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Old 03-01-2021, 05:29 PM   #1
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New Start and House Battery Selection (cost/value based)

...positive this has been covered but couldn't find a relevant thread.

I'm planning to buy SIX or EIGHT new batteries for my House, Engine Start, and GenSet banks on my still new-to-me-after-three-years trawler. It's not a small expense and I have two or three choices.

Start banks: Four GC-2 6V batteries, two on each 12V start bank - showing age and prior overcharging/overheating - one supplying the Lehman 120 main (and bow thruster) and one supplying the GenSet (and stern thruster). These have a manual combiner switch. Batteries need to be replaced. Battery ages 16 years.

House banks: The two house banks appear to be configured for AGM batteries, but POs have mixed around the batteries. There are two existing Lifeline AGM batteries on one house bank that don't seem to need an immediate replacement. But, the second house bank is lead-acid and batteries are bad, showing signs of (predictable) overcharging. Battery ages 5-6 years.

Charging: The Start banks share a Mastervolt AC-DC charger (set for lead-acid) and each one has a Balmar DC-DC DuoCharge (also set for lead-acid) to charge from the selected house bank. The House banks are charged from a Balmar 100A+ smart alternator-regulator and/or the Freedom inverter-charger that are set up for AGM. Optionally, charging of the non-selected house bank is accomplished by an ACR between the two house banks.

Priorities: Make start/house banks compatible - similar chemistry and age, preserve resale value in 3-4 years, reliability over next 5-7 years, lower shorter-term cost. (Note: I do expect to sell the boat when I retire in 3-4 years.)

Choice A: Would it be a mistake to go with all new lower-cost lead-acid types everywhere (Either Costco's cheapest GC2 or Trojan T-105/T-125) dumping the two currently good AGMs and recycle all old batteries?
Cost US $900 - 1,800 depending on battery quality


Choice B: Or keep the two currently good AGMs and get a new pair of AGMs for the house and new lead-acid batteries like Trojan T-105s for start banks?
Cost US $575 (4xT-105s) + 750 (2xLifeline AGM) = $1,325
(plus in future replace the older AGMS)

Choice C: Make everything AGM.
Cost US $2,800

My charging systems can't accommodate LIFO, just Lead-Acid or AGM. I don't spend much time away from shore power for more than two days so Amp-hour needs are smallish, but start reliability and thrusters are mission-critical.

Seems that the deep cycle batteries are not rated on CCA so not sure if they have enough oomph as start batteries or if it matters. The AGMs have huge available amperage. Will cheaper GC2 lead-acid batteries provide enough CCA starting current for the SINGLE Lehman 120 and/or GenSet in combined-use with the thrusters?

Thanks for listening. Appreciate any brief wisdom...
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Old 03-01-2021, 06:49 PM   #2
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You need to get info on the recommended cranking amps for your Lehmans 120. Tehn figure your starting requirements. I don't know if this will help but I recently replaced all batteries because my failing inverter damaged them. A PO had done some rewiring and the port engine was started by a single FLA 8D. There were three other 8Ds that were the Stb start and house bank. I didn't realize that changing to a more conventional one 8D for each Cat 3208 and two for the house bank was not possible with out pulling out the washer dryer to do lots of rewiring. So I left two 8Ds to start the port engine wired for 12v and replaced two 8Ds with six Trojan L16s giving me 1300 ah in the house. So the house bank is also the start system for the stb engine. Those L16s are deep cycle but turn over the Cat perfectly. I replaced the dead Xantrex inverter/charger with a Victron set for the FLA house bank and added a smaller Victron charger for the AGM start batteries and AGM generator start battery. If I had know all from the beginning, I would purchased only FLA so all were compatible and I would have only put in one 8D and replaced the other with two more L16s increasing the house bank to 1735 ah and giving the Stb engine even more starting power.
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Old 03-01-2021, 07:19 PM   #3
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First off, I don't like the set up but it is not horrible. Second, you have the wrong type of batteries for the start/thruster set up. You should switch to lead acid (FLA) group 31 12v starting batteries for this application. Two of these in parallel would be fine. Third, I don't like two house banks. The natural thing to do is run one bank down then switch to second bank. This method over works and shortens the life of the batteries. It is much better to have one battery bank that discharges to 80% than to have two banks one at 50% and one at 95%.

Doesn't matter if you go with AGM or FLA, just don't mix. It is also not good to combine house and Start for charging as they have different charging rates. Also not good to combine two house banks at different levels of discharge and then charge them, some batteries will get cooked in the process.
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Old 03-01-2021, 08:06 PM   #4
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Along with the group-size numbers, you might see letters printed on your battery. For marine applications, look for group sizes indicating the letter “M.” These batteries are designed for watercraft applications.

Although you may find the right group size for your vessel, don’t use a battery without the “M” designation. The internal construction won’t work in the long run for your boat. Batteries will decline with rapid ease. Don’t leave yourself stranded with an improper battery.
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Old 03-01-2021, 08:18 PM   #5
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What is different about them other than the "M"?
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Originally Posted by fgarriso View Post
Along with the group-size numbers, you might see letters printed on your battery. For marine applications, look for group sizes indicating the letter “M.” These batteries are designed for watercraft applications.

Although you may find the right group size for your vessel, don’t use a battery without the “M” designation. The internal construction won’t work in the long run for your boat. Batteries will decline with rapid ease. Don’t leave yourself stranded with an improper battery.
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Old 03-01-2021, 08:44 PM   #6
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Found this thread so know now that this has been beaten to death.
https://www.trawlerforum.com/forums/...0-a-46299.html

Still not sure what to do regarding reworking my setup. At least all the wiring is easy to access if I make layout changes...
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Old 03-02-2021, 05:05 AM   #7
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I have two Lehman 120s. No starting batteries, just a house bank of eight golf car batteries. Engines start easily even with batteries depleted to as low as 30%.
Quote:
Originally Posted by RickyD View Post
You need to get info on the recommended cranking amps for your Lehmans 120. Tehn figure your starting requirements. I don't know if this will help but I recently replaced all batteries because my failing inverter damaged them. A PO had done some rewiring and the port engine was started by a single FLA 8D. There were three other 8Ds that were the Stb start and house bank. I didn't realize that changing to a more conventional one 8D for each Cat 3208 and two for the house bank was not possible with out pulling out the washer dryer to do lots of rewiring. So I left two 8Ds to start the port engine wired for 12v and replaced two 8Ds with six Trojan L16s giving me 1300 ah in the house. So the house bank is also the start system for the stb engine. Those L16s are deep cycle but turn over the Cat perfectly. I replaced the dead Xantrex inverter/charger with a Victron set for the FLA house bank and added a smaller Victron charger for the AGM start batteries and AGM generator start battery. If I had know all from the beginning, I would purchased only FLA so all were compatible and I would have only put in one 8D and replaced the other with two more L16s increasing the house bank to 1735 ah and giving the Stb engine even more starting power.
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Old 03-02-2021, 07:45 AM   #8
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Quote:
Originally Posted by warfdog View Post
Start banks: Four GC-2 6V batteries, two on each 12V start bank - showing age and prior overcharging/overheating - one supplying the Lehman 120 main (and bow thruster) and one supplying the GenSet (and stern thruster). These have a manual combiner switch. Batteries need to be replaced. Battery ages 16 years.

House banks: The two house banks appear to be configured for AGM batteries, but POs have mixed around the batteries. There are two existing Lifeline AGM batteries on one house bank that don't seem to need an immediate replacement. But, the second house bank is lead-acid and batteries are bad, showing signs of (predictable) overcharging. Battery ages 5-6 years.

First, learn Lehman minimum cranking amps. The bow thruster manual may also have some recommendations about cranking amps/RC, etc. Wouldn't surprise me if a single G31 starting battery works for your main engine; a pair of decent G31s could well be a good answer for both Lehman and bow thruster.

Then ditto cranking amps for your genset. Wouldn't surprise me if a G24 works fine. (We used a G34 for our 8 kW genny.)

I don't see any huge need for those batteries to all be identical, as long as you've got the same (enough) chemistry to be serviced with a shared charger. In the grand scheme of things, your Lehman and genset alternators may well be doing most of the charging for these, anyway.

Then combine the two house banks into one. Maybe a boatload of 6V golf cart batteries...

Which AGMs do you have now? Lifeline makes several (G31, GC2, 8D, etc.), so depending on what you've got now, maybe something could be moved to become (some of) those start batteries...

I'd say the choice between FLA and AGM is mostly about servicing ease, less off-gassing, and faster charge acceptance rates. If servicing is easy and you're good to go with other issues, FLA is good cost/benefit. Otherwise, AGM might better float your boat.

There's also the "get what you pay for" thing. We've had good luck with Odyssey (~11/12 seasons per bank), and the Lifeline GC-2 AGMs were showing great promise. Can't say as I've read less brands have been as long-lived (but then circumstances vary, so comparison -- especially at internet distance -- would be difficult).

-Chris
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Old 03-02-2021, 11:31 AM   #9
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Thanks, Chris...

I can't fit two G31's or G27's in the existing fixed battery boxes but two G24's or one G31 might fit in each box. Might go that way with the start banks. All AGM is probably too expensive given my priorities.

Economically speaking, seems the choice for the start banks is now either (a) four FLA GC2's 6-volt batteries in series (two for each Engine/GenSet box), (b) four FLA G24's 12-volts (two in each box in parallel), or one FLA/AGM G31's 12-volt in each box with some spacers. Any of those will provide the amps required to start either load.

Curious if the parallel configuration or the series configuration provides any damage-protection advantage if one battery fails? Also, I should check how the banks are isolated by the AC charger.

As for the house banks, the existing AGMs are Lifeline GC2's. I have a 1-2-BOTH-OFF switch so maybe for the health of the batteries it would be best to leave it on "Both". Or maybe I'll just delay replacing the second pair of house batteries until next year.

Really appreciate your insights!
- Joe

Quote:
Originally Posted by ranger42c View Post
First, learn Lehman minimum cranking amps. The bow thruster manual may also have some recommendations about cranking amps/RC, etc. Wouldn't surprise me if a single G31 starting battery works for your main engine; a pair of decent G31s could well be a good answer for both Lehman and bow thruster.

Then ditto cranking amps for your Genset. Wouldn't surprise me if a G24 works fine. (We used a G34 for our 8 kW genny.)

I don't see any huge need for those batteries to all be identical, as long as you've got the same (enough) chemistry to be serviced with a shared charger. In the grand scheme of things, your Lehman and Genset alternators may well be doing most of the charging for these, anyway.

Then combine the two house banks into one. Maybe a boatload of 6V golf cart batteries...

Which AGMs do you have now? Lifeline makes several (G31, GC2, 8D, etc.), so depending on what you've got now, maybe something could be moved to become (some of) those start batteries...

I'd say the choice between FLA and AGM is mostly about servicing ease, less off-gassing, and faster charge acceptance rates. If servicing is easy and you're good to go with other issues, FLA is good cost/benefit. Otherwise, AGM might better float your boat.

There's also the "get what you pay for" thing. We've had good luck with Odyssey (~11/12 seasons per bank), and the Lifeline GC-2 AGMs were showing great promise. Can't say as I've read less brands have been as long-lived (but then circumstances vary, so comparison -- especially at internet distance -- would be difficult).

-Chris
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Old 03-02-2021, 12:34 PM   #10
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In choice B, I would not choose T-105s for start batteries. You need start batteries for this application, either group 27 or group 31 start batteries in any chemistry, a pair of them will do just fine staring your Lehmans.

I'm with the combine house banks into one group, but that's a separate issue. Since you say you are mostly on shore power, I'd be tempted to just go AGM for everything and keep it simple. Two new lifelines for the house bank in need, and Costco group 31 or 27 (whatever fits the space) start batteries for the start bank(s) in AGM as well. I can't imagine why your start bank is currently GC-2 batteries. ???

Keep in mind that the DC-DC duo charge cannot boost voltage, it can only reduce it. So you can't properly charge an AGM (higher voltage) from a bank that is setup with flooded (lower voltage), but you CAN do the reverse.
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Old 03-02-2021, 02:25 PM   #11
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I can't fit two G31's or G27's in the existing fixed battery boxes but two G24's or one G31 might fit in each box. Might go that way with the start banks. All AGM is probably too expensive given my priorities.

Economically speaking, seems the choice for the start banks is now either (a) four FLA GC2's 6-volt batteries in series (two for each Engine/GenSet box), (b) four FLA G24's 12-volts (two in each box in parallel), or one FLA/AGM G31's 12-volt in each box with some spacers. Any of those will provide the amps required to start either load.

Curious if the parallel configuration or the series configuration provides any damage-protection advantage if one battery fails? Also, I should check how the banks are isolated by the AC charger.
Could you replace the boxes? One box with two G31s for main and thruster, one smaller box with a G24 or G34 for the genny? Standard size boxes are cheap, if you've got some space discretion.

I assume your Lehman, your genset, and your thruster all need 12V.... if one battery in a pair of 6V GCs goes south... you've got squat. If one in a pair of G31s goes south, you can still have 12V.

I'm not aware of any damage protection "because of" either parallel or series configuration.

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Old 03-02-2021, 05:21 PM   #12
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Joe
I am in a somewhat similar situation and prepping for eventual batty replacements.

I now have one 8D AGM for bow & stern thrusters and recently moved my single engine start to this bank. I like and plan to stick w/ AGMs when needed in future. A pair of GP31 AGMs (Sams Club Duracell) provide 1600 CCA, 210 AH and cost $360 for the pair. This is equal or a little higher CCA than an 8D which is working fine for me for the above use.

House - currently two 8D AGMs - were managed with a 1-2-all-off switch but I wired them together so I could accurately measure & manage the house bank with a Balmar batty mgmt system (doesn't work with a switched bank)
I considered both GP31 and GC AGMs for house bank and plan on a bank of four total. I contacted East Penn & Trojan to ask if either of these sizes in AGM were better suited for start or deep cycle use. Their answer was they were equivalent and provided no advantage either way (other than the small difference in spec AH or CCA). This makes some sense as you will find in many / most cases with AGM the mfg spec both AH and CCA and they do not list differences in plate thickness / design like they do in their FLA line.
My decision is to use 4 GP31 AGMs in parallel for the house for a couple reasons... Provides total 420 AH (similar to 4 GCs) That makes all 6 battys the same and allows me to drop one GP31 from the house if one goes bad leaving 75% capacity (vs having to drop a pair of 6V GCs and only have 50%) It would also allow swapping one or two house to start in an emergency with them all the same size. My last (minor) consideration is if some of the GP31s are going bad / getting weak having them all the same size (and age) it will allow me to combine 2 or 4 that are still good and replace the other bank as a short term lower cost alternative to replacing all 6 again.

Sams Club AGMs run about the same for GP31s and GCs - $180/ea so for about $1,100 I can start fresh with all new AGMs - 2 - start/thruster and 4 - house

Having a gen with a separate start batty provides some level of insurance / redundancy that adds a comfort level for little expense.
If you go all AGM you may be able to sell you current boxes and use a lower cost tray / retention system than needed for FLA.

Food for thought - as you can tell there are many different ways to set up batty systems and a lot depends on your cruising style and AH needs and no matter how adamant any of us are about our solution - there is no one right answer - just pluses / minuses and compromises.
I have a gen with a separate GP 24 AGM batty charged by the gen alt.
When I charge both start/thruster bank and house via an ACR and at the dock my shore powered 3 bank charger with each leg on one of the 8Ds.
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Old 03-02-2021, 06:27 PM   #13
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I am choosing to stick with FLAs. As weekenders with the occasional week or two away but with more time in a marina (wife work and dog) than at anchor, I looked at all the options. I can fully replace the entire bank several times and still have enough power to have fun.



That said... your system has way too many points of failure. Optimally, one start bank and one house bank is good (with maybe a small genset start battery). Make your house bank all GC2 6V in series parallel and two or three 12V dual purpose batteries to start both engines and provide backup house power should the need arise. Route all charging sources to the house bank with a charger that is at least 10% of the bank capacity, with a single DC-DC charger, Duo Charge, or VSR to top off the start bank while underway. My system centers around two 1/2/Off/Both switches. One switches where the house power comes from and the other where the engine start power comes from. I would get professional help to make sure you are fused correctly and use the correct gauge wiring. Otherwise, the rest is pretty DIY.



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Old 03-02-2021, 06:28 PM   #14
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I would go with all AGMs. AGM start batts for that application and AGM deep cycling style for the house. That's what I have here.

HOWEVER, you claim budget concerns; so I'd do the AGMs for house and FLA for starts, especially since you have the alternator and seoarate charger set for the AGMs. Interesting that you do not seem to have an alternator charge for the start battss?
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Old 03-02-2021, 07:22 PM   #15
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Well, I will say that no matter what you decide, go with at least AGM, firefly, Gel, or any other maintenance free battery. Although a bit more money, you won't be a slave to filling the water in the FLA's once a week. Leaving them on the charger/inverter while plugged into shore power slowly consumes the water. I have 8 trojan 6 volt golf cart batteries that are always hungry.
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