Modifying battery system

I'm noodling modifications to my battery system. I'll have a professional help me with the design and implementation. I just want to get my brain around the options and if any of them simply fail the makes-sense test.

I currently have 3 x Group 31 FLA house batteries and I want to up my usable AH. I don't have any additional real estate for house batteries without an extensive move. That's an option, but not my preference so I'm looking at going with Firefly batteries, possibly LiFePO4 (not likely - they will outlive me at this point). I can probably fit 3 x GC-12 AGM batteries if I can ditch the battery box - but I understand even this will require some changes to my alternators.

I have 2 x Mahle 95 amp stock alternators (one per engine) on John Deere 4045's. Each alternator charges a Group 31 FLA start battery. I have a Blue Sea ML-ACR between each start battery and the house bank and I have 320 watts of solar (but about 1/2 the panels suffer from some shading at any given time - so practically speaking I'm only getting a couple hundred watts out of them).

Any different chemistry I go to with the house batteries generates some other system changes and I'm curious about the relative pain between three different options:

1) I can disable the VSRs then add two B2B chargers after the start batteries to charge the house. Then I can go with something like Firefly or LiFePO4 (probably Group 31 Firefly because my Magnum remote would have to be upgraded for LiFePO4 - but that's an option). I would keep the FLA start batteries. This would give me two alternators working together to keep the house charged but requires installing 2 B2B chargers.

2) I can change out one of my alternators to a smarter alternator with external regulation and have it charge house bank and keep the other stock alternator to charge the two start batteries. Then I can go with almost any chemistry of house battery and keep the FLA start batteries.

3) I can have an alternator shop add an external regulator to the two alternators. Then I can go with 3 x GC-12 size AGM and 2 x Group 31 AGM start batteries. [For this option - I'm assuming my stock alternator won't properly charge AGM batteries - but I'm happy to be proven wrong. If all I had to do was swap batteries to AGM, this would be the option I'd go with and the 3 x GC-12 would satisfy my requirements even though I don't love AGM batteries.]

4) I can buy a Honda generator...

Since I've never messed with alternators or B2B chargers - how much more pain (and money) is involved in either adding multiple B2B chargers versus changing out an alternator and putting external voltage regulator in place?

Also, is it viable to keep the two stock alternators, but change the regulators and then drop in AGM?

Any experience is appreciated.

One thought on external regulators - as you increase usable storage you also increase the load/duration while recharging, which can be hard on the alternators if they get too hot. Good regulators will monitor alternator (and battery) temp and reduce load as appropriate. That's an argument on its own for upgrading the regulators. I don't think changing out all the batteries without upgrading the regulators is a good plan.

If you don't care about recharging the house bank as fast as possible from the alternators and want to minimize changes/$$ a couple of small (20-30 amp) b2b chargers replacing the VSRs would allow changing the house bank while leaving everything else unchanged, and offer protection against overloading the alternators. Lots of folks have done this when installing lifpo house systems. Downside is that the charge rate on the house bank is capped.

If real estate is limited do you have height clearance to use taller battys for house?

Clearly what you need is a manly (pronounced Man-Lee) Leece Neville 220 amp alternator with a Balmar external regulator mounted on your JD 4045. You're in luck, because thats what I did. This only charges the house bank.

https://www.trawlerforum.com/forums/members/1458-albums983.html

This fall I upgraded from 8 Trojan T-105s to 4 Firefly batteries, and couldn't be happier.

Ted

Ted, I studied your setup carefully when I was making changes to Escapade. It's slick. I took a more moderate approach and swapped the OEM alternator for a 170a Balmar kit. That charges the house bank, and then I have a b2b charger to maintain the start battery.

Brian, thinking about this a little more, maybe your option #2 is a good one, with a heavier alternator as well as a regulator. That would give you faster house charging capabilities. If you're buying a Balmar regulator the kits make the alternator pricing more reasonable.

I vote for option two. I never needed to plow heavy power to my four FLA GC house bank with both alternators and so altered my twin engine setup tp have a 100-amp alternator charging the house and the OEM alternator charge the two GP31 main engine start batts with an ACR to the generator batt, a GP31. On my current single engine boat I charge the two AGM house bank with the stock alternator with ACR link to the twin AGM start batts without issue. Its the battery cahrger I worried about and got one which plays well with the AGMs.

Bacchus said:

If real estate is limited do you have height clearance to use taller battys for house?

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Thanks for the question. I could fit the GC-12, but I'd have to go with AGM because I'd need to ditch the battery box for that to fit and I'd not longer have easy access to servicing the batteries. But going this route is my least preferred option.

Dave

O C Diver said:

Clearly what you need is a manly (pronounced Man-Lee) Leece Neville 220 amp alternator with a Balmar external regulator mounted on your JD 4045. You're in luck, because thats what I did. This only charges the house bank.

https://www.trawlerforum.com/forums/members/1458-albums983.html

This fall I upgraded from 8 Trojan T-105s to 4 Firefly batteries, and couldn't be happier.

Ted

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I don't know if it's "clearly" what I need...but that would certainly scratch the itch. I've read all of your comments I came across on batteries (and most other subjects). I know you've been happy with the Firefly batteries, that's a good selling point for me.

I understand the current distributer in the US is going to stop carrying those batteries soon. They say there will be other distributers, but I want to hold off until the dust settles before going Firefly just incase there is a gap in the ability to get replacements/warranty issues.

Thanks for commenting. I'm now focused on option 1 or 2. I'll probably discuss both with my guru once I get a better handle on how each option would be implemented.

Dave

rgano said:

I vote for option two. I never needed to plow heavy power to my four FLA GC house bank with both alternators and so altered my twin engine setup tp have a 100-amp alternator charging the house and the OEM alternator charge the two GP31 main engine start batts with an ACR to the generator batt, a GP31. On my current single engine boat I charge the two AGM house bank with the stock alternator with ACR link to the twin AGM start batts without issue. Its the battery cahrger I worried about and got one which plays well with the AGMs.

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Hmmm...seems most of you who have been through this type of decision like option 2. I feel the same as you, plowing huge power into batteries fast under power is not a critical requirement. When I move, its at least a few hours underway and all I need is to pump a decent amount of amp hours into the battery and (if conditions are good) solar does the rest; if they are not good, it's just another PSOC day. Changing the batteries to a chemistry that charges faster means I can get by with a smaller alternator (in the 100 amp range) and still meet all my charging requirements.

With a couple cable moves I can change my ACRs to combine the start batteries and have the old alternator service them only; then rig the other ACR to be an emergency parallel switch only (I think).

I think the only downside of this is my start batteries would only be charged by engines. I couldn't have them connected to my Magnum charger or solar since both of those would be configured for the house bank's chemistry. But I might have the same problem if I went with Option 1 - so I have to noodle that as well. I'd rather avoid installing a small B2B charger to charge start from house. But I guess a small charger is an option there.

As the military says, if this was easy, everyone would do it.

Thanks guys.

Bkay said:

...Changing the batteries to a chemistry that charges faster means I can get by with a smaller alternator (in the 100 amp range) and still meet all my charging requirements.

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Just keep in mind that the alternator is unlikely to deliver its rated current during bulk charging when properly regulated. A 100a unit may only deliver a sustained 60 amps at a conservative temperature limit. Not sure if there's a rule of thumb on this, but heat buildup is definitely a controlling factor for alternator output.

I am no pro!! But on option 2, if for same reason one engine fails. Than ether the house or the starting batteries will not be charging, Yes?

I would try to make it so ether bank can charge from ether engine.

Iggy said:

I am no pro!! But on option 2, if for same reason one engine fails. Than ether the house or the starting batteries will not be charging, Yes?

I would try to make it so ether bank can charge from ether engine.

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The ML-ACRs will still be in place, but switched to "Off" and wire tied open in both 1 and 2 (slightly different configuration in each option, but they will still be there). So manually combining the banks should be easy enough.

Jeff F said:

Just keep in mind that the alternator is unlikely to deliver its rated current during bulk charging when properly regulated. A 100a unit may only deliver a sustained 60 amps at a conservative temperature limit. Not sure if there's a rule of thumb on this, but heat buildup is definitely a controlling factor for alternator output.

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That's exactly what I get out of each of my two 100amp units.