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Old 08-10-2020, 10:32 PM   #1
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Battery Banks

Hi all,

My batteries have recently passed on from this world (7+ years old and there have been times where I have not been kind to them) and I'm looking at replacement. Currently, I have two banks (port and starboard, located on the outboard side of each engine), each consisting of 2 8D batteries. These have functioned as both my house banks and have been used to start the engine as well.

After nearly killing myself removing the 8Ds, I've decided to change the battery setup and go with something easier to move and with more capacity. I'm staying with FLA batteries and am looking at Trojan T-105s, 4 per bank.

Can the T-105s work as a starting batteries or would they be damaged by the large draw upon starting. Would I be better running some group 31s? My boat is powered by twin Caterpillar 3208NA engines.

Another sticky part, since the battery banks are on opposite sides of the hull, I'd like to keep them even from a weight standpoint so the boat keeps on an even keel.

Thanks for any input,

Matt
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Old 08-10-2020, 11:28 PM   #2
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My suggestion is two Group 31s in parallel per engine for starting. Easier to handle and massive MCA.
T105s for a house bank make good sense. Ensure equal lengfh cables from the dispersed bank to the collecting bus bars.
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Old 08-11-2020, 12:16 AM   #3
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I heard it was a chiropractor who invented 8D batteries. They have no place on boats.
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Old 08-11-2020, 12:30 AM   #4
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I wouldn’t use the 6 volt GC batteries for starting on a regular basis. I would convert one bank to house and one to starting. Use starting batteries for starting and deep cycle for house.
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Old 08-11-2020, 06:11 AM   #5
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I wouldn’t use the 6 volt GC batteries for starting on a regular basis. I would convert one bank to house and one to starting. Use starting batteries for starting and deep cycle for house.
True for FLA as plate design is significantly different. That said I know several folks that use GCs for starting and have no reported issues.

It's a different story if you go AGM. At least East Penn has confirmed GC2s and GP31 in AGM have comparable deep cycle and start characteristics. I assume that is why they publish both CCA and AH specs for both.
I inquired as I was developing a plan for when it's time to replace my 3 8Ds and based on above and their specs I plan to go with 6 GP 31... 4 for house and 2 for start / thruster bank. 2 -GP 31s are pretty close to 1- 8D if you compare specs. With no deep cycle advantage for GC2s why mix sizes? My thinking if 1-2 or more battys in either bank die or are weak I can replace with others from the other bank and have about the same age. Replacing the opposite bank in its entirety with new.
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Old 08-11-2020, 06:44 AM   #6
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Currently, I have two banks (port and starboard, located on the outboard side of each engine), each consisting of 2 8D batteries. These have functioned as both my house banks and have been used to start the engine as well.

Can the T-105s work as a starting batteries or would they be damaged by the large draw upon starting. Would I be better running some group 31s? My boat is powered by twin Caterpillar 3208NA engines.

If you have a large enough bank of 6V batteries, it should work OK. You'll want to exceed minimum cranking amp requirements for your engines.

I asked Lifeline if I could use a bank of 4x of their GPL-4CTs as a combined house/start bank (for a 450 Cummins) and Justin said it should be fine. 6x would have been even better but I didn't have the space.

My preference for AGMs started out being all about (bad) access for service, but it eventually turned out I could go to a 6V bank (and increase capacity a lot) by burying a couple of the batteries in that bank underneath a stairwell.

Dual-purpose G31s can make a good choice too, but it takes more of them to match your 2x 8D capacity. OTOH, Firefly Oasis G31 batteries might give you some additional flexibility (at high $$$).

-Chris
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Old 08-11-2020, 04:11 PM   #7
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My battery bank is constructed with Trojan t105. Before that it was generic 6 volt golf cart batteries. In both cases they started my 3208 cats Never a problem.
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Old 08-11-2020, 04:24 PM   #8
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My suggestion is two Group 31s in parallel per engine for starting. Easier to handle and massive MCA.
T105s for a house bank make good sense. Ensure equal lengfh cables from the dispersed bank to the collecting bus bars.

Currently my boat has a Lifeline 8D for a starting battery. For my Cummins 5.9 QSB it is really overkill. When it dies, I'll likely replace it with 1 grp 31. If I lived in cold country and didn't have an oil pan heater, I'd go for two.


Keep in mind that in a pinch I can easily switch the house to start the engine.
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Old 08-11-2020, 05:31 PM   #9
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Currently my boat has a Lifeline 8D for a starting battery. For my Cummins 5.9 QSB it is really overkill. When it dies, I'll likely replace it with 1 grp 31. If I lived in cold country and didn't have an oil pan heater, I'd go for two.


Keep in mind that in a pinch I can easily switch the house to start the engine.
That’s what I did. It was a happy occasion to see the last 8D leave the boat. I now have a single Group 31 that’s entirely adequate for starting both Lehmans and the genset. Like you, I can also tie it to the house bank in a pinch. Not sure why I”d ever need more than that for a start bank.
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Old 08-11-2020, 05:57 PM   #10
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Quote:
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I heard it was a chiropractor who invented 8D batteries. They have no place on boats.
Who, chiropractors?
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Old 08-12-2020, 12:11 AM   #11
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Who, chiropractors?
I know a chiropractor who made a bunch of money when I tried to move a little 4D by myself! I gotta say he did ease the pain.
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Old 08-12-2020, 06:12 AM   #12
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Start batts have many thin plates to get large surface area for a high CCA.

Surface area keeps the volts up , till the plated get covered with gas bubbles.

GC batts if in a large enough bank can have even higher surface area and work fine as start batts usually takes 4 or more.

GC work great even when down 50% . Most starters are 9,5v motors and are not bothered by lower voltage at the batts.
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Old 08-12-2020, 02:55 PM   #13
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Originally Posted by FF View Post
Start batts have many thin plates to get large surface area for a high CCA.

Surface area keeps the volts up , till the plated get covered with gas bubbles.

GC batts if in a large enough bank can have even higher surface area and work fine as start batts usually takes 4 or more.

GC work great even when down 50% . Most starters are 9,5v motors and are not bothered by lower voltage at the batts.
FF
You make a great point that I haven't heard expressed exactly that way before.
With relatively large house banks - 2 - 6+ deep cycle battys - the plate area is often higher than a smaller - 1- 2 batty start bank.

My prior bias that this reinforces is... better to employ deep cycle house banks to start than use starting battys in a deep cycle application
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Old 08-12-2020, 03:32 PM   #14
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Thanks for the responses. I totally agree regarding the need for chiropractic help after moving those batteries.

Based on Motion 30's experience and FF's explanation, It sounds like I'd be good. I'll have two banks of 4 6V batteries each (8 total). When starting, I can tie them together. That would certainly the simplest solution.

The other option would be to tie all 8 6V batteries together and add two group 31s as starting batteries. This would involve changing around the wiring. If I did this, would I be able to wire both 6V banks to one side of my battery selector and put two group 31 (one on each side of the boat) in parallel as start wired to the second side of my battery selector?

Currently, it's set up with two 8Ds on one side of the selector and two 8Ds on the other side.
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Old 08-12-2020, 05:34 PM   #15
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I like the 4 GCs per side as your house and a G31 Start on each side as the best option. Alternatively, since your 2 8D boxes per side will accommodate 6 GCs per side, you could supersize your house/start banks with 12 GCs total. If you have enough charging capacity for ~1300 AH, you'd have plenty of electrons and redundancy for all needs.

As others said, going with 4 GCs per side and no G31s would probably also be sufficient.
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Old 08-13-2020, 06:26 AM   #16
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With batts in series I have found the fewer on a string the lower the chance of one failing and killing them all.

(2) 6v batts on one rotary knob selection serves 4 batts .

When operating both rotaries would be in ALL only split up when dockside charging.

With multiple chargers long term storage might boil out a pair when one dies , but only 2 would be lost not 8.
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Old 08-13-2020, 07:00 AM   #17
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I'll have two banks of 4 6V batteries each (8 total).

Currently, it's set up with two 8Ds on one side of the selector and two 8Ds on the other side.
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Alternatively, since your 2 8D boxes per side will accommodate 6 GCs per side, you could supersize your house/start banks with 12 GCs total. If you have enough charging capacity for ~1300 AH, you'd have plenty of electrons and redundancy for all needs.

That's probably what I'd do. I understand three 6Vs will fit in an 8D box... if you have boxes...

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Old 08-13-2020, 12:55 PM   #18
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I have six US2200 batteries, similar to the T105's. When I got our boat a couple months ago the charging system was a mess, and batteries were seeing unequal voltages from a nonsensical switching scheme, battery isolators, etc.

To get out of the dock quickly (just returned from 2 weeks circumnavigating Catalina) I decided on a radical simplification strategy, where I wired them all together into a single bank, eliminated the battery isolators, and just charged from the 2 small alternators and 200W of portable solar. Figured I'd keep regular tabs on things with a Balmar monitor, hydrometer, etc. and use the generator if necessary. Was never necessary.

Bottom line was that it worked out great - I'm not certain why such complicated switching/banking/isolation schemes are necessary. If I were to lose a cell (unlikely) the monitor would pick up on it, and I could quickly disconnect it from the pack. The batteries are rated for 133A discharge rates for 1 hour (6V) meaning my six batteries could in theory discharge at 400A for a full hour. Cranking a Lehman 120 over is maybe 300A for a few seconds - it won't even touch the pack.
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Old 08-13-2020, 01:33 PM   #19
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If you have a large enough bank of 6V batteries, it should work OK. You'll want to exceed minimum cranking amp requirements for your engines.

I asked Lifeline if I could use a bank of 4x of their GPL-4CTs as a combined house/start bank (for a 450 Cummins) and Justin said it should be fine. 6x would have been even better but I didn't have the space.

My preference for AGMs started out being all about (bad) access for service, but it eventually turned out I could go to a 6V bank (and increase capacity a lot) by burying a couple of the batteries in that bank underneath a stairwell.

Dual-purpose G31s can make a good choice too, but it takes more of them to match your 2x 8D capacity. OTOH, Firefly Oasis G31 batteries might give you some additional flexibility (at high $$$).

-Chris

I've got similar:


Lifeline AGM Starting GPL3100T 12v Group 31 for starting.


6 Lifeline Lifeline GPL-4CT 6v batteries in series/parallel for the house, and serve as back up to the start battery.


The gen battery is a lead acid group 31 start battery only 6 mo old that will be replace with the Lifeline in a few year when it dies.


The above work GREAT for my Mainship, providing 330 ah for the house.


If I replace the above it will be the same or Oasis or LifePo depending on the numbers when I replace them.


(I have another thread out there on what battery to get)
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Old 08-21-2020, 02:31 PM   #20
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My suggestion is two Group 31s in parallel per engine for starting. Easier to handle and massive MCA.
T105s for a house bank make good sense. Ensure equal lengfh cables from the dispersed bank to the collecting bus bars.
My old 8D banks similarly died a couple weeks ago, it was on the replacement project plan for the November haul-out so just a little sooner on the wallet. I went with 7 - Group 31 AGM. I have Twin 120 Lehman - starter for PT, starter for STB, and genset - then 4 for the house bank with 2 each redundant for the engines. Will likely get another one to for a bit more redundancy.

Promariner Tournament 4-bank 360. Went with Optima Blue tops, not totally high-end but I think serviceable ROI at $250/each. Series connections on two for 24V for the windless, thrusters. At least I can lift them!
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