Choosing deep-cycle (house) batteries

[Adelie]

Originally Posted by zengirl

I have 4 -50ah each LiFepo4 on one bank and was thinking of buying Interstate agm next. Any feedback on that would be welcomed.

Are you replacing the LiFePo with AGM or adding a second bank?

You can’t mix the 2 in a single bank. The differing voltages mean that the Lion batteries would discharge themselves trying to charge or overcharge the AGMs.

They have differing charging requirements so if you are adding a second bank you need a whole separate charging system. If they are in separate banks you can never use the Both option on the battery switch because that makes the 2 banks act as a single bank.

Why AGMs for the new batteries?

[john61ct]

Interstate does not make batteries, just relabels and sells on.

JCI is afaik their OEM of choice.

OK for automotive use, but not deep cycling.

The three top makers of true deep cycling AGM in NA are Lifeline Odyssey and Northstar.

If you really need AGM.

[zengirl]

Thank you John! I'll stick with new LiFepo4's.

[AndyEss]

Originally Posted by zengirl

Thank you John! I'll stick with new LiFepo4's.

What kind of problems are you having with the existing LFP bank that you believe you need to replace them?

[sailingharry]

Originally Posted by OneHullPaul

Firefly batteries will give you 70% usable Amp hours, AGM 50%, Regular lead acid 30% and sulfuric acid in your bilge eating your keel bolts.

From 80-100% batteries cannot be bulk charged so isn't usable in the same way. Lead acid shouldn't be drawn down below50% AGM 30% and 10% for firefly.

Hope that helps some. Bluefly are the priciest but will probably last you a lifetime with the number of charging cycles of them.

Good luck. Just don't let the smoke out and the job will be easy.

This doesn't really apply to OP's use regime. He frequently gets 100% charge with any battery ("usually on marina"), and so the problem with getting to full charge just isn't a problem.


Also, after 9 years of sailing with flooded -- well, if he's OK with that, stay with it! Flooded are a maintenance headache for people who think it's a headache. People who are used to it don't have a problem with it.


I sailed with FLA for nearly a decade on my Sabre 34, mostly weekends and kept at a slip with shorepower. Even longer cruises (week+) weren't much of an issue because we usually hit a marina every 2-3 days.


Of note, even if you have AGM, sailors often won't get anywhere close to 100% SoC -- I have many days when out sailing where the engine gets well under an hour a day. And coastal sailors won't have 500+ W of solar. On our Saga 43 with 800 Ah of AGM and 360W of solar, we lose about 200Ah/day when cruising. But that marina every 2-3 days fixes that problem. (and before anyone comments on that draw, we've only had the boat since July and are still sorting things out -- including why the solar doesn't seem to carry its share of the load and why the 120A alternator only puts out 70A).

[zengirl]

Originally Posted by AndyEss

What kind of problems are you having with the existing LFP bank that you believe you need to replace them?

Thank you for asking, but I'm not having any problems. But I live on Soc Sec. and I have to pace my buying. I will purchase one a year so if I do have a failure, I have backups. And I want to put in solar and I'll need a separate for that. I can't have problems sprung on me and be able to fix immediately, so I have to have backups.

[daletournier]

Originally Posted by roland stockham

Quite true but unfortunatly irrelevant. What the starter needs is volts and a battery cabable of maintaining them for 30sec at cranking amps. My engine manual specifies a batt rated to 660cca so able to supply 660 amps. Although my house bank is 400a/hrs its max recomended discharge rate is 86a so no comparison. Starting your engine with a house bank is like trying to tow the boat with a Farrari, on paper it may have the power but it wont like it, it's a speed machine and so is a start batt. Your house bank is the equivelent of a tow truck, no speed but will pull forever.

Been starting my engines with deep cycle Trojans for ten years, no problems, real world example.

[Exile]

Originally Posted by daletournier

Been starting my engines with deep cycle Trojans for ten years, no problems, real world example.

So Dale -- do you have just one bank that does double-duty as the starter for the engine and supplying the house?

[daletournier]

Originally Posted by Exile

So Dale -- do you have just one bank that does double-duty as the starter for the engine and supplying the house?

Hi Exile, I have two banks of t105 Trojans, one 675ah and one 225ah.

Although its goes against traditional wisdom I mostly have them combined, I cant see the point of having 225ah sitting there doing nothing. If the bank was to fail due to a dead short I have the generator to get the motor started and a lithium starter pack. Off shore I do separate them, not that my back up plan wouldnt work out there as well.

I monitor my batteries closely, use a hydrometer once a week and of course the daily Xantrex Link battery monitor.

I start the engine from the combined bank.

[sailingharry]

Yeah, what Dale said.


Deep cycle batteries are, pound for pound, inferior for starting as compared to start batteries. However, since our house batteries are 3 or 4 or more times as heavy as recommended start batteries, it's not an issue. Actually, the issue is that our house batteries these days are SO INCREDIBLY powerful in terms of CCA, that is is virtually impossible to fuse them in accordance with ABYC standards.


Two more real world examples.


My ancient Volvo MD11C (late 1970's), no glow plugs (compression release for manual cranking, but I never use that), starts day in and day out on a single pair of Trojan 6V. There is a Group 30 sitting as backup on the "2" position of the 1-2 switch, but I've only used it for real once or twice in the last 10 years.


My father's ancient (also 1970's) Perkins 4-236, a beast of an engine, also without glow plugs, cruises from the FL Keys to Annapolis and back every year for the last 20 years using a single bank (no reserve) of 4 Golf Carts (they are actually two banks, but always paralleled). Lest the uber conservative in the crowd get upset, the backup options (never actually used) include a generator pushing over 100A of charge over to the house/start bank. And as an ultimate fall back, jumper cables to the generator start battery.


FLA house batteries work great, and AGM are beyond comment as start batteries (Trojan does rate their AGMs, and their 100Ah Deep Cycle Group 31 AGM has 600 CCA). Note that while Trojan won't state FLA CCA, they do state that a T-105 can put out 75A for 115 minutes. Since the starter on my Volvo is rated at 1.2KW (100A), I suspect that the Trojans can probably provide that current non-stop for about an hour.


Oh, also note that the 54HP Yanmar 4JH2E on our new boat is rated at 1.4KW, or 120A. It doesn't take much to start these diesels! But also note that Yanmar doesn't specify CCA -- they specify a minimum of 80Ah (yeah, Ah, like deep cycle batteries are rated with).

[newhaul]

Originally Posted by suiramor

What factors should I consider when looking for new house batteries for my Benetau 46 (I currently have 2x NG-4D, 9 yrs old! - I think 500AH)? At this time I am mainly doing coastal sailing, day trips, sometimes on anchor but usually on marina power in cooler (Pacific NW) climes.

If you are still in seattle just go up to fisheries on lake union and get a couple of dyno 4Dd batteries they are the same size as what you have now but top of the line manufacturer.
They are 180ah each a pair will give you about 200ah usable with uour current usage

[ranger58sb]

Originally Posted by sailingharry

...and AGM are beyond comment as start batteries...

What does this mean?

-Chris

[FAST FRED]

"Starting your engine with a house bank is like trying to tow the boat with a Farrari, on paper it may have the power but it wont like it, it's a speed machine and so is a start batt."

Depends , a start batt has many many thin plates to help keep the voltage up while cranking. Happily they quickly get bubbles on the plates , so after a pause will allow another crank attempt or two.

Deep cycle batts have far thicker plates with less surface area, so don't do as well for starting individually..

BUT if the deep cycle bank is large (4 batts not just 1) the plate surface area may be as large as the single start batt and actually better for starting as it will maintain a higher voltage cranking for a longer time.

To me the "marine" marketed batts are best as used by outboard fisherman.
The can troll hours with a tiny 12 v motor while fishing , and still have enough voltage left to start their outboard.

[sailingharry]

Originally Posted by ranger42c

What does this mean?

-Chris

Yeah, I wasn't terribly clear on that comment. I was trying to say that AGM are inherently a very high amp power source, and when you talk about a house-bank size battery, the CCA's are in orbit. As I mentioned, the Group 31 Deep Discharge Trojan battery (AGM-31) is a 100Ah battery with 600 CCA. A typical house battery would be, what, 300Ah, or 3 of these? That's 1800 CCA from a battery sold as a deep cycle. They sell "dual purpose" AGM with even more CCA.


The point is that deep cycle AGM, of any size, has far more cranking amps than the boat it is on will need, and "is beyond comment." But here I am commenting... LOL

[Exile]

Originally Posted by daletournier

Hi Exile, I have two banks of t105 Trojans, one 675ah and one 225ah.

Although its goes against traditional wisdom I mostly have them combined, I cant see the point of having 225ah sitting there doing nothing. If the bank was to fail due to a dead short I have the generator to get the motor started and a lithium starter pack. Off shore I do separate them, not that my back up plan wouldnt work out there as well.

I monitor my batteries closely, use a hydrometer once a week and of course the daily Xantrex Link battery monitor.

I start the engine from the combined bank.

Thanks Dale, and sorry if I already asked this before (I may have), but I think it's come up because we have rather similar set-ups. Except in my case I have an 8D with 255ah (rated) as my engine start batt just sitting there doing nothing, and I have yet to combine it. In addition to a backup lithium starter pack and a genset (with its own dedicated start batt), I also have crossover relays which allow me to easily use the house bank (510ah) to supplement the start batt if needed (never has). Although my system of separating start & house banks is definitely a product of traditional wisdom, like you I think I'm better off at least having the option of combining the two banks.

Although there are many ways of doing this, my thought was along the lines of a simple pos cable (2/0 for my 8Ds) running btwn the two banks with a manual on-off rotary batt switch. That way there's no mistaking whether the banks are combined or not. My other thought is that, because each bank has its own dedicated, rather small capacity (55A) alternator, by leaving the banks separated while running the engine I can be assured that both alternators are providing a full charge to each bank (as opposed to one potentially trying to charge both banks). While this set-up may not be ideal, it's the one I inherited with the boat and anything I do that's more complex I KNOW will wind up costing major boat bucks $$$. Besides, the existing system has always worked well and I've already taken the cruiser's version of the Hippocratic oath to try and "do no harm".

Sorry for the thread drift. Just 'talking' out loud here . . . .