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Old 11-19-2017, 05:27 PM   #1
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Battery banks are different type batteries

Hi All,

I have finally started digging into my electrical systems and trying to figure it all out (I've been installing the new holding tank and plumbing).

This Taiwanese Trawler has a single Lehman 120 with 2 alternators, a gen set, shore power (of course) and a monster charger/inverter.

One set of batteries is (4) GC2-XDL-UTL and the other battery is an 8D. I thought the 8D had to be the starting battery. Neither bank is dedicated to the starter, they both go to the battery switch and the "out" from the battery switch goes to the starter.

Is it odd to have different battery setups from bank to bank?

Dave
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Old 11-19-2017, 06:02 PM   #2
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Four GC2 batteries and an 8D (although heavy, a lighter Group 31 will easily start that engine) is a good setup. You just need to configure them properly.

What I suspect you have is the GC2s go to to the 1 terminal on the switch and the 8D goes to the 2 terminal or visa versa. The common terminal goes to the starter as well as the main DC house load panels.

Keep the switch set to all (pulling from both the GC2s and the 8D) while at the dock. Then when you get to an anchorage, drop your anchor, stop the engine and switch to the GC2 bank- switch position 1 or 2. That way the 8D will be isolated while at anchor and can't be discharged so it won't start when you need it. When you get ready to go, switch to the 8D, start the engine and then switch to all so the engine alternator will charge both battery banks back up.

As long as both battery banks are flooded cell lead acid batteries they will work fine in tandem.

There are more automated ways to do the above with combiners, ACRs etc but they require significant rewiring and for casual overnights at anchor the above procedure works fine- as long as you remember to do it .

If your DC system isn't set up this way, I would encourage you to get a marine electrician to look at the right way to set it up.

David
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Old 11-19-2017, 06:04 PM   #3
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Originally Posted by Dave_E View Post
Hi All,

One set of batteries is (4) GC2-XDL-UTL and the other battery is an 8D. I thought the 8D had to be the starting battery. Neither bank is dedicated to the starter, they both go to the battery switch and the "out" from the battery switch goes to the starter.

Is it odd to have different battery setups from bank to bank?
Dave
If the batteries are tied together at the battery switch, one would think you would want the same type of batteries on both sides of the switch for the times when the switch is in the "both" position. I'm not familiar with the GC2's and you didn't specify the type/chemistry of the 8D battery. I can't imagine having gel, deepcycle or Lead Acid batteries charging or discharging together would be a very good idea.

I have different battery makes and ages in my three banks, but they are all the same chemistry (lead acid) and separated from each other. Unless the engines are running and charging the batteries. When the engines are off or not running on the charger then they are separated as a house or starting battery.
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Old 11-19-2017, 07:57 PM   #4
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Sounds like a good setup to me.

Which bank you crank from really doesn't matter.

The bigger / healthier one should be day to day Main house bank.

Keep the other one as Reserve in case of trouble with Main. Use it as starter once in a while just to confirm it's working.

Relevant thread: http://www.sailnet.com/forums/showthread.php?t=298497
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Old 11-19-2017, 08:29 PM   #5
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It’s far from an optimal set up. Ideally you want one starting battery(not a deep cycle battery) wired to a 1,2,all switch with the out put to the starter. All remaining space should be dedicated to the house batteries which should all be similar. The house bank should be wired to 2 on the start switch as well as wired to the house panel. The generator should have its own starting battery not connected to anything but the generator.

This is a rough description and I have left out many details.

The setup you have probably functions adequately for most people but battery life is being compromised.

Starting batteries should not be combined with house for charging. An echo charger should be installed between the house bank and the starting bank. Combining deep cycle and starting batteries will shorten the life of the starting battery.
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Old 11-19-2017, 10:33 PM   #6
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Sorry I missed a couple details. All batteries are flooded cell. There is also a Blue Sea Systems ACR next to the battery switch. It works...

Maybe things were wired differently at one time, it just looked to me like that giant 8D would have been the starter battery, but this is my first experience with more than (2) group 27's that were in my sailboat.

Thanks.
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Old 11-19-2017, 11:02 PM   #7
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Again, the system probably works adequately for most people.

ACR - automatic combining relay- these are popular but they are usually used improperly. Combing deep cycle and starting batteries will shorten the life of the starting battery even if both are lead acid type.

Echo chargers- ecentialy a one way electrical circuit allows a starting battery to be charged from the house system with out being over charged.

It is best to have only one large house bank instead of two smaller banks.

Question, battery charger and alternators are wired to what?
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Old 11-19-2017, 11:08 PM   #8
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An 8 D battery for starting is over kill but not wrong. Running one alt. To each bank is not wrong. A multi bank charger to each bank is ok. Adding an ACR to this type of set up would not be wise.

There are often several ways to get to the same place, just some ways are better than others.
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Old 11-20-2017, 06:25 AM   #9
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"Combing deep cycle and starting batteries will shorten the life of the starting battery even if both are lead acid type."

I am not so sure of this.

Modern vehicles usually operate at over 14V , as the loads of electric goodies delight in good voltage .

The vehicle start batts are fine with this voltage for long periods of time the V regulator doesn't have a "float" concept built in.

House batts discharged 50% will still be over 12V resting and come up over 13V very rapidly as about a volt over is required to do much charging.

Rapidly the house sees 13,5 , climbing as the battery gets more charged.

IF the start batt only sees 12,6v to 14.4v , its usual operating voltage , how would the service life be reduced?

Using a start AS a deep cycle always does reduce the service life as the many thin plates die rapidly, but charging together both styles should hardly be a problem.
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Old 11-20-2017, 07:27 AM   #10
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"Combing deep cycle and starting batteries will shorten the life of the starting battery even if both are lead acid type."

I am not so sure of this.

Modern vehicles usually operate at over 14V , as the loads of electric goodies delight in good voltage .

The vehicle start batts are fine with this voltage for long periods of time the V regulator doesn't have a "float" concept built in.

House batts discharged 50% will still be over 12V resting and come up over 13V very rapidly as about a volt over is required to do much charging.

Rapidly the house sees 13,5 , climbing as the battery gets more charged.

IF the start batt only sees 12,6v to 14.4v , its usual operating voltage , how would the service life be reduced?

Using a start AS a deep cycle always does reduce the service life as the many thin plates die rapidly, but charging together both styles should hardly be a problem.
Yes.

Only real problem combining is if the voltage is out of spec for one of the batts.

Or if Starter, as the less-depleted batt is an expensive AGM. Absorb V held rather than float may cause it to lose electrolyte.

Echo charger will do exactly the same as ACR, except if primary source V is above 14.4V it limits to that. The 15A limit won't be relevant.

If the Starter is FLA it may be thirstier, just keep water level up, no harm no problem.
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Old 11-20-2017, 10:07 AM   #11
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Starting batteries and deep cycle batteries have different construction which leads to different absorption rates so if you combine them for charging you will over charge the starting battery even if they are both lead acid. They are also designed to dissipate differently so if combined for house use you will simple sulfate the starting battery. Most people get 5 years out of their batteries and think thatís normal. I get 8 to 10years out of my batteries.
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Old 11-20-2017, 10:38 AM   #12
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> Starting batteries and deep cycle batteries have different construction which leads to different absorption rates so if you combine them for charging you will over charge the starting battery even if they are both lead acid.

The Starter isn't ever depleted at all in normal operations, so never actually absorbing anything, just a trickle at Float is enough.

But sitting with Absorb voltage present - if a flooded batt - does not hurt anything, just keep water topped up.


> They are also designed to dissipate differently so if combined for house use you will simple sulfate the starting battery.

No one is talking about combining except during charging.
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Old 11-20-2017, 11:39 AM   #13
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Sorry I missed a couple details. All batteries are flooded cell. There is also a Blue Sea Systems ACR next to the battery switch. It works...

Maybe things were wired differently at one time, it just looked to me like that giant 8D would have been the starter battery, but this is my first experience with more than (2) group 27's that were in my sailboat.
That's not so uncommon a setup for the time when these boats were made. If you had a generator, you probably didn't have an inverter and ran the generator to power your boat.

Californian Trawlers for example, came from the factory with two 8-D Lead Acid batteries, as a standard, split into two banks by a battery switch. And a separate group 27 battery for the genny. The two LA's were fine for starting the engines and running interior lights, but when inverters were added to the mix, that changed the amperage demand and adversely impacted the battery life.

Larger chargers, battery banks and more exotic battery chemistry/technology was needed to support the increased demand on the batteries.
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Old 11-20-2017, 09:17 PM   #14
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John, if you use an ACR, you can’t charge one bank and float the other. What you do is charge one and cook the other.
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Old 11-20-2017, 10:05 PM   #15
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You keep on saying that over and over doesn't make it true.

Tens of thousands of installs, zero problems.

Reasons and qualifiers all spelled out in my posts above.

But feel free to do what you like with your own setup.
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Old 11-21-2017, 01:53 AM   #16
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Dave_E I sent you a PM
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