only charge your bank of 145's using a smart charger or on board charger. and the alternator will be able to take care of the starting battery that way you don't run it on both. Another option which cost much more is the the Balmar Duo Charge which will put most of the alt voltage back into your bank and trickle off some to your starting battery. www.balmar.net

My suggestion is to get rid of the extra switches and simplify the set up. Bank of 145 and starting battery. On board charger for 2 banks like a ProMariner 100 or ProSport 20 to charge the banks when you take the boat out. The 145's should give you enough power to run a good sized stereo for a weekend without having to charge it. I know many who keep their bank seperate from their alt and only charge it using a smart charger.

http://www.promariner.com/

[Tanner]

Already got a smart charger installed ... I had put it in earlier this year when I was gonna run a dedicated battery bank that was not tied into the alternator at all.

As for the balmar unit you mentioned above.... The way I understand it from Andrew.... the isolator system that Tige is using works in this way. Now I could be wrong on this, but this was how I understood it. He was very adamant about using this system instead of the perko switch as it was better for charging.

[Coach]

Originally posted by Tanner
Already got a smart charger installed ... I had put it in earlier this year when I was gonna run a dedicated battery bank that was not tied into the alternator at all.

Good call. I don't understand the isolator and 2 switches that just seem like overkill for what one perko would do. I was looking at putting in 4 Trojan 6V AGM on my next boat for a total of 400 Ah. How many Ah do you get with the 145's. I am lazy about looking it up right now.

[Tanner]

Wait coach... are you saying pull the one on/off switch, replace it w/ a perko. Use that to parallel the two T145 12 V strings together instead of just paralleling them together directly. Then basically my perko is already tied in to the rest of the system and the isolator as I just replaced the one off switch with the perko.

This will leave the starting battery with it's factory on/off switch but eliminate the parallel connection between the starting battery and the house. (which I don't have a problem with as I shouldn't have a starting problem).

That's actually a viable option if I'm understanding you correctly. Of course, I'm waiting on trojan's and andrews response to just wiring up the T145's in a 12V set-up the way Tige did originally.

[Tanner]

Oops... well now I saw your post... I didn't realize you were talking about eliminating the isolator all together. Actually I kind of like the isolator system.

I can't remember how many amp hours the T145's get. What I concern myself with on batteries usually is the capacity min. at a 75amp draw. Which on the T145's is 145 mins. @ 75amps. The T105's is 115 mins @ 75 amps.

I THINK the T145's are a 215AH battery @ 5 hours, and 260 @ 20 hours... but don't qoute me on that.

[Coach]

How many 145's are you going to have total? 2, 4, 6? You will need to run them in series to get the 12V's (which you know) then run each 12V series in parallel if you are running more than 2.

Like I said an isolator is a nice option but IMO a perko is a cheaper manual version of the same thing. I would keep the isolator if you have it. I am not a fan of having multiple switches. On the water I want reliablity and simplicity because getting towed home sucks.

With those 145's you need to get a bow sack and you will be throwing a killer wake!

And yes you should unhook the parallel conection from the 145's and starting and just leave the on/off switch for the starting. The isolator will act as the perko and regulate the flow from the alternator which means your alt is hooked into your bank, or at least that is how I am seeing it. If not then you wouldn't need an isolator.

I am understanding the 2 switches now I am thinking more about it. You can turn one bank off and the alt will run all of the charge one direction. And it allows you to completely turn off each bank when you are done. It is not the way I would do it, but there are 100 ways to skin a cat. Everything makes sence now execpt why the starting battery and bank are in parallel.

[Tanner]

Okkkkk now we're getting somewhere. I had the same question coach... my only answer to why the batteries were in parallel is so that the starting battery could pull power from the house battery in the event that the house battery died. But I thought the isolator did that. Maybe it was finishing out the circuit that the on/off switches started w/ the positive terminals? Sound's like Andrew is gonna be getting another call from me tomorrow...lol.

And there will be four.... two 12V strings paralleled together.

[chpthril]

Here is how i am going to wire in a 3rd (2nd deepcycle) battery and a perco 1/2/both/off switch.
all you need to do is sudstitute your twin 6v's for my deepcycle's and the rest will stay the same.
The isolator will keep all the banks topped off, and the switch will allow you start off of the 6v's if needed. (I think thats what you are looking to do, right)

If your load requires that many batteries, than a smart charger is a good idea because the alternator will not keep up.

Hope this helps.

[Tanner]

Well ok, so been on the phone a couple times w/ Andrew and Trojan today... and here's what we've found out.

As to why the batteries are paralleled... According to andrew, this is needed to allow both batteries to charge. Otherwise only one would charge.

Trojan seems to think it would work, their only concern was that if I drained down the deep cycle's the parallel connection would allow my starting battery to drain down. Which makes sense to me. However Andrew said the isolator prevents this. So guess we'll see in about 30 mins.

So if you all don't hear from me in a week it means I've blown myself up!

[chpthril]

As to why the batteries are paralleled... According to andrew, this is needed to allow both batteries to charge. Otherwise only one would charge.

Dont you have to wire 2 6v's in series to get 12v, and then parallel 2 (or more) pairs of 6v's??????????? or did I just miss that in there some were.

[Tanner]

LOL... well you are correct... but we haven't been talking about how the wiring of the four 6 volts was going to be done, as that's a given. 2 6volts series'd together to give a 12V string... this will be done twice for two seperate 12V strings. Then these two 12V strings will be paralleled together for one large 12V string.

I was looking at the charging system tonight and I'm just not sure why andrew says the house and the starting battery need to paralleled together to get a charge. The only reason I can see that this needs to be done is so that the starting battery can pull from the house batteries if need be. Which is not what I want... as my starting battery will be totally isolated and no draw on it whatsoever. There should be no reason for me to need to that.

I'm going to remove the parallel connection from the house and starting battery as from what I can tell it does not need to be there for the batteries to charge... as the alternator runs into the isolator and the isolator runs into the two on/off switches and then to the positive leads on the batteries.

[Coach]

Originally posted by Tanner
LOL... well you are correct... but we haven't been talking about how the wiring of the four 6 volts was going to be done, as that's a given. 2 6volts series'd together to give a 12V string... this will be done twice for two seperate 12V strings. Then these two 12V strings will be paralleled together for one large 12V string.

I was looking at the charging system tonight and I'm just not sure why andrew says the house and the starting battery need to paralleled together to get a charge. The only reason I can see that this needs to be done is so that the starting battery can pull from the house batteries if need be. Which is not what I want... as my starting battery will be totally isolated and no draw on it whatsoever. There should be no reason for me to need to that.

I'm going to remove the parallel connection from the house and starting battery as from what I can tell it does not need to be there for the batteries to charge... as the alternator runs into the isolator and the isolator runs into the two on/off switches and then to the positive leads on the batteries.

That sound like the best option. I believe in always isolating your starting battery and stereo in a boat.